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

[Mike]

<sigh> Adam,

WHy are you so damn dogmatic, ironic you are active
on this user group or maybe you are looking at this
and trying to talk me out of even considering something
you are exploring ~`:o

At 10:51 PM 5/12/2002 -0800, you wrote:
>--- Mike <erazmus at iinet.net.au> wrote:
>
>> Moving the caliper back by a short amount does not
>> *have to* mean the pedal travel is increased at all.
>
>Maybe the laws of physics are different in Australia
>than here.

Doubt it, has nothing to do with that paradigm, have you not 
heard of accumulators, solenoids, surge tanks and the like,
this in concert with electronic controls does not mean
relationships have to be fixed - ah la movement of caliper
meaning a certain movement of pedal in symmetry - after
all we use vacuum assisted brakes on most cars and this
doesnt change the laws of physcis - they are exploited
to achieve a result - *obviously* the aim I have is not
fixated on a symmetrical setup...

>Here, to take up air gap, the piston in the caliper
>has to move a like amount.  Which means fluid has to
>be moved through the lines in sufficient quantity to
>push the piston out that much.

Yes *and* it *can* be diverted - who said it has to follow
the same lines and path when the pedal is at its highest
or prior to applying pressure from that 1mm or so of travel
most pedals seem to have to actuate the switch for the lights ?

>I already gave some sample math.

Which is irrelevant unless you are fixated on an unsophisticated
system which doesnt care whether the pedal is at its highest
or any other discontinuous relationship is speculated upon
to give the required result.

>> 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' ;)
>
>Not a sensible example to be using to prove your
>conclusion.  With little or no pressure in the system,
>the master cylinder piston is fully retracted, and has
>a mechanical stop.  A bleed from the master cylinder
>allows return of excess fluid into the reservoir.

I didnt use that to prove anything, I used it to
illustrate that it need not be a symmetrical relationship
and as I also suggested - some combination of accumulators
and the like might well be worthy considering, even more
so when one appreciates there is a switch on the pedal
which goes to the brake lights, this could double as
asolenoid changeover or release an accumulator to send
back the very same qty of oil retracted so one doesnt
have to have the symmetrical oil flow you seem to be fixated
upon as being the concrete issue we cannot change !

The rest of your response is irrelevant and not worthy of
response as you seem to be fixated on a fully symmetrical
unsophisticated arrangement, here was I thinking there might
be a respondent who observed the ABS discussion and might
consider a sophisticated solution rather then someone fixated
on 'if it aint broke dont fix it', sure some brake systems
may well have been static - that does not give reason for
people not think of exploring alternatives, strange you
are on this list then if that is one of your core philosophical
tenets in approach to considering issues requiring speculation
outside normal parameters.

It should be obvious to anyone why one would want to minimise
pad drag on an economy run of 3000 Kms...

So can anyone suggest a discontinuous setup which might
(for example, one possible) return the oil that was retracted to achieve
the minimal additional pedal push prior to full application
and still achieve satisfactory brake operation when required ?

It might well be complex or <sigh> a bit more sophisticated then
the 'olden' ways of doing things which you dont seem to want to
entertain - but hey whats wrong with thought along those lines ?

rdgs

mike


>Using your example, what happens the first time you
>step on the brake pedal after pushing the caliper
>pistons back in?  What makes you think that would be
>any different if the pushing (or pulling) was done by
>something other than a screwdriver or c-clamp?
>
>> I'm not sure what you mean be being reminded - I
>> dont understand this at all.
>
>No offense, but that is becoming increasingly
>apparent.  ;)  You will get the same result as you
>would prying the pistons back into the calipers during
>a pad change, and then stepping on the brakes the
>first time -- a long, sloppy pedal travel without full
>pressure at full stroke of the master cylinder piston 
>(or not, if you are lucky).
>
>> a.	Normal pedal operation when braking
>> and
>> b.	Some hydraulic arrangement to retract the pads
>> from the discs to *be sure* there is negligible
>> chance of drag
>
>Those two objectives are directly opposed.
>
>I still don't see why you want no drag from the pads. 
>What is it you are hoping to gain?
>
>> In terms of 'if it aint broke dont fix it' I think
>> you should be speaking to religious dogmatic groups
>> who are not interested in how technology could be
>> improved with a little thought and not to people
>> interested in alternate solutions and improving on
>> what has gone before.
>
>*sigh*  I've had this discussion here before.  If you
>want to get worse results with a great deal more
>expense and difficulty, more power to you, but don't
>expect anyone else to have spent a lot of time doing
>it, and thus being able to tell you how.  You'll
>probably have to spend a lot of time and money
>experimenting to come to the same conclusion that
>aircraft components manufacturers did half a century
>ago when they came up with production disc brakes that
>have stayed static in design for that time period.
>
>*snip remainder of insulting rant from one who
>apparently hasn't had to spend time and money
>developing something useful*
>
>The point of development, resumably, is to devote an
>appropriate amount of time, money and effort to obtain
>a given set of results.  If you wish to aim for
>different goals, by all means, but insulting people
>who take a practical approach certainly isn't going to
>help you reach your goals.
>
>=====
>| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
>|   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
>| "It was like an emergency ward after a great catastrophe; it  |
>|   didn't matter what race or class the victims belonged to.   |
>|  They were all given the same miracle drug, which was coffee. |
>|   The catastrophe in this case, of course, was that the sun   |
>|     had come up again."                    -Kurt Vonnegut     |
>
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