Thread: Swerve Concept
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Unread 01-07-2014, 19:34
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Re: Swerve Concept

Quote:
Originally Posted by jimbo493 View Post
2 Wheels allow for more traction
Quote:
Originally Posted by Greg Woelki View Post
Well keep in mind that, while more wheels will keep the tread pattern from wearing down as quickly, doubling the number of wheels will give only a very minor improvement in traction since, while it is simplified, friction very closely equals N*mu.
Quote:
Originally Posted by Bryce Paputa View Post
On a deformable surface like carpet, the n mu approximation isn't a valid assumption, he'd pretty much need to test it himself with his wheel setup in order to figure out how friction would be effected. With a rough top tread I would think you would get more friction
Quote:
Originally Posted by Greg Woelki View Post
Do you know of any quantitative data that teams have collected about this with different wheels/treads? I have been unable to find any.
MOE just did this test last week. Our test rig was a simple 4 wheel cart with the wheels locked in place. We used 4 inch AM Performance Wheels (1 inch wide) with riveted on blue nitrile*. The cart was first weighed down to 127lb total and dragged with a force gauge. It slipped when the gauge read ~108lb. The test was then repeated with more weight (192lb total) and slipped at ~160lb. We took this to mean that the relationship between weight and force needed to slip was relatively linear as the % increase in force needed to pull was about the same. We then added 4 more identical wheels to the same 4 axles and locked them in place effectively creating a 2 inch wide, 4 inch diameter wheel. The cart was pulled a third time and the reading was ~180lb. This shows that (at least for a 4 inch diameter wheel with blue nitrile) wheel width will certainly give you more traction but it is not anywhere close to 1:1. More like 100% increase in width = 13% increase in traction, so it's worth is still subject to some debate.

We opted to go with the force gauge test because we felt it was safer, easier and more accurate than the ramp test (the cart tended to fall forward off the ramp before it slipped)

*not new, slight wear.
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