Likely you'd put yourself though the windshield.
--Roger van Hoy
----- Original Message -----
From: "Eastern Sierra Adjustment Svc" <esierraadj@xxxxxxxxxxx>
To: <L-FORWARDLOOK@xxxxxxxxxxxxx>
Sent: Thursday, February 11, 2010 11:20 AM
Subject: Re: [FWDLK] Hissy-fitting brake booster
So, what do you think about the mechanical advantage of installing a
manual pedal to my P/B system,
assuming that the pedal may be a bolt on replacement deal?
Should I try to find one, anyway???
Neil Vedder
Dave Homstad wrote:
On my car, I converted the non-power brakes to PB. I bought my car with
non-power brakes. Then I rebuilt the original wheel cylinders and
linings, turned the drums slightly, and replaced the linings and hoses.
Everything worked OK, but the car required more pedal pressure to stop
than before. A hard stop took both feet. I concluded that modern
off-the-shelf lining materials are designed for power brakes, which seem
to be standard on most everything, and these require more pressure.
Then I installed a factory power brake set up from a parts car. I thought
I could just install the PB pedal, but it didn't fit the old support
structure. So the entire structure got replaced. The master cylinder
didn't even need to be disconnected from the hose, so no bleeding was
necessary. Wth the power brakes, the car now needs half the pedal
pressure to get twice the stopping power of the old system. I am sure
that with the same pedal pressure, such as one foot as hard as possible,
the line hydraulic pressure is much higher. Probably as earlier stated
going from 750 psi non-PB to 1100 psi with PB.
Dave Homstad
56 Dodge D500
---- jrawa@xxxxxxx wrote:
interesting note they published... the line pressures should inevitably
be the same to create the same stopping effect- whether manual or power-
figuring all master cylinders are 1-1/8 bore as are all 6 wheel
cylinders- and, the same amount of fluid [under the same systemic
pressure] would have to be displaced from the master to all cylinders to
achieve stopping pressure, shoes to drum.... i dont buy into higher
line pressure of power brake systems. the position of the pushrod in
relation to the point of pivot of the brake pedal arm is different-
giving a less advantageous aspect ratio of pedal:master piston travel in
a situaution of "manualized" power brakes, the manual ratio has a higher
multiplication ration of applied pedal pressure>piston displacement.
i can attest that the instantaneous line pressure may be higher upon
brake aplication, but a higher systemic pressure would mean nothing more
than the fact that in comparison to pedal pressure- the booster adds
that much more applied pressure- raising line pressure- causing the car
to stop quicker, giving a more touchy pedal [which i feel in my bellows
and cannister booster 57-61s] but by laws of physics, a panic stop would
lock all 4 wheels, which i havent had the wonder of experiencing....
my fastest fwdlk cars run manual discs, one with a fully retrofitted gm
pedal/booster/master assy. other commonly driven fwdlk's have dual
masters in manual and boosted apps... the resto cars all retain single
masters, man and power...
so from the fluid dynamic engineering standpoint- the systemic fluid
pressure is in proportional relativity to applied stopping power....
so.... back to basics, power brake cars stop "sooner" or easier- using
the same components from master to drum, and differ only in pedal apply
ratio and have that good old booster making your footwork a little less
arduous
-----Original Message-----
From: Eastern Sierra Adjustment Svc <esierraadj@xxxxxxxxxxx>
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Sent: Wed, Feb 10, 2010 12:36 pm
Subject: [FWDLK] Hissy-fitting brake booster
Well, for anyone interested, you might recall that my car's
canister-type power
brake booster has been hissing badly, whenever the pedal is depressed,
and
that I'd been quoted O/H prices of several hundreds, and up, for that
work.
When this condition occurs, with our cars, a mere reversion to manual-
braking-effort results, and if so, that is NO big-deal, believe me.
Biggest
PITA is the hissing noise, at red lights (so, don't STOP there, I hear
you say).
As I never like risking sending out an essential part with the car
remaining
undriveable, I bought a flea-pay booster, very economically, which was
claimed
to be in working condition, and sent it out to "Booster Dewey", in
Portland OR
for O/H, at the VERY reasonable cost of $175.00.
They just called and will be returning that guy to me; they say that
they use a very
viscous lubricant to seal up the booster's internal compression.
I've asked them to send me some pics of their representative internal
work, as I may be
praising their product to others. They say that my 'new' booster has
been tested by
them to work like a champ!
So, I may be interested in selling my car's canister to someone who
might be interested
in having IT be O/H'ed, and installed in (one of-) your car(s), too.
Anyway: and here's a question for you Engineering-types: the manual
brakes apparently
have a different configuration of the brake pedals/system, from the
power brake models (called
the "aspect ratio"--IIRC) which allow for different p.s.i. line pressure
ratings, between the two
systems.
E.G.: according to the 1957 D501 A.M.A. specs, the manual brakes have a
750 p.s.i.
rating, while the power brakes have a 1,100 p.s.i. rating ; a
considerable difference.
(Here it comes: ) so, to what extent would a manual brake car realize
an increase in
braking effort/effect if a power brake's pedal-lever-connections were
to be installed
onto it, and, vice-versa---given, that the master cylinders are
identical, which I
believe that they are????
Neil Vedder
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