View Single Post
  #19   Spotlight this post!  
Unread 13-07-2007, 01:14
Doug G's Avatar
Doug G Doug G is offline
Coach / Teacher
FRC #0701 (Robovikes)
Team Role: Coach
 
Join Date: Dec 2002
Rookie Year: 2001
Location: Fairfield, CA
Posts: 880
Doug G has a reputation beyond reputeDoug G has a reputation beyond reputeDoug G has a reputation beyond reputeDoug G has a reputation beyond reputeDoug G has a reputation beyond reputeDoug G has a reputation beyond reputeDoug G has a reputation beyond reputeDoug G has a reputation beyond reputeDoug G has a reputation beyond reputeDoug G has a reputation beyond reputeDoug G has a reputation beyond repute
Re: what motor did you use(arm)

Quote:
Originally Posted by AdamHeard View Post
If there is something to be learned here it is that any motor in the kit (even the globe) can be used to power the arm.

I like the philosophy of 330 on arms though; keep them simple, and then gear them down A LOT so that they have so much torque you never have to worry about it. A mentor of theirs, Chris Husmann, gave a great presentation last fall on arms that I would love to get a copy of.

When we had to redo our arm after a regional this year, we took that advice and used a small CIM paired with an AM planetary for each joint (the "team 60" arm).
I can't emphasize this enough. Over design the power transmission on the arm. If calculations show that you need 30 ft-lbs of torque to lift the arm and object at the end of the arm, then design a motor/transmission combination that can supply that while drawing < 10 Amps! (somewhat dependant on the motor choice)

If you need 30 ft-lbs, then stall torque should be at least 120-150!! Also this way, you can throw in some feedback and PID will have lots of headroom for tuning and working correctly.

In the 7 years of doing FIRST ... In my opinion the ratio of "under-designed arms" to "over-designed (or simply well-designed) arms" is at least 25 to 1.
__________________
Work Hard, Have Fun, Make a Difference!