Quote:
Originally Posted by wyatt
Is there a simple way to get the viscous drag component? I have seen where people get the rolling resistance by warming up their car and stopping in a level area (parking lot), and then either push or pull the car with a scale to see what the resulting rolling resistance would be. Would a person be able to get the rolling resistance this way, and then calculate the viscous drag from the equation above? It should work. Is there a more simple way? Does viscous drag account for much, or is it able to hide in the cDA component ealily?
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As one is bound to find (from all of the discussions in this forum), there are no simple solutions. But there are rules of thumb.
In a spreadsheet that I have developed (its a beast!), I do include the viscous component - and guestimated it to be ~1 for a 2-wheel drive vehicle (where F(viscous) = cV*v (v in [m/s]). It could be ignored, but will have an influence on the standard pair of coast-down tests (high speed and low speed). Hint: (greater than) 3-speed coast down tests will show this minor factor (did this in uni many years ago w/ driveshaft torque measurement and data logger).
This is notably small when compared to the other two inputs:
eg. '90 Firefly:
@ 25 m/s:
F(friction) = 81.3N (cF = 0.010, m = 830kg)
F(viscous) = 25.0N
F(aero) = 236.3N (cD = 0.36, A = 1.75m^2)
[Disclaimer: YMMV, above numbers may or may not simulate real life, ...]