Weight Issues

[Matt Adams]

Originally Posted by AdamL118

Our gearing is 3:1 using the two drill motors tied to two wheels apiece set in low speed.

Short story:
At 100 lbs with those wheels, you'll need to be a little slower than that if you don't want to trip your breakers on the drill motors in pushing matches...


Long story:

Drill in Low Speed:
Free Speed: 450
Stall Torque: 320 in-lbs
Stall Current: 127 Amps
Breaker Current: 40 Amps
Torque at stall current: (40 / 127) (320 in-lbs) = 103.3 in lbs

100 lbs / 4 wheels = 25 lbs / wheel
25 lbs * 1.2 COF = 30 lbs

12.5 in diameter wheel = 6.25" radius

30 * 6.25 = 187.5 in-lbs * 2 wheels / motor = 375 in lbs of torque needed.

Minumum Ratio Needed: 375 in-lbs / 103.3 in lbs = 3.63

The ratio of 4:1 that FIRST gives you in the kit is a good choice, even though you have less weight. Try running your robot against a wall on carpet- if the circuit breakers trip, you should considering reducing the gear ratio in your drive train.

I hope this helps!

Good luck everyone.

Matt