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Unread 27-09-2011, 17:19
crazyStone crazyStone is offline
Cad posessed
AKA: Derek Stone
no team (Charger Robotics)
Team Role: CAD
 
Join Date: Mar 2011
Rookie Year: 2010
Location: Sussex, WI
Posts: 41
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Re: pic: 2 Speed Switching Module

Quote:
Originally Posted by sdcantrell56 View Post
That's exactly what I was saying. The whole purpose of engineering and math and theory is so you don't have to experiment to determine if basic systems are going to work or work well. If you want to throw away money on a less than optimized prototype then no one will stop you but if you take the literally 3 minutes required to run basic calculations to determine your traction limited wheel speed you will save precious time in the long run and end up with a much better performing module.
The calculations were done today with some help from two physics majors, so hopefully they were correct.
CIM normal load = 4320 rpm
Torque = 64 in-oz’s
Ff= (c.o.f.) * Fnorm
T= r * Ff
Ratio between high and low gears is approximately 1:2.5
These numbers were calculated using the max weight of a full robot , 150 lbs.
4” Traction Wheel (C.o.f. = 1.25 – 1.5)
Low- 1:30 gear ratio, 6000 in-oz’s torque, 2.5 ft/sec, 144 rpm ( before slipping occurs at 6056 oz-inches)
High- 1:12 gear ratio, 2500 in-oz’s torque, 6.3ft/sec¸ 360 rpm


6” Omni Wheel (C.o.f. =1)
Low- 1:18 gear ratio, 4000 in-oz’s torque, 6.0ft/sec, 230 rpm
High- 1:7.4 gear ratio, 1800 in-oz’s torque, 15.25ft/sec, 580 rpm
(forward/backward direction only)

Slipping occurred at 10.7nM and at 12.7Nm depending on the tread material, so these projected ratios have the torque coming in lower than that value. If the math proves to be grossly off the only true loss is in the traction wheel. So the sprocket ratio from Omni to traction would simply be changed and that should solve any issues with stalling or being too slow and not gaining torque. Any corrections of the math are welcomed, better to fix it now before the pieces are made/ordered.

Last edited by crazyStone : 27-09-2011 at 17:24.
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