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      05-26-2010, 12:41 AM   #54

Drives: 2014 Shelby GT500
Join Date: Apr 2008
Location: Vancouver, BC

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For those of you who find this of interest, here's the raw acceleration data that allowed me to build the motion analysis above. The accel data is sampled at 800 samples a second. 980 cm/sec^2 is the force of gravity (one "G"). The max force at the wheel is around 4 G's upward and the max force at the chassis is around 1.8 G's upward and 0 G's (free fall) downward.

Name:  Stock BMW M3 Suspension Acceleration over Speed Bump.jpg
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The position plot of the suspension is computed by integrating the acceleration to calculate velocity, then integrating the velocity to position.

I'm theorizing that the roughly 80 ms (12 Hertz) oscillation in the differential and hub acceleration time-series is actually "hum" from the tire. It was a 235/40x18 Dunlop 3D snow tire when I captured the data back in March. Referring to the motion picture (the first post above) the red wiggly line in the wheel position picture (the "hub" position) drops below zero when the tire sidewall compresses and absorbs the fall of the car as it falls off the back side of the speed bump.

It's amazing what you can see.

Last edited by JAJ; 05-26-2010 at 01:17 AM.