Master cylinders

[[email protected]]

I have some Gerdes master cylinders that were given to me years ago
which I am just now planning on using. Don't know much about them,
but was wondering if it wouldn't be prudent to have them be rebuilt
( overhauled ) before I use them, since they've been on the shelf for
so long. Is it actually possible to have them be overhauled and would
it be cost effective to do so? Thanks

Neal

[Stealth Pilot[_2_]]

On Fri, 11 Jul 2008 23:59:21 -0700 (PDT), wrote:

>I have some Gerdes master cylinders that were given to me years ago
>which I am just now planning on using. Don't know much about them,
>but was wondering if it wouldn't be prudent to have them be rebuilt
>( overhauled ) before I use them, since they've been on the shelf for
>so long. Is it actually possible to have them be overhauled and would
>it be cost effective to do so? Thanks
>
>Neal

Neal you have a gem there in your hands.they are one of the neatest
little pieces of aviation kit ever invented.

the aircraft brake fluid in them, the red stuff, is not hydroscopic so
it never absorbs moisture. the innards of your master cylinders should
be in absolutely pristine condition. they may need a flush out to
remove accumulated crap but the worst you should find is worn o-rings.

in each side of your brake system there are 3 o-rings. 2 in the master
cylinder and 1 in the wheel puck.
the master cylinder has a feature known as a free piston. this piston
has one o-ring that makes the side seal. in the face of the pushrod is
another tiny o-ring that seals against the face of the free piston
when you apply toe brake to push the piston down.
these are the easiest things in the world to recondition if they are
old but in good nick.
buy the proper o-rings from your local aviation shop, my last ones
were under $aus20 for the 6 o-rings.

getting most of them apart involves taking the circlip out of the top.
this is a standard circlip and is about 3,000 times as stiff as it
needs to be. once you get that out without damaging anything the rest
is easy.
just slide it all apart. take the old o-rings out and put in the new
ones and your "reconditioning" is done. just remember to lube up the
new rings in brake fluid before putting them in position to prevent
nicking them.
reassemble, refill with red aviation brake fluid (actually an
automatic transmission fluid) and you will have pristine reconditioned
master cylinders.

you can find an exploded view of the innards of your cylinders in the
middle of an old cessna repair manual. in the 100 series cessna manual
it is figure 5-23 on page 5-37. it gives a perfect idea of how it all
goes together.

......actually I'm lying. they've been on the shelf for so long now
they'll be totally stuffed. mate I'll take them off your hands for $15
and I'll pay the express postage :-) :-) :-)

Stealth (you have a gem there) Pilot

[Ernest Christley]

Stealth Pilot wrote:

> reassemble, refill with red aviation brake fluid (actually an
> automatic transmission fluid) and you will have pristine reconditioned
> master cylinders.

Excellent post, Stealth, except avoid the red aviation fluid. Well, some of the red aviation fluid. The stuff is
fairly flammable. Many designs use a hard aluminum line down to the brakes. Overform the hard line, and aluminum will
eventually break, and possibly spew flammable brake fluid onto a hot break. If that happens to you, you'll be damn
lucky if you have a quick thinking nephew handy with a gallon just of anti-freeze or some such silly thing.

The airforce got tired for brake fires and had a drop-in replacement formulated with a higher break point. If it is
good enough for the Stealth Fighter, it should be good enough for the Stealth Pilot 8*)

8351 is the magic number the stuff is called (I think). I ordered a gallon online for $20 or so. Enough for SEVERAL
airplanes. Big metal can. I use a sheet metal screw through a small o-ring to seal up all the extra.

[Orval Fairbairn[_2_]]

In article >,
Ernest Christley > wrote:

> Stealth Pilot wrote:
>
> > reassemble, refill with red aviation brake fluid (actually an
> > automatic transmission fluid) and you will have pristine reconditioned
> > master cylinders.
>
> Excellent post, Stealth, except avoid the red aviation fluid. Well, some of
> the red aviation fluid. The stuff is
> fairly flammable. Many designs use a hard aluminum line down to the brakes.
> Overform the hard line, and aluminum will
> eventually break, and possibly spew flammable brake fluid onto a hot break.
> If that happens to you, you'll be damn
> lucky if you have a quick thinking nephew handy with a gallon just of
> anti-freeze or some such silly thing.
>
> The airforce got tired for brake fires and had a drop-in replacement
> formulated with a higher break point. If it is
> good enough for the Stealth Fighter, it should be good enough for the Stealth
> Pilot 8*)
>
> 8351 is the magic number the stuff is called (I think). I ordered a gallon
> online for $20 or so. Enough for SEVERAL
> airplanes. Big metal can. I use a sheet metal screw through a small o-ring
> to seal up all the extra.

What about materials compatibility with standard O-rings? What about
toxicity and special handling requirements? Some fluids are quite toxic.

--
Remove _'s from email address to talk to me.

[Stealth Pilot[_2_]]

On Mon, 14 Jul 2008 20:36:22 -0400, Orval Fairbairn
> wrote:

>In article >,
> Ernest Christley > wrote:
>
>> Stealth Pilot wrote:
>>
>> > reassemble, refill with red aviation brake fluid (actually an
>> > automatic transmission fluid) and you will have pristine reconditioned
>> > master cylinders.
>>
>> Excellent post, Stealth, except avoid the red aviation fluid. Well, some of
>> the red aviation fluid. The stuff is
>> fairly flammable. Many designs use a hard aluminum line down to the brakes.
>> Overform the hard line, and aluminum will
>> eventually break, and possibly spew flammable brake fluid onto a hot break.
>> If that happens to you, you'll be damn
>> lucky if you have a quick thinking nephew handy with a gallon just of
>> anti-freeze or some such silly thing.
>>
>> The airforce got tired for brake fires and had a drop-in replacement
>> formulated with a higher break point. If it is
>> good enough for the Stealth Fighter, it should be good enough for the Stealth
>> Pilot 8*)
>>
>> 8351 is the magic number the stuff is called (I think). I ordered a gallon
>> online for $20 or so. Enough for SEVERAL
>> airplanes. Big metal can. I use a sheet metal screw through a small o-ring
>> to seal up all the extra.
>
>What about materials compatibility with standard O-rings? What about
>toxicity and special handling requirements? Some fluids are quite toxic.

I've never heard of a fire in a light aircraft's brakes so I'll
continue using armour braided flexible lines, standard aircraft grade
o-rings and red aviation brake fluid.
it works, it has had no problems in 20 years use, so I'll keep using
it.

the tin I've got will last me about 180 years. :-)

you realise of course dont you that there are brake fluids designed
for other types of aircraft that you wouldnt want within miles of a
light aircraft. some are quite toxic.
just because it was made for the stealth fighter doesnt mean it is
even remotely suitable for use in cleveland 5.00x5 systems.

btw he hasnt replied. do you think I offerred too much for the stuffed
units he has? :-) :-) :-)
Stealth Pilot

[Ernest Christley]

Stealth Pilot wrote:

> I've never heard of a fire in a light aircraft's brakes so I'll

http://lancair.net/lists/flyrotary/Message/28204.html
Now you have 8*)
For the full story go to http://lancair.net/lists/flyrotary/List.html and enter "brake fire" in the search box.

http://www.vansairforce.com/community/printthread.php?t=4737
And so has Cirrus.

> continue using armour braided flexible lines, standard aircraft grade
> o-rings and red aviation brake fluid.

My gear retracts, so I pretty much had to use flex lines, but I've concluded that one-off, hand-formed hard lines all
the way out to the brakes is a serious problem waiting to happen. The hand-forming work hardens the aluminum, making it
prone to eventually cracking.

> you realise of course dont you that there are brake fluids designed
> for other types of aircraft that you wouldnt want within miles of a
> light aircraft. some are quite toxic.
> just because it was made for the stealth fighter doesnt mean it is
> even remotely suitable for use in cleveland 5.00x5 systems.

It was designed as a drop in replacement. The correct number is MIL-H 83282. This thread contains a little more
information: http://www.vansairforce.com/community/printthread.php?t=4737 Includes information about o-ring compatibility.

If I had a gallon of 5606 sitting on the shelf, I probably wouldn't switch; but if I was looking to buy a gallon, I
would be remiss not to look at the 83282

>
> btw he hasnt replied. do you think I offerred too much for the stuffed
> units he has? :-) :-) :-)
> Stealth Pilot
>
>

Your price was so high that he probably didn't think you were serious. 8*)

[[email protected]]

On Mon, 14 Jul 2008, Ernest Christley wrote:

> Excellent post, Stealth, except avoid the red aviation fluid. Well, some of
> the red aviation fluid. The stuff is fairly flammable.

What about using plain old DOT3 automotive brake fluid? It's cheap,
available everywhere, and non-flammable.

[Ernest Christley]

wrote:
> On Mon, 14 Jul 2008, Ernest Christley wrote:
>
>> Excellent post, Stealth, except avoid the red aviation fluid. Well,
>> some of the red aviation fluid. The stuff is fairly flammable.
>
> What about using plain old DOT3 automotive brake fluid? It's cheap,
> available everywhere, and non-flammable.


http://www.xs11.com/tips/maintenance/maint1.shtml

[Anthony W]

Ernest Christley wrote:
> wrote:
>> On Mon, 14 Jul 2008, Ernest Christley wrote:
>>
>>> Excellent post, Stealth, except avoid the red aviation fluid. Well,
>>> some of the red aviation fluid. The stuff is fairly flammable.
>>
>> What about using plain old DOT3 automotive brake fluid? It's cheap,
>> available everywhere, and non-flammable.
>
>
> http://www.xs11.com/tips/maintenance/maint1.shtml

I don't believe it another XS11 rider here of all places...

Tony
aka Geezer

[[email protected]]

On Tue, 15 Jul 2008, Ernest Christley wrote:

> wrote:
>> What about using plain old DOT3 automotive brake fluid? It's cheap,
>> available everywhere, and non-flammable.
>
> http://www.xs11.com/tips/maintenance/maint1.shtml

Well I guess that's the definitive answer. From now on it's DOT3 for my
bird's brakes, not that dangerous flammable stuff the spamcan drivers are
stuck with. The only potential downside I can see is water absorption,
which is more than handled by an annual flushing with a couple bucks'
worth of brake fluid.

[clare at snyder dot ontario dot canada]

On Tue, 15 Jul 2008 09:26:56 -0400, Ernest Christley
> wrote:

>Stealth Pilot wrote:
>
>> I've never heard of a fire in a light aircraft's brakes so I'll
>
>http://lancair.net/lists/flyrotary/Message/28204.html
>Now you have 8*)
>For the full story go to http://lancair.net/lists/flyrotary/List.html and enter "brake fire" in the search box.
>
>http://www.vansairforce.com/community/printthread.php?t=4737
>And so has Cirrus.
>
>> continue using armour braided flexible lines, standard aircraft grade
>> o-rings and red aviation brake fluid.
>
>My gear retracts, so I pretty much had to use flex lines, but I've concluded that one-off, hand-formed hard lines all
>the way out to the brakes is a serious problem waiting to happen. The hand-forming work hardens the aluminum, making it
>prone to eventually cracking.



You NEED to anneal aluminum lines after bending.
>
>> you realise of course dont you that there are brake fluids designed
>> for other types of aircraft that you wouldnt want within miles of a
>> light aircraft. some are quite toxic.
>> just because it was made for the stealth fighter doesnt mean it is
>> even remotely suitable for use in cleveland 5.00x5 systems.
>
>It was designed as a drop in replacement. The correct number is MIL-H 83282. This thread contains a little more
>information: http://www.vansairforce.com/community/printthread.php?t=4737 Includes information about o-ring compatibility.
>
>If I had a gallon of 5606 sitting on the shelf, I probably wouldn't switch; but if I was looking to buy a gallon, I
>would be remiss not to look at the 83282
>
>>
>> btw he hasnt replied. do you think I offerred too much for the stuffed
>> units he has? :-) :-) :-)
>> Stealth Pilot
>>
>>
>
>Your price was so high that he probably didn't think you were serious. 8*)

** Posted from http://www.teranews.com **

[clare at snyder dot ontario dot canada]

On Tue, 15 Jul 2008 11:40:17 -0700, wrote:

>On Mon, 14 Jul 2008, Ernest Christley wrote:
>
>> Excellent post, Stealth, except avoid the red aviation fluid. Well, some of
>> the red aviation fluid. The stuff is fairly flammable.
>
>What about using plain old DOT3 automotive brake fluid? It's cheap,
>available everywhere, and non-flammable.


NOT nan flammable, by a LONG shot - and not compatible with aircraft
"O" rings.
** Posted from http://www.teranews.com **

[Stealth Pilot[_2_]]

On Tue, 15 Jul 2008 11:40:17 -0700, wrote:

>On Mon, 14 Jul 2008, Ernest Christley wrote:
>
>> Excellent post, Stealth, except avoid the red aviation fluid. Well, some of
>> the red aviation fluid. The stuff is fairly flammable.
>
>What about using plain old DOT3 automotive brake fluid? It's cheap,
>available everywhere, and non-flammable.

absolutely not.
it is the wrong chemistry for the o-rings.
and being hydroscopic it entrains moisture which leads to corrosion on
the internal polished surfaces of the master cylinder.

the correct red aviation brake fluid is cheaper as well.

I have personally pulled apart master cylinders that have had 40 years
in service and internally are still absolutely polished and pristine.
they used red aviation brake fluid. new o-rings bought them back to
life.

this is one area where aviation standard technology has really got it
right.

the stuff I'm using is Royco 756 petroleum base hydraulic fluid. it is
milspec mil-h-5606.
pretty inexpensive stuff too.
Stealth Pilot

[[email protected]]

On Tue, 15 Jul 2008, clare@snyder wrote:

> On Tue, 15 Jul 2008 11:40:17 -0700, wrote:
>> What about using plain old DOT3 automotive brake fluid?
>
> NOT nan flammable, by a LONG shot

It's always been my understanding that it's non-flammable, so I looked up
several MSDS's for DOT 3 brake fluid of verious brands. Some say, "Not
classified by OSHA as combustible"; and some say, "OSHA/NFPA Class IIIB
combustible liquid", which near as I can determine, means the vapors can
be made to burn, but apparently it's much less flammable than anything
petroleum-based. Looks to me like a better bet, flammability-wise, than
something I know WILL burn very well, given the chance.

> and not compatible with aircraft "O" rings.

Now that could be a problem. A little research with Google indicates some
aircraft brakes are fine with it, and some aren't. So I'll have to check
into that, and change seals if necessary, before making the switch.

[Steve Hix]

In article >,
Stealth Pilot > wrote:

> On Tue, 15 Jul 2008 11:40:17 -0700, wrote:
>
> >On Mon, 14 Jul 2008, Ernest Christley wrote:
> >
> >> Excellent post, Stealth, except avoid the red aviation fluid. Well, some
> >> of
> >> the red aviation fluid. The stuff is fairly flammable.
> >
> >What about using plain old DOT3 automotive brake fluid? It's cheap,
> >available everywhere, and non-flammable.
>
> absolutely not.
> it is the wrong chemistry for the o-rings.
> and being hydroscopic

Hygroscopic (literally "water seeking") is something that readily
absorbs water (usually from the atmosphere). Like some salts, or some
types of brake fluid.

Hydroscopic refers to an instrument used for making observations of
underwater objects.

Don't blame me, blame the Greeks, they had a word for everything.

Now we resume our regular programming...

/pedant


> it entrains moisture which leads to corrosion on
> the internal polished surfaces of the master cylinder.
>
> the correct red aviation brake fluid is cheaper as well.
>
> I have personally pulled apart master cylinders that have had 40 years
> in service and internally are still absolutely polished and pristine.
> they used red aviation brake fluid. new o-rings bought them back to
> life.
>
> this is one area where aviation standard technology has really got it
> right.
>
> the stuff I'm using is Royco 756 petroleum base hydraulic fluid. it is
> milspec mil-h-5606.
> pretty inexpensive stuff too.
> Stealth Pilot

[[email protected]]

On Wed, 16 Jul 2008, Stealth Pilot wrote:

> On Tue, 15 Jul 2008 11:40:17 -0700, wrote:
>> What about using plain old DOT3 automotive brake fluid?
>
> and being hydroscopic it entrains moisture which leads to corrosion on
> the internal polished surfaces of the master cylinder.

That's easily handled by replacing the brake fluid every year or so.
Brake systems on cars routinely work for many years without any
maintenance at all. If the fluid is changed even every few years,
corrosion is a non-issue.

> the correct red aviation brake fluid is cheaper as well.

LOL, in Oz maybe, but not here in the US. The last DOT 3 brake fluid I
bought was $0.99 per 12oz bottle.

> the stuff I'm using is Royco 756 petroleum base hydraulic fluid. it is
> milspec mil-h-5606.

hmm, flash point 105C / 221F, and burns about as good as diesel fuel. If
I were starting with a clean slate and looking for a fluid to fill a
hydraulic brake system, that would be second to last on the list, right
above gasoline. Of course most of us will never have a brake line fail
and spray fluid on a hot disk & caliper, but I'm more than willing to
change the seals in my brake system and change the fluid every year if
that's what it takes to drastically reduce the fire danger in case it does
happen.

[clare at snyder dot ontario dot canada]

On Wed, 16 Jul 2008 10:30:02 -0700, wrote:

>On Tue, 15 Jul 2008, clare@snyder wrote:
>
>> On Tue, 15 Jul 2008 11:40:17 -0700, wrote:
>>> What about using plain old DOT3 automotive brake fluid?
>>
>> NOT nan flammable, by a LONG shot
>
>It's always been my understanding that it's non-flammable, so I looked up
>several MSDS's for DOT 3 brake fluid of verious brands. Some say, "Not
>classified by OSHA as combustible"; and some say, "OSHA/NFPA Class IIIB
>combustible liquid", which near as I can determine, means the vapors can
>be made to burn, but apparently it's much less flammable than anything
>petroleum-based. Looks to me like a better bet, flammability-wise, than
>something I know WILL burn very well, given the chance.
>
>> and not compatible with aircraft "O" rings.
>
>Now that could be a problem. A little research with Google indicates some
>aircraft brakes are fine with it, and some aren't. So I'll have to check
>into that, and change seals if necessary, before making the switch.


Have you ever had to heat up a brake line fitting to get it out of a
cyl on a car? When that stuff gets hot, it burns (and blows all over
the place too)
** Posted from http://www.teranews.com **

[Stealth Pilot[_2_]]

On Wed, 16 Jul 2008 10:33:58 -0700, Steve Hix
> wrote:

>In article >,
> Stealth Pilot > wrote:
>
>> On Tue, 15 Jul 2008 11:40:17 -0700, wrote:
>>
>> >On Mon, 14 Jul 2008, Ernest Christley wrote:
>> >
>> >> Excellent post, Stealth, except avoid the red aviation fluid. Well, some
>> >> of
>> >> the red aviation fluid. The stuff is fairly flammable.
>> >
>> >What about using plain old DOT3 automotive brake fluid? It's cheap,
>> >available everywhere, and non-flammable.
>>
>> absolutely not.
>> it is the wrong chemistry for the o-rings.
>> and being hydroscopic
>
>Hygroscopic (literally "water seeking") is something that readily
>absorbs water (usually from the atmosphere). Like some salts, or some
>types of brake fluid.
>
>Hydroscopic refers to an instrument used for making observations of
>underwater objects.
>
>Don't blame me, blame the Greeks, they had a word for everything.
>
>Now we resume our regular programming...
>
>/pedant
>

pedantic - the antics of a pedant??

yes muffed it but we understand each other.
Stealth Pilot

[Stealth Pilot[_2_]]

On Wed, 16 Jul 2008 11:09:39 -0700, wrote:

>On Wed, 16 Jul 2008, Stealth Pilot wrote:
>
>> On Tue, 15 Jul 2008 11:40:17 -0700, wrote:
>>> What about using plain old DOT3 automotive brake fluid?
>>
>> and being hydroscopic it entrains moisture which leads to corrosion on
>> the internal polished surfaces of the master cylinder.
>
>That's easily handled by replacing the brake fluid every year or so.
>Brake systems on cars routinely work for many years without any
>maintenance at all. If the fluid is changed even every few years,
>corrosion is a non-issue.
>
>> the correct red aviation brake fluid is cheaper as well.
>
>LOL, in Oz maybe, but not here in the US. The last DOT 3 brake fluid I
>bought was $0.99 per 12oz bottle.
>
>> the stuff I'm using is Royco 756 petroleum base hydraulic fluid. it is
>> milspec mil-h-5606.
>
>hmm, flash point 105C / 221F, and burns about as good as diesel fuel. If
>I were starting with a clean slate and looking for a fluid to fill a
>hydraulic brake system, that would be second to last on the list, right
>above gasoline. Of course most of us will never have a brake line fail
>and spray fluid on a hot disk & caliper, but I'm more than willing to
>change the seals in my brake system and change the fluid every year if
>that's what it takes to drastically reduce the fire danger in case it does
>happen.

so go to it! this is experimental.

but what of the corrosion to the polished face of the cylinder the
o-ring mates to?
I'll have non corrosive over cheap any day.

btw we all use flexible brake lines in oz. I cant recall ever seeing
one in metal tube.

Stealth Pilot

[Steve Hix]

In article >,
Stealth Pilot > wrote:

> On Wed, 16 Jul 2008 10:33:58 -0700, Steve Hix
> > wrote:
>
> >In article >,
> > Stealth Pilot > wrote:
> >
> >> On Tue, 15 Jul 2008 11:40:17 -0700, wrote:
> >>
> >> >On Mon, 14 Jul 2008, Ernest Christley wrote:
> >> >
> >> >> Excellent post, Stealth, except avoid the red aviation fluid. Well,
> >> >> some
> >> >> of
> >> >> the red aviation fluid. The stuff is fairly flammable.
> >> >
> >> >What about using plain old DOT3 automotive brake fluid? It's cheap,
> >> >available everywhere, and non-flammable.
> >>
> >> absolutely not.
> >> it is the wrong chemistry for the o-rings.
> >> and being hydroscopic
> >
> >Hygroscopic (literally "water seeking") is something that readily
> >absorbs water (usually from the atmosphere). Like some salts, or some
> >types of brake fluid.
> >
> >Hydroscopic refers to an instrument used for making observations of
> >underwater objects.
> >
> >Don't blame me, blame the Greeks, they had a word for everything.
> >
> >Now we resume our regular programming...
> >
> >/pedant
> >
>
> pedantic - the antics of a pedant??
>
> yes muffed it but we understand each other.
> Stealth Pilot

I has been a techinical writer for about 30 years. Sometimes I can't
he'p myself.

[[email protected]]

On Thu, 17 Jul 2008, Stealth Pilot wrote:

> but what of the corrosion to the polished face of the cylinder the
> o-ring mates to?

Why do you think corrosion will be a problem in an airplane, when it's not
a problem in cars if the brake fluid is changed occasionally? DOT 3 brake
fluid has additives that deal with the water absorption, so corrosion is
only an issue if additives are overwhelmed because the brake fluid never
gets changed.

> I'll have non corrosive over cheap any day.

As will we all, if that's the question. But the question at hand is
somewhat different -- VERY flammable vs. slightly flammable. The fluid
you use is VERY flammable, and has a very low flash point. That's your
choice, of course, but I'll go with the slightly flammable stuff with a
higher flash point.

[Orval Fairbairn[_2_]]

In article l.org>,
wrote:

> On Thu, 17 Jul 2008, Stealth Pilot wrote:
>
> > but what of the corrosion to the polished face of the cylinder the
> > o-ring mates to?
>
> Why do you think corrosion will be a problem in an airplane, when it's not
> a problem in cars if the brake fluid is changed occasionally? DOT 3 brake
> fluid has additives that deal with the water absorption, so corrosion is
> only an issue if additives are overwhelmed because the brake fluid never
> gets changed.
>
> > I'll have non corrosive over cheap any day.
>
> As will we all, if that's the question. But the question at hand is
> somewhat different -- VERY flammable vs. slightly flammable. The fluid
> you use is VERY flammable, and has a very low flash point. That's your
> choice, of course, but I'll go with the slightly flammable stuff with a
> higher flash point.

DOT 3 fluid is chemically geared to steel components -- not aluminum. It
is also incompatible with Buna-N O-rings.

How about silicone DOT-5? That does not attract water and is not
flammable.

As a side note, I have not heard of brake fires in light aircraft,
almost all of which use Mil-5606.

--
Remove _'s from email address to talk to me.

[Ernest Christley]

Orval Fairbairn wrote:

> DOT 3 fluid is chemically geared to steel components -- not aluminum. It
> is also incompatible with Buna-N O-rings.
>

Of course, O-rings are cheap. Just replace 'em.

> How about silicone DOT-5? That does not attract water and is not
> flammable.
>
> As a side note, I have not heard of brake fires in light aircraft,
> almost all of which use Mil-5606.
>

Read a few posts up. I posted several links, including one incident that I know of personally. Ed helped me rebuild my
engine, so I know he actually exists.

[[email protected]]

On Jul 12, 6:24*am, Stealth Pilot >
wrote:
> On Fri, 11 Jul 2008 23:59:21 -0700 (PDT), wrote:
> >I have some Gerdes master cylinders that were given to me years ago
> >which I am just now planning on using. *Don't know much about them,
> >but was wondering if it wouldn't be prudent to have them be rebuilt
> >( overhauled ) before I use them, since they've been on the shelf for
> >so long. *Is it actually possible to have them be overhauled and would
> >it be cost effective to do so? *Thanks
>
> >Neal
>
> Neal you have a gem there in your hands.they are one of the neatest
> little pieces of aviation kit ever invented.
>
> the aircraft brake fluid in them, the red stuff, is not hydroscopic so
> it never absorbs moisture. the innards of your master cylinders should
> be in absolutely pristine condition. they may need a flush out to
> remove accumulated crap but the worst you should find is worn o-rings.
>
> in each side of your brake system there are 3 o-rings. 2 in the master
> cylinder and 1 in the wheel puck.
> the master cylinder has a feature known as a free piston. this piston
> has one o-ring that makes the side seal. in the face of the pushrod is
> another tiny o-ring that seals against the face of the free piston
> when you apply toe brake to push the piston down.
> these are the easiest things in the world to recondition if they are
> old but in good nick.
> buy the proper o-rings from your local aviation shop, my last ones
> were under $aus20 for the 6 o-rings.
>
> getting most of them apart involves taking the circlip out of the top.
> this is a standard circlip and is about 3,000 times as stiff as it
> needs to be. once you get that out without damaging anything the rest
> is easy.
> just slide it all apart. take the old o-rings out and put in the new
> ones and your "reconditioning" is done. just remember to lube up the
> new rings in brake fluid before putting them in position to prevent
> nicking them.
> reassemble, refill with red aviation brake fluid (actually an
> automatic transmission fluid) and you will have pristine reconditioned
> master cylinders.
>
> you can find an exploded view of the innards of your cylinders in the
> middle of an old cessna repair manual. in the 100 series cessna manual
> it is figure 5-23 on page 5-37. it gives a perfect idea of how it all
> goes together.
>
> .....actually I'm lying. they've been on the shelf for so long now
> they'll be totally stuffed. mate I'll take them off your hands for $15
> and I'll pay the express postage :-) *:-) *:-)
>
> Stealth (you have a gem there) Pilot

Thanks for the replies, guys. I was away from my computer for a few
days and actually had a chance to do some airplane building, so I
thought I'd jump at the chance. Not that I'm gullible or anything,
but I'm assuming I should keep these things and give them a shot. And
to think....I thought it was only British humor I didn't
"get." ( mate )

Neal

[Highflyer]

> wrote in message
eshell.org...
> On Mon, 14 Jul 2008, Ernest Christley wrote:
>
>> Excellent post, Stealth, except avoid the red aviation fluid. Well, some
>> of the red aviation fluid. The stuff is fairly flammable.
>
> What about using plain old DOT3 automotive brake fluid? It's cheap,
> available everywhere, and non-flammable.

I do not recommend it. Ever, in an aircraft. Had a friend who used DOT3
fluid in his brakes. Worked fine until he actually used the brakes. He
tapped the brakes on landing. The brakes heated up inside those itty bitty
wheels we use on airplanes. The DOT3 fluid BOILED. Brakes locked up REAL
tight. Airplane went on its back. Made for some really expensive cheap
brake fluid.

Most aircraft brakes and hydraulic systems are made for 5606. Cherry juice.

Aircraft built prior to the end of WWII were probably NOT built for 5606.
In the thirties and early forties GA aircraft with hydraulic brakes ( there
weren't all that many of them ) use a mixture of glycerin and alcohol for
brake fluid. For those systems you can use a DOT fluid but NOT DOT3. Use
the silicone fluid. It costs about $20 a quart. It will not cause the
natural rubber parts in your brake system to melt like 5606 will! Been
there, had that done to me!

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

[[email protected]]

On Jul 15, 2:28 pm, wrote:

> Well I guess that's the definitive answer. From now on it's DOT3 for my
> bird's brakes, not that dangerous flammable stuff the spamcan drivers are
> stuck with. The only potential downside I can see is water absorption,
> which is more than handled by an annual flushing with a couple bucks'
> worth of brake fluid.

And a few hundred bucks to fix the rubber bits. DOT-3 is a
vegetable-based fluid that is used with natural rubber. 5606 is a
mineral oil that is used with synthetic rubber. 5606 attacks natural
rubber, and DOT-3 attacks synthetic rubber. The flammability of 5606
is not an issue. I have no idea why anyone would risk trashing their
brakes and maybe the whole airplane when they either seize up or fail
altogether. The manufacturers of various vehicles specify certain
fluids for certain applications for very good reasons. A quart of 5606
would last the average owner about 10 years.
I spent 12 years building up and managing a machine shop that
rebuilt air brake equipment for trucks and earthmoving equipment and
hydraulic brake boosters for medium-duty trucks and some autos. We
made a LOT of money off people who put the wrong fluids in their brake
systems. We found motor oil (which is mineral oil) in systems designed
for DOT-3, and evidence of DOT-3 in air brake systems. Some of those
air brakes had alcohol injectors (for methyl hydrate) to prevent
freeze-up of the controls in cold weather (caused by condensation in
the compressed air) and guys would occasionally use anything handy
that had "alcohol" in it, like DOT-3 does. Wrong alcohol, though, and
boy, did it get expensive. The o-rings and other rubber bits would
swell and crumble and blow out and get into absolutely everything. If
you've had anything to do with modern air brake systems you'll realize
how extensive the damage can be. Those systems aren't simple.
Just drop some DOT-3 on your car's synthetic paint sometime and
see what happens.

Dan