Plaction Vs. Banebots Vs. HiGrip friction coefficients

[Dan.Tyler]

Originally Posted by Madison

This is a really strange way of talking about coefficient of friction. The CoF between the materials doesn't change -- it's an experimentally derived constant. I understand what you're getting at with respect to the green material -- it's capable of destroying itself. I do not understand at all what you're saying regarding the orange material.

Can you restate your observation in a manner that reconciles with physics? Can you further explain what you intend to convey by listing two coefficients of friction?

Sorry for the confusion.

What I mean is:

The material has a very high coefficient of friction, but a low physical strength.
Although the material can hold a higher amount of traction, depending on the conditions, it will fall apart.

The friction coefficient in each case is 2.5 for green and 2.1 for orange. Material was removed from a wheel (somewhat used), then weighted down and tested on an incline plane covered in carpet for initial slip/angle to determine CoF.
Specific loading scenarios are required to reach this coefficient without the grip material shredding. Specifically, lightweight bots or lots of wheels (Probably why colsons aren't 0.8" wide...)

In our lightweight bot from last year (sub 100lb with bumpers and battery), we could only realize the lower number (~2.0) on green before the rubber started shaving off, leaving debris similar to what pencil erasers leave behind. We still had tons of traction, but it tore the wheels up some to operate in this regime.

For the orange wheels, if you test it for shear strength, mechanically bonding or restraining the material above its traction limit, it will fail at around 240lb in shear with the cross-section that is on a wheel. The greens will start to fail in shear at about 200lb with the cross-section that is on a wheel.

So... you have more than enough traction available to push people out of the way. But you'll burn up your wheels doing it if you push too much, too often.



Tl;dr i was giving both experimental and real-world coefficients in an extremely confusing manner. If I still don't make sense... sorry.