[Fot] Brake line question

[Bill Babcock]

Certainly. I spent a considerable part of my life in Nuclear Power plants, and
we used lots of seamless stainless tubing with stainless compression fittings
operating at very high pressure and very high reliability. They require
special tools to cut, shape, and make up that are probably close to the price
of one of our engines. And of course that has absolutely nothing to do wtih
trying to fix a brake line cheaply.


On Jan 22, 2014, at 2:14 PM, Michael Porter <mdporter at dfn.com> wrote:

> On 1/22/2014 12:15 PM, robertten1 at aol.com wrote:
>> Compression fitting(s) in this application will not hold under the
pressure
>> generated in any hydraulic brake system.  Unfortunately you will have
instant
>> brake failure.  Follow the advice of our fellow racers on the list
responding
>> to your question.
>>
>>
>
> Ah, well, let me just throw some sand in these gears for a moment. I think
you're right if you mean _ordinary_ compression fittings, i.e., those suitable
for plumbing work (nominally 100-150 psi) and _ordinary_ steel lines.  Those
together will not produce a safe and satisfactory outcome.  But, to make that
blanket statement is probably incorrect.  There are compression fittings and
lines available from most major manufacturers, SwageLok, Parker-Hannifin,
Aeroquip, etc.,which will greatly exceed the pressure generated by any master
cylinder.  Compression fittings are typically used on CNG fuel systems with
ratings well above the working pressures of 5-6000 psi, five to six times the
maximum pressure generated by most brake systems.  I've seen compression
fittings in high-temperature supercritical fluid applications that worked well
at 600 deg. C and nearly 10,000 psi.
>
> It's a question of cost, and the size of the overall installation. The
fittings are expensive and must be used with precisely-made seamless tubing of
aerospace alloys with very small circumferential TIR, but for the brake lines
in a car, would not be horribly expensive to do--just unnecessary, since there
are safe and suitable alternatives at much lower cost.  I think it also would
be a pain in the ass to find the necessary adapters from SAE or DIN to British
flare to mate the lines to the operating bits, but not impossible.
>
> Cars, for the most part, have the benefit of not being very long, so single
pieces of tubing can be used throughout, requiring no splices if the tubing
material is malleable enough, a necessary feature for cheap mass
manufacturing, so brake system maximum pressures have usually been designed
with that in mind. In fact, single, double and bubble flares are only possible
because the line material is relatively soft and fairly malleable (and
therefore not capable of higher operating pressures).  Line materials and
fittings have generally followed that practice from the advent of hydraulic
brakes. That's what makes the usually available equipment suitable for the
task, rather than compression fittings being unsuitable.
>
>
> Cheers.
>
> --
>
>
> Michael Porter
> Roswell, NM
>
>
> Never let anyone drive you crazy when you know it's within walking
distance....
> _______________________________________________
> fot at autox.team.net
>
> http://www.fot-racing.com
>
> Donate: http://www.team.net/donate.html
> Archive: http://www.team.net/archive
> Forums: http://www.team.net/forums
> Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/billb@bnj.com