TB4.5MCESP1 Update 17: Last build report!

After a 14 hour nonstop work session at the Media Lab, SP1 is finally in some form of running order, sans arm ESC of course. I think I was in the building from 5 in the afternoon, through the night, to around 7AM when I decided to stop and take care of the little details at the event.

Usually, in the mad rush to finish, I don’t get around to taking pictures, but I did this time.

Poseur-finish picture with bent wedges. I wandered over to Central Machine Shop and got these made on a shitnormously huge metal brake. Best part? It was gratis. So, big thanks to the guys at CMS, because otherwise I would have to run non-curvy wedges.

One of the fixes I came up with to deter arm jamming was this additional half-bearing/chassis extension which cradles the motor shaft. It actually took three tries to get this right because it was about 3AM and I kept missing at least one small detail which made things not fit.

In the end, it doesn’t prevent the jamming as well as I’d like, because the motor still exerts enough brute force to bend the UHMW. If this piece were aluminum, it would work significantly better.

The last ditch solution is to glue the bottom of the motor to the baseplate such that it cannot flex, at least as much. I might also take the hard stop pins out to give me some more reaction time.

Unfortunately, the loss of that extra flex may have other consequences. I managed to explode a tooth off the pinion during testing. I’m beginning to have a feeling that the lifter is going to be less reliable than I expected.  And I didn’t expect much to begin with.

To fix the offset hinge holes, I popped them on the Media Lab mill and slotted the holes with a 3/16″ endmill. This not only lets me line the wedges back up, but also allows them to be mildly adjustable so I can trim them to the floor.

Speaking of trimming the wedges, here’s one of them in an angle vise. This was just one of about 4 different setups I tried for milling down the wedges, so some of the surfaces are a bit inconsistent. However, since they’re just going to get banged up anyway, it doesn’t really matter.

One finished wedge, with a partially finished one behind it. The mill’s Y-axis travel is too small for me to do both wedges in the same vise setup.

Test mount and gratuitous botshot. Things do fit.
And this is just a gratuitous botshot!

So, as of Thursday morning, the bot does move, and is decently maneuverable. It’s not fast on 11.1 volts, but I’ll manage. I still need to scrounge an arm controller at the event, and take care of some minor issues such as the charging lead and a power light of some sort. I’m not too worried about the charging lead since I can take the top off the bot to charge it.

Oh, and I wrote this from Harrisburg, PA. Event begins tomorrow!