[DFTF] Motors... ...Drive Motors...

[Travis Hoffman]

Originally Posted by Jim Zondag

Gone are the days of 2WD caster machines we all built in the 90s.

Hey Bill Miller -

Welcome to the 2013 FRC Game Challenge, "Retro-bution". In this game, 2WD castered robots will score points by.....corn.....rotating light....Goooood luck.

Just sayin'.

[IKE]

Originally Posted by Jim Zondag

Joe,
In the testing that Isaac and I have done, both in simuation and on real chassis, we have found that there is a "scrappiness threshold' at about 1kW for 150lb GVW FIRST Robots. We did most of this work on a standard 6x6 dropcenter configuration chassis. ...

We did a lot of modeling in 2008 trying to understand how to improve dynamic performance. We also experimented with different wheel types. Over the last few years, I have been working with skid steer vehicles with similar aspect ratio (length/width), and I was introduced to a recommended ratio of 20HP/Ton. Basically 1HP/100lbs or 1.1KW for a 150lb robot (120(robot)+12(battery)+15(bumpers)=147lbs) which is perfect for the 4 CIM combo.

[Jared Russell]

We will never use another BB 775 motor unless there are no other viable alternatives. We simply were unable to attain motors that didn't eventually develop case shorts from debris left over inside of them from the manufacturing process. This caused a number of hard-to-track down electrical issues, leaving us dead in the water for a number of matches until the offending motors were removed.

[PAR_WIG1350]

Although nothing can be done to prevent the case short issue with the 775s, the associated electrical issues can be completely eliminated if you have the motor totally electrically isolated. That means no metal gears, gearboxes, or structure in contact with the motors case, shaft, or pinion (if that is made of metal).
Last year, 1350 used 2 of them, mounted in two (PLASTIC) fisher price gearboxes, to power our main arm joint and they worked flawlessly. The FP gearboxes already had the appropriate mounting holes for a 700 sized can and totally isolated the motor from the frame. Also, torque wasn't an issue for the gearboxes at all. In one match, the arm got hung up on the rack and the operator inadvertently lifted the robot a bit; the point of failure was a 5/8th inch aluminum shaft and a small steel sprocket located in the multi-stage chain reduction between arm and the gearbox outputs. The shaft was bent and the sprocket broke into 3 pieces.