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.
|Controller board on floor of Stata dock|
|Cabinet with microwave|
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.
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.
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.
|Heatsink on mill table|
|Heatsink with some fins removed|
|The shaft is in the background.|
|There are two bearings in there.|
I goofed and didn't get a good press fit, so I added some bearing retaining screws.
|Two bearing blocks on MITERS bench|
|Victor Mill with lamp and aluminum plate|
We ordered sprockets from Vex Pro, which were received by a man(?) named MICHEEEL
|Cutting Fluid removes Sharpie, so this was a bad idea.|
|I should have used a flycutter.|
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.
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.
|The motor is rated for 2600 watts|
|Another questionable bearing.|
|We needed to remove almost 2 lbs of material.|
|The chips were beautiful shades of blue, gold, and purple.|
|This wasn't the first time somebody has machined a pot at MITERS.|
|Cast iron is cool.|
|I used the flycutter this time...|
|I gave up.|
|Dialing in the part was a massive pain.|
|Shown without bearings or bolts|
On the final night before leaving, everything was very rushed. We added an idler wheel for the shell,
|Shown from the inside of the weapon shell|
chamfered the inner bearing block and removed the square part to avoid interference
We tested it:
and brought it to Motorama, where we tested it again:
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.