ASRA - Australian Skateboard Racing Association

Ballpark figures for coefficient of friction of wheel urethanes?

Hiiiiii everybody!

I'm trying to put together some more interesting Physics tutorial questions on friction using longboard wheels. I can't find anything on coefficients of friction of urethanes. I know it's like asking how long is a piece of string and the range is going to be huge, but does anyone have a ballpark figure for COF of a fairly generic 80A urethane for example? A datasheet? Anything? The info just isn't out there - at least nowhere I can find it.

Fitz.....I'm expecting at least some sort of reply from you at some point....

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Here's a case of some bird going arse-over in heels on a concrete slab - polyurethane heel on shoe (not sure the durometer rating of her shoes - sorry) - seems to suggest somewhere between 0.35 and 0.55

http://www.tandfonline.com/doi/abs/10.1080/13599370010060140#preview

I think that you you may have to calculate it your self, I know that I did a few of them for different wheels on different surfaces, the main problem is that urethane acts differently on different surfaces. I'm pretty sure I threw away my results.

coefficients are dependant on both surfaces, so no one can just give you the COF of an 80a wheel. you would need it in relation to a surface.

Yeah, I realise it depends on surface, wheel shape, mould release, time of day, gender, mood, the number of spanners in a Sidchrome toolkit.....

I'm just trying to figure out a realistic number - e.g. car tyres are typically 0.7 on dry bitument so would longboard wheels be similar around the 80A mark?

It's given me a good idea for an open-ended prac anyway. Hey kids, here's a bunch of wheels, a durometer and a force gauge.....get busy!

Deeks, thanks for the link. Doesn't say if it was a dress shoe or sneaker. The sole hardness would be very different.

try and make sure that when they are measuring force that they are doing it parallel to the ground or that they measure the angles other wise they will get hugely varied results.

You need to get onto Trikes in Hobart, he is the Man when it comes to this sort of stuff. You should be able to message him on here or through the Tasmanian Gravity sites

hi this may be a bum lead but i worked in the ureathane industry for a company called wear resistant materials we did industrial coatings for mainly the mining industry but coateded everything from aircraft to grain terminals.but back to the point we applied the to reduce wear in agitators and drill equipment huge peices of machenery they would possibly have that sort of info on there fact sheets use to have copies but tossed them years ago. we also sold what we called 80c and 90c to nolathane to make car bushes

80 c being the softer of the two

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