Weight Issues

[AdamL118]

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

We have been doing some tests with our plow. We have put rollers on our plow that help to prevent our robot from riding up over balls and getting jammed. We have two ~20'' arms (with latex tubing as a safety shock absorber allowing full retraction when rammed into things), giving us ~50'' of reach. Our strategy will be to run into as many balls as possible and push/shoot them into our goal (controlling them is too hard).

We are setting aside the last week for testing and will go to a regional pre competition event before shipping.

How do our designs look?

http://members.cox.net/rambot/DocumentsPage.htm
I am sure they are not terribly original but we hope it produces a sturdy and simple machine. Any thoughts?

Best regards

[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