On Thu, 1 Apr 2010 05:02:07 -0600, "Pintlar"
wrote:

Many many thanks again, Stealth Pilot.
. . . I don't even feel I need the Cessna manual as your description was so
clear and concise. I feel we'll get it done now on the first pass (4th). I
soldered up a vacumn bottle to hold the fill fluid, and a recovery bottle to
use at the (refrig) vacumn pump to recover the fluid.
. . . Now the biggest problem I see is the terribly small awkward space
under the dash. And the fact that we have to do it a minimum of four times
to be sure to purge all the air from all 4 master cylinders.
Again, thanks. . . . . charlie


hang on a second charlie that doesnt quite make sense.

4????? master cylinders.

if you have braking from both sides of the aircraft, pilot and
passenger/co-pilot, there usually arent 4 master cylinders.

what you should find is that one side will have the reservoirs and the
other side will have a thinner pair of master cylinders. these thinner
ones are the same cylinders but without the reservoirs.

the way it should be connected is that the master cylinder with the
reservoir will be piped with flexible hydraulic hose to the top of the
cylinder without the reservoir. this cylinder then connects to the
slave unit in the wheel. you should be able to confirm this quickly by
looking at the hydraulic line down to the leg. there should only be
one each side.

this is how it works. remember the loose piston I described before.
that is the secret.
in the cylinder without the reservoir when the pilot pushes the toe
brake the rod seals the top of the loose piston and pushes it down
activating the brakes.
if the pilot with the reservoirs also pushes on the brakes his rod
also moves down and seals his loose piston and puts pressure into the
line to the other brakes. if his braking pressure is higher than the
pressure in the non reservoir side his pressure will actually unseat
the other loose piston and push more hydraulic fluid past the unseated
piston and activate the brakes with more force.

when the pilot without the reservoirs takes his feet off the brakes
the piston unseats and the pressure becomes that in the upstream line.
(this means that the pilot can press the brakes and the brakes work)

when the pilot with the reservoirs also takes his feet off the brakes
the entire system depressurises to local atmospheric.

so... with both brakes off you should be able to ignore the presence
of the non reservoir cylinders and just bleed and fill the system as
though there was only the reservoir master cylinders.

this brake arrangement is unique to aviation. I think it is a damn
cunning design!

Stealth Pilot (who illegally fixed his brakes 6 years ago and has 19
years before they need to be done again)