From: "Chris Kent Kantarjiev" <emory!parc.xerox.com!cak>
X-Source: The Hotrod Mailing list
Date: Apr 1993
Subject: Re: Brake line 
X-Sequence: 5077

Of course, Scott Griffith will probably pipe up hear and swear against
the double flare. I have a quote here somewhere from a different list
(the > part is the original message and the non-> part is Scott). 

[On Jan 29, Scott.Griffith@eng.sun.com wrote:]

On Jan 29, John Lupien wrote:

> I have a double-flare kit. It also does single-flares. I have about a
> 50% success rate in making a good double flare. So on any given run of
> line, I have about a 25% chance of getting two good double flares.
> My hit rate for single flares is closer to 95%, so I get a good pair
> of single-flares about 90% of the time. This means that double-flare
> lines are quite annoying to make by comparison. 

Right- if you're still trying to seal to an SAE 45deg flare. This
usually has a male-threaded tube nut that bears directly on the OD of
the flared tube- so you need a double flare to help control galling
that can result in stress cracking right at the flare. In short, you
need "give" there. Problem is, the deformation that results is kind of
irreversible, so the next cycle or two will result in your having to
use astronomical torques to keep the flare from weeping. It's even
worse if you use a single flare in an SAE flare nut and seat, and
worse still if the seat is brass- the flared tube is sqaushed from
both sides, even as it is deformed by the nut galling on it. The brass
seat deforms and work hardens. It may seal _once_, with a ton of
torque and some luck. I've done it (to repair a split hard line), but
I felt _very_ spooky about it and got it outta there ASAP.

The AN single flare is an entirely different kettle of fish. It is
still a concave flare, but its 37deg angle seals by stretching, not
squashing.  And the tube is supported by a separate sleeve that the
female-threaded tube nut bears upon. This isolates the flare from the
torques imparted by the nut. So rather than trying to get a seal
despite the presence of rotating torques and the resulting galling,
you press the flare between precisely-machined (steel!) seat and
precisely-machined support sleeve.  The sealing area under compression
is at least double that of the SAE flare.

This works a hell of a lot better. An additional bonus is that the OD
of the nut is a lot larger than the 3/8" of an SAE nut, which means you
won't kill as many trying to get the proper sealing torque. Even so,
I'd still never attack _any_ tube nut without using a flare nut
wrench.

The SAE stuff was designed to go together once on the assembly line,
and then be "immortal", as defined by Detroit. It's pretty good at it,
too! The AN stuff is designed for field serviceability, long fatigue
life, and a level of bulletproofness the SAE never considered. It
could be worse- we could be talking about the ISO "bubble" flares,
which I've still never successfully made yet- and not for lack of
trying. 

The whole reason I harp on repeatability and multiple mate-demate
cycles is that, to the best of my knowledge, I have never once put
something on the car, and had it _stay_ put on. I always forgot
something, or broke something during the season, or needed to swap out
something because it was at the end of its service life. Race cars
ain't Detroit, thank Gawd.

> Regarding performance, on the other hand, although I have never
> experienced a failure on either type of flare, the double-flare has that
> nice "squish" feeling as you tighten the flare nut, that indicates to me
> that it is getting a superior seal. It's like the difference between a
> steel washer and an aluminum crush washer on the oil drain plug: the
> steel doesn't crush, and although if you torque it enough it seals, the
> crush washer seals better at a lower torque.

Just wait'll you try the AN stuff- the torque required for a seal
during the _second_ mating cycle is the same as that required the
first.

-skod

From: emory!Eng.Sun.COM!Scott.Griffith (Scott Griffith, Sun Microsystems Lumpyware)
X-Source: The Hotrod Mailing list
Date: Apr 1993
Subject: Re: Brake Lines - Copper
X-Sequence: 5092

On Apr 21, Timothy Collins wrote:

>      Isn't it true that copper tubing is available for brake lines which is
> much different than the copper tubing available from the hardware store?

The copper-looking tubing you can get for brake plumbing is actually
mild steel with a very thin copper cladding on the OD. This helps in
corrosion resistance, and also helps the line seal if used in a double
flare- the soft copper cladding deforms and seals on the brass seat.

This is one of the reasons that people have sometimes gotten confused
about what kind of hard line is acceptable. They see the copper
cladding, and assume that pure copper is the right stuff. Most
hardware store folks aren't astute enough to ask what application
they're using it for, or know the difference, so they end up building
unsafe brake systems. It does happen...

I once fished a very nicely turned out Formula Atlantic out of a
tirewall at Lime Rock when a pure copper brake line broke at a
fitting. Turns out the car's previous owner had used some to
field-repair crash damage, and had sold the car without changing it
out. Since then, I have advised friends who are buying used race cars
to take a magnet to any coppery-looking lines, just in case. If it
doesn't stick, inspect it _very_ closely- it may be copper-clad
stainless, but it probably isn't. But I'm wierd about my braking
systems, after all. I like them to _work_.

-skod

--
Scott Griffith, Sun Microsystems Lumpyware
expatriate SCCA New England Region Flagging/Communications worker
(and sometimes driver, of anything that turns both right and left,
and can pass tech...) Return Path : skod@sun.COM

From: emory!Eng.Sun.COM!Scott.Griffith (Scott Griffith, Sun Microsystems Lumpyware)
X-Source: The Hotrod Mailing list
Date: Apr 1993
Subject: Re: Brake lines
X-Sequence: 5149

On Apr 28, The Hotrod List wrote:

> Well, after the recent discussion on SAE versus AN flares for
> brake line plumbing, I twisted off and bought the Rol-Aire
> flare tool from Aircraft Spruce. As I read the instructions
> on this little $80. wonder, I noted with some consternation
> that it is not for use on steel or stainless steel line.

I'll look at the poop sheet that came with mine, if I can still find
it, tonight. I remember no such prohibition on mine. Anyway- if you're
not supposed to use it for steel or stainless, then the Rol-Aire folks
will just have to come and haul me away, kicking and screaming. I've
been using it on both steel and stainless, wth uniformly good success,
since 1987. That's about 8 cars' worth of flares.  Haven't hurt the
tool or myself yet. I'd say go for it, and ignore the instructions.

By the way, I was originally turned on to the tool for steel hard
lines by reading Carroll Smith's car prep series, and he intimates
that it's his tool of choice for flaring steel. So if it's good enough
for him...

> Also, you can buy AN tube nuts, sleeves and fittings in either
> aluminum or steel. What is the best mix for converting a SAE
> brake system to AN. I assume aluminum would be okay for the
> tube nuts and sleeves, but what about the adaptor fittings and
> tees that are required for the rest of the hardware? Any 
> comments or suggestions?

Steel. Steel everywhere. Nuts, sleeves, tees, unions- everything. In a
pinch, there are some brass fittings that can be used, but _only_ if
the steel equivalents aren't available. Not even the weight-mad F1
guys use aluminum- they go straight from steel to titanium.

The aluminum stuff isn't really suitable for brake use, at least for a
heavy car that sees roadracing duty. Some light cars may use it, or
cars that seldom use their brakes (sprint cars sometimes use it). You
can make a judgement call based on the weight of the car, and its
intended use, but in my book the braking system is the wrong place to
shave ounces...

The only aluminum I use is in the castings that I can't get away from,
and I keep a _very_ close eye on the threads for the banjos and
nipples. Brake system pressures can get well up there, and the
cyclical loading is not your friend.

-skod

--
Scott Griffith, Sun Microsystems Lumpyware
expatriate SCCA New England Region Flagging/Communications worker
(and sometimes driver, of anything that turns both right and left,
and can pass tech...) Return Path : skod@sun.COM

From: emory!Eng.Sun.COM!Scott.Griffith (Scott Griffith, Sun Microsystems Lumpyware)
X-Source: The Hotrod Mailing list
Date: Apr 1993
Subject: Re:  Brake line
X-Sequence: 5073

On Apr 20, James Swonger wrote:

>  I've seen brake line advertised by the roll; can't remember just where. A
> mag like Cars & Parts or other restoration-oriented, advertising-heavy
> magazine should have enough leads.
>
>  Brake lines use a double flare (the end is folded in so the flare has two
> layers and the outside becomes the inner sealing face) and in all my tool
> shopping, scrounging and scavenging I've yet to find a double flaring
> tool. I don't think either single flare or compression unions will stand up
> to high pressure as well as the double flare.

Amen on this topic. The only fittings to use for brake plumbing are
either SAE double flare, ISO metric (bubble) flare, or preferably AN
37deg single flare. And the only hard line to use is real honest to
Gawd Bundyweld or the equivalent- you can get it in 20 foot rolls from
many vendors, such as Pegasus, Aircraft Spruce, and your friendly
neighborhood dirt-track store, for about $8. I always trade at the
local circletrack hangout, primarily because I like the people, and
secondly because you can't beat the prices.

_Never_ use compression fittings for brake plumbing. I have a further
rule that I use, which is to never use anything but steel fittings.
For my track car, I've purged all the SAE double flare fittings out of
the plumbing except for the two I'm stuck with at the master cylinder-
everything else is AN single flares, and 3AN tube nuts and sleeves. It
was a lot of work, but the parts are universally available at every
race shop in every backwater in the country, so I know I can get what
I need.

Good flaring tools are easy to come by. Get the catalog from:

Aircraft Spruce and Specialty Company
201 West Truslow Ave.
Fullerton, Ca 92632
714-870-7551

This company specializes in selling stuff to aircraft homebuilders-
which makes it an exellent source for wierd tools, small quantities of
raw materials (ever try to buy just 2 feet of 4130 chromoly tubing
before?), GOOD hardware (meaning NAS and AN mil/aero-spec fasteners)
and other nifty arcane thinguses. If you are in a part of the country
that doesn't have places that sell to us crazed enthusiast-types, you
need this catalog.

They have the Rol-Aire Imperial, which is the flaring tool of choice
for 37deg AN single flares, and several SAE and ISO flaring tools as
well. I forget whose SAE tool I use- it's basically rusting from
neglect now.

I'll put in this next part even though I know most readers of this
list know this already, since the topic of compression fittings has
come up. If I save even one person from making a big mistake, this
will be worth the bandwidth wasted:

Under no circumstances use pure copper tubing in brake or fuel
plumbing, despite the fact that it is easily available and appears to
be easy to work with. The problem is that it work-hardens and becomes
very, very brittle- especially at flare fittings. Under the cyclical
loadings seen from brake applications, and in the presence of moisture
(and possibly high concentrations of chlorides, if you live in a road
salt area), they will almost certainly fail. They will tend to crack
and fail right at the flare, generally with little or no warning.

[Well said.  Copper also catalyzes the auto-oxidation of fuel, the
mechanism of sludge formation.  Copper should never be in contact
with fuel.  JGD]

There, I feel better. Best of luck!

-skod

--
Scott Griffith, Sun Microsystems Lumpyware
expatriate SCCA New England Region Flagging/Communications worker
(and sometimes driver, of anything that turns both right and left,
and can pass tech...) Return Path : skod@sun.COM