Tost Disk Brake rebuild?

On Apr 16, 8:46 am, Greg Arnold wrote:
Why does Tost change the parts to use DOT fluid?

Which glider manufactures use brakes that take the red stuff, and which
use DOT fluid?

bumper wrote:
Paul,

As Gary Evans mentioned, there are basically two brake fluids used in
gliders. The "red stuff" Mil Spec 5606 oil (which most GA aircraft use) and
DOT # automotive type fluid. 5605 wants to have Buna-N seals and O-rings
while the DOT fluid uses EPDM rubber.

You mentioned corrosion and this raises some flags. Cleveland parts, that
Tost uses - changing the rubber parts to EPDM, were never really intended
for use with DOT fluid. The problem is that DOT fluid is hygroscopic and
whatever moisture gets into the fluid can corrode the bare aluminum surfaces
of the caliper and piston (later pistons were anodized and this helps some).
To find out if the piston is anodized, see if it conducts when touched with
the leads of an ohm meter as the anodize surface is an insulator.

If you have corrosion in the caliper bore or in the O-ring groove of the
piston, you will likely have leakage again, probably sooner than later. One
fix is to have the caliper bore machined and brass sleeved along with
anodizing the piston.

If anyone needs a free EPDM O-ring (for DOT fluid) for the Cleveland 300
series caliper, contact me via email (bumperm at att dot fish net) - remove
the scaley thing) to get the address to send a self-addressed stamped
envelope.

bumper
Quiet Vent - reduces vent noise by 10 dba

"Paul Cordell" wrote in message
...
It's Done!

Thanks Dave Nadler and Uncle Hank for the off-line notes.

This Soaring community is always surprising. I talked to Monty@ M &
H Soaring this morning about the spec's for the Pads and O-ring.
Then went over to Aircraft Spruce to get the parts. After I looked
at their web site, I still had some questions about the rivets. I
called a buddy that is an ex '20 owner and RV-7 builder to ask about
the rivets. He lives about 100 miles away. As we talked, he
walked out to his Hanger and went thru some stuff on his work
bench. He had exactly the parts I needed. When would you like to
do this he asked?? I told him that if he wanted to "help", it would
be on his schedule........He responded, I'll be there in an Hour. He
was and did the whole job as I "supervised". Cleaned and polished,
pads and ring with a full bleed and new fluid. The system in general
was in good shape. Just slight corrosion and some gunk. I
supplied him with 1 soda for all the trouble. He'll be back next
weekend for a test flight.

Paul

I've wondered myself - Possibly for compatibility with the master
cylinder components scavenged from motorcycles ?

Beringer systems use DOT fluid (and work extremely well,
and are light). I had an HP that used the red stuff. I don't know
about other glider hydraulic brakes out there.
The Cleveland adaptations are, um, a bit problematic...

See ya, Dave