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Brakes and Physics.
At 08:59 PM 3/25/2002, Christian Els wrote:
>Go here: <http://www.stoptech.com/technical/> and become enlightened.
>
>These guys make a living at this stuff, and many satisfied customers will
>tell you they have it right.
Dammit Christian! :) You should have posted that a half-hour ago -- it
would have saved me 10 pages of typing. :)
Jason
>Cheers,
>
>
>Christian Els
>1987 Scirocco 16V, For Sale
>www.schnellpc.com/scirocco.htm
>
>
>
>----- Original Message -----
>From: "Brian McGarvey" <brianm@zbt62.eastnet.gatech.edu>
>To: <scirocco-l@scirocco.org>
>Sent: Monday, 25 March, 2002 19:40
>Subject: Brakes and Physics.
>
>
> > Ok Folks...
> > I got tired of the argument. So I've whipped out the Physics book. Any
> > ME's out there or ppl
> >
> > that are better at ACTUAL REAL non-Relativistic or mumbo jumbo my ass
> > tells me... physics
> >
> > feel free to pop in.
> >
> > Disclaimer... most things exemplified here are in normal braking
> > conditions. ie. you have not
> >
> > done two footed driving for say 20 or 30 min. or heavy braking to get the
> > fluid near the
> >
> > boiling point.
> >
> > #1. The brake linings in our cars are better now then ever before. If you
> > brakes are turing
> >
> > to shit. Go buy race or near compound brake linings. You have to replace
> > em more often, but
> >
> > they do work and they make big messes. The race linings will behave more
> > like ideal friction
> >
> > surfaces than most.
> >
> > #2. There is nothing else at all in the system that can expand or
> > compress. Period. As the
> >
> > volume of fluid gets reduced in container A it goes into the other
> > containers ie. your wheel
> >
> > clynders.
> >
> > Basic PHYSICS lesson. (yes im on my soapbox)
> > A vehicle moving has inertia. It takes the same amount of WORK to stop the
> > vehicle in a given
> >
> > length. ie. F=ma
> > if you solve for a then it is a = F/m
> >
> > the m is constant or very near constant as a small change of less than .1%
> > is not going to
> >
> > make a difference in this calculation.
> > So that means that in order to get a larger negative acceleration a larger
> > F is required.
> >
> > Assumption. Your tires are not crap. Your tires are relatively sticky. ie
> > they have a decent
> >
> > coeffienct of friction and maximum force point before they turn to
> > dust/liquid/gas.
> >
> > so now you are trying to increase the force to increase the negative
> > accleration. no mind you
> >
> > were are still living in the linear force section of the friction curve.
> >
> > (FORCE lesson)
> > IF the force applied to the disc is constant. the ONLY method for
> > increasing the torque
> >
> > applied to the rotating mass is to increase the distance from the center.
> >
> > If you want to increase the force in the exsisting caliper and disc you
> > basic choices are.
> > -- depress the pedal farther but past the point where the master clyn is
> > empty.
> > -- increase the lever arm of the pedal (less force by you.)
> > -- move a larger volume of fluid. ie a larger master clyn diameter and the
> > same bore length.
> > -- longer bore length (more pedal travel) same diameter
> > -- or a combination of increasing bore diameter or length.
> > -- this whole master clyn description basically boils down to more volume
> > in the master clyn
> >
> > so now you know that to get more force with the same pads, calipers, and
> > discs it takes a
> >
> > bigger master clyn to get more force.
> >
> > What does increasing the size of the rotors/discs do?
> > by using the SAME size calipers on a larger diameter disc with the same
> > CONTACT patch. ie.
> >
> > the Force being applied to the brakes using the same master clyn and
> > caliper are the same,
> >
> > but the distance from the center of the disc is now longer. so now with a
> > little simplified
> >
> > physics magic. Im sure the ME's here will expand on the physics.
> >
> > so there..
> >
> > and fade can occur for several basic reasons.
> >
> > * the amount of force at the wheel decreases due to losses in the system
> > -- ie. the master clynder hits the stops and has no more volume of fluid
> > to press.
> > -- losses can be due to a leaky master clyn, leaky wheel clyn.
> > -- the rubber hoses expanding enough to lower the volume of fluid
> > transferred to the
> > wheel clyn there by reducing the force applied.
> >
> > * the coefficient of friction decreases at the disc/lining interface.
> > -- get better pads.
> > -- cool the system.
> >
> > * the coefficient of friction decreases at the road/tire interface.
> > -- drive on better roads <VBG>
> > -- get stickier tires... and no complainin' metzler
> > ME-1 CompK's last 1500 - 5000 miles(not a miss print) and are
> > 150 - 200 a Tire.
> > but hey you can leave a thumb print in em after riding around
> > the block.
> > they actually pick up loose dirt. Ive gone thru two sets in a
> > riding season before
> >
> > ________speculation below ________________
> >
> > does improving the front brakes alone make a difference.
> > I suppose its time to try it out.
> > we'll have to have everybody with all the diff combinations all get the
> > same pads.
> > change em. and bed them in properly. verify that all brake systems work
> > properly.
> > and do panic brake tests on the runway measuring distance. with different
> > drivers swapping
> >
> > cars.
> >
> > but my prediction based on the number of times ive panic braked on
> > motorclcyes where i get to
> >
> > actually modulate the rear brakes seperately from the front is that as
> > long as the rear
> >
> > brakes are adjusted properly according to the bently the larger brakes in
> > the front will
> >
> > decrease the stopping distanc.
> >
> > make more passes
> >
> >
> > brian
> >
> >
> >
> > _______________________________________________
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> > Scirocco-l@scirocco.org
> > http://neubayern.net/mailman/listinfo/scirocco-l
>
>
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