pic: Team 8 accumulator up close

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close-up view of team 8’s accumulator mechanism.

You can pretty much see everything here.

Each arm is ran by a globe with its gearbox, and then has an additional reduction of about 3:1 using chain and sprojcets. The wheel is a 4" diameter colson wheel ran by a fisher price connected to an AM Planetary. Each system has a 10-turn pot (what broke and killed us at Portland) with a sproket mounted on it spinning with the chain, using independently tuned PID loops to control the position of each arm. There is also an IR range finder mounted on the lexan block (right above the tether cable connection in the picture) used to monitor whether or not we have a ball, and stop the wheels accordingly.

We have broken so many pots. Or should I say I have broken so many pots. All I hear from our head electrical mentor is “Harrison! You broke another one?” I think it’s just my calling in life…

We’re putting most on the blame on not watching it and letting hit the end of travel, and on using a cheapo pot from Fry’s. We oredered a bunch of quality ones from Digikey, and those coupled with some more care should treat us better (and some more spares).

Glad to see we’re not the only ones having trouble with pots.

a 30" lever arm is about all you should need to break just about any pot, but the Fry’s ones weren’t particularly good…