Re[2]: Aircraft fittings and brake lines

[Richard Welty <rwelty@domain.elided>]

continuing my follow up on this subject:

in a typical track car installation (this setup is a legal one in an SCCA
IT car, by the way), you will end up with something like the following:

adapters from metric 10x1.25 to 3AN at each caliper and the master
cylinder.

remove the fixed proportioning valve altogether.

make replacement hardline for the front two calipers, following the same
route as the OE ones. the passenger side line may be tricky with the engine
in place. splitting it into two lines with a fitting in the middle would be
easiest unless you have the motor out.

the way the hard line works is this: you buy 3/16" brake line (bundyweld is
best; i've used a lot of NAPA and occasionally have problems with seams
splitting. bundyweld is seamless.) straighten out sections as you need
them (it comes coiled in a box), and then bend to fit using a tubing bender
like the one i mentioned earlier. at the ends, file smooth where the tubing
cutter was used (you do own a tubing cutter, don't you), fit the tube
sleeve bits over the end, and then flare.

to join hard line to hard line, and hard line to flex line, use a bulkhead
adapter. these are 3AN-3AN fittings with a little extra thread and a nut
cast in; you put them through a bracket or a bulkhead with washers and a
nut, and then screw hard or flex line on either side.

bulkhead adapters are available in both straight and in 90 degree bend
variants, there are also bulkhead tees which might, for example, be used in
the rear of a transaxle car to split to the rear calipers.

in the front wheel wells, the way to hook the hard lines up to the flex
lines is to put a straight bulkhead fitting in the existing bracket, and
attach the hard line on one side and the flex on the other.

for the lines to the rear, i take those through the firewall with a
bulkhead fitting (a 90 degree bend on the engine side makes this easier)
and run the line down the transmission tunnel. this way, you can plumb an
adjustable proportioning valve in the middle near the shift lever and the
handbrake. no, it's not as nice as as the fancy dual master cylinder
setups with the adjustable lever for proportioning, but it's a much easier
install and the dual master setups aren't legal in SCCA IT racing.
the inexpensive proportioning valves may have pipe thread; pipe thread to
AN adapters are available. the pipe thread will be the only place you use
teflon tape or pipe dope in the entire setup. teflon tape and pipe dope are
basically pointless on flare fittings which is what the rest of the system
is.

take the line down through the floor in the rear some place convenient for
the plumbing to the rear brakes. dispense with the original bias bit under
the floor if you have installed the adjustable unit up above. plumb to the
rear brakes in a generally similar pattern to what was done up front,
modulo any physical variations (e.g., in the transaxle cars, you only have
one flex line from the body to the transaxle case, and hard lines to the
calipers. if the hard lines to the calipers are in good shape, you may just
want to install an adapter at the existing T and not change the hard lines
from the T to the calipers. i did this out of expedience in my IT car, and
someday i'll get around to replacing those last two hard lines.)

any questions?

richard
--
Richard Welty                                         rwelty@domain.elided
Averill Park Networking                                         518-573-7592
              Unix, Linux, IP Network Engineering, Security
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