Braking Dynamics question- COMPLETLY Theoretical
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From: looking for a flow bench so Brook and I can race
Originally posted by Eric Bryant
You got it. If my buddy and I ran the same tire pressure in our cars of identical weight (we do, at least within a couple PSI or so), the contact patch would be the same size even though I've got much wider tires. However, due to the difference in width, the shape of the patch is different, and the skinnier tires on my friend's car require more carcass distortion/deflection to put down the same amount of rubber. This is one reason why wider tires will generate more traction than skinny ones for a given vehicle weight and tire pressure.
All of this just barely scratches the surface of the traction issue, and after looking back on the topic I think we've gone a bit off-course. From a brake standpoint, generating maximum stopping force actually isn't terribly difficult - if you've got enough force to lock the tires, the thermal capacity to avoid overheating during the particular length and number of stops that you'll be making, and the proportioning to make sure that you don't lock one up prematurely, stopping distance becomes a tire issue and not a brake issue. Generating stopping force isn't a problem, but generating it without a great deal of noise, dust, and wear and in a controlled manner is. Thermal capacity isn't difficult to acheive until you throw in cost and weight targets; oh, and we'd like to be able to stick these brakes behind tiny steel wheels on the base model, too. Proportioning appears to be a real SOB, at least in my (extremely limited) brake design experience. Anti-lock helps to cover up warts in your proportioning scheme, at least to a certain extent.
You got it. If my buddy and I ran the same tire pressure in our cars of identical weight (we do, at least within a couple PSI or so), the contact patch would be the same size even though I've got much wider tires. However, due to the difference in width, the shape of the patch is different, and the skinnier tires on my friend's car require more carcass distortion/deflection to put down the same amount of rubber. This is one reason why wider tires will generate more traction than skinny ones for a given vehicle weight and tire pressure.
All of this just barely scratches the surface of the traction issue, and after looking back on the topic I think we've gone a bit off-course. From a brake standpoint, generating maximum stopping force actually isn't terribly difficult - if you've got enough force to lock the tires, the thermal capacity to avoid overheating during the particular length and number of stops that you'll be making, and the proportioning to make sure that you don't lock one up prematurely, stopping distance becomes a tire issue and not a brake issue. Generating stopping force isn't a problem, but generating it without a great deal of noise, dust, and wear and in a controlled manner is. Thermal capacity isn't difficult to acheive until you throw in cost and weight targets; oh, and we'd like to be able to stick these brakes behind tiny steel wheels on the base model, too. Proportioning appears to be a real SOB, at least in my (extremely limited) brake design experience. Anti-lock helps to cover up warts in your proportioning scheme, at least to a certain extent.
I cant remember if correctly its 7 -10% on the tires for a good rule of thumb.But you are right- proportioning does seem to be a real pita. Caliper size, rotor size and and all that stuff takes an engineer here at the least 8 40 hr days
Yup, just to figure the raduis of the rotor. No wonder it takes 3 years to create a rotor
Someone here developed a program that takes about 2hrs to process all the data and about 4 hrs to enter it for their six sima project. not too shabby, 8 days to 6 hrs. It has its flaws though.
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