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Unread 02-06-2005, 02:43
sanddrag sanddrag is offline
On to my 16th year in FRC
FRC #0696 (Circuit Breakers)
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Join Date: Jul 2002
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Re: Most Impressive/Advanced/Unique/Cool drivetrain you've ever seen

Quote:
Originally Posted by santosh
Okay thanks a lot. What are the advantages of that over 4 wheels? I guess you use lss motors, but isn't it more stable with 4 wheels?
I don't know if it is really an advantage or disadvantage but I will point out one difference between the two.

With 3 wheels at 120* intervals when going straight forward you have only 2 of the 3 motors driving. But each of the two motors is getting roughly 86% of it's speed being applied in the forward direction.

With 4 wheels at 90* intervals when going straight forward (or sideways or backward) all 4 motors are driving but you are getting roughly 70% of the speed of the motors being applied to the direction of travel.

So I suppose you could say 3 wheels is more efficient because there is less vector cancellation.

With 4 wheels it is naturally square while with 3 wheels it is naturally triangular

4 wheels/motors gives more traction

3 wheels/motors looks cooler?


When it comes down to it, I don't see any reasons for picking 3 over 4 other than less weight and less power consumption and possibly greater speed for the same gearing. If anyone has any other benefits of only 3 wheels I'd sure like to hear about them.

The main reason I'm building mine with 3 is so I can use one of these nifty little doo-dads http://www.robotlogic.com/product_omx3.html So I don't have to program a thing.
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Teacher/Engineer/Machinist - Team 696 Circuit Breakers, 2011 - Present
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Technical Mentor, Team 696 Circuit Breakers, 2005-2007
Student Mechanical Leader and Driver, Team 696 Circuit Breakers, 2002-2004