cyclistgo wrote:
RChung wrote:
So the test to determine dependence of Crr on speed is to estimate the coefficients of a model that looks like
Force = A + B*m*g*v + C* v^2
and see whether the coefficient B is different from zero. The problem is that you also think that C is speed dependent, so interpreting B may be hard -- but at least you'd know if dependence was an issue. You might also be able to vary m to separately estimate a Crr dependence and a CdA dependence, but I have to think on that a bit more.
what would it be in this case A, B and C?
Well, I was simplifying. In the usual Martin model, A is an estimate of the quantity Crr*m*g and C is an estimate of the quantity 0.5*rho*CdA. In this case, you'd be testing to see whether B is non-zero. If it is, you'd have to do another test to determine whether it's non-zero because of speed dependence of Crr, of CdA, or of both. I was thinking that would require some variation in m, since rolling drag is affected by mass but CdA isn't.
And, of course, VE is actually designed as a diagnostic for these kinds of things -- and it's pretty sensitive.
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I can find here https://www.tiresciencetechnology.org/....2346/tire.20.190207 that Crr have non-linear relation for velocity above 45 km/h.That's interesting. I'd like to see how they tested. As I mentioned above, I have some data on actual speed runs at Battle Mountain and if the dependence of Crr on speed were large I think it would've shown up. (I was actually kind of surprised when I first saw the data because I was expecting to see a "regime" change in Crr and CdA but I didn't).