bleeding Duo Discus brakes

On Jan 16, 1:56*pm, Morgan wrote:
This pretty much nails what ended up working for me. *I ended up
removing the whole system from the ship and flushing it forwards and
backwards to make sure there wasn't any old fluid or particles in the
system. *Popped the piston out and inspected it and the cylinder wall
for corrosion and pitting. *Overall things looked pretty good, but it
got a good cleaning while I was in there.

Funny, you'll jump through all sorts of hoops and delays to avoid
doing it the "hard way" and in the end that was the least traumatic
and fastest way to get it to work. *It took me way longer than it
should have, but the upside is that I know my braking system inside an
out now and it is time for new pads as well.

Thanks for the tips.

Morgan

On Jan 16, 9:23*am, rhwoody wrote:



On Jan 11, 12:30*am, Morgan wrote:

Looking for advice on bleeding the brakes on my Duo with the tost 30-9
caliper. *I replaced a shot bleeder valve with a new stahlbus valve,
but after futzing with the system for over an hour, I can't get the
brake to firm up to an acceptable level.

I've tried using a suction device to pull fluid (Dot 4 in the Duo)
down through the line. *I've also gone with my normal old standby of
pushing fluid up through the brake using a syringe. *The Stahlbus
valve is not working as advertised or rather the brake isn't. *The
brake doesn't seem to be creating enough pressure to overcome the
spring tension on the check valve.

The best I've been able to get to so far is a fairly spongy grip on
the rotor. Enough that turning by hand isn't possible, but it doesn't
feel like it would slow you down much when you needed it.

Basically it just doesn't feel like the master cylinder is drawing
fluid in or maybe there is a hidden air bubble.

Any thoughts from the internet hive on the quirks of this beast?
It's certainly been a much greater hassle than I expected. *I'm
guessing at this point that either there is a trick that I don't know
about or something is malfunctioning.

Thanks,

Morgan

Hi All, *I have owned a lot of SH gliders and have had success doing
the following -
unbolt the brake cylinder and raise it up so there is no "loop" in the
brake line -
so the path from the brake calipers to the brake cylinder goes only
uphill -
first try to actuate the brake cylinder lever - sometimes this will
"burp" the air
bubble up into the brake cylinder - otherwise fill fluid from the
bottom nipple
until the air bubble goes into the brake cylinder reservoir - *most
times the
air bubble will burp into the reservoir and no filling is necessary -
good luck,
Ralph Woodward- Hide quoted text -

- Show quoted text -

Changing the fluid every 6 or 8 years is a very good idea. I checked
my system last year by having a helper (wife) pump the master cylinder
a few strokes and then hold the pressure as I bled out the pressure at
the brake.............just like we did in the 1934 Ford. You wouldn't
believe what came out, thick gooey stuff that wasn't even red anymore!
I had to repeat this for several cycles before the bled fluid started
showing red fluid. I also replace my pads when they show less than
1/8" which can be easuly seen with a flashlight and mirror.
Cheers,
JJ

On Jan 16, 6:05*pm, JJ Sinclair wrote:
On Jan 16, 1:56*pm, Morgan wrote:





This pretty much nails what ended up working for me. *I ended up
removing the whole system from the ship and flushing it forwards and
backwards to make sure there wasn't any old fluid or particles in the
system. *Popped the piston out and inspected it and the cylinder wall
for corrosion and pitting. *Overall things looked pretty good, but it
got a good cleaning while I was in there.

Funny, you'll jump through all sorts of hoops and delays to avoid
doing it the "hard way" and in the end that was the least traumatic
and fastest way to get it to work. *It took me way longer than it
should have, but the upside is that I know my braking system inside an
out now and it is time for new pads as well.

Thanks for the tips.

Morgan

On Jan 16, 9:23*am, rhwoody wrote:

On Jan 11, 12:30*am, Morgan wrote:

Looking for advice on bleeding the brakes on my Duo with the tost 30-9
caliper. *I replaced a shot bleeder valve with a new stahlbus valve,
but after futzing with the system for over an hour, I can't get the
brake to firm up to an acceptable level.

I've tried using a suction device to pull fluid (Dot 4 in the Duo)
down through the line. *I've also gone with my normal old standby of
pushing fluid up through the brake using a syringe. *The Stahlbus
valve is not working as advertised or rather the brake isn't. *The
brake doesn't seem to be creating enough pressure to overcome the
spring tension on the check valve.

The best I've been able to get to so far is a fairly spongy grip on
the rotor. Enough that turning by hand isn't possible, but it doesn't
feel like it would slow you down much when you needed it.

Basically it just doesn't feel like the master cylinder is drawing
fluid in or maybe there is a hidden air bubble.

Any thoughts from the internet hive on the quirks of this beast?
It's certainly been a much greater hassle than I expected. *I'm
guessing at this point that either there is a trick that I don't know
about or something is malfunctioning.

Thanks,

Morgan

Hi All, *I have owned a lot of SH gliders and have had success doing
the following -
unbolt the brake cylinder and raise it up so there is no "loop" in the
brake line -
so the path from the brake calipers to the brake cylinder goes only
uphill -
first try to actuate the brake cylinder lever - sometimes this will
"burp" the air
bubble up into the brake cylinder - otherwise fill fluid from the
bottom nipple
until the air bubble goes into the brake cylinder reservoir - *most
times the
air bubble will burp into the reservoir and no filling is necessary -
good luck,
Ralph Woodward- Hide quoted text -

- Show quoted text -

Changing the fluid every 6 or 8 years is a very good idea. I checked
my system last year by having a helper (wife) pump the master cylinder
a few strokes and then hold the pressure as I bled out the pressure at
the brake.............just like we did in the 1934 Ford. You wouldn't
believe what came out, thick gooey stuff that wasn't even red anymore!
I had to repeat this for several cycles before the bled fluid started
showing red fluid. I also replace my pads when they show less than
1/8" which can be easuly seen with a flashlight and mirror.
Cheers,
JJ

I've been unable to get the Duo wheel brake to work as it should. This
includes removing the entire system (caliper, lines, master cylinder)
and operating it on the bench with a piece of metal to simulate the
disc. In this configuration it works great - rock hard "brake pedal."
But it has to be disassembled to go back in the glider, and there it
is spongy again, no matter how much or how you bleed it. I thought the
problem might be partial retraction of the pucks due to temperature
changes, "potato chipped" disc, or vibration, so installed small
springs behind the pucks to keep them lightly against the disc. No
improvement.

It helps to pump up the brake with the stick mounted brake lever if
you have one, while in the landing pattern. Or cycle the air brakes
fully if you don't have the stick grip.

Another wheel brake problem with the Duo is a fundamental mechanical
issue. The force required to cycle the speed brakes all the way open
to the wheel brake actuation point gets higher as you slow down. While
flying at pattern speed the spoilers stay open by air pressure, but as
you slow down on the ground they get heavier as air speed no longer
helps keep the handle back. With little or no airspeed the amount of
force required to pull the handle all the way back is considerable,
with little left over to apply brake.

One solution I've employed for the latter is a long bungee cord that
pulls back on the spoiler handle. But this has a couple significant
safety issues that must be addressed. It must not be hooked up until
landing, and the pilot must then keep his/her hand on the spoiler
handle. A better procedure is to have the back seater help with the
pull.

On Jan 16, 7:39*pm, Karl Striedieck
wrote:
On Jan 16, 6:05*pm, JJ Sinclair wrote:





On Jan 16, 1:56*pm, Morgan wrote:

This pretty much nails what ended up working for me. *I ended up
removing the whole system from the ship and flushing it forwards and
backwards to make sure there wasn't any old fluid or particles in the
system. *Popped the piston out and inspected it and the cylinder wall
for corrosion and pitting. *Overall things looked pretty good, but it
got a good cleaning while I was in there.

Funny, you'll jump through all sorts of hoops and delays to avoid
doing it the "hard way" and in the end that was the least traumatic
and fastest way to get it to work. *It took me way longer than it
should have, but the upside is that I know my braking system inside an
out now and it is time for new pads as well.

Thanks for the tips.

Morgan

On Jan 16, 9:23*am, rhwoody wrote:

On Jan 11, 12:30*am, Morgan wrote:

Looking for advice on bleeding the brakes on my Duo with the tost 30-9
caliper. *I replaced a shot bleeder valve with a new stahlbus valve,
but after futzing with the system for over an hour, I can't get the
brake to firm up to an acceptable level.

I've tried using a suction device to pull fluid (Dot 4 in the Duo)
down through the line. *I've also gone with my normal old standby of
pushing fluid up through the brake using a syringe. *The Stahlbus
valve is not working as advertised or rather the brake isn't. *The
brake doesn't seem to be creating enough pressure to overcome the
spring tension on the check valve.

The best I've been able to get to so far is a fairly spongy grip on
the rotor. Enough that turning by hand isn't possible, but it doesn't
feel like it would slow you down much when you needed it.

Basically it just doesn't feel like the master cylinder is drawing
fluid in or maybe there is a hidden air bubble.

Any thoughts from the internet hive on the quirks of this beast?
It's certainly been a much greater hassle than I expected. *I'm
guessing at this point that either there is a trick that I don't know
about or something is malfunctioning.

Thanks,

Morgan

Hi All, *I have owned a lot of SH gliders and have had success doing
the following -
unbolt the brake cylinder and raise it up so there is no "loop" in the
brake line -
so the path from the brake calipers to the brake cylinder goes only
uphill -
first try to actuate the brake cylinder lever - sometimes this will
"burp" the air
bubble up into the brake cylinder - otherwise fill fluid from the
bottom nipple
until the air bubble goes into the brake cylinder reservoir - *most
times the
air bubble will burp into the reservoir and no filling is necessary -
good luck,
Ralph Woodward- Hide quoted text -

- Show quoted text -

Changing the fluid every 6 or 8 years is a very good idea. I checked
my system last year by having a helper (wife) pump the master cylinder
a few strokes and then hold the pressure as I bled out the pressure at
the brake.............just like we did in the 1934 Ford. You wouldn't
believe what came out, thick gooey stuff that wasn't even red anymore!
I had to repeat this for several cycles before the bled fluid started
showing red fluid. I also replace my pads when they show less than
1/8" which can be easuly seen with a flashlight and mirror.
Cheers,
JJ

I've been unable to get the Duo wheel brake to work as it should. This
includes removing the entire system (caliper, lines, master cylinder)
and operating it on the bench with a piece of metal to simulate the
disc. In this configuration it works great - rock hard "brake pedal."
But it has to be disassembled to go back in the glider, and there it
is spongy again, no matter how much or how you bleed it. I thought the
problem might be partial retraction of the pucks due to temperature
changes, "potato chipped" disc, or vibration, so installed small
springs behind the pucks to keep them lightly against the disc. No
improvement.

It helps to pump up the brake with the stick mounted brake lever if
you have one, while in the landing pattern. Or cycle the air brakes
fully if you don't have the stick grip.

Another wheel brake problem with the Duo is a fundamental mechanical
issue. The force required to cycle the speed brakes all the way open
to the wheel brake actuation point gets higher as you slow down. While
flying at pattern speed the spoilers stay open by air pressure, but as
you slow down on the ground they get heavier as air speed no longer
helps keep the handle back. With little or no airspeed the amount of
force required to pull the handle all the way back is considerable,
with little left over to apply brake.

One solution I've employed for the latter is a long bungee cord that
pulls back on the spoiler handle. But this has a couple significant
safety issues that must be addressed. It must not be hooked up until
landing, and the pilot must then keep his/her hand on the spoiler
handle. A better procedure is to have the back seater help with the
pull.- Hide quoted text -

- Show quoted text -

I have had similar problems with the Grob 103, just couldn't get the
air bubble to break loose. You might try tilting the fuselage as far
as possible (away from the brake side), then bleed the brakes. This
might allow the bubble to rise up to the master cylinder.
See you at Parowan,
JJ

Originally Posted by JJ Sinclair[_2_]

On Jan 16, 7:39*pm, Karl Striedieck
wrote:
On Jan 16, 6:05*pm, JJ Sinclair wrote:





On Jan 16, 1:56*pm, Morgan wrote:

This pretty much nails what ended up working for me. *I ended up
removing the whole system from the ship and flushing it forwards and
backwards to make sure there wasn't any old fluid or particles in the
system. *Popped the piston out and inspected it and the cylinder wall
for corrosion and pitting. *Overall things looked pretty good, but it
got a good cleaning while I was in there.

Funny, you'll jump through all sorts of hoops and delays to avoid
doing it the "hard way" and in the end that was the least traumatic
and fastest way to get it to work. *It took me way longer than it
should have, but the upside is that I know my braking system inside an
out now and it is time for new pads as well.

Thanks for the tips.

Morgan

On Jan 16, 9:23*am, rhwoody wrote:

On Jan 11, 12:30*am, Morgan wrote:

Looking for advice on bleeding the brakes on my Duo with the tost 30-9
caliper. *I replaced a shot bleeder valve with a new stahlbus valve,
but after futzing with the system for over an hour, I can't get the
brake to firm up to an acceptable level.

I've tried using a suction device to pull fluid (Dot 4 in the Duo)
down through the line. *I've also gone with my normal old standby of
pushing fluid up through the brake using a syringe. *The Stahlbus
valve is not working as advertised or rather the brake isn't. *The
brake doesn't seem to be creating enough pressure to overcome the
spring tension on the check valve.

The best I've been able to get to so far is a fairly spongy grip on
the rotor. Enough that turning by hand isn't possible, but it doesn't
feel like it would slow you down much when you needed it.

Basically it just doesn't feel like the master cylinder is drawing
fluid in or maybe there is a hidden air bubble.

Any thoughts from the internet hive on the quirks of this beast?
It's certainly been a much greater hassle than I expected. *I'm
guessing at this point that either there is a trick that I don't know
about or something is malfunctioning.

Thanks,

Morgan

Hi All, *I have owned a lot of SH gliders and have had success doing
the following -
unbolt the brake cylinder and raise it up so there is no "loop" in the
brake line -
so the path from the brake calipers to the brake cylinder goes only
uphill -
first try to actuate the brake cylinder lever - sometimes this will
"burp" the air
bubble up into the brake cylinder - otherwise fill fluid from the
bottom nipple
until the air bubble goes into the brake cylinder reservoir - *most
times the
air bubble will burp into the reservoir and no filling is necessary -
good luck,
Ralph Woodward- Hide quoted text -

- Show quoted text -

Changing the fluid every 6 or 8 years is a very good idea. I checked
my system last year by having a helper (wife) pump the master cylinder
a few strokes and then hold the pressure as I bled out the pressure at
the brake.............just like we did in the 1934 Ford. You wouldn't
believe what came out, thick gooey stuff that wasn't even red anymore!
I had to repeat this for several cycles before the bled fluid started
showing red fluid. I also replace my pads when they show less than
1/8" which can be easuly seen with a flashlight and mirror.
Cheers,
JJ

I've been unable to get the Duo wheel brake to work as it should. This
includes removing the entire system (caliper, lines, master cylinder)
and operating it on the bench with a piece of metal to simulate the
disc. In this configuration it works great - rock hard "brake pedal."
But it has to be disassembled to go back in the glider, and there it
is spongy again, no matter how much or how you bleed it. I thought the
problem might be partial retraction of the pucks due to temperature
changes, "potato chipped" disc, or vibration, so installed small
springs behind the pucks to keep them lightly against the disc. No
improvement.

It helps to pump up the brake with the stick mounted brake lever if
you have one, while in the landing pattern. Or cycle the air brakes
fully if you don't have the stick grip.

Another wheel brake problem with the Duo is a fundamental mechanical
issue. The force required to cycle the speed brakes all the way open
to the wheel brake actuation point gets higher as you slow down. While
flying at pattern speed the spoilers stay open by air pressure, but as
you slow down on the ground they get heavier as air speed no longer
helps keep the handle back. With little or no airspeed the amount of
force required to pull the handle all the way back is considerable,
with little left over to apply brake.

One solution I've employed for the latter is a long bungee cord that
pulls back on the spoiler handle. But this has a couple significant
safety issues that must be addressed. It must not be hooked up until
landing, and the pilot must then keep his/her hand on the spoiler
handle. A better procedure is to have the back seater help with the
pull.- Hide quoted text -

- Show quoted text -

I have had similar problems with the Grob 103, just couldn't get the
air bubble to break loose. You might try tilting the fuselage as far
as possible (away from the brake side), then bleed the brakes. This
might allow the bubble to rise up to the master cylinder.
See you at Parowan,
JJ

Old motorcycle trick is to elevate the mastercylinder and lever then cable tie the lever with some pressure overnight. Any microscopic bubbles will come out then.
Sounds like a more serios issue is at foot though

bagger

On Jan 18, 5:36*pm, bagmaker
wrote:
'JJ Sinclair[_2_ Wrote:





;807799']On Jan 16, 7:39*pm, Karl Striedieck

wrote:-
On Jan 16, 6:05*pm, JJ Sinclair wrote:

-
On Jan 16, 1:56*pm, Morgan wrote:-
--
This pretty much nails what ended up working for me. *I ended up
removing the whole system from the ship and flushing it forwards and
backwards to make sure there wasn't any old fluid or particles in
the
system. *Popped the piston out and inspected it and the cylinder
wall
for corrosion and pitting. *Overall things looked pretty good, but
it
got a good cleaning while I was in there.--
--
Funny, you'll jump through all sorts of hoops and delays to avoid
doing it the "hard way" and in the end that was the least traumatic
and fastest way to get it to work. *It took me way longer than it
should have, but the upside is that I know my braking system inside
an
out now and it is time for new pads as well.--
--
Thanks for the tips.--
--
Morgan--
--
On Jan 16, 9:23*am, rhwoody wrote:--
--
On Jan 11, 12:30*am, Morgan wrote:--
--
Looking for advice on bleeding the brakes on my Duo with the tost
30-9
caliper. *I replaced a shot bleeder valve with a new stahlbus
valve,
but after futzing with the system for over an hour, I can't get
the
brake to firm up to an acceptable level.--
--
I've tried using a suction device to pull fluid (Dot 4 in the Duo)
down through the line. *I've also gone with my normal old standby
of
pushing fluid up through the brake using a syringe. *The Stahlbus
valve is not working as advertised or rather the brake isn't. *The
brake doesn't seem to be creating enough pressure to overcome the
spring tension on the check valve.--
--
The best I've been able to get to so far is a fairly spongy grip
on
the rotor. Enough that turning by hand isn't possible, but it
doesn't
feel like it would slow you down much when you needed it.--
--
Basically it just doesn't feel like the master cylinder is drawing
fluid in or maybe there is a hidden air bubble.--
--
Any thoughts from the internet hive on the quirks of this beast?
It's certainly been a much greater hassle than I expected. *I'm
guessing at this point that either there is a trick that I don't
know
about or something is malfunctioning.--
--
Thanks,--
--
Morgan--
--
Hi All, *I have owned a lot of SH gliders and have had success
doing
the following -
unbolt the brake cylinder and raise it up so there is no "loop" in
the
brake line -
so the path from the brake calipers to the brake cylinder goes only
uphill -
first try to actuate the brake cylinder lever - sometimes this will
"burp" the air
bubble up into the brake cylinder - otherwise fill fluid from the
bottom nipple
until the air bubble goes into the brake cylinder reservoir - *most
times the
air bubble will burp into the reservoir and no filling is necessary
-
good luck,
Ralph Woodward- Hide quoted text ---
--
- Show quoted text ---
-
Changing the fluid every 6 or 8 years is a very good idea. I checked
my system last year by having a helper (wife) pump the master
cylinder
a few strokes and then hold the pressure as I bled out the pressure
at
the brake.............just like we did in the 1934 Ford. You wouldn't
believe what came out, thick gooey stuff that wasn't even red
anymore!
I had to repeat this for several cycles before the bled fluid started
showing red fluid. I also replace my pads when they show less than
1/8" which can be easuly seen with a flashlight and mirror.
Cheers,
JJ-

I've been unable to get the Duo wheel brake to work as it should. This
includes removing the entire system (caliper, lines, master cylinder)
and operating it on the bench with a piece of metal to simulate the
disc. In this configuration it works great - rock hard "brake pedal."
But it has to be disassembled to go back in the glider, and there it
is spongy again, no matter how much or how you bleed it. I thought the
problem might be partial retraction of the pucks due to temperature
changes, "potato chipped" disc, or vibration, so installed small
springs behind the pucks to keep them lightly against the disc. No
improvement.

It helps to pump up the brake with the stick mounted brake lever if
you have one, while in the landing pattern. Or cycle the air brakes
fully if you don't have the stick grip.

Another wheel brake problem with the Duo is a fundamental mechanical
issue. The force required to cycle the speed brakes all the way open
to the wheel brake actuation point gets higher as you slow down. While
flying at pattern speed the spoilers stay open by air pressure, but as
you slow down on the ground they get heavier as air speed no longer
helps keep the handle back. With little or no airspeed the amount of
force required to pull the handle all the way back is considerable,
with little left over to apply brake.

One solution I've employed for the latter is a long bungee cord that
pulls back on the spoiler handle. But this has a couple significant
safety issues that must be addressed. It must not be hooked up until
landing, and the pilot must then keep his/her hand on the spoiler
handle. A better procedure is to have the back seater help with the
pull.- Hide quoted text -

- Show quoted text --

I have had similar problems with the Grob 103, just couldn't get the
air bubble to break loose. You might try tilting the fuselage as far
as possible (away from the brake side), then bleed the brakes. This
might allow the bubble to rise up to the master cylinder.
See you at Parowan,
JJ

Old motorcycle trick is to elevate the mastercylinder and lever then
cable tie the lever with some pressure overnight. Any microscopic
bubbles will come out then.
Sounds like a more serios issue is at foot though

bagger

--
bagmaker

My next attempt to get a solid "brake pedal" will be to unmount the
master cylinder and elevate it so that the brake line is as close to
vertical as possible. As it lies in the ship the line is about
horizontal and not much better with the tail raised. I'll try Bagger's
suggestion as well if necessary.

KS

On Jan 18, 6:44*pm, Karl Striedieck
wrote:
On Jan 18, 5:36*pm, bagmaker
wrote:









'JJ Sinclair[_2_ Wrote:

;807799']On Jan 16, 7:39*pm, Karl Striedieck

wrote:-
On Jan 16, 6:05*pm, JJ Sinclair wrote:

-
On Jan 16, 1:56*pm, Morgan wrote:-
--
This pretty much nails what ended up working for me. *I ended up
removing the whole system from the ship and flushing it forwards and
backwards to make sure there wasn't any old fluid or particles in
the
system. *Popped the piston out and inspected it and the cylinder
wall
for corrosion and pitting. *Overall things looked pretty good, but
it
got a good cleaning while I was in there.--
--
Funny, you'll jump through all sorts of hoops and delays to avoid
doing it the "hard way" and in the end that was the least traumatic
and fastest way to get it to work. *It took me way longer than it
should have, but the upside is that I know my braking system inside
an
out now and it is time for new pads as well.--
--
Thanks for the tips.--
--
Morgan--
--
On Jan 16, 9:23*am, rhwoody wrote:--
--
On Jan 11, 12:30*am, Morgan wrote:--
--
Looking for advice on bleeding the brakes on my Duo with the tost
30-9
caliper. *I replaced a shot bleeder valve with a new stahlbus
valve,
but after futzing with the system for over an hour, I can't get
the
brake to firm up to an acceptable level.--
--
I've tried using a suction device to pull fluid (Dot 4 in the Duo)
down through the line. *I've also gone with my normal old standby
of
pushing fluid up through the brake using a syringe. *The Stahlbus
valve is not working as advertised or rather the brake isn't. *The
brake doesn't seem to be creating enough pressure to overcome the
spring tension on the check valve.--
--
The best I've been able to get to so far is a fairly spongy grip
on
the rotor. Enough that turning by hand isn't possible, but it
doesn't
feel like it would slow you down much when you needed it.--
--
Basically it just doesn't feel like the master cylinder is drawing
fluid in or maybe there is a hidden air bubble.--
--
Any thoughts from the internet hive on the quirks of this beast?
It's certainly been a much greater hassle than I expected. *I'm
guessing at this point that either there is a trick that I don't
know
about or something is malfunctioning.--
--
Thanks,--
--
Morgan--
--
Hi All, *I have owned a lot of SH gliders and have had success
doing
the following -
unbolt the brake cylinder and raise it up so there is no "loop" in
the
brake line -
so the path from the brake calipers to the brake cylinder goes only
uphill -
first try to actuate the brake cylinder lever - sometimes this will
"burp" the air
bubble up into the brake cylinder - otherwise fill fluid from the
bottom nipple
until the air bubble goes into the brake cylinder reservoir - *most
times the
air bubble will burp into the reservoir and no filling is necessary
-
good luck,
Ralph Woodward- Hide quoted text ---
--
- Show quoted text ---
-
Changing the fluid every 6 or 8 years is a very good idea. I checked
my system last year by having a helper (wife) pump the master
cylinder
a few strokes and then hold the pressure as I bled out the pressure
at
the brake.............just like we did in the 1934 Ford. You wouldn't
believe what came out, thick gooey stuff that wasn't even red
anymore!
I had to repeat this for several cycles before the bled fluid started
showing red fluid. I also replace my pads when they show less than
1/8" which can be easuly seen with a flashlight and mirror.
Cheers,
JJ-

I've been unable to get the Duo wheel brake to work as it should. This
includes removing the entire system (caliper, lines, master cylinder)
and operating it on the bench with a piece of metal to simulate the
disc. In this configuration it works great - rock hard "brake pedal."
But it has to be disassembled to go back in the glider, and there it
is spongy again, no matter how much or how you bleed it. I thought the
problem might be partial retraction of the pucks due to temperature
changes, "potato chipped" disc, or vibration, so installed small
springs behind the pucks to keep them lightly against the disc. No
improvement.

It helps to pump up the brake with the stick mounted brake lever if
you have one, while in the landing pattern. Or cycle the air brakes
fully if you don't have the stick grip.

Another wheel brake problem with the Duo is a fundamental mechanical
issue. The force required to cycle the speed brakes all the way open
to the wheel brake actuation point gets higher as you slow down. While
flying at pattern speed the spoilers stay open by air pressure, but as
you slow down on the ground they get heavier as air speed no longer
helps keep the handle back. With little or no airspeed the amount of
force required to pull the handle all the way back is considerable,
with little left over to apply brake.

One solution I've employed for the latter is a long bungee cord that
pulls back on the spoiler handle. But this has a couple significant
safety issues that must be addressed. It must not be hooked up until
landing, and the pilot must then keep his/her hand on the spoiler
handle. A better procedure is to have the back seater help with the
pull.- Hide quoted text -

- Show quoted text --

I have had similar problems with the Grob 103, just couldn't get the
air bubble to break loose. You might try tilting the fuselage as far
as possible (away from the brake side), then bleed the brakes. This
might allow the bubble to rise up to the master cylinder.
See you at Parowan,
JJ

Old motorcycle trick is to elevate the mastercylinder and lever then
cable tie the lever with some pressure overnight. Any microscopic
bubbles will come out then.
Sounds like a more serios issue is at foot though

bagger

--
bagmaker

My next attempt to get a solid "brake pedal" will be to unmount the
master cylinder and elevate it so that the brake line is as close to
vertical as possible. As it lies in the ship the line is about
horizontal and not much better with the tail raised. I'll try Bagger's
suggestion as well if necessary.

KS

That's the tactic I finally chose. The biggest hassle is dealing with
the handbrake cables when you reconnect them, but total time to pull
the master cylinder was only a few minutes. Excluding the seat
removal, but I already had that out for cleaning the glider for it's
annual. With the master cylinder free and practically a vertical run
from the caliper to the master cylinder, I was able to get good
pressure and a firm pedal, but I'll see tomorrow when I get the new
pads installed and can properly adjust the brake throw with the dive
brakes.

I've always had powerful brakes on my Duo until the last time I flew
it and they were a bit spongy. Just felt like they needed bleeding
though.

I've certainly learned way more about the braking system in the Duo
than I'd thought I'd need to know for a "simple" bleeding job.

Lots of snippage


Old motorcycle trick is to elevate the mastercylinder and lever then
cable tie the lever with some pressure overnight. Any microscopic
bubbles will come out then.
Sounds like a more serios issue is at foot though

bagger




--
bagmaker

Does air dissolve in brake fluid? Wouldn't pressurizing the system
overnight cause the air bubbles to dissolve only to come out later after the
pressure is relieved? This is the reason for decompression during deep
dives.

My glider has a mechanical brake (which works quite well, thank you), but on
my motorcycles, I service the brakes with an oil can full of brake fluid. I
draw off as much fluid as I can from the master cylinder and then, using the
oil can, pump it up from the bleed valve at the caliper. It's pretty easy
on the bike to remove the caliper and hold it so that the hose is at the
top, allowing the air to go up the brake line to the master cylinder where
it'll escape as a bubble.

I have nearly the same problem on my V2C. 2 seasons ago I noticed
something dripping from the vent hole in the bottom of the fuselage.
Until then my brake had been rock hard. Inspection showed that yellow
brake fluid was leaking from the master cylinder and gum had formed
around the master. Fluid probably 14 years old. I could not find a
revision set and decided to buy a new Magura master (from the
motorcycle store, used on many BMWs). Instead of a 20mm master, I got
a 16mm master.
The 16mm master should only give a bit more travel. Re-installed and
had the same described spongyness. Took the Cleveland caliper apart
and observed significant corrosion on the caliper, less on the piston.
Sanded carefully a bit, installed new O-ring and re-mounted. Still the
spongyness, even after pumping a pint of new clean fluid both ways (up
and down).
Part of the problem is that the piston retracts a bit upon release of
the brake handle, instead of taking new fluid from the master
reservoir to fill the void.
I need to do more work before the season starts

Question to Bumper:
Can the brass liners and anodized piston be retrofitted ?
Where ?

3U

On Jan 23, 10:03*pm, Three Uniform wrote:
I have nearly the same problem on my V2C. 2 seasons ago I noticed
something dripping from the vent hole in the bottom of the fuselage.
Until then my brake had been rock hard. Inspection showed that yellow
brake fluid was leaking from the master cylinder and gum had formed
around the master. Fluid probably 14 years old. I could not find a
revision set and decided to buy a new Magura master (from the
motorcycle store, used on many BMWs). Instead of a 20mm master, I got
a 16mm master.
The 16mm master should only give a bit more travel. Re-installed and
had the same described spongyness. Took the Cleveland caliper apart
and observed significant corrosion on the caliper, less on the piston.
Sanded carefully a bit, installed new O-ring and re-mounted. Still the
spongyness, even after pumping a pint of new clean fluid both ways (up
and down).
Part of the problem is that the piston retracts a bit upon release of
the brake handle, instead of taking new fluid from the master
reservoir to fill the void.
I need to do more work before the season starts

Question to Bumper:
Can the brass liners and anodized piston be retrofitted ?
Where ?

3U

I saved this link last time Bumper recommended it.
http://www.brakecylinder.com/index.htm

Good luck with the brakes. You may want to look at replacing the
brake line. The one SH used was disintegrating & the brake works much
better after replacing it with a stainless braided unit. The Hot Rod
crowd has great sources.

http://www.jegs.com/i/JEGS-Performan...ductId=1117442
http://www.jegs.com/webapp/wcs/store... hTerm=670501

Cheers,
Craig