Actually the same pressure over a smaller area would result in a smaller net
force applied to the pads.
Brake hydraulic pressure is independent of slave cylinder size. Pressure is
given by the ratio of the force applied to the master cylider piston and its
diameter. (50 lbs appied to a 1/2 inch square surface = 100 lbs/inch
square). The force applied to the brakes is that pressure multiplied by the
area of the slave cylinder. The ratio of the master to slave cylinders gives
the amount of travel required to actuate the system. Thus if the area of the
slave is 3 times the master, then the slave will travel 1/3 the amount the
master travels. However this ratio will have no impact on the pressing force
once the slave is tight against the pads and disk. That force, as previously
mentioned, is entirely dictated by the pressure from the master multiplied
by the slave piston area.
The reason that one cannot have enormous forces applied to the disks is that
the pedal travel becomes unreasonable. With a tiny master cylinder piston
and a huge slave cylinder one could press the disks flat. However one would
arrive at a ridiculous situation of a multi-foot pedal travel giving a
micrometer movement of the pads. Bearing movement would soak that up
immediately.
Mark Hooper
72 TR6
-----Original Message-----
From: Joe Curry [mailto:spitlist@gte.net]
Sent: Wednesday, June 20, 2001 10:51 AM
To: Randall
Cc: Jim Gambony; Cwn74@aol.com; tedtsimx@q1.net; MJSUKEY@cs.com;
fot@autox.team.net; Triumphs@autox.team.net
Subject: Re: GT-6/Spitfire brakes
Actually, The question came up in relation to the clutch slave rather than
brakes. The delimma I had was whether to use a larger or smaller slave
cylinder. The explanation I got is that since the pressure exerted by the
master cylinder was constant, the smaller slave cylinder would receive that
constant pressure spread out over a smaller area and therefore give more
force than a larger cylinder.
Think about it this way: If the master and slave cylinders were the same
size, the force of your foot would be what is driving the clutch. As the
size of the slave is reduced and the master left alone, the resulting
pressure on the clutch would increase. Therefore, smaller creates more
pressure
in relation to the master. I can't find any fault with that argument.
oe
Randall wrote:
>
> Joe :
>
> It gets confusing here, since there are many different places to measure
> pressure.
>
> The force exerted by a hydraulic piston is the hydraulic pressure times
> the area of the piston. So, if the system pressure stays the same, a
> larger slave piston means more force applied to the shoes.
>
> Perhaps your authority said the _pedal_ pressure (or the hydraulic
> pressure), would be higher with a smaller cylinder (for the same braking
> force). Or, perhaps he was talking about the master cylinder (where a
> smaller piston gives you more braking force for the same pedal
> pressure).
>
> Randall
>
> Joe Curry wrote:
> >
> > Someone (who is supposed to know these things) once told me that if you
use a smaller wheel (or slave) cylinder, you will actually get a higher
> > pressure than if you use a larger one. It makes sense to me since the
ratio between the size of the master and slave cylinders is what determines
the
> > pressure exerted on the thing that the hydraulics are driving.
> >
> > So, would going to a smaller wheel cylinder give you lower pressure?
According to this source, it would be greater.
> >
> > Anyone care to weigh in on this issue?
/// triumphs@autox.team.net mailing list
/// To unsubscribe send a plain text message to majordomo@autox.team.net
/// with nothing in it but
///
/// unsubscribe triumphs
///
|