Gearing/motor questions.

[Josh Siegel]

Hi everybody, I’m here to ask for a little bit of shared knowledge regarding arm control. Team 448’s arm for this year (still conceptual) is all laid out except for our motors and gearboxes. We are working with the kitbot chassis, and using both gearboxes and 4 CIM motors for the drive wheels. We considered using the FP motor (tilt) and tageine motor (lift) to power our arm, but would like your opinions.

I have two separate questions –
1. The arm will telescope using a cascading cable system (lots of tension, but less length to move the cable). Our empty arm will weigh approximately 18lbs, or 27lbs with a vision tetra (not counting potential friction). Though the arm extends about 15 feet, we will only need to move about 6 feet of cable as our arm extends every segment at the same rate. This needs to be quick and most importantly reliable. How would you suggest powering a drum to wind the cable? We also need to know how to figure out the proper drum diameter for the extending segment and the contracting segment (they work at different speeds). Also, links to cable drums that are FIRST legal would be appreciated.
2. The arm must be able to tilt with a tetra on it while extended. This is another cable mechanism, powering the arm both forward and back. A 9lb tetra + an 18lb arm, over 15 feet should be able to travel to about 30 degrees forward of vertical and 5 degrees back. Due to constraints on our CG, this system must be low to the ground (maybe a foot above the base of the arm, tops). Speed is not so much of an issue, but it is always nice to have. Back drive does not need to be eliminated, but reduced, if possible.

Thank you!
Joshua Siegel