tag:blogger.com,1999:blog-14685145392057488452024-03-21T12:07:19.541-07:00Top NotchJaredhttp://www.blogger.com/profile/02241918879329048444noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-1468514539205748845.post-30301038458509187932017-09-21T15:40:00.001-07:002017-09-21T15:40:11.231-07:00Playing MIDI on an STM32F446 Part 1: Square WavesI've decided to try to make an 8-bit style music player out of a microcontroller. There are some really cool arduino versions of this project, but they all seem to require a very confusing custom file format to describe the song. My goal is to use a simple format that can be easily generated from a midi file. As a proof of concept, I wrote some code which plays a midi file converted to a list of note data in the format "start time, duration, pitch, volume".<br />
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<script src="https://gist.github.com/dicarlo236/6bcc4ed472b5e26ab4d88dfb4143d52f.js"></script>
This version has a known issue with high pitch notes. If a note requires a duty cycle of 80.5 DAC cycles, it will just round down to 80 cycles, which makes it sound flat. Instead, it should alternate between 80 and 81.<br />
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Eventually, I plan to add more sounds and effects other than "square wave with 50% duty cycle", but for now, that's the only choice. The plan is to make each instrument kind of like a script. Each instrument would have an array of function pointers and arguments which get executed in order. Functions could do things like "delay 20 instrument cycles", "set output to triangle wave", "increase pitch by major third", "do a vibrato effect", or even "move function pointer array pointer back n steps".<br />
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I plugged the DAC into my computer's line in port, and recorded this:<br />
<a href="https://www.youtube.com/watch?v=bGQ_Zj2jo8s">https://www.youtube.com/watch?v=bGQ_Zj2jo8s</a>Jaredhttp://www.blogger.com/profile/02241918879329048444noreply@blogger.com0tag:blogger.com,1999:blog-1468514539205748845.post-57422242693036050072017-07-22T20:51:00.002-07:002017-07-22T20:51:57.060-07:00Hoverboard Robot Arm Part 1: The Class ProjectI decided to build a robot arm for my 6.115 final project, which was a bad idea. The project is open ended, but requires you to use an Intel 8051 and a Cypress PSoC microcontroller. The 8051 is from the 1980's and is useless, and the PSoC is only there because Cypress gave MIT a ton of money. The PSoC is honestly a very bad microcontroller - it's neither high performance nor cheap. It's big feature is that there's some sort of vaguely FPGA-like thing that allows certain pins to be remapped. As a result it does many things, but nothing well. It is very slow at floating point math. The analog inputs are slow. It can literally do half the PWM and encoder decoding of the similarly priced ST micro. It has no hardware serial support. You can even turn some pins into a really bad op-amp! Cypress gave MIT lots of money and development kits, so the class teaches you that your choices in microcontroller are old 8051's or Cypress PSoC, so of course, everybody leaves thinking the PSoC is the pinnacle of high-performance electronics.<br />
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The final projects are supposed to be very ambitious. My original final project proposal included the following<br />
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<ol>
<li>Designing a 3-phase inverter capable of running at 400V, 20A with low side current sensing</li>
<li>Laying out a PCB for the motor controller</li>
<li>Populating/debugging the PCB</li>
<li>Implementing field oriented motor control for torque control of a brushless motor</li>
<li>Designing a discrete-time current controller</li>
<li>Characterizing a motor from an electric hoverboard</li>
<li>Designing a full state feedback controller for robot arm endpoint position control</li>
<li>Implementing code to compute the robot arm's Jacobian to have force control of the robot arm</li>
<li>Designing and fabricating an extremely low inertia, direct drive robot arm</li>
<li>Simulating the robot arm force/torque control in MATLAB</li>
<li>Writing a motor simulator to test the field oriented control logic</li>
<li>Coming up with a robust communication protocol for the motor controller to talk to the 8051</li>
<li>Hooking the 8051 to the timer chip, the serial chip (to talk to the motor controller), two ADC's (for controlling the robot arm), a keypad encoder (for changing settings), and one of those Hitachi displays (for showing position error)</li>
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and I was told "it wasn't enough" and "wasn't related to the class", even though we learned about motors, current control, first order circuits, feedback control, switching regulators, feedback control of switching regulators, stepper motors, digital signal processing, digital filters, and characterizing systems. The suggestion was to add code that takes in a JPEG, vectorizes it, then draws the image. On an Intel 8051. The idea is to get people to branch out, but I think it's setting people up to get super stressed and have a partially working final project. I still managed to get all the points without doing anything more that what's listed above, but I didn't know this would happen until after I turned in the project.</div>
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This project was submitted as a "safe" robot arm with "small" electric motors, driven by "little 3 phase inverter ICs" powered from a "low-power" bench supply. There's a huge number of safety requirements for the project, which is pretty reasonable given some of the proposed ideas. The "safe" and "small" motors are around 1.5 kW motors from an electric hoverboard, the "little" IC is actually a 75A, 600V IGBT in a package that can dissipate 225W, and the "low-power bench supply" is, well, actually a completely reasonable 3A, 15V bench supply that we're required to use.<br />
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We were taught in class that using words like "low-power" or "large" were relative and meaningless in engineering, so I didn't feel bad about submitting something that could potentially be dangerous.<br />
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Building the Arm</h3>
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Bayley recently bought 15 hoverboards from a man in New York, and gave me a few motors to use for this project. I started by removing the tire from the motors and disassembling.<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjy8KcolwcjF31kUr4xbZRixgAqU5nCSai0Tsjj8rJuWsnTf7l87jk1gn2ftGwHeR0rT16HuuXi6ub84IrOhYg6SD0p0LL4Xpds_RQhlEaZCOc9fDCab_B7SW8QQm8slqCzemr5ZePqOYo/s1600/SAM_1780.JPG" imageanchor="1"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjy8KcolwcjF31kUr4xbZRixgAqU5nCSai0Tsjj8rJuWsnTf7l87jk1gn2ftGwHeR0rT16HuuXi6ub84IrOhYg6SD0p0LL4Xpds_RQhlEaZCOc9fDCab_B7SW8QQm8slqCzemr5ZePqOYo/s320/SAM_1780.JPG" width="320" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhHc_b0rb1F9q3EGzYkKD7PqRoWTJf8ob4nnrZDCrSCl_eBRFBeMMfIBE92u8LFnVfgdN-bbWQnzvwClWr8JzLUgEcDfcJJBnQk3xzkBXeSYekuhfeg2GU0tKfvu8lyFlqSAas2ZSF4ZhA/s1600/SAM_1781.JPG" imageanchor="1"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhHc_b0rb1F9q3EGzYkKD7PqRoWTJf8ob4nnrZDCrSCl_eBRFBeMMfIBE92u8LFnVfgdN-bbWQnzvwClWr8JzLUgEcDfcJJBnQk3xzkBXeSYekuhfeg2GU0tKfvu8lyFlqSAas2ZSF4ZhA/s320/SAM_1781.JPG" width="320" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEju5Qu7yF5Obg8655qUGu_Jy2gsFKcQAk_gM2elWIWDSOJpn3tXuXzmynZiUN10oPos0xJClCPvJS1DxfwAEgIPfBBLYdWxYCc2avTmJ2CieUEQpNN4NXcKpaaqqR5gIodErdgZhMWPhJg/s1600/SAM_1782.JPG" imageanchor="1"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEju5Qu7yF5Obg8655qUGu_Jy2gsFKcQAk_gM2elWIWDSOJpn3tXuXzmynZiUN10oPos0xJClCPvJS1DxfwAEgIPfBBLYdWxYCc2avTmJ2CieUEQpNN4NXcKpaaqqR5gIodErdgZhMWPhJg/s320/SAM_1782.JPG" width="320" /></a></div>
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There's a lot of motor inside! Unfortunately, I couldn't come up with a clever way to hide an encoder on the inside of the motor, so I bored a hole in the casing to give me access to the fixed shaft from the front of the motor. There aren't very many circular features on this motor, so finding the center is challenging. I ended up putting it in a four-jaw chuck on the lathe, but was only able to get within .001" because nothing on this thing is actually round. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5DrMTAgQwXfNmaJ6eK80SPib28uOuK_GOpaQvYbRaK6d9rBzUpUedylig9Jw6XVAc43CbBNizsXeTDnoadNQLzT9IHOYbF1x0pICtiqpK8D324sROKJcmKTr5Wf0Y9SGHccMKaJ0iK2c/s1600/Photo+Apr+03%252C+10+49+11+PM.jpg" imageanchor="1"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5DrMTAgQwXfNmaJ6eK80SPib28uOuK_GOpaQvYbRaK6d9rBzUpUedylig9Jw6XVAc43CbBNizsXeTDnoadNQLzT9IHOYbF1x0pICtiqpK8D324sROKJcmKTr5Wf0Y9SGHccMKaJ0iK2c/s320/Photo+Apr+03%252C+10+49+11+PM.jpg" width="320" /></a></div>
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During the next week, I made all the brackets and clamps. Some were made on the MITERS CNC<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiMG9q9yWR3aaVYAYr6G-wXphKqzKa3wt9czN6hV7-b89F5znHp5TfbFEJv0g2LNl6zmi0n6x2FCFb715yOzTcp_mrtmxhE0lbAncznVpyAvcwdmWaGe7vjKHJqMw1XAsrE4FSFuNM2Zvs/s1600/Photo+Mar+25%252C+4+31+13+PM.jpg" imageanchor="1"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiMG9q9yWR3aaVYAYr6G-wXphKqzKa3wt9czN6hV7-b89F5znHp5TfbFEJv0g2LNl6zmi0n6x2FCFb715yOzTcp_mrtmxhE0lbAncznVpyAvcwdmWaGe7vjKHJqMw1XAsrE4FSFuNM2Zvs/s320/Photo+Mar+25%252C+4+31+13+PM.jpg" width="320" /></a></div>
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and other were made on the Haas VF-2 next door</div>
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The last three parts were done on all manual equipment because the CNC's were in use<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjm5JVKKS_9gQK8slm42jkkyzxu3Zy-rVb0evgS8Ikr0lobnkPERqd1qIrbNjPKzYJvsKpw3sghPajITBt2kk1XIKpkZkgQAVTgBvm4V-PENIWYc64sKpIUHCyZjrD68Wk5M42PGsB9DY0/s1600/Photo+Apr+03%252C+7+52+43+PM.jpg" imageanchor="1"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjm5JVKKS_9gQK8slm42jkkyzxu3Zy-rVb0evgS8Ikr0lobnkPERqd1qIrbNjPKzYJvsKpw3sghPajITBt2kk1XIKpkZkgQAVTgBvm4V-PENIWYc64sKpIUHCyZjrD68Wk5M42PGsB9DY0/s320/Photo+Apr+03%252C+7+52+43+PM.jpg" width="320" /></a></div>
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After a week of machining, I had bunch of shiny aluminum parts</div>
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Next, I found some thin wall tube laying around MITERS and assembled the two arms</div>
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<h2 style="clear: both; text-align: left;">
Electronics</h2>
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The controller for this arm is overkill. The IGBT module (FNA27560) is good for 50A, 400V continuous with good heatsinking, so it's more of an electric vehicle controller than a robotics controller. I created a schematic inspired by the reference design for the IGBT module and added a microcontroller and differential serial. There are no power supplies on the board. I'm not sure if this was a good decision or not, but I planned to put the 5V, 3.3V, 15V supplies on a separate board that connected to both boards. Unfortunately, I wasn't allowed to use the ST microcontroller for the class project as the class <strike>was bought out by Cypress and forbids knowledge of other companies</strike> has received generous donations of money and parts from Cypress. Instead I <strike>was forced to</strike> decided to take advantage of the Cypress Programmable System on a Chip 5LP microcontroller development platform, and created a controller that <strike>was in every way worse than the ST based controller</strike> was easy to implement with the Cypress "PSoC Creator" software (a 3GB IDE that vaguely resembles Office 2003). For a class that's about "teaching design concepts more than a specific platform", it's suspicious to forbid investigation of other platforms that may have their own pros and cons...</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRoyh5iuMLk69rWQXgZq1QGSRHZ1jrEPBZCL7CPQG1sBn7DQU3L7OCYgrpJeRE1RSYS12CgtTmcRWYBuz1Hf4tvQZVSYXefyOqbc7wrUsFsT0M3XVpdsakXgJiuWjye3lQbvswTqQAW4U/s1600/board.PNG" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRoyh5iuMLk69rWQXgZq1QGSRHZ1jrEPBZCL7CPQG1sBn7DQU3L7OCYgrpJeRE1RSYS12CgtTmcRWYBuz1Hf4tvQZVSYXefyOqbc7wrUsFsT0M3XVpdsakXgJiuWjye3lQbvswTqQAW4U/s1600/board.PNG" style="cursor: move;" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhl9xlhDloVymBcUFPLi1Me6F-X8AnFZ1LyycS6HdcCUCwwj1enk6viHEXkuNoJNs2tjBVSlF1Mmc-Tf8O9ePA1zT6wKNRvWz-ViGWPp223cQlDW_YGJsECbR2Z7tRALrZYwKacB6Xzza4/s1600/schematic.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhl9xlhDloVymBcUFPLi1Me6F-X8AnFZ1LyycS6HdcCUCwwj1enk6viHEXkuNoJNs2tjBVSlF1Mmc-Tf8O9ePA1zT6wKNRvWz-ViGWPp223cQlDW_YGJsECbR2Z7tRALrZYwKacB6Xzza4/s1600/schematic.PNG" /></a></div>
The board I drew up was a little bit scary - there's not much ground plane and the micro is directly under the IGBT. The reference design seemed incredibly conservative and only put components on the top layer, so I moved things around a bit to get a tighter layout. </div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJ7L9rkkPW7ztIN9p6Lmvm_DpPS6I9HdAFsElIjrRCLAqrqrmJfdTlrUpdsf0ImF4GlkuhrzGFdDbM4YPSV7Ig3RlZwr88RtT_Y2UCcZAEGKqNIjtvWyT8CyGrAgTzeDw8nz48aiu7cm8/s1600/Photo+Apr+14%252C+12+06+59+PM.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJ7L9rkkPW7ztIN9p6Lmvm_DpPS6I9HdAFsElIjrRCLAqrqrmJfdTlrUpdsf0ImF4GlkuhrzGFdDbM4YPSV7Ig3RlZwr88RtT_Y2UCcZAEGKqNIjtvWyT8CyGrAgTzeDw8nz48aiu7cm8/s320/Photo+Apr+14%252C+12+06+59+PM.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">"Small" Power ICs</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRoyh5iuMLk69rWQXgZq1QGSRHZ1jrEPBZCL7CPQG1sBn7DQU3L7OCYgrpJeRE1RSYS12CgtTmcRWYBuz1Hf4tvQZVSYXefyOqbc7wrUsFsT0M3XVpdsakXgJiuWjye3lQbvswTqQAW4U/s1600/board.PNG" imageanchor="1"></a></div>
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Around 6 days after placing the order to 3-PCB, the boards arrived. I somehow screwed up the gerber file generation so I missed mounting holes, heatsink holes, and my text. Populating the board was uneventful. I screwed up and bought a through hole diode instead of the correct surface mount one (not sure how I screwed up that bad) and the holes for the large IGBT module pins were slightly too small, requiring the pins to be filed down. </div>
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Fiddling with PSOC Creator to give me the center-aligned PWM with deadtime took an hour or so, which isn't too bad. I ended up with my board in a state where the clock is set "too fast" for reliable programming, so it fails to erase flash one in four times, causing the whole PSOC Creator program to throw endless memory out of bounds errors until you restart it. It's not a well written application.</div>
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The trick to aligning the PWMs is to set the counter reset on a control register. When toggling the control register, all three counters zero at exactly the same time, aligning the PWMs. </div>
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Once I had control of the inverter with the PSOC, I fed open loop sinusoidal phase voltages into the motor:</div>
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<iframe allowfullscreen="" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/66VX3ejAsc8/0.jpg" frameborder="0" height="266" src="https://www.youtube.com/embed/66VX3ejAsc8?feature=player_embedded" width="320"></iframe></div>
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Next, I got the DAC working. The PSOC has no easy to use print statements for debugging (piece of junk), so the DAC is the main debugging output. If I add debugging serial, I need to provide my own USB to serial adapter, and I use a ton of CPU power to implement the software serial, which prevented the FOC loop from running fast enough. Once I configured the quadrature encoder "block", I wrote a little automatic calibration routine. The motor spins open loop until it hits an index pulse. To figure out the electrical offset, it raises one phase high and leaves the other two low, causing the motor to lock at the d axis. From here, the microcontroller calculates the electrical offset and applies q axis volts, causing the motor to speed up. Here's a video (don't forget your safety tupperware when doing class projects):</div>
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<iframe allowfullscreen="" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/mJXvz2C-FI4/0.jpg" frameborder="0" height="266" src="https://www.youtube.com/embed/mJXvz2C-FI4?feature=player_embedded" width="320"></iframe></div>
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I wrote some other stuff with some nice pictures, but google blogger is terrible and messed up the formatting, so I got frustrated and copied everything into a video. Watch as I slowly lose interest in the project and things get crappier and crappier. The robot arm gets clamped to an old cart and the electronics get really bad.</div>
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<iframe allowfullscreen="" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/I4p15UPBjCI/0.jpg" frameborder="0" height="266" src="https://www.youtube.com/embed/I4p15UPBjCI?feature=player_embedded" width="320"></iframe><br />
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In the end, after failing at least 3 different safety inspections, I finally added a bunch of clamps and polycard shields, hid it in the corner of the lab underneath unused benches, and passed the final safety inspection the day before checkoff. I demoed it slowly moving in a circle to a TA for 3 seconds and got an A. </div>
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In the future, I plan to come back to this project and make it less terrible, with better encoders and motor control. </div>
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Jaredhttp://www.blogger.com/profile/02241918879329048444noreply@blogger.com3tag:blogger.com,1999:blog-1468514539205748845.post-63062432804012858952017-05-22T22:12:00.000-07:002017-05-22T22:12:01.035-07:00Parrot Drone Reverse Engineering to View Camera Stream, Edit Settings, and Flash LEDMy friend had a camera board out of some old Parrot quadcopter thing. When powered on, it creates a wi-fi network that you connect to with your smartphone. Then user downloads an app on their smart phone, and can control the quadcopter and view the video. As a fun project, I decided to find out how easy it is to view the camera feed without an app and see how much was open. In the end, the project turned out to be really easy - there's no security.<br />
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We powered on the board from a 12V power supply and waited for it to boot. It created a wi-fi network with a visible SSID. I connected to the network with my laptop running MATE 14.04 with DHCP enabled and was assigned an IP address of 192.168.1.3.<br />
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The IP address of the camera board was found with<br />
<span style="font-family: Courier New, Courier, monospace;">arp -a</span><br />
<span style="font-family: inherit;">which was 192.168.1.1 for mine.</span><br />
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<span style="font-family: inherit;">To see which ports were open, I ran </span><br />
<span style="font-family: Courier New, Courier, monospace;">nmap 192.168.1.1</span><br />
<span style="font-family: inherit;">which revealed three open ports: ftp, telnet, and port 5555, which nmap (incorrectly) identified as some sort of multiplayer Linux game.</span><br />
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<span style="font-family: inherit;">The ftp server accepted an anonymous connection, but put me in an empty directory. I'm assuming it's for sending firmware updates, so I didn't try much else from here.</span><br />
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Next, I investigated the mysterious port 5555. I first pointed windows media player at this port, and nothing happened. Same with VLC. Running<br />
<span style="font-family: Courier New, Courier, monospace;">ffplay tcp://192.168.1.1:5555/</span><br />
gave me a ~25 fps, 320x240 video stream with around 5 seconds of latency from the big camera. You'll have to add the PPA for ffmpeg and install ffmpeg if you're on 14.04 - ubuntu was dumb and switched to libav, which I still haven't gotten around to learning about.<br />
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Finally, I connected with telnet and got a busybox bash shell. The board has a fairly complete basic Linux install and has things like grep and vi. You can toggle the red/green on the LED just by running `export 1 > /.....path_to_gpio....`. The root user has no password, so you have full access to the system. This is usually a good idea - ssh doesn't let users without passwords connect, but they set up telnet. From a security standpoint, the telnet without password is really dumb. If somebody malicious gets root access, you're screwed. They can delete everything on the device, retune your gains, or even mess with settings for the device's power management, which stand a good chance to damage the hardware. Even if the remote user executed rm -rf /, the device is unrecoverable for consumers. <br />
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<br />Jaredhttp://www.blogger.com/profile/02241918879329048444noreply@blogger.com1tag:blogger.com,1999:blog-1468514539205748845.post-85517677043011181392016-12-15T22:13:00.000-08:002016-12-15T22:13:19.519-08:00Cantaloupe Scooter - BuildCantaloupe Scooter is my first attempt to build an electric vehicle at MITERS. The inspiration for the name comes from Charles Guan's Melon-Scooter, which was powered by a "melon" - a "6 kW" brushless outrunner that used to sell on HobbyKing. Cantaloupe Scooter isn't powered by a melon, but does have a cantilevered rear wheel, a cantilevered belt tensioner, and a cantilevered motor and motor shaft.<br />
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The main reason I wanted to build an electric vehicle was to have a way to get to and from MITERS quickly. I picked a scooter because it's easy to ride, fairly compact, and can double as a cart to carry heavy items from the loading dock.<br />
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Cantaloupe scooter was also built for almost no cost - I only purchased connectors and wire from eBay, which cost around $15. The project was also done without the help of CAD - and as a result has some questionable design. The front part of the scooter was built between the hours of 2 and 5 am, and as a result, isn't quite right. Staying upright at full speed requires a lot of concentration.</div>
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Parts</h3>
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The aluminum used for the sides and top of the frame came from Straight Razer and are almost unmodified. There are a few bonus holes and slots I added to mount the front and rear assemblies.</div>
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The acrylic used for the bottom of the scooter is a leftover from some freshman maker class.</div>
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I got the HDPE blocks used in the front from the IDC scrap pile. They look like they came from those weird white pedal powered things with a USB logo.</div>
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The front fork, handlebars, and wheels came from MITERS.</div>
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The belt is a leftover from Frozen Chainsaw Massacre, a powerwheels car that used electric chainsaw motors.</div>
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The twist throttle came from a convert-a-bike-to-electric kit found in the loading dock.</div>
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The aluminum billets used in the back came out of science equipment found at the loading dock and some plates found in the basement of building 5.</div>
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The pulley flange was made out of the lid from some biology equipment.</div>
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The bolts, spacers, and nuts came from MITERS.</div>
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Half the batteries came from some boxes of "dead" A123's found in the loading dock. Roughly 30 of the 500 batteries were successfully revived. </div>
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The other half of the batteries came from a trade - I traded 4 massive 40 Ah 3.3V LiFe batteries for 24 A123's that originally came from reuse.</div>
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The Battery</h3>
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It all started when Alex and I found 500 A123's at the loading dock. After carting them back to MITERS, we measured the voltage of every cell and ended up with this:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0hdYu7_th_9s7BhhWk8H0j4nUxkBr9Xuj3ubQ84zUpbvDouaFMNSLInPTn6k1KUrp-X2mxubQMGpQUOikvAuUljq1GqnmOdTDhzu85_7o66ioqSiBEggHsM6GFVyIYVURF-j4cOCLa2Y/s1600/buttery.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0hdYu7_th_9s7BhhWk8H0j4nUxkBr9Xuj3ubQ84zUpbvDouaFMNSLInPTn6k1KUrp-X2mxubQMGpQUOikvAuUljq1GqnmOdTDhzu85_7o66ioqSiBEggHsM6GFVyIYVURF-j4cOCLa2Y/s320/buttery.jpg" width="320" /></a></div>
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The cells to the left all have 1.9V or more, and the ones on the right have between 1.5 and 1.9V. First, the cells were all charged to 3.6V, and were allowed to sit for a week. After, they were discharged on the Dyna-Load at 10 amps.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2M0dnSjBGJuTFox5yBLXisYEuHETsdQyN_igwWHhPmxljssw4oCEHRIr6plflCCTy1Tp4Qnar6R5Q94b5qCR8l0KD300YbaCBxuTXdJAwLaEhMXCCloI9gEnfzjNpNTzrfoZ7blWriVQ/s1600/Photo+Oct+12%252C+12+21+34+AM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2M0dnSjBGJuTFox5yBLXisYEuHETsdQyN_igwWHhPmxljssw4oCEHRIr6plflCCTy1Tp4Qnar6R5Q94b5qCR8l0KD300YbaCBxuTXdJAwLaEhMXCCloI9gEnfzjNpNTzrfoZ7blWriVQ/s320/Photo+Oct+12%252C+12+21+34+AM.jpg" width="320" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimBcn0NROoh0ur7oNZOzGdMk_W8LO6le9VYl8TmBImXWdlV9zuOF9ztYYn6uTMY_QksXw9XSHiN_CtdXPcgjpLYS8KadA-k5NMfqO6ZGtuLjBrHHiCIVTCTJx90WP3B6h3I0sALwhjWO8/s1600/Photo+Oct+12%252C+12+21+43+AM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimBcn0NROoh0ur7oNZOzGdMk_W8LO6le9VYl8TmBImXWdlV9zuOF9ztYYn6uTMY_QksXw9XSHiN_CtdXPcgjpLYS8KadA-k5NMfqO6ZGtuLjBrHHiCIVTCTJx90WP3B6h3I0sALwhjWO8/s320/Photo+Oct+12%252C+12+21+43+AM.jpg" width="320" /></a></div>
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As they were discharging, the cell voltage was monitored by a microcontroller (our favorite stm32f446re), which streamed the voltage over serial at a relaxing 10 Hz to a laptop. The laptop was running plotter, an application I wrote for the motor controller. It plots the cell voltage in real time, and logs it to a CSV file, which can later be opened in MATLAB. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguyuxgtc3l2mkZWHijiNCh4LuaZVbKv3SLNXVewuJLssx9LZmYG_MLxvP6ADj9XNHuw_zgmaAjTDq4AjyiyNUEOnn7jy6hs11WxiMOVr9L71TaFnrP0bWpL6Lwwe0PIjVUfnK7wFK579s/s1600/Photo+Oct+12%252C+1+19+37+AM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguyuxgtc3l2mkZWHijiNCh4LuaZVbKv3SLNXVewuJLssx9LZmYG_MLxvP6ADj9XNHuw_zgmaAjTDq4AjyiyNUEOnn7jy6hs11WxiMOVr9L71TaFnrP0bWpL6Lwwe0PIjVUfnK7wFK579s/s320/Photo+Oct+12%252C+1+19+37+AM.jpg" width="320" /></a></div>
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A demo of plotter with some random signals, 200 Hz to laptop</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjyS3WO_AbvhVp4rK0e-Yzs0_rPHv8Lxd_6D2wSIOjgnPEfT2cCXHwo4NNzPuXXNsaUO53YBPDQUwXzu7SkbOxGBh_4R9P6TJUS0SNQZukKSqeqAiZBfnJwGCrHZQzioZSRJLgE6H0cnco/s1600/Video+Oct+10%252C+1+58+15+AM.mov" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjyS3WO_AbvhVp4rK0e-Yzs0_rPHv8Lxd_6D2wSIOjgnPEfT2cCXHwo4NNzPuXXNsaUO53YBPDQUwXzu7SkbOxGBh_4R9P6TJUS0SNQZukKSqeqAiZBfnJwGCrHZQzioZSRJLgE6H0cnco/s1600/Video+Oct+10%252C+1+58+15+AM.mov" /></a></div>
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The end result of this charge and discharge test was a big spreadsheet of cell data. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5WBAJhpFiBsgN08jy6nB9n18tt1oo5Rv6DMWfwyVR-IdMIqxO4M9HWWU2bdIXMcKgtakIGGorh4V6CzW4JLw9ak0c4cLIgxrTKM2Jwfq5euKV7Lgwk0Uk-F-DRjs9kbA42oQtC5QPWe0/s1600/cell_sheet.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5WBAJhpFiBsgN08jy6nB9n18tt1oo5Rv6DMWfwyVR-IdMIqxO4M9HWWU2bdIXMcKgtakIGGorh4V6CzW4JLw9ak0c4cLIgxrTKM2Jwfq5euKV7Lgwk0Uk-F-DRjs9kbA42oQtC5QPWe0/s320/cell_sheet.PNG" width="320" /></a></div>
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These were my conclusions</div>
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<ul>
<li>These cells were thrown away 8 years ago because they were below their rated discharge voltage when they arrived new in box. I picked them up at a cold loading dock. All these cells appeared to recover perfectly. There were four dead cells in the spreadsheet - these came out of a bag of mystery cells given to me. To revive, simply charge at 0.5A until the cell gets to 3.3V, then go to 3A.</li>
<li>The last 10% of capacity goes away if the cell is charged fast. On average, the recovered cells had 94% of their rated capacity when charged at 3A. The 6 cells I slow charged at 0.5A got to between 98 and 100% of rated capacity. </li>
<li>There appears to be no damage to the cells after 8 years of sitting in extreme discharge. They have a comparable discharge curve to a brand new A123</li>
<li>It takes one or two cycles to "wake up" the extremely low voltage cells. For the first two cycles, the cell voltage sagged to 3.4V or below when fully charged, though they still had comparable discharge curves under load. After a few cycles, they sag to 3.5V after charging.</li>
<li>It's a total mystery as to why these cells showed up from the factory with low voltage. There's nothing wrong with them that I can see.</li>
<li>1.5V is the cutoff for reviving long-term discharged A123's. I revived a set of 0.5V cells, but they had an order of magnitude more internal resistance than they should have. Other than that, they seemed to work though.</li>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjrl9QzGCQv8G_RpKBsrvNAv_9GYEk90pviRKG4yXx0ZClIS7dVeDhWjJh4g7ef2TNjQIwF-hyXJ3VtSMlXztfi17bsc4E4eQIrZOGW2vHwz47mlGhU2GlipPGwSRQS_isL6REK_wfxkI8/s1600/Photo+Oct+12%252C+12+21+21+AM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjrl9QzGCQv8G_RpKBsrvNAv_9GYEk90pviRKG4yXx0ZClIS7dVeDhWjJh4g7ef2TNjQIwF-hyXJ3VtSMlXztfi17bsc4E4eQIrZOGW2vHwz47mlGhU2GlipPGwSRQS_isL6REK_wfxkI8/s320/Photo+Oct+12%252C+12+21+21+AM.jpg" width="320" /></a></div>
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In the end, I was short a few cells to put together a 12S3P pack, so I traded 4 very large 40 Ah LiFe cells for a few more bricks of A123s. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjay5OHta4L165kzpZ8w9pIkH1MOhRcECX9t_t8_u6Uxa6D7aYdLfZxrOrqNFktVTRq3546bgDa3VrYn_nav8jwDlMKxiueGTE7oed78drQSyWEgp6kEnwOM7t_If0BUAkdublu_R_ZnCI/s1600/IMG_1520.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjay5OHta4L165kzpZ8w9pIkH1MOhRcECX9t_t8_u6Uxa6D7aYdLfZxrOrqNFktVTRq3546bgDa3VrYn_nav8jwDlMKxiueGTE7oed78drQSyWEgp6kEnwOM7t_If0BUAkdublu_R_ZnCI/s320/IMG_1520.JPG" width="320" /></a></div>
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In the first and second picture, I was playing around will different shapes of packs to see what fit best in the remains of Straight Razer. In the end, I went with what's pictured in the second picture - two rows of 18 cells in a 6S3P configuration. Each row could be charged and balanced by an ordinary 6S balance charger.</div>
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Each row of cells was put in massive heatshrink, which worked extremely well.</div>
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<h3 style="clear: both; text-align: left;">
The Drive Assembly</h3>
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For the drive motor, I used an 8fun brushless outrunner with sheared shaft that came from Dane. This motor is usually used in ebike wheels, and is a great motor for vehicles. Usually, this motor is part of a planetary gearbox, but I removed the gear and CNC'd a new adapter. I was too lazy to CNC a pulley, so I 3D printed one instead. It's a little smushed, but seems to work.<br />
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Motor with sheared shaft</div>
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The old gear</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWZdVVhH1IcnTCNsnqSdiTJqqzuQLkQ09_HLgKClJNRQ73sa2JpcDrjZz-D7XQwO5szjz5I9mbeao0DZYH96uE9iMBIK6faFXL9-nGkLROYyKqsTgOawksW1H6n5vH7jU1o6P6Co7X-wQ/s1600/IMG_1540.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWZdVVhH1IcnTCNsnqSdiTJqqzuQLkQ09_HLgKClJNRQ73sa2JpcDrjZz-D7XQwO5szjz5I9mbeao0DZYH96uE9iMBIK6faFXL9-nGkLROYyKqsTgOawksW1H6n5vH7jU1o6P6Co7X-wQ/s320/IMG_1540.JPG" width="320" /></a></div>
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The new adapter</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiidPrTzZaZXEw7QzpMrclYO6X_se6b1E_MMFQP2J0QUzt9kPSJK135i5IGVMWx8KMwjTONa_3FUah7gE9RHXw2xsgNEE0oDLBjuAWitG7hWlPrjiD_bgkZ8uDj6ld6jf5tvzfJoTttBQo/s1600/IMG_1541.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiidPrTzZaZXEw7QzpMrclYO6X_se6b1E_MMFQP2J0QUzt9kPSJK135i5IGVMWx8KMwjTONa_3FUah7gE9RHXw2xsgNEE0oDLBjuAWitG7hWlPrjiD_bgkZ8uDj6ld6jf5tvzfJoTttBQo/s320/IMG_1541.JPG" width="320" /></a></div>
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Adapter on motor</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgK5TlFB8DB0zOSGDmZEMenpngrhehRZOHPTkTlEh4f-9hGGbCiluAX27JqDNYIQDlYzl8N2DGbQRVeQxxpB2-qGF4jgaHa9LdQ2y5sRCLdWylUvhveFViigdGkHrUmwRnFbmgGZvM8_g4/s1600/IMG_1551.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgK5TlFB8DB0zOSGDmZEMenpngrhehRZOHPTkTlEh4f-9hGGbCiluAX27JqDNYIQDlYzl8N2DGbQRVeQxxpB2-qGF4jgaHa9LdQ2y5sRCLdWylUvhveFViigdGkHrUmwRnFbmgGZvM8_g4/s320/IMG_1551.JPG" width="320" /></a></div>
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Adapter on pulley</div>
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To mount the motor, I machined two pieces of bar stock that came from an FSAE frame jig. Unfortunately, the pieces had been "faced" to make them "flat", but they were around .05" off over 6", so all the mating sides needed to be remachined.</div>
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Clamping mount</div>
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Clamping mount with frame mount</div>
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Shiny Scotch-Brite Surface</div>
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Assembled motor mount and frame mount</div>
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Motor mounted to frame</div>
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Motor, frame, batteries, controller</div>
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Up next was the mount for the rear wheel. I went with a cantilevered rear wheel because I couldn't find a 10mm bolt that was long enough. The rear wheel mount is shaped like a cake so it can fit into the bore of the wheel.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoPUN-lmiY8HyMlfVOYyhaWRgoExWSBKmq-IjJsk_8q3lXhnzHgXhcS0KNnq5UADpkItFWASwIdVLaRtHXv4HhCPX03PMBXhP4zK0oeZZUuPhhq_nS45ojIGEi_l_iVMkPn-MyaaeN4O0/s1600/Photo+Dec+03%252C+7+29+07+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoPUN-lmiY8HyMlfVOYyhaWRgoExWSBKmq-IjJsk_8q3lXhnzHgXhcS0KNnq5UADpkItFWASwIdVLaRtHXv4HhCPX03PMBXhP4zK0oeZZUuPhhq_nS45ojIGEi_l_iVMkPn-MyaaeN4O0/s320/Photo+Dec+03%252C+7+29+07+PM.jpg" width="320" /></a></div>
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The stock</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgZkFBrTuryWHZDEGDCmDiSrKo8Z5u-hAg1VPd2vX8MhKEpK6SyELWP3qL6rBOTJLP6j-RkYhQco4MpyOflxDYiIjCgh9mbEuB3MrLQOS_P2WWJ_ydc_0IOPL9-0s-EV2t0LA2DIv1a5E/s1600/Photo+Dec+03%252C+8+59+07+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgZkFBrTuryWHZDEGDCmDiSrKo8Z5u-hAg1VPd2vX8MhKEpK6SyELWP3qL6rBOTJLP6j-RkYhQco4MpyOflxDYiIjCgh9mbEuB3MrLQOS_P2WWJ_ydc_0IOPL9-0s-EV2t0LA2DIv1a5E/s320/Photo+Dec+03%252C+8+59+07+PM.jpg" width="320" /></a></div>
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The cake</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglprxxK0qUmL11GGW5bNKfHsRvFReAU-5OupeEdIXlubqxMkb8uucOav9XkQdyblurx-bFrNDBB6wkuitVogf10StInLAMtn9fMa_nnKL2wjXdLztB_X-0QA6dwovMYJ3akfQaZhKQ9Zo/s1600/Photo+Dec+03%252C+10+32+47+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglprxxK0qUmL11GGW5bNKfHsRvFReAU-5OupeEdIXlubqxMkb8uucOav9XkQdyblurx-bFrNDBB6wkuitVogf10StInLAMtn9fMa_nnKL2wjXdLztB_X-0QA6dwovMYJ3akfQaZhKQ9Zo/s320/Photo+Dec+03%252C+10+32+47+PM.jpg" width="320" /></a></div>
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Cake with holes</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR_Rrsk2hNP7ohIYZJ7sXrwPc_tSFw7KZy6a8Ikfj5_X-RgpAaYMZV081cWFrWWqKdaZdr1iL9UgHqmi77Pwi5JrMapqNxpM7lHv6VPbA3CorOuIxW33mCZ2FAuZeZkDDBKvhIPxwbBPM/s1600/Photo+Dec+03%252C+10+35+21+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR_Rrsk2hNP7ohIYZJ7sXrwPc_tSFw7KZy6a8Ikfj5_X-RgpAaYMZV081cWFrWWqKdaZdr1iL9UgHqmi77Pwi5JrMapqNxpM7lHv6VPbA3CorOuIxW33mCZ2FAuZeZkDDBKvhIPxwbBPM/s320/Photo+Dec+03%252C+10+35+21+PM.jpg" width="320" /></a></div>
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Cake with screws</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPoDGnz8jO4PQneSAzXaLabaw9clpRcJLZV7RBU0Nt4hQ2Bnmb04n79q4OtNt-P8XGOyNnAhRNgHAHMiKmhPBRPirnQN2-_dzjB2-PX9UPojMJxVGTcf98jsoNxVE7Z1jQ34-xmnGCR-Y/s1600/Photo+Dec+03%252C+10+35+32+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPoDGnz8jO4PQneSAzXaLabaw9clpRcJLZV7RBU0Nt4hQ2Bnmb04n79q4OtNt-P8XGOyNnAhRNgHAHMiKmhPBRPirnQN2-_dzjB2-PX9UPojMJxVGTcf98jsoNxVE7Z1jQ34-xmnGCR-Y/s320/Photo+Dec+03%252C+10+35+32+PM.jpg" width="320" /></a></div>
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I originally planned to make a cool looking block of aluminum on the CNC that connected the cake to the frame, but this was annoying to design ahead of time. I put the frame of the scooter about 2 inches above the ground, and held everything in place with clamps, and came up with some plans for belt tensionsing and rear wheel mounting.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3L8c6l7lNUOPDwyrwWiQGS10Wy6Ze03nREJiTDx79PhXwed_A-jyfGe7i-NRV-bL2Uh70D04vPhyhhXqWZKiuYSSwzoANpznd8jA109juOnVp0jhBi820vww9wB5k6NfzVJC7G7fm6X0/s1600/Photo+Dec+13%252C+8+55+24+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3L8c6l7lNUOPDwyrwWiQGS10Wy6Ze03nREJiTDx79PhXwed_A-jyfGe7i-NRV-bL2Uh70D04vPhyhhXqWZKiuYSSwzoANpznd8jA109juOnVp0jhBi820vww9wB5k6NfzVJC7G7fm6X0/s320/Photo+Dec+13%252C+8+55+24+PM.jpg" width="320" /></a></div>
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The block connects the frame to the cake, and has a slot for the bolts that serves as the axle for the tensioning pulley.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHQNSpPCt3-fHvtV-aBqSzfX8ivuhsqnoqb7gSkpdEkJKtz0RJcwyuZSSdFZOBErc4AUvKsiDWlIiaLB4-0zQGlqhBVtpR5ddJlTcC7XVvGHLJgEehFNdMaq57PTIHjf2awPgT-ZJ7AWg/s1600/Photo+Dec+13%252C+8+55+29+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHQNSpPCt3-fHvtV-aBqSzfX8ivuhsqnoqb7gSkpdEkJKtz0RJcwyuZSSdFZOBErc4AUvKsiDWlIiaLB4-0zQGlqhBVtpR5ddJlTcC7XVvGHLJgEehFNdMaq57PTIHjf2awPgT-ZJ7AWg/s320/Photo+Dec+13%252C+8+55+29+PM.jpg" width="320" /></a></div>
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The slightly smushed pulley caused the belt to slip off, so I cut out this roughly circular pulley flange. It turns out MITERS has nothing circular that's 4.5" in diameter to trace a circle with...</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgE_SRhOAsfvSeRYvxH-hU0vboe2wMNrRYp0xwhLWrdenpx3UrFXysTpC8KyDArm2ecdEgdbDYtBImpGk09_GP6YCHeqd-azSuZNLHY2uDJGXmklBOARTD6sBXIVi9e2le6thfroaDnXuw/s1600/Photo+Dec+13%252C+8+55+37+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgE_SRhOAsfvSeRYvxH-hU0vboe2wMNrRYp0xwhLWrdenpx3UrFXysTpC8KyDArm2ecdEgdbDYtBImpGk09_GP6YCHeqd-azSuZNLHY2uDJGXmklBOARTD6sBXIVi9e2le6thfroaDnXuw/s320/Photo+Dec+13%252C+8+55+37+PM.jpg" width="320" /></a></div>
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There slot for the tensioner is designed so the head of the bolt won't spin.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiC1tq9TNRJ-VkEdTQldh6u0Im7YnK2_ezd4OSSrtYp1nG9Kc1N01sytdqQ72Pemg4HAK4Msw9VrgHB-WMxA37zBhqhlEIYvTB1gwsq4yhlMVacN6yC_xbaDxu94XYI0sRLXJB4MfMFT2k/s1600/Photo+Dec+13%252C+8+56+06+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiC1tq9TNRJ-VkEdTQldh6u0Im7YnK2_ezd4OSSrtYp1nG9Kc1N01sytdqQ72Pemg4HAK4Msw9VrgHB-WMxA37zBhqhlEIYvTB1gwsq4yhlMVacN6yC_xbaDxu94XYI0sRLXJB4MfMFT2k/s320/Photo+Dec+13%252C+8+56+06+PM.jpg" width="240" /></a></div>
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The cantilevered wheel looks weird</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSvJIJ61YaTsPgCxSRdC8NHnvTipIyZFjmcmoBvBlE8yTvgQxzVcLnSkvAJzkiQX0WY7XNNMqTf1j9K5BEG7nhDpMXWDQProXo3Iw2INLRflDRFcYe7alSexaH1M7vO6Rw4qfeEPyhWfk/s1600/Photo+Dec+13%252C+8+56+13+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSvJIJ61YaTsPgCxSRdC8NHnvTipIyZFjmcmoBvBlE8yTvgQxzVcLnSkvAJzkiQX0WY7XNNMqTf1j9K5BEG7nhDpMXWDQProXo3Iw2INLRflDRFcYe7alSexaH1M7vO6Rw4qfeEPyhWfk/s320/Photo+Dec+13%252C+8+56+13+PM.jpg" width="320" /></a></div>
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A delrin round thing was bored out and bearings were pressed in.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjxkeofjeqvvodLp9zcF8Vhcce58JmWHuJ8s8zn7iPSJqsRRfVx1Tw0V1AwbqN08VeusXDttDUz3AIsjNL6-9PGa8tFg48n2m4nPzoS6FIU44XJE4BHfOgYPezrzUk_gV6OTxHGtwaU3l0/s1600/Photo+Dec+13%252C+8+59+15+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjxkeofjeqvvodLp9zcF8Vhcce58JmWHuJ8s8zn7iPSJqsRRfVx1Tw0V1AwbqN08VeusXDttDUz3AIsjNL6-9PGa8tFg48n2m4nPzoS6FIU44XJE4BHfOgYPezrzUk_gV6OTxHGtwaU3l0/s320/Photo+Dec+13%252C+8+59+15+PM.jpg" width="320" /></a></div>
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There's an additional piece of 1" x 1" bar stock used to join the cake to the plate</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDScS7I4AHygmttrO4V5Cq9OE08bN08MQ8GC5xAW8Z84apFtgmqJ2JOfz8Thh6sWZ1tgWJpQgZY0k4D0WBcWB9GXGAcpSNcYo3G3x7ob86JjOcgXUQmeB7uyqrpMoE9sRtEWb2lpoaf3Q/s1600/Photo+Dec+13%252C+8+56+19+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDScS7I4AHygmttrO4V5Cq9OE08bN08MQ8GC5xAW8Z84apFtgmqJ2JOfz8Thh6sWZ1tgWJpQgZY0k4D0WBcWB9GXGAcpSNcYo3G3x7ob86JjOcgXUQmeB7uyqrpMoE9sRtEWb2lpoaf3Q/s320/Photo+Dec+13%252C+8+56+19+PM.jpg" width="320" /></a></div>
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The laser cut bottom plate fit on the first try!</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNGVyzs82WKoKE0BnmiMUeL9GKUyd7LuCaJWpOdU6ax_ODidjh4PSI8FWm1vsm5DnITrpJ9LdTIVXWcw2Qw4Y6ggelfF8nGoF0pGxVWfRsjhdMiVFGK7dqbUq8_mi-xP4_syzCm4avMXI/s1600/Photo+Dec+13%252C+8+56+34+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNGVyzs82WKoKE0BnmiMUeL9GKUyd7LuCaJWpOdU6ax_ODidjh4PSI8FWm1vsm5DnITrpJ9LdTIVXWcw2Qw4Y6ggelfF8nGoF0pGxVWfRsjhdMiVFGK7dqbUq8_mi-xP4_syzCm4avMXI/s320/Photo+Dec+13%252C+8+56+34+PM.jpg" width="240" /></a></div>
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No vehicle is complete without a name</div>
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The front of the scooter is a total disaster. I took some huge chunks of HDPE, made them roughly the same size, then drilled a 1" hole at a roughly 5 degree angle.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjrVORC-nuRz-DNhR2PUDya_mWWA2LyvxaC0K_rUVZMlo23d0_FJm9nOFW_cQzhneGsPLhTnHsG4mG9BvZ-vrUv3mr1pc5C3mmSr05lCFr7P2Oen_NCrLLswaHwyaKjQyPq13ykS7u7Ry4/s1600/Photo+Dec+13%252C+8+57+00+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjrVORC-nuRz-DNhR2PUDya_mWWA2LyvxaC0K_rUVZMlo23d0_FJm9nOFW_cQzhneGsPLhTnHsG4mG9BvZ-vrUv3mr1pc5C3mmSr05lCFr7P2Oen_NCrLLswaHwyaKjQyPq13ykS7u7Ry4/s320/Photo+Dec+13%252C+8+57+00+PM.jpg" width="240" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7DLSza3wtKm92M3L39Btrt5wjNow9rt8nbg2VUli_ed7_UjVAn_hf0-OrZDPqgrtKvZxl9-V0d-jknwiRxOXpueum3WqeZZVkkyQeSDtncgBdg-rnYhOj03-SW-9PYN6asddMO8j4x-c/s1600/Photo+Dec+13%252C+8+57+18+PM.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7DLSza3wtKm92M3L39Btrt5wjNow9rt8nbg2VUli_ed7_UjVAn_hf0-OrZDPqgrtKvZxl9-V0d-jknwiRxOXpueum3WqeZZVkkyQeSDtncgBdg-rnYhOj03-SW-9PYN6asddMO8j4x-c/s320/Photo+Dec+13%252C+8+57+18+PM.jpg" width="320" /></a></div>
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The completed scooter has a a current top speed of around 18 mph, and a range of around 5 miles. At high speeds, it's a challenge to keep everything stable due to the excessive steering friction. I'm hoping the HDPE wears out over time.</div>
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Jaredhttp://www.blogger.com/profile/02241918879329048444noreply@blogger.com1tag:blogger.com,1999:blog-1468514539205748845.post-10507883240133229082016-10-16T22:48:00.001-07:002016-10-16T22:48:03.923-07:00Electric Boat using a SEVCON espAC motor controllerIt all started with a donation by Sevcon. They gave some people at MIT some motor controllers, but they were difficult to turn on, and don't work with very many motors, so the controllers eventually trickled down to MITERS. The controllers are 80V controllers, though they will drive motors from 44 to 116V. It is one of the most robust motor controllers I've ever seen - the battery inputs are protected against reverse battery connection, and the phase outputs are protected from phase to phase shorts at any time and phase to battery shorts at power on. They're current limited to 600 amps for 1 minute, meaning you can get 48 kW at 80 volts, or 66 kW at 110 volts. While this is a lot of power, it's at a relatively low 80 V. Most motors (like the common hybrid car motors) like to be run at 400 V or so. It's much more efficient to run at a higher voltage, and generally cars have enough cells and boost converter to get to a high voltage. This might be why Sevcon had a few extra controllers. The controller also has 8 digital inputs, 12V and 5V rails, 2 analog inputs, 2 isolated potentiometer inputs (to avoid voltage drop from massive amps messing with your throttle), and 6 voltage controllable contactor outputs that can provide 6A peak, 3A continuous. The whole case is rated for 2kV isolation, and is IP66 rated, meaning it's very water resistant. It's been tested to 50 g shock, and 3 g vibration, 5 to 500 Hz. I'm not familiar with any of their drop or EMC testing standards, but I'm assuming this controller is quite good. It's designed for fork lifts, airport ground support vehicles/tow tractors, golf carts, scooters, and 'marine'.<br />
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There are a few drawbacks:</div>
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1). The controller is physically large. It weighs 25 lbs and is 1 ft wide.</div>
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2). It is difficult to turn on. More on this later.</div>
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3). There's no great way to interface with it - there's really only an analog input that has lots of filter and is difficult to adjust, so there's no way to update the torque setpoint very quickly.</div>
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4). It requires a lot of things to be plugged in for the controller to work.</div>
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5). It only can drive induction motors, no brushless permanent magnet motors</div>
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6). The controller needs to be tuned to each motor used with it, which is a difficult and involved process</div>
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7). It takes forever to set up. Peter, Bayley, Dane, and I worked on this terrible thing for a whole week from 7 pm to 3 am each night to get it to an acceptable state.</div>
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8). The software has lots of weird bugs. This is probably because ours says 'engineering prototype: do not operate' on the label.</div>
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Dane took apart one of the controllers to see what was inside:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRHyttX-syIIHiYmHOcmVV2NSlvshrg__qaBpxruXXiut3RqxMmC_f7sk_iW7hWNwNl6Ib0fmf7K1iI_Dvl5DdRQRK3p67_Xf7IKRZ4AeVuM_JisolWKDEZc7CP-K5t-RCSO7DJ-iStVw/s1600/IMG_0880.JPG" imageanchor="1"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRHyttX-syIIHiYmHOcmVV2NSlvshrg__qaBpxruXXiut3RqxMmC_f7sk_iW7hWNwNl6Ib0fmf7K1iI_Dvl5DdRQRK3p67_Xf7IKRZ4AeVuM_JisolWKDEZc7CP-K5t-RCSO7DJ-iStVw/s320/IMG_0880.JPG" width="320" /></a></div>
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The heatsink is a nice aluminum extrusion that's connected to the board with all the FETs. There are a TON of FETs in this device, each with their own BJT gate drive. The FETs are relatively high resistance (19 mohms I believe).</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlGwPRNVvPSX-EJd-gKXU02bYRk22zkndaSUIKtj27fElAIhX4e0N-oYi1CLJfrZ9y5PyOHeK9gJTTjTY-VBx_f_f0nB5TIMWpGYp6vuc01jZhlhh9F7KtGfeSlb8JmGELWcZwjQJg14w/s1600/P1060267.JPG" imageanchor="1"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlGwPRNVvPSX-EJd-gKXU02bYRk22zkndaSUIKtj27fElAIhX4e0N-oYi1CLJfrZ9y5PyOHeK9gJTTjTY-VBx_f_f0nB5TIMWpGYp6vuc01jZhlhh9F7KtGfeSlb8JmGELWcZwjQJg14w/s320/P1060267.JPG" width="320" /></a></div>
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The logic board on this controller is equally impressive/bizarre:<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhn49mKzpTFlIlmOJEkU6pmNni2pPhmsY8qDuSORSKhuEHg7SmCJaBOrihPW9fEsBfBYx6r9c07aXj4b3rUQAv-sH9QDQMtXZAgpX9i3bFjz8Bm5ipqFnY4o4oyuh5xaFDYs0bXhWTWOBU/s1600/P1060275.JPG" imageanchor="1"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhn49mKzpTFlIlmOJEkU6pmNni2pPhmsY8qDuSORSKhuEHg7SmCJaBOrihPW9fEsBfBYx6r9c07aXj4b3rUQAv-sH9QDQMtXZAgpX9i3bFjz8Bm5ipqFnY4o4oyuh5xaFDYs0bXhWTWOBU/s320/P1060275.JPG" width="320" /></a></div>
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Bayley, who enjoys searching the internet for interesting motors from cars, found the first car part for this project: a nice 'eAssist' induction motor from a Buick LaCrosse for around $100 that was roughly sized to work on this controller. It claimed to be a 15kW motor, but it can do much more for a short period of time. It's also nicely sealed and comes with a resolver and is water cooled.</div>
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We started by building a test load for the motor: a supercharger from a Buick ????. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0laCyIFRfmc3SiNNxXYE7O_Sx1EWcAX6G9iVIQrh6tJJttiaTDcXMUjDk7HSObQXxbDEmw21ohcJhHbtJc15yBPykcAsTpIOgvm37W1AiTtow0xc3jsC4jXr2d1GLD59xvXKo3J2CW8I/s1600/IMG_1317.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0laCyIFRfmc3SiNNxXYE7O_Sx1EWcAX6G9iVIQrh6tJJttiaTDcXMUjDk7HSObQXxbDEmw21ohcJhHbtJc15yBPykcAsTpIOgvm37W1AiTtow0xc3jsC4jXr2d1GLD59xvXKo3J2CW8I/s320/IMG_1317.JPG" width="320" /></a></div>
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In the end, we were able to put around 10 kW into the supercharger.</div>
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Dane ordered a collection of connectors and pins to plug into the Sevcon. Over the course of roughly a week, Peter, Dane, Bayley, and I managed to trick the controller into spinning the induction motor.</div>
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Debugging the controller was a massively annoying process that included:</div>
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<ul>
<li>Reading and writing x86 assembly</li>
<li>Programming a nucleo to scale down a high resolution encoder</li>
<li>Cross compiling code for STM32's on linux because mbed compiler website was down</li>
<li>Fiddling with linux usb interrupts</li>
<li>Hooking up a large water cooling loop from the MITERS sink to the electronics bench</li>
<li>and many other strange activities</li>
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We don't fully understand everything there is to understand about these controllers, but the some of the knowledge we gained in the process might be useful to others. This next section is formatted more as a list of helpful information. The debugging process is too boring to blog fully. </div>
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POWERING ON THE CONTROLLER<br />
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The startup sequences is initialized by providing low current fused (5A I think) power to the logic board. If it decides to enter the 'operational state', it will precharge the bus capacitors then turn on a contactor to provide power to the DC bus. The controller will try to enter 'operational state' unless it was manually transitioned to 'preoperational (preop)' before being turned off. If there is an error, the controller will go into preop automatically, but it will still attempt to go into operational the next time it is turned on. Going into operational state when the controller is not properly configured can dump a huge amount of current into the motor without the motor spinning or applied throttle, so be prepared! We used an 80V 25A power supply, which often current limited and browned out the controller during testing. It doesn't take long for 2 kW to heat up even a large motor, so external cooling is recommended during testing.<br />
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It's very important that you don't use a 'smart' contactor that goes and lowers the coil voltage once powered on. The sevcon contactor driver will go into an overcurrent state and prevent the controller from entering operational mode. We also encountered a strange issue where our 80V power supply wasn't quite isolated properly and floated a few volts above ground, causing random overcurrent faults on the contactor. Properly grounding the controller fixed this issue. The sevcon also has adjustable settings for contactor voltage, as well as the ability to lower the contactor voltage after a few seconds if you don't want to burn out your contactor coils.</div>
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<tr><td class="tr-caption" style="text-align: center;">3 switches, contactor, and enable switch</td></tr>
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You also need to provide an additional three switches - forward, seat switch, and throttle switch, to get the controller to drive the motor. The I/O section of the configuration tool must be used to map these switches.<br />
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We also encountered strange behavior where we were able to read an analog channel, but the throttle position in 'driveline' wouldn't update. I currently don't remember what the fix was, but I hope to update this section once I have a chance.</div>
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The sevcon connects to the computer through an IXAAT USB to CAN adapter and is programmed with DVT. The DVT installer can be found on the internet if you look hard enough (it's a little tricky - the download link appears in an image of a PDF document) and can also be acquired from SEVCON customer support if you ask nicely. Their engineering department is super awesome and gave us software called MOTOR-WIZARD, which installs firmware on a device to allow it to characterize a motor and generate configuration data for the specific motor. Unfortunately, MOTOR-WIZARD goes and flashes some new firmware onto your motor controller that replaces the default firmware. We didn't have a copy of the original firmware for our controller, so installing MOTOR-WIZARD permanently turns the controller into a motor characterization device. If you only have one controller, this will be a problem - you can't use a MOTOR-WIZARD flashed controller as a normal controller. It might be that sevcon engineering will give out firmware to restore your controller, but you should definitely check before you flash your controller with DRIVE-WIZARD firmware. If you are interested in getting the configuration file we created with drive wizard or have questions, leave a comment with your email address and I will send it to you.</div>
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DVT comes in many different flavors - there's a generic customer version DVTC, several versions customized for specific customers with specific device support and customized window titles, and DVT engineering, which has the most settings. It doesn't look like license codes are different between software versions, but your license code is tied to a single computer. License codes can be obtained from sevcon technical support for a single computer in some cases, but are only valid for lower 'customer' access level. The CAN packets are built/decoded in a single dll that also implements their licensing and 'access level' code, which can be fiddled with to make work if you are desperate, but it's much more pleasant dealing with helpful sevcon engineers than x86 assembly... Even if you manage to "validate" your license (either with a license key or with some clever fiddling), the license reading code in the dll needs to do additional checking to determine your access level. Again, some amount of clever "fiddling" can adjust your access level to let you modify certain "advanced" settings, but again, dealing with Sevcon engineers is better than trying to outsmart the software. The highest possible license is 5, which is the SEVCON engineering level. This lets you change every setting of the controller, including ones that are stored in device configuration files (.dcf's) that might go and blow up your controller if they are incorrect. We found that having access level 5 gives you very few new settings - I believe we only changed a level 5 setting once, which turned out to be not needed.</div>
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Unfortunately, the DVT GUI doesn't expose all the settings necessary to program the controller to work with a motor. .dcf's are stored as plain text and contain lots of useful settings, though you will need to decode the hex values and scale by the appropriate amount and deal with endless 'param dyn range' errors. This error means that you have entered some value in the .dcf that doesn't make sense or is out of range. I highly recommend changing one setting at a time, power cycling, and checking for param dyn range errors to avoid having to remember the last 20 changes you made trying to figure out how you broke the incredibly fragile configuraiton data. DRIVE-WIZARD will spit out a .tcl script that can be loaded with "File->Source" to go and change the settings to work with the motor. This is the best way that we found to configure the Sevcon.</div>
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<tr><td class="tr-caption" style="text-align: center;">The workbench</td></tr>
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We also needed to provide encoder position feedback to the controller. It needs to be a quadrature signal that's not too fast.<br />
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<tr><td class="tr-caption" style="text-align: center;">Peter's soda can/hot glue coupling worked great!</td></tr>
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Unfortunately, this encoder was high resolution and generated quadrature signals in the 100's of kHz range, which was too fast for the slow TI brand DSP on the Sevcon logic board. Using some of the encoder code created by Ben, we tricked an STM32 nucleo board into becoming an encoder divider. My implementation of the encoder-divider is available here: LINK</div>
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The nucleo's 3.3V outputs weren't enough to drive the Sevcon inputs, so we added some transistors</div>
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<tr><td class="tr-caption" style="text-align: center;">The board is taped to the table so it doesn't fall off.</td></tr>
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Amazingly, all this nonsense worked, and the motor spun up. Here it's spinning at around 2000 rpm, out of a maximum of around 8000.</div>
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<a href="https://vimeo.com/181750368">https://vimeo.com/181750368</a></div>
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At full speed it sounds like this: </div>
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<iframe allowfullscreen="" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/dbGz0xBDIkY/0.jpg" frameborder="0" height="266" src="https://www.youtube.com/embed/dbGz0xBDIkY?feature=player_embedded" width="320"></iframe><br />
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which is absolutely terrifying. We had to hook up water cooling from the sink to keep the motor at a comfortable temperature. </div>
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The next stage of the project was completed extremely quickly and with few pictures taken, so documentation is brief. The "outboard" uses an alternator belt from a Kia that runs in the water to drive the propeller. This actually worked, but only with extreme tension on the belt. Dane performed a small miracle, and somehow determined the spline on the propeller was the same as the spline on a Fiat 500 steering wheel, so we used steering parts from a Fiat as the propeller shaft. Rob Reeve created a beautiful copper coil for the cooling loop, which was driven by the amazing brushless Toyota Prius water pump. </div>
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Peter and I mounted the sevcon and created some more legitimate wiring:</div>
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<tr><td class="tr-caption" style="text-align: center;">Sevcon in boat</td></tr>
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<tr><td class="tr-caption" style="text-align: center;">Box of Switches</td></tr>
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<tr><td class="tr-caption" style="text-align: center;">battery</td></tr>
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<tr><td class="tr-caption" style="text-align: center;">Motor on boat</td></tr>
</tbody></table>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7YCdEwnIsaXN2W1pD-zMRdPXopnLVpfV0FSGWvwQOWU58fzxu-X4Th6jzgRF04SlnDTNk_UQBV07azm_1l_HhpuvAXrps1OosNjPE9JezO7Cyhi_CVRXW3FF3jYtaXx5BwmxkBPqPpMk/s1600/IMG_1361.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7YCdEwnIsaXN2W1pD-zMRdPXopnLVpfV0FSGWvwQOWU58fzxu-X4Th6jzgRF04SlnDTNk_UQBV07azm_1l_HhpuvAXrps1OosNjPE9JezO7Cyhi_CVRXW3FF3jYtaXx5BwmxkBPqPpMk/s320/IMG_1361.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">4 of these packs should be enough...</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhd_OACoRfHaky08ZAmcNYU6Q69t5iMtpW7rbUtVBkrQdTdMADBbqxw8UhpszYYuaaVo7DDr6-bIyqZwUwARBt7DbLbP7obS9VuyRlZDX2AJarcLTVrnN2Dm21StRZbBcCLcYtKf4YLFcY/s1600/IMG_1367.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhd_OACoRfHaky08ZAmcNYU6Q69t5iMtpW7rbUtVBkrQdTdMADBbqxw8UhpszYYuaaVo7DDr6-bIyqZwUwARBt7DbLbP7obS9VuyRlZDX2AJarcLTVrnN2Dm21StRZbBcCLcYtKf4YLFcY/s320/IMG_1367.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Loaded boat</td></tr>
</tbody></table>
<br />
The boat worked moderately well. Unfortunately, our pulley ratio was off by a factor of two. Our motor could only spin at a very low speed, in a range where it can give us only around 9 kW, instead of the 30 we designed for. The boat did not plane, which also might have been because it was a small aluminum fishing boat, not a speedboat. We were unable to increase the motor velocity because the controller was operating at the 600 amp phase current limit. At this low speed, we were only at around 20% DC bus utilization, but we could not safely put any more volts across our motor. The mechanical disadvantage from the incorrect pulley ratio would have caused the phase current to exceed the limit. At full speed we could only put 9.6 kW into the motor, which was enough to get to 8 mph.<br />
<div>
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<div>
See a video of the boat in action here:</div>
<div>
<a href="https://vimeo.com/182904726">https://vimeo.com/182904726</a><br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbcuS8rWd1h7fZcNAUAYRBQx87xpHsA1oQR8Ej15cF4icAlDmCtMaA9XgD-2K7nuS18t_vxehGhnTImP1A60RKePPXR5xl_B4pjwoeOmfSx8RCDTfn_cIK36gXQykHcIfwEkPdIDdpONQ/s1600/2016-09-11+18.12.48.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbcuS8rWd1h7fZcNAUAYRBQx87xpHsA1oQR8Ej15cF4icAlDmCtMaA9XgD-2K7nuS18t_vxehGhnTImP1A60RKePPXR5xl_B4pjwoeOmfSx8RCDTfn_cIK36gXQykHcIfwEkPdIDdpONQ/s320/2016-09-11+18.12.48.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">questionable underwater alternator belt.</td></tr>
</tbody></table>
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<div>
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</div>
Jaredhttp://www.blogger.com/profile/02241918879329048444noreply@blogger.com1tag:blogger.com,1999:blog-1468514539205748845.post-87674238553003037842016-09-11T20:37:00.002-07:002016-09-11T20:37:21.220-07:00PMTH Build ReportsPMTH began some time early in December, when Alex and I decided we should try to build a battlebot. We didn't really know what we were doing, and the project turned out to be mostly a failure, but it was a great introduction to battlebots. We began with some ideas and material.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7qKRaLjNm8DLivMevXTEBZJdWaWfORl29jVRYYrjEMtilN1hypCisPvIgW1UbybnzSc3VcMUsm6ed6PnaNBvhGjTufB7gI9KuUfPfSf31eOxOHNgw221BYOL_5oJBLipZhiSd451KeCI/s1600/whitebard1.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7qKRaLjNm8DLivMevXTEBZJdWaWfORl29jVRYYrjEMtilN1hypCisPvIgW1UbybnzSc3VcMUsm6ed6PnaNBvhGjTufB7gI9KuUfPfSf31eOxOHNgw221BYOL_5oJBLipZhiSd451KeCI/s320/whitebard1.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Ideas</td></tr>
</tbody></table>
<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-bzKWzcoiWjQetj7gRKQ6WOrINLuMe8jvezVWGON5vivBiWDhJXM-Q5muIi68n3NLZo9u1cEwiNRoh7S2_gpxY_IijFcLxP2hq5YkIh3h9MMMJuF7dk9L81sMMgy2EFqP188msRY66Ks/s1600/f2.jpg" imageanchor="1"></a><br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-bzKWzcoiWjQetj7gRKQ6WOrINLuMe8jvezVWGON5vivBiWDhJXM-Q5muIi68n3NLZo9u1cEwiNRoh7S2_gpxY_IijFcLxP2hq5YkIh3h9MMMJuF7dk9L81sMMgy2EFqP188msRY66Ks/s320/f2.jpg" style="margin-left: auto; margin-right: auto;" width="320" /></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Material</td></tr>
</tbody></table>
At first, we were planning on building some sort of automatic flywheel powered flipper, but we would later scrap the idea due to complexity and lack of space/time. We used many parts from Alex's class project, which was supposed to be a speaker, but actually was a battlebot drivetrain in disguise. <br />
<div>
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<div>
Almost all of the material shown came from the Stata loading dock. On December 8th, I found some sort of giant old industrial motor controller with some large heatsinks. As far as I can tell, they were machined from solid 6061 aluminum.</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0nvChjGmfLBeUBPXuHlp2XmJAIHvvFnR5W3jAaL3mZRUckYqo_YykxDDFawWamgmDrvvpaeOBGPkyvmOskmlfs-svJ0fEeMCB9iBNY5UuIeKdjb4dHk2KlfWdcDbfjNAA8rIsJob4T1s/s1600/File_001+%25281%2529.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0nvChjGmfLBeUBPXuHlp2XmJAIHvvFnR5W3jAaL3mZRUckYqo_YykxDDFawWamgmDrvvpaeOBGPkyvmOskmlfs-svJ0fEeMCB9iBNY5UuIeKdjb4dHk2KlfWdcDbfjNAA8rIsJob4T1s/s320/File_001+%25281%2529.jpeg" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Controller board on floor of Stata dock</td></tr>
</tbody></table>
<div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNGH73rDTuwPMGriE_v8O5-tVP7R75dTOCCi3jTUHiOWI7ptw0VfLwkfLxAycJJqfCYkSxQGDLIKJTG6U_ytjEhEHGeugXqFvvaN-zWrGelO1-6_lbBirjvMNwWqmEEZYLGdqIy8cERP8/s1600/File_000+%25281%2529.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNGH73rDTuwPMGriE_v8O5-tVP7R75dTOCCi3jTUHiOWI7ptw0VfLwkfLxAycJJqfCYkSxQGDLIKJTG6U_ytjEhEHGeugXqFvvaN-zWrGelO1-6_lbBirjvMNwWqmEEZYLGdqIy8cERP8/s320/File_000+%25281%2529.jpeg" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Cabinet with microwave</td></tr>
</tbody></table>
<br />
After lots of CAD, we decided we'd have more fun if we designed the robot as we made it, so we threw our designs in the trash and got to work making parts. </div>
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<div>
On January 21st, we went to MITERS to begin construction of the robot. We clamped the heatsink to the table of the Bridgeport, and removed the fins.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiX6wz8NrRnECV66V7PeICbr3BKuGf4wiTxVJIGcr7_7TODSsHJvBavUitUFEAIADXk_VjqBTfCl802iiYC2jpyh0RwMvqbggmW8k_tHthHdegtKSqsdFouaep1mDmp_jSjMXCc-2l-lgA/s1600/IMG_0745.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiX6wz8NrRnECV66V7PeICbr3BKuGf4wiTxVJIGcr7_7TODSsHJvBavUitUFEAIADXk_VjqBTfCl802iiYC2jpyh0RwMvqbggmW8k_tHthHdegtKSqsdFouaep1mDmp_jSjMXCc-2l-lgA/s320/IMG_0745.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Heatsink on mill table</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi33OTDq0FDKFa3eW_OQ6LB1T2tNB1KpjVoJnUs3LVJDjwiSD1TuPwddNOEgXtyVNdIhrP34z74sCHY-g6Z2x2p-dmDXPZCxQmor_bGrCMZRKCulz8nbs9GpA5xKCmRMusRYptEixpMGkI/s1600/IMG_0747.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi33OTDq0FDKFa3eW_OQ6LB1T2tNB1KpjVoJnUs3LVJDjwiSD1TuPwddNOEgXtyVNdIhrP34z74sCHY-g6Z2x2p-dmDXPZCxQmor_bGrCMZRKCulz8nbs9GpA5xKCmRMusRYptEixpMGkI/s320/IMG_0747.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Heatsink with some fins removed</td></tr>
</tbody></table>
The next day, we made some motor mounts. They have little slots milled in them to fit around the plastic gearbox housing. We also made shafts from the really awesome 1/2" 7075 Hex shaft from Vex Pro.</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8aZhk5BDlIfrYfLqDiP2m7cL3cocCNSF9_CQU6Ea27cqbyKg4KuFQVNwLZyg0H3xcraTQEfZxOdLG4sQ1arbPPqR5Xhwispo0FXrjqee3rHe2SBTQFXpqYaPguf4REv3Lu-FV7XyuXH0/s1600/IMG_0751.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8aZhk5BDlIfrYfLqDiP2m7cL3cocCNSF9_CQU6Ea27cqbyKg4KuFQVNwLZyg0H3xcraTQEfZxOdLG4sQ1arbPPqR5Xhwispo0FXrjqee3rHe2SBTQFXpqYaPguf4REv3Lu-FV7XyuXH0/s320/IMG_0751.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The shaft is in the background.</td></tr>
</tbody></table>
After that, we made bearing blocks for the wheels that weren't driven by the motors. I started by making a rectangle<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDWGvhm0UP2tv2nohrGUOaUP7n3KK66NOmpeRHmLw2mr8Z8TKsV7TQzSMQN0A7D2eATz2y-kY9KZlYPcaKhpNf9yIPciZnM0eYaBogK4V_MmSgdMwp8nub_C1HERQMN-zR2NX8hP8-2JA/s1600/IMG_0776.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDWGvhm0UP2tv2nohrGUOaUP7n3KK66NOmpeRHmLw2mr8Z8TKsV7TQzSMQN0A7D2eATz2y-kY9KZlYPcaKhpNf9yIPciZnM0eYaBogK4V_MmSgdMwp8nub_C1HERQMN-zR2NX8hP8-2JA/s320/IMG_0776.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Shiny!</td></tr>
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then bored a hole for two bearings.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRj7Ty7odhCqbTW7hv_Bzj-FC9NSLXc0Fi-9iym4g-K6hpXRV4sZyuhrdPrwbvbUguA6YTPbGeVG4QaHO8mBy7eNNsjzrtLuMch1_Inu2DIjMCK6B3EMFAE15-Q6bOTWxl3CKFmuaVn6w/s1600/IMG_0780.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="284" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRj7Ty7odhCqbTW7hv_Bzj-FC9NSLXc0Fi-9iym4g-K6hpXRV4sZyuhrdPrwbvbUguA6YTPbGeVG4QaHO8mBy7eNNsjzrtLuMch1_Inu2DIjMCK6B3EMFAE15-Q6bOTWxl3CKFmuaVn6w/s320/IMG_0780.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">There are two bearings in there.</td></tr>
</tbody></table>
<br />
I goofed and didn't get a good press fit, so I added some bearing retaining screws.<br />
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<div class="separator" style="clear: both; text-align: center;">
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7T8bEJTnuOYsnD0WzpPHp8ifITAcpaEyhfpV_T8Is4EK80JRXvd87GmkigAMz2ZUNVffYwUIGg7vyTMyz2zFJtAdndbNnsAlXY8HH9t4yuy-wwzTgJqOdjqTNCn5k9kSLJrukvfC_6vQ/s1600/IMG_0784.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7T8bEJTnuOYsnD0WzpPHp8ifITAcpaEyhfpV_T8Is4EK80JRXvd87GmkigAMz2ZUNVffYwUIGg7vyTMyz2zFJtAdndbNnsAlXY8HH9t4yuy-wwzTgJqOdjqTNCn5k9kSLJrukvfC_6vQ/s320/IMG_0784.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Two bearing blocks on MITERS bench</td></tr>
</tbody></table>
<span style="text-align: left;">The next step was to cut up the heatsink plate and put holes in it.</span><br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj39PskK9D0Smkix9ocMu_pZDDe30ZEj_7POKs4ZnrKIB92ZytK7A8LEAHmrk8EBiKCoTNLMohON-Z4L8Dug427UR87PY28tVXv9r1HqCJwf_9TpHlUo2ujRKiqV41YN-5dMCNZYAJI-J4/s1600/IMG_0788.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj39PskK9D0Smkix9ocMu_pZDDe30ZEj_7POKs4ZnrKIB92ZytK7A8LEAHmrk8EBiKCoTNLMohON-Z4L8Dug427UR87PY28tVXv9r1HqCJwf_9TpHlUo2ujRKiqV41YN-5dMCNZYAJI-J4/s320/IMG_0788.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Victor Mill with lamp and aluminum plate</td></tr>
</tbody></table>
<div style="text-align: left;">
We ordered sprockets from Vex Pro, which were received by a man(?) named MICHEEEL</div>
<div style="text-align: left;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEih3MdKrHZeU9xBLDFWjymudyRdUNVYjq_fg6wxiBxvHmCQBsYpax5TwTmUHYE5D66VcCsteRFCmQWwWzkwvXcmrK6TTuMk-mppcccj7PKKqMc79gWyMmIZYychD61vj1DDHz-JPddHfAI/s1600/IMG_0789.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEih3MdKrHZeU9xBLDFWjymudyRdUNVYjq_fg6wxiBxvHmCQBsYpax5TwTmUHYE5D66VcCsteRFCmQWwWzkwvXcmrK6TTuMk-mppcccj7PKKqMc79gWyMmIZYychD61vj1DDHz-JPddHfAI/s320/IMG_0789.JPG" width="240" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyFkT1YIs0PNvprPQbxIed-0JQcvV4Aii8IF9Y5lWyRaT16zcpbcn0LrLelRiPcC1CWTqFjqC9x7zVKkp2NLFrZpRMYHXCoQAV_JFinhxdVfKfFnuThyphenhyphenJ_4sXkEbEozqKc0vSsyaKOYWs/s1600/IMG_0791.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyFkT1YIs0PNvprPQbxIed-0JQcvV4Aii8IF9Y5lWyRaT16zcpbcn0LrLelRiPcC1CWTqFjqC9x7zVKkp2NLFrZpRMYHXCoQAV_JFinhxdVfKfFnuThyphenhyphenJ_4sXkEbEozqKc0vSsyaKOYWs/s320/IMG_0791.JPG" width="240" /></a></div>
The plates also needed to be modified to let the chuck of the drill fit.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgeLtTV0YLJqlruoqZTvEVYfc95XBVXx2vCCj_S7DmhvRwv01H3Npqpn2DcsDpDGRK6kq7VzGkpsP7dwsyc-Y2iEGfZLrWG5jVjJlRPFXrBz4LH-a5WLBfHKhJ58s6OQlvpETtNZsMs6y0/s1600/IMG_0792.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgeLtTV0YLJqlruoqZTvEVYfc95XBVXx2vCCj_S7DmhvRwv01H3Npqpn2DcsDpDGRK6kq7VzGkpsP7dwsyc-Y2iEGfZLrWG5jVjJlRPFXrBz4LH-a5WLBfHKhJ58s6OQlvpETtNZsMs6y0/s320/IMG_0792.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Cutting Fluid removes Sharpie, so this was a bad idea.</td></tr>
</tbody></table>
Suddenly, it began to look like a robot.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUnoJ23uXg1MwvXABnhyHATpoZxFVGsy6fNeHqQ4ANFG7JAYLVVdm-RtV_l9b2lQt7RexdTwosJR7CDGMUGDaNDXvqFxUas5Von8-S4cAxLvTE48UIsYmzCSTkL-zbA9ANr0jY19n1yvg/s1600/IMG_0797.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUnoJ23uXg1MwvXABnhyHATpoZxFVGsy6fNeHqQ4ANFG7JAYLVVdm-RtV_l9b2lQt7RexdTwosJR7CDGMUGDaNDXvqFxUas5Von8-S4cAxLvTE48UIsYmzCSTkL-zbA9ANr0jY19n1yvg/s320/IMG_0797.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">I should have used a flycutter.</td></tr>
</tbody></table>
<div>
<br /></div>
<div>
Our next challenge was to create the weapon drive. We looked in the large bearing drawer at MITERS and found some gross looking bearings that seemed suitable. At first, we couldn't even get the bearings to turn, but we were able to get them rolling after a bath in acetone.<br />
<div class="separator" style="clear: both; text-align: center;">
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<div style="text-align: left;">
</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjV-Dh-jM-cWID-YhMILNclc8fL5N_tDqSAfVIEjr8XUvjiL4xi_2uwIzewmBn3j5osGaplFRJm-tfFno-LkQWb5FHNpPgzsJuuNBqOgnl5GLMLaprHiQ7OjZB19LDt5gO81UwBriPtVh0/s1600/IMG_0801.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjV-Dh-jM-cWID-YhMILNclc8fL5N_tDqSAfVIEjr8XUvjiL4xi_2uwIzewmBn3j5osGaplFRJm-tfFno-LkQWb5FHNpPgzsJuuNBqOgnl5GLMLaprHiQ7OjZB19LDt5gO81UwBriPtVh0/s320/IMG_0801.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Questionable Bearings.</td></tr>
</tbody></table>
Finding a suitable shell was difficult too. All the woks were flimsy, so we went with a really small cast iron skillet. Unfortunately, it is very small, so getting everything to fit will be a real challenge.<br />
<div style="text-align: left;">
</div>
</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtYIn67i5tyb6fm9KSlhTAX8TneiJwfaNCtGIDPRT-2CyNEbEACeES5236t7fmSIaM02elPS0XteOPhCkLtxtipleOXWqKLlTTBNlffI-uB66m3Y5qbwiNZHua5XG7x2GI002Q2lXaXy0/s1600/IMG_0808.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtYIn67i5tyb6fm9KSlhTAX8TneiJwfaNCtGIDPRT-2CyNEbEACeES5236t7fmSIaM02elPS0XteOPhCkLtxtipleOXWqKLlTTBNlffI-uB66m3Y5qbwiNZHua5XG7x2GI002Q2lXaXy0/s320/IMG_0808.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Robot Soup.</td></tr>
</tbody></table>
We also encountered an extremely unusual left-hand end mill. <br />
<div>
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
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<div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbrDbQiDxzhMJZOdpW3BwPsZcEpfcva8FuWoDTwjgsI69AhGOiLorQxmcpEG8k000Q99qlcVteJ4H9Z1BdNibtpqUQnU8wqnyDHPt6RErtjXkDv6ljCZ5n-Xb6e4MsFdUUXRL37QdHSPc/s1600/IMG_0815.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbrDbQiDxzhMJZOdpW3BwPsZcEpfcva8FuWoDTwjgsI69AhGOiLorQxmcpEG8k000Q99qlcVteJ4H9Z1BdNibtpqUQnU8wqnyDHPt6RErtjXkDv6ljCZ5n-Xb6e4MsFdUUXRL37QdHSPc/s320/IMG_0815.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">WHY?</td></tr>
</tbody></table>
To drive the weapon, we are using an NTM Prop Drive 50-60 380KV motor with a bored out skateboard wheel.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiaMLXrK_JanA0zDYIOP_nJa69l8UpETio4NeSxehxWtL501QTq0oWFlnL0KtnELIHX3pGgwkOO3KmZdrXEAxki2xlapPFJ4tXhhbfCBpvaTnbljFDKexvB9NOSvAZ4oLasEvAQLzrH1oI/s1600/IMG_0817.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiaMLXrK_JanA0zDYIOP_nJa69l8UpETio4NeSxehxWtL501QTq0oWFlnL0KtnELIHX3pGgwkOO3KmZdrXEAxki2xlapPFJ4tXhhbfCBpvaTnbljFDKexvB9NOSvAZ4oLasEvAQLzrH1oI/s320/IMG_0817.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The motor is rated for 2600 watts</td></tr>
</tbody></table>
At first, we didn't support the shaft, but we later created a little block that held everybody's favorite 8mm ID 22mm OD skateboard bearing.<br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8MaOrqhGnvz4TLLlCmhWi_3MgpjHoFRvRtCBzjkgE1x4GEOe3EXnVjAbJHX3mUBGjSQLrwBR6jg4zcyALk9j10Sj9Wtc5H3kT6ldr2Y8XlmjsD1jKs20L8mjfBYAUtFjWU4hVI0wDP-U/s1600/File_000+%25282%2529.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8MaOrqhGnvz4TLLlCmhWi_3MgpjHoFRvRtCBzjkgE1x4GEOe3EXnVjAbJHX3mUBGjSQLrwBR6jg4zcyALk9j10Sj9Wtc5H3kT6ldr2Y8XlmjsD1jKs20L8mjfBYAUtFjWU4hVI0wDP-U/s320/File_000+%25282%2529.jpeg" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Another questionable bearing.</td></tr>
</tbody></table>
To make an axle for the weapon, we used a 304 stainless steel pressure vessel we found at the loading dock. 304 is not one of the free machining stainless steels, and part temperature quickly became an issue on the MITERS lathe.</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfF5K-uN8sgokdfXOVQCmekle7tr4D7DjnduizZ2pd1by6HUYZdFNrbhS4uANnaiJ3xB_sfbBvvQf7O8CnPOFzg2Xet22Pr9sMmq3AW6Gw7uDiv4pdDCFcKhElbcNWZrEog89gPktpOAg/s1600/IMG_0841.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto; text-align: center;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfF5K-uN8sgokdfXOVQCmekle7tr4D7DjnduizZ2pd1by6HUYZdFNrbhS4uANnaiJ3xB_sfbBvvQf7O8CnPOFzg2Xet22Pr9sMmq3AW6Gw7uDiv4pdDCFcKhElbcNWZrEog89gPktpOAg/s320/IMG_0841.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">We needed to remove almost 2 lbs of material.</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPOH5lApafrQL7rxEkfsEQmGlUMR8HwktPlIYg2BzwuC4sac6KbjbJaEmjsbsP-11tBh3_nA0Ep38VSCUhCRGNU5gzQMgbEuyRkW7ALZihYsJWaRmqmGCHkqvJImRUpa6p9c6BwBZM2z0/s1600/IMG_0840.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPOH5lApafrQL7rxEkfsEQmGlUMR8HwktPlIYg2BzwuC4sac6KbjbJaEmjsbsP-11tBh3_nA0Ep38VSCUhCRGNU5gzQMgbEuyRkW7ALZihYsJWaRmqmGCHkqvJImRUpa6p9c6BwBZM2z0/s320/IMG_0840.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">The chips were beautiful shades of blue, gold, and purple.</td></tr>
</tbody></table>
I finished the axle on one of the lathes in the FSAE shop that has flood coolant and a more powerful spindle. They currently use only one type of insert, which is terrible for stainless, so I dug through the collection of damaged/used up inserts and found something good for stainless. Running flood coolant, I could get around .100" off the diameter in each pass. This was the limit for this lathe - any more and the servo drives would give errors.<br />
<div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipPN90DcNjbbzBDslFHMJFnK9rn8BmZG16aXuo9I6rlhP2QuMTmElwuGGJW2sXzc-9aWVqRdxeiNRp75OJcK0QGLSVN9dkolvty5Bkim6aT8txOpXGRZM7c7isIzIWjusq2paf1loAh4c/s1600/IMG_0845.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipPN90DcNjbbzBDslFHMJFnK9rn8BmZG16aXuo9I6rlhP2QuMTmElwuGGJW2sXzc-9aWVqRdxeiNRp75OJcK0QGLSVN9dkolvty5Bkim6aT8txOpXGRZM7c7isIzIWjusq2paf1loAh4c/s320/IMG_0845.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Shiny!</td></tr>
</tbody></table>
I put a 3.25" diameter bolt circle in the skillet by clamping it to the table of the Bridgeport.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiR6_lhoDRPGOAMvO_jO0v8u1uQ5_UgNcixt8P6g0WYbtUTU-_OBPyp1yk41XOcTvcoWMIZBHzQVVtQvaxrWEqEAbTFPRAUorK_e0AWutLixitRR8BF3rSnhybqyNlvU4kdyawyLVzpHoQ/s1600/IMG_0847.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiR6_lhoDRPGOAMvO_jO0v8u1uQ5_UgNcixt8P6g0WYbtUTU-_OBPyp1yk41XOcTvcoWMIZBHzQVVtQvaxrWEqEAbTFPRAUorK_e0AWutLixitRR8BF3rSnhybqyNlvU4kdyawyLVzpHoQ/s320/IMG_0847.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">This wasn't the first time somebody has machined a pot at MITERS.</td></tr>
</tbody></table>
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgooQ4irhSDgzRYjdiAd8G8_Cyb7R8KZXkiQYK4Hb-_SBchku6ciTCl6GAbs4fFthxomQpsyXHnr7bfYhcmG0N3WI3bEfCbDIMtjwoKRRQSxlgHXcYxnOu_tqr5rm9jOnpLWGkou9HFcJk/s1600/IMG_0850.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgooQ4irhSDgzRYjdiAd8G8_Cyb7R8KZXkiQYK4Hb-_SBchku6ciTCl6GAbs4fFthxomQpsyXHnr7bfYhcmG0N3WI3bEfCbDIMtjwoKRRQSxlgHXcYxnOu_tqr5rm9jOnpLWGkou9HFcJk/s320/IMG_0850.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="font-size: 12.8px;">Cast iron is cool.</td></tr>
</tbody></table>
We needed a way to attach bearings to the pan, so I made a set of bearing blocks. Looking back, these are probably the two best parts made in this project, and I'll likely find some better use for them in the future. The first operation was to bring the stock to size</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9UAe2nE8p7NKuoEF3BTAldPKk9wUIGZX6FLC6xEhyphenhyphenu0Sdi373vSBdKZkMtCa0vD8LByGKUyu_hL6QPFcXcY1W2m33uD_U4TXKOhXH32f7GRB7hniuFdceGTBUAANoX5xYBm28LueVxwU/s1600/File_003.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9UAe2nE8p7NKuoEF3BTAldPKk9wUIGZX6FLC6xEhyphenhyphenu0Sdi373vSBdKZkMtCa0vD8LByGKUyu_hL6QPFcXcY1W2m33uD_U4TXKOhXH32f7GRB7hniuFdceGTBUAANoX5xYBm28LueVxwU/s320/File_003.jpeg" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">I used the flycutter this time...</td></tr>
</tbody></table>
<div>
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<div class="separator" style="clear: both; text-align: center;">
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I started to create the bearing bore using the boring head on the mill, but this was too slow, so I switched to the lathe.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPJ5ky1iGxX_e_nm_Xtg6O01GrUCf2UCMdwys5N_I1EzGR14ouMxfPaDgYKfbIsmIm6FndWPtXoTllCt4Tjc5NsmjoRfdzhMlG6Zu_IhxLR2XrDNym5ADc5MXaay1y5ooZs88vjKB3id0/s1600/File_006.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPJ5ky1iGxX_e_nm_Xtg6O01GrUCf2UCMdwys5N_I1EzGR14ouMxfPaDgYKfbIsmIm6FndWPtXoTllCt4Tjc5NsmjoRfdzhMlG6Zu_IhxLR2XrDNym5ADc5MXaay1y5ooZs88vjKB3id0/s320/File_006.jpeg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">I gave up.</td></tr>
</tbody></table>
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiozJGsutO8AnqTU22L5c1UHxcZ1YtywAwioXh-iWj1aAAsfz4j2UStcj0UKjH2PzQ_hKRImn_n51fw-aOFHW1P6UG9Y4HEx5KhI-sikDpeUrIf32JFUozmzWHNf5ApHa4VtpJWOH4TQ1E/s1600/File_007.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiozJGsutO8AnqTU22L5c1UHxcZ1YtywAwioXh-iWj1aAAsfz4j2UStcj0UKjH2PzQ_hKRImn_n51fw-aOFHW1P6UG9Y4HEx5KhI-sikDpeUrIf32JFUozmzWHNf5ApHa4VtpJWOH4TQ1E/s320/File_007.jpeg" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Dialing in the part was a massive pain.</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjL8pkfBv4Bhp2y9jE8v460TigKQLTDfm5ewJ54fwsHFqnQz9PTfNTLttBi0RZzdDJdRzuubfH2jTZp6Oan0Emz-wfUB-uJQX_nxNVUCW2PzQdpzA4vdCGoYe22wcC0t9gxXhuNZXOpFZo/s1600/IMG_0870.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjL8pkfBv4Bhp2y9jE8v460TigKQLTDfm5ewJ54fwsHFqnQz9PTfNTLttBi0RZzdDJdRzuubfH2jTZp6Oan0Emz-wfUB-uJQX_nxNVUCW2PzQdpzA4vdCGoYe22wcC0t9gxXhuNZXOpFZo/s320/IMG_0870.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Shown without bearings or bolts</td></tr>
</tbody></table>
<br /><br />On the final night before leaving, everything was very rushed. We added an idler wheel for the shell,<br />
<br />
<br />
<div>
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzm_mi24wTaHwuTNg5SQoagcutetHt6z0JlybNh-mkCm544xUzm726uoc5fGSSaUvVfWb1E_XC1ssTmveYeXXsmgLd0VBeW46fBUchQE74Gae9VMGDjE1keWhSUJf5_7DO-xz3h8h2nVE/s1600/IMG_0872.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzm_mi24wTaHwuTNg5SQoagcutetHt6z0JlybNh-mkCm544xUzm726uoc5fGSSaUvVfWb1E_XC1ssTmveYeXXsmgLd0VBeW46fBUchQE74Gae9VMGDjE1keWhSUJf5_7DO-xz3h8h2nVE/s320/IMG_0872.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">With delrin wheel</td></tr>
</tbody></table>
added some holes in the plate for mounting the weapon shaft,</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwH5QrdesX4fZ26sM3ZKK9eajSFC6OodUpVMgsz9LgEVvmz4hTpyM-QMOeozLViNYRgljEmcbou-ijarN6gHf-nOpM82QeCIQWge4mERZZ1AjTWGEn__VaQkkCj4oJ66XEiGxEuFBSjZE/s1600/IMG_0877.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwH5QrdesX4fZ26sM3ZKK9eajSFC6OodUpVMgsz9LgEVvmz4hTpyM-QMOeozLViNYRgljEmcbou-ijarN6gHf-nOpM82QeCIQWge4mERZZ1AjTWGEn__VaQkkCj4oJ66XEiGxEuFBSjZE/s320/IMG_0877.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Add caption</td></tr>
</tbody></table>
made a pocket in the bottom of the weapon shaft (I don't remember why the larger pocket is there, but the bigger one is to hold the nut from turning),</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEig_Seo5SkpVYyhOvQfJDVJPWZYiBMz8sv9PDtjo11ofunGJYjN9LGJ3FKpeI4tUMmfv6LDKUfHIcRpXOgYgUhMyRvdRG55kwMSz-FPwdwWDwc6WrJZbqTPrdHraIWR3oydh2kww2bsr8g/s1600/IMG_0882.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEig_Seo5SkpVYyhOvQfJDVJPWZYiBMz8sv9PDtjo11ofunGJYjN9LGJ3FKpeI4tUMmfv6LDKUfHIcRpXOgYgUhMyRvdRG55kwMSz-FPwdwWDwc6WrJZbqTPrdHraIWR3oydh2kww2bsr8g/s320/IMG_0882.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Shown from the inside of the weapon shell</td></tr>
</tbody></table>
<br /><div>
chamfered the inner bearing block and removed the square part to avoid interference<br /><div>
<br /><br /></div>
</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjNK3-0OVlTIm_AOxf1Ml_dgqhW_DIsoj-qOMT-xNw6oHoeONeBgG_6uNzFU3mNEHdJFxSCGdfAuweEc67D-uGV5pdrvzr8i64kKMfijdp7ACURPAOPf7B2-AkC5vUWnQOEJKdb3tTkQQw/s1600/IMG_0889.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjNK3-0OVlTIm_AOxf1Ml_dgqhW_DIsoj-qOMT-xNw6oHoeONeBgG_6uNzFU3mNEHdJFxSCGdfAuweEc67D-uGV5pdrvzr8i64kKMfijdp7ACURPAOPf7B2-AkC5vUWnQOEJKdb3tTkQQw/s320/IMG_0889.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">it was still scarily close!</td></tr>
</tbody></table>
and finally put the whole frame together!<br /><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiwrUdyFCpiBhwyDvbJdeFfT2f5x9X1fNVHteiGyieA6N9yuZT1c7r8aFS2Yj82EoiKsNtzLDRZSyP4rJplhAg8ZEno6cz2yk3HAYxBEpvdpCzmg7ttR4I6LBt5Kj8KH1OCiz9xAuiOF8/s1600/IMG_0894.JPG" imageanchor="1"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiwrUdyFCpiBhwyDvbJdeFfT2f5x9X1fNVHteiGyieA6N9yuZT1c7r8aFS2Yj82EoiKsNtzLDRZSyP4rJplhAg8ZEno6cz2yk3HAYxBEpvdpCzmg7ttR4I6LBt5Kj8KH1OCiz9xAuiOF8/s320/IMG_0894.JPG" width="240" /></a></div>
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We tested it: <iframe width="320" height="266" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/XmkqnDN3Fts/0.jpg" src="https://www.youtube.com/embed/XmkqnDN3Fts?feature=player_embedded" frameborder="0" allowfullscreen></iframe></div>
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and brought it to Motorama, where we tested it again: <iframe width="320" height="266" class="YOUTUBE-iframe-video" data-thumbnail-src="https://i.ytimg.com/vi/noygvnXGiQU/0.jpg" src="https://www.youtube.com/embed/noygvnXGiQU?feature=player_embedded" frameborder="0" allowfullscreen></iframe></div>
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Unfortunately, PMTH was a terrible failure of a battlebot, losing both of its matches at Motorama. The drive system was absolutely terrible and the center of gravity was too high, making the robot difficult to control. It would also destabilize and dip into the ground, causing it to tip over and roll around. The 'shell' was made of cast iron, which cracked and chipped with every impact. Currently, I don't plan to build another robot for the next Motorama, but there's always the chance that Alex and I will be inspired for the next Motorama and we'll build another.</div>
Jaredhttp://www.blogger.com/profile/02241918879329048444noreply@blogger.com0tag:blogger.com,1999:blog-1468514539205748845.post-71571213669252902372016-02-13T21:31:00.002-08:002016-06-10T12:08:13.249-07:00Reactor Chamber Machining<div class="MsoNormal" style="line-height: 14.25pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;">
<span style="font-family: "georgia" , serif; font-size: 10pt;">My friend builds nuclear reactors, and didn't want to spend a
small fortune at MIT's Central Machine Shop getting parts modified, so I
offered to help him out. You can read more about his crazy projects
on </span><a href="http://ac-science.weebly.com/construction.html"><span style="color: blue; font-family: "georgia" , serif; font-size: 10.0pt;">his blog</span></a><span style="font-family: "georgia" , serif; font-size: 10pt;">. I
started this project with access to none of MIT's machine shops, so I could
only work at MITERS, the only shop on campus that's open to absolutely anybody.
All the other shops required safety training, or thought the parts were too
complicated. <o:p></o:p></span></div>
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<span style="font-family: "georgia" , serif; font-size: 10pt;">The reactor chamber is made from a 304 stainless 6" diamter
hollow hemisphere with .125" thick walls. My job was to put 5 holes,
each 1.500" in diameter, in the hemisphere. The end product
should look like this:<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiz4fwOPI6aBLZnhsohzFnG80rgig9gLuqRaHaGSfND1KvbAa55pUXQgs6jwOoJuBxUqybspLvfKhbVfcY2xJHTCgGhlQZZuUa_btxOWqwKpJeBNGu5yRlQnDGrjJlaNt4HKtIsLAarwxI/s1600/1449448_orig.jpg" imageanchor="1"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiz4fwOPI6aBLZnhsohzFnG80rgig9gLuqRaHaGSfND1KvbAa55pUXQgs6jwOoJuBxUqybspLvfKhbVfcY2xJHTCgGhlQZZuUa_btxOWqwKpJeBNGu5yRlQnDGrjJlaNt4HKtIsLAarwxI/s320/1449448_orig.jpg" width="294" /></a><o:p></o:p></span></div>
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<span style="font-family: "georgia" , serif; font-size: 10pt;">I didn't have access to a boring head or a chuck large enough to
hold the sphere, so I had to get clever with a rotary table. The first
step was to align the axis of rotation of the rotary table with the center of
the rectangular stock. To make it easier, I put a collet block with the same
thickness as my stock in the vise and dialed that in. The vise didn't
quite fit on the rotary table, so one bolt (not shown) goes through a slot in
the middle of the vise with a bunch of washers.<o:p></o:p></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizkymBJq3G-VSclcmNJYVFk1V2TGFJMG5Ho1O_HTP-E_djTIxzJr0aIlfT4Uk8NSWWCr_8PaUAzQ9yDTyRy-42GmfZXXYWA0CiP4fYWoTYQ5w_t9MfBVYoiNtZMwJVKaLUkyngBsxOWH8/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizkymBJq3G-VSclcmNJYVFk1V2TGFJMG5Ho1O_HTP-E_djTIxzJr0aIlfT4Uk8NSWWCr_8PaUAzQ9yDTyRy-42GmfZXXYWA0CiP4fYWoTYQ5w_t9MfBVYoiNtZMwJVKaLUkyngBsxOWH8/s320/a.jpg" width="320" /></a></div>
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<span style="font-family: "georgia" , serif; font-size: 10pt;">Once the block was in the right spot, I used an indicator in the
spindle to set my zero on the DRO as the center of the collet block. <o:p></o:p></span></div>
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<span style="font-family: "georgia" , serif; font-size: 10pt;">The fixture I made has a circular edge that rests on the inside of
the hemisphere and a tapped 1/2-13 (same as typical Bridgeport hold down) hole
for bolting the hemisphere down. This single bolt attachment was a little
sketchy, but I never had any trouble with the part moving.<o:p></o:p></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjFfrxrfLRe5egrbXLrLmLphhwH_O-pcpW-ZkVRwMWp7jgyR6ni7AMPCzCBxaj-HrPC1msmY_hDsdL8DIu_haaN7gA746jNwhyphenhyphenEbS1NPult1G-SBC2bpvFb4ShY69eiE8Vnx3-scpiOvQ/s1600/reactorfixture.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjFfrxrfLRe5egrbXLrLmLphhwH_O-pcpW-ZkVRwMWp7jgyR6ni7AMPCzCBxaj-HrPC1msmY_hDsdL8DIu_haaN7gA746jNwhyphenhyphenEbS1NPult1G-SBC2bpvFb4ShY69eiE8Vnx3-scpiOvQ/s320/reactorfixture.jpg" width="320" /></a></div>
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<span style="font-family: "georgia" , serif; font-size: 10pt;">I first tried to put a hole in the center of the hemisphere with
one of the MITERS center drills. Unfortunately it was very dull and
caused work hardening even with a lot of force – I was worried I would break
the tip of the center drill if I pushed harder. In the end, I used a 3/8”
3 flute carbide end mill with a small corner radius in the lathe tailstock, but
a sharp center drill would work too.<o:p></o:p></span></div>
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<span style="font-family: "georgia" , serif; font-size: 10pt;">Next, I bolted the hemisphere to the fixture and set it up in the
vise with a 45 degree angle block. Indicating the sphere was frustrating
because the hemisphere was not perfectly spherical. When rotating around
any diameter of a sphere, the indicator should not move, but I was seeing .01”
maximum deviation near the edges. I also didn’t see the typical high/low
pattern that normally appears with a spherical/cylindrical part being turned
eccentrically, meaning the sphere must have some weird distortion. The
hemisphere appears to be formed, so this isn’t too surprising. I found it
useful to put a 1/2" diameter steel rod in the drill chuck and line up the
sphere so that the plane of the bottom of the rod is tangent with the sphere to
get an approximate location of the sphere before using the indicator.<o:p></o:p></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNMe6tUW8tk-qjQlnA6eTAg3cXzKjuFbAGcbKPXaO2iLA596ZGxKW1R5MpvE00ehfCQq-_dko2y-WLI7maeC31cWw_p4nziPoSXe3gSSocEq7igSKtjA5alEeqnAYOfmG2DuWpzKKCLT4/s1600/hemisphere.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="" border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNMe6tUW8tk-qjQlnA6eTAg3cXzKjuFbAGcbKPXaO2iLA596ZGxKW1R5MpvE00ehfCQq-_dko2y-WLI7maeC31cWw_p4nziPoSXe3gSSocEq7igSKtjA5alEeqnAYOfmG2DuWpzKKCLT4/s320/hemisphere.jpg" title="" width="320" /></a></div>
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<span style="font-family: "georgia" , serif; font-size: 10pt;">-Notice the bolt holding down the vise!<o:p></o:p></span></div>
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<span style="font-family: "georgia" , serif; font-size: 10pt;">The hemisphere is a terrible shape for ringing and chatter, so I
had to go quite slow. I found that at a certain feed rate the part would
make a pleasant ringing noise similar to a tuning fork. I was using one
of my end mills – MITERS had nothing that could cut stainless. I used a
½” carbide six flute coated end mill. I was taking .05” to .10” wide
passes at 1100 rpm and around 3 ipm or so. The chips created were sharp
and got stuck in my hands, which was very annoying. The finish left
behind was quite good.<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjw_oRYd5o2nSdIN7KY96hCaCAGV9zz3j5EQkoHd80CETgcGjPFUJJG9bP1PJZfdV8pF3MuCGdPdWR7CmJuVKp7yK6NtgdIpo0w_gR8b8aMp9tainQwf6CywlGYHBEbiGS_cT5I0Y85Bx0/s1600/stdsho2.jpg" imageanchor="1"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjw_oRYd5o2nSdIN7KY96hCaCAGV9zz3j5EQkoHd80CETgcGjPFUJJG9bP1PJZfdV8pF3MuCGdPdWR7CmJuVKp7yK6NtgdIpo0w_gR8b8aMp9tainQwf6CywlGYHBEbiGS_cT5I0Y85Bx0/s320/stdsho2.jpg" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0V37qVklQuxy2rlUbvkYjdC-u_tLPpaMPluHh2B8jCC1PSEwJtVTmFdBpWHp-KHawhEGt40b3-QB5Eie3mKjRtd7qMEewC90YadrQ1CA1V32coSAipwnd_ZMEQKGXyuNF1EtDlJghDTg/s1600/student_shop.jpg" imageanchor="1"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0V37qVklQuxy2rlUbvkYjdC-u_tLPpaMPluHh2B8jCC1PSEwJtVTmFdBpWHp-KHawhEGt40b3-QB5Eie3mKjRtd7qMEewC90YadrQ1CA1V32coSAipwnd_ZMEQKGXyuNF1EtDlJghDTg/s320/student_shop.jpg" width="240" /></a><o:p></o:p></span></div>
<br />
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<span style="font-family: "georgia" , serif; font-size: 10pt;">Once I had one hole done, I walked in to the Edgerton Student
Shop, which has nice equipment, and asked if I could continue machining the
part there. After showing the instructor there that I was able to make one of
the holes, they were much more willing to let me work there. The guy there did
not like my fixture, so he suggested that I use a very small end mill
to reduce cutting forces. I used a 3/16” 3 flute carbide end mill to make
a .01” undersize hole first using a CNC ez-trak Bridgeport. It was one of
the fancy 3 axis ones that had a canned helix cycle, so I set it up to
continuously ramp down as it cut the circle. I used a .04” deep cut at 6
IPM. It was completely happy slotting at this depth, but sometimes
chattered before the cutter was fully engaged. As I did more holes I
cheated it down so the cutter would be fully engaged sooner. I got a
great surface finish with a .005” wide finish pass at full depth and 8
IPM. <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifK68JMxJ7I0S9mGO3rm5btqYcdaywG30u6iPDBsVR5pIm2E8JJJd5JS-ytFRm2OtClFNDOBkEjfqx5YsFprlPug_fkEickFFsAeHzoE4EaB9iZzVtzmhdx7HSS0AJssTlGcUwk6_yU-Q/s1600/img_0560.jpg" imageanchor="1"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifK68JMxJ7I0S9mGO3rm5btqYcdaywG30u6iPDBsVR5pIm2E8JJJd5JS-ytFRm2OtClFNDOBkEjfqx5YsFprlPug_fkEickFFsAeHzoE4EaB9iZzVtzmhdx7HSS0AJssTlGcUwk6_yU-Q/s320/img_0560.jpg" width="240" /></a><o:p></o:p></span></div>
Jaredhttp://www.blogger.com/profile/02241918879329048444noreply@blogger.com0