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Unread 09-12-2013, 15:57
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JVN JVN is offline
@JohnVNeun
AKA: John Vielkind-Neun
FRC #0148 (Robowranglers)
Team Role: Engineer
 
Join Date: May 2001
Rookie Year: 2000
Location: Greenville, Tx
Posts: 3,159
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Re: Omni vs Mecanum CoF ?

Quote:
Originally Posted by gpetilli View Post
Thanks John for the quick reply. That helps clarify things, and I agree that incline method is best.

Would I be possible to update the specifications with the side CoF for your wheels? It would help greatly with part selection verses other vendors. Is there a good way for measuring dynamic CoF? I am simply assuming 85% of static.

BTW: we just received shipment of 4 VEXpro 6" Omnis and we were very impressed with the design and build quality. Assuming the 2014 game is appropriate, we intend to use them for an asymmetric Killough drive.
I will look into posting the sideways CoF. I don't believe we tested that when we did our experimentation last year.

Our omni directional wheels should have very very low CoF Side-Side, since we're pretty happy with how freely the rollers spin.

Unless I'm missing something, using the locked-wheel test, shouldn't the Mecanum Side-Side be identical to front-back? (Isn't that the simplifying virtue of a 45-degree angle?)

Regarding a method to measure dynamic CoF -- one method I've used in the past is:
Get the robot sliding, using the incline test. Slowly reduce the amount of tilt until it stops moving. Measure the angle and calculate like normal.

Out of curiosity -- what sort of design are you doing for FRC which requires dynamic CoF?
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In the interest of full disclosure: I work for VEX Robotics a subsidiary of Innovation First International (IFI) Crown Supplier & Proud Supporter of FIRST