[Thad House]

Originally Posted by marccenter

Dear CD,

I was wondering if any teams that have progressed further into their build so far have determined that the elevator CIM motors overheat due to stalling?
I am assuming you are using a gearmotor attached to a CIM with a gear reduction ratio in the order of 50 to perhaps 90:1.

When the CIM elevator motor stops moving to hold a tote at a given height it is effectively stalled (motor speed nearly zero) and maximum current is drawn.

Have you found that your CIM elevator mount overheats in a two minute match? Were you holding one, two, three, or four totes?

Have you found it necessary to add an active braking mechanism to aid in the problem?

Why use such a big reduction? Unless you are using a pulley that is about a foot in diameter, that will most likely be too much reduction, and too slow.

If an average pulley/sprocket is about 2.5 inches in diameter, a 70:1 reduction off of a CIM will have a free speed of 0.87 ft/s, and a stall force of 1200 lbs. If you had to stall a CIM to hold up 60 lbs at that reduction, you would be using 5% of your stall torque. A CIM could do that basically forever without problems.