[Diy_efi] (off topic) Disk pad wear reduction with hydraulic reverse

[Shannen Durphey]

Mike wrote:
> 
> No, I think your wires are crossed a bit here...
> 
> Moving the caliper back by a short amount does not *have to*
> mean the pedal travel is increased at all. Of course it might
> well do that in an unsophisticated arrangement.
> 
> Eg. When I service the brakes, the pedal is in its top (normal)
> position. Yet when I remove the pads, I can push on the calipers
> a little - they will retract - say 1mm, yet the pedal does not
> move, the oil clearly goes 'somewhere' ;) Why cant this type
> of paradigm be replicated under control when pedal is released
> in normal operation,

There are many newer GM cars that use a "quick takeup" master cylinder. 
The caliper piston seals are designed to pull the piston back slightly on
release of the breakes to reduce drag.  The master effectively incorporates
a 2 stage pump, in that the initial portion of pedal travel is pushing a
large volume of fluid at a lower pressure.  As the pressure increases, a
smaller (read "the usual" ) volume of fluid is moved by the high pressure
pump.

The fluid does go "somewhere."  It returns to the master cylinder just like
any traditional brake system.

> 
> I am thinking the equivalent should be possible to achieve by some
> valving or solenoid arrangement - which obviously is not going to
> be directly coupled to the pedal travel in terms of length of
> travel, there may well be some
> accumulator arrangement which is a bellows/alternate piston ect
> which could well work off engine vacuum etc To achieve the desired
> result.

Don't bother re-inventing the wheel.  Change the master cylinder.  Quick
takeup types are sometimes identifiable by a portion of the casting that
makes up the body of the cylinder near the mounting flange being larger
diameter than the rest.  They should be in junkyards aroud the country. 
The design is over ten years old.
Shannen

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi