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Unread 23-04-2003, 08:57
Andy A. Andy A. is offline
Getting old
FRC #0095
Team Role: Coach
 
Join Date: Jun 2001
Rookie Year: 2001
Location: New Hampshire
Posts: 1,015
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Team 95

7 years (I think)

Drive motors: 2 drills, 2 CIM; one for each wheel

4, 8 inch skyway wheels, heavily modified.

2 window motors and 2 Globe motors for steering. Each wheel is independently driven and steered (full crab)

Drive was through worm gears. Steering was originally done with cable, but later changed to timing belt. Theoretically, we had full Ackermen steering and crabbing.

Sensors: no optics, we did use 4 pots to sense each wheel modules orientation.

Problems: Lots of them.

First, worm gears are very, very inefficient. Due to binding problems, this was even worse and we just lost to much power. Our speed was targeted to 8fps, it ended up being around 4.

Second, we had lots of issues regarding the pots. simply put, they drifted out of calibration after hard hits and just were never accurate enough.

Third, there was never enough time to get the custom circuit running. Because of this, all the calculations for steering was done on the RC. Because of the limitations of the RC, the math was very round about and filled every bit of memory we had. It's slow and inaccurate.

Fourth, the original design called for the wheel modules to be steered by motors connected via a capstan like cable setup. It actually worked and saved a good deal of weight. However, we found that in competition we would get rammed against the wall and the repeated blows would rip the cable out. So we replaced them with timing belts in Houston. But, because belts only come in 10 tooth increments sizing was a huge hassle.

Fifth, It was a bear to drive, and the complete lack of practice killed us. Ultimately, we got the mechanical problems pretty much figured out but our driver had never gotten the chance to play with it.

So ya, next time around we'll know what we are doing. It was a learning experience for sure. It's kinda tough to go from balls, which is something we know backwards and forwards, to making a complex drive train (past years have always been 2 drills end of story). It was easily the most complex thing we've ever made, and next time around it'll be fine.

-Andy A.