Braking Bias effects on a Road Race Car
03-18-2009, 06:13 PM
#63
Rennlist Member
Thread Starter
Good explanation. Ive heard that before, but didnt know how that was possible. Thanks.
mk
mk
Dive changes the orientation which changes the accelerometer output. So does driving down a hill. If you park the car at a standstill pointing downhill, the accelerometer isn't going to read 0. If you hang the car with a chain from the rear bumper, even though the car isn't moving, much less accelerating, the accelerometer isn't going to read 0. If you drive a car down the hill at a constant rate of speed (i.e. no acceleration), the accelerometer isn't going to read 0. The accelerometer is zeroed based on a stationary car on a flat surface.
No one is arguing that, all other things being equal, a car won't take more time to stop in a downhill braking zone than it will to stop in a flat braking zone. That's a given. That will obviously lower the rate of deceleration. But, because the car is pointing downhill (and experiencing dive), your accelerometer is going to read a higher rate of deceleration than the car is actually experiencing.
No one is arguing that, all other things being equal, a car won't take more time to stop in a downhill braking zone than it will to stop in a flat braking zone. That's a given. That will obviously lower the rate of deceleration. But, because the car is pointing downhill (and experiencing dive), your accelerometer is going to read a higher rate of deceleration than the car is actually experiencing.
03-18-2009, 08:29 PM
#65
Rennlist Member
Thread Starter
But i dont know squat about the telemetry sensors. I guess if it is just an accelerometer, then it makes perfect sense. tilt an accelerometer on its toward the ground and it will show 1g
mk
mk
03-18-2009, 10:54 PM
#66
Three Wheelin'
There you go. Now since the hill has a known slope you can calculate the expected offset to the accelerometer with...f=ma. Same thing will happen with pitch and roll motions although the angle is very small and can be assumed to be neglible. Most hills can be considered neglible, but once you get beyond roughly ten degrees the effect will be measurable.
03-18-2009, 11:08 PM
#67
Rennlist Member
03-18-2009, 11:10 PM
#68
Rennlist Member
03-19-2009, 09:37 AM
#69
Rennlist Member
What would be the best way to add an adjustable controller to a stock brake configuration ? (similar to what Mark and I have)
Is there a system available that can be adjusted from inside the car on the fly?
Thanks,
Ken
Is there a system available that can be adjusted from inside the car on the fly?
Thanks,
Ken
03-19-2009, 09:58 AM
#70
Drifting
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If I were driving a stock based system, I'd consider removing any pressure limiting bias device installed by the factory and then using an in-line device to the rear brakes so that I could make the adjustment on my own.
Here are mulitple options:
http://www.pitstopusa.com/SearchResu...CategoryID=577
You should be able to find them from your favorite race parts supplier.
Last edited by Bryan Watts; 03-19-2009 at 01:51 PM. Reason: me speelll baad
03-19-2009, 02:47 PM
#72
I love all the science, my son is a physisisiststst (I am not).......one question though from a low tech point of view.
Am I wrong or is it true that with the proportion type bias all you can do is LESSEN the amount of braking to get the right bias?
Am I wrong or is it true that with the proportion type bias all you can do is LESSEN the amount of braking to get the right bias?
03-19-2009, 02:56 PM
#73
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03-19-2009, 03:25 PM
#74
Three Wheelin'
There is another way to accomplish this but it involves an ABS system. You don't necessarily need to control from lockup, but you can cap the pressure in the rear axle to your preference. It could "match" the bias you would use otherwise.
03-19-2009, 03:28 PM
#75
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Yeah...the problem is that the cost of programmable ABS is prohibitive. I've got someone who is an expert on doing the programming. Just don't have the funds to afford the hardware.