|
Re: Frictional Discrepancies
Doing an incline plane test with four wheels and a frame we found almost no difference between the lateral and transverse static COF as measured by the angle of the incline. We are using the correct surface too.
Just to make it clear:
1. Point the locked wheels down the incline and gradually raise one end of the surface until the frame breaks free slides down. Measure the height at which the frame breaks free (8.5" over a 6ft sheet). This is a measure of the lateral static COF (tan of the angle between the horizontal and the incline). Our result is around 0.12 or an angle of 6.7 degrees.
2. Turn the frame 90 degrees. The wheels are now sideways down the slope. Repeat test. This is the transverse static COF.
Our result 8.5 - 9". Almost the same as the lateral value.
We expected that the heights of the two tests should almost be a factor of two or more different given 0.6 and 1.4 as the printed static COFs.
Can other teams please repeat this test and report the angles they are finding for both lateral and transverse static friction.
__________________
Andrew Nicholson
2011 FRC Robot Inspector (Seattle, Portland)
Mentor FRC 1778 "Chill Out", FTC 3018, 3940 "Hawks", 4434 "Heat Misers"
"Everything should be made as simple as possible, but no simpler."
|