brake pedal force to lock up wheels
brake pedal force to lock up wheels
(OP)
On a single seat 1400 lb. offroad race car what do you think would be a good brake pedal force to lock up the wheels. Its a two master cylindar system with no power assist. I was using a coeficient of friction of .8 assuming dry asphalt, which would be the highest friction situation this car would experience.





RE: brake pedal force to lock up wheels
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RE: brake pedal force to lock up wheels
Cheers
Greg Locock
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RE: brake pedal force to lock up wheels
RE: brake pedal force to lock up wheels
Don't take my answer to seriously. I attempted to match the OP level of effort and clarity before posting.
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RE: brake pedal force to lock up wheels
The OP was merely seeking a sensible starting point for his own calculations. Greg's 110 Lb upper limit sounds about right too.
RE: brake pedal force to lock up wheels
A fit professional driver should be able to muster considerably more, but may not be able to maintain it for the duration of a race.
Of course an off road race car would rarely be on asphalt for any substantial time, and required forces would be lower on dirt.
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RE: brake pedal force to lock up wheels
Norm
RE: brake pedal force to lock up wheels
There is a broad compromise between being over sensitive, and fatigue after perhaps hundreds of sequential brake applications on a demanding circuit.
The frictional coefficients of both the tires and the brake material will both vary over a range that cannot always be precisely known. But some basis, and a few assumptions for engineering a braking system from scratch, would have to be better than none at all.
RE: brake pedal force to lock up wheels
There is a distinct lack of detail in the OP so we really are guessing.
Also, the system is NOT boosted, so there will be a real compromise of acceptable travel vs acceptable load.
Also being a race car implies it might use stainless steel braided (aircraft type) brake lines. These expand a lot more than rigid steel tube brake lines and lose pedal in the process.
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RE: brake pedal force to lock up wheels
I tried to use a bathroom scale to test it out but the two I have are digital and dont work when they are vertical, who would have guessed? Its hard to find a scale with a dial anymore!
RE: brake pedal force to lock up wheels
They will think you are completely out of your mind, but may humor you if you can come up with a really good story.
Or you could rig up a fifty pound weight to a rope and pulley with a stirrup on the end, and experiment in the privacy of your own home.
RE: brake pedal force to lock up wheels
RE: brake pedal force to lock up wheels
If possible reduce results by 20% to correct for driver putting in extra effort to "pass" the test. It will end up a compromise between pedal force and pedal travel.
I expect a driver will adapt to lighter pressure easier than heavier pressure at the levels required for a disk brake unboosted system.
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RE: brake pedal force to lock up wheels
It is quite easy to lock up the wheels on this buggy even on pavement. The toggle joint provides light pressure for most use and the end of travel toggle action really clamps down when necessary.
Just from our testing I would guess there is about 50 pounds force for most use and maybe 75 for the full locking action. It is very easy to hold the brake pedal down by hand maybe 40 pounds and the buggy can be dragged with the wheels locked on pavement.
I tested 40 pounds hand force at about the same angle with the bathroom scale and that's about what the pedal pressure is. We did the scale measure test blind for "accuracy".
99 Dodge CTD dually.
RE: brake pedal force to lock up wheels
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.