Need G-103 Acro Master Cylinder

Our club's G-103 Acro needs a new brake master cylinder.
We can probably get one from Grob in Ohio within several
weeks, but we would like to get one sooner.

Does anyone, anywhere, have a master cylinder they
would sell us? Then, we would pay overnight freight
to our club's location in North Carolina, USA.

Please contact me at:

Thanks,
Ray Lovinggood
Carrboro, North Carolina, USA

Ray,

Could your master cylinder be rebuilt? If corrosion is the problem, a
possible fix might be to have a machine shop bore it out and then epoxy a
brass sleeve in the bore . . . no more corrosion problems.

This is a common fix for antique car and other auto restoration projects.

--
bumper
"Dare to be different . . . circle in sink."
to reply, the last half is right to left

"Ray Lovinggood" wrote in message
...
Our club's G-103 Acro needs a new brake master cylinder.
We can probably get one from Grob in Ohio within several
weeks, but we would like to get one sooner.

Does anyone, anywhere, have a master cylinder they
would sell us? Then, we would pay overnight freight
to our club's location in North Carolina, USA.

Please contact me at:

Thanks,
Ray Lovinggood
Carrboro, North Carolina, USA





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Ray,
I have found it very difficult to bleed the G-103 master cylinder. The old
*hold pressure with the dive brake lever and open the bleeder valve* has NEVER
worked for me. The only thing I have found that works is to *pressure bleed*,
form the wheel bleeder valve, up through the master cylinder.
Hope this helps,
JJ Sinclair

This is a common fix for antique car and other auto restoration projects.


but is it a valid repair for an aircraft?
is the Grob flown under a Standard airworthiness certificate or an
Experimental?

it does make a difference..

I can see the accident report now, Grob on Commercial passenger carrying
scenic glider ride, lands long and goes off the end of runway.. brake fails
to stop the glider before hitting airport fence. Fencing injures passenger's
face in front seat. Discovered improper repair to brake master cylinder.
Lawsuit follows.....

you get the picture.

BT

With our Grob G109B motorglider the wheel brake master cylinders are an item
supplied by Tost at www.tost.de . We have been able to buy replacement seal
kits and replacement master cylinders from Tost easily. No hassle. The
Tost people may have their catalogue on-line for perusal.

Possibly the master cylinder for the Grob G103 is also available from Tost.
There are a few variants. My faint recollection is that the G103 has a side
lever actuation rather than a top lever actuation, but my memory could be
imperfect.

The master cylinder in the G109B is the same as used in the hydraulic disc
braked mainwheel installations in our Janus B (which we converted to
hydraulic disc brake from drum brakes using a kit from Tost), Janus C (which
came so equipped from manufacture), etc.

Tost also can supply a five page document headed "Disc brake systems -
Maintenance" and subtitled "Service and maintenance of disc brake systems
with master brake cylinder of type 3,4 6 and 7". This document assists with
info on bleeding. I think they would be happy to email it to you if you ask
nicely. They sent me a copy when we were installing the Tost kit for
hydrauilic braked main wheel system into our Puchacz. (Best thing we've
done with our Puchacz maintenance and operations wise was getting rid of the
Polish mainwheeel and wheel brake.)

I agree with JJ Sinclair that bleeding these systems can be a bugger.
Whereas by contrast with our Piper Pawnee it is easy as pie, so to speak.
With a Tost master cylinder in the system, you have to have the brake lever
as far towards brakes off as it can be.

Hope this helps.
Roger Druce
(Australia)


"JJ Sinclair" wrote in message
...
Ray,
I have found it very difficult to bleed the G-103 master cylinder. The old
*hold pressure with the dive brake lever and open the bleeder valve* has
NEVER
worked for me. The only thing I have found that works is to *pressure
bleed*,
form the wheel bleeder valve, up through the master cylinder.
Hope this helps,
JJ Sinclair

Exactly! I recognized it as soon as I saw it. It is a 13mm bore Magura
master cylinder common on many BMW and other motorcycles from the early to
mid-eighties. I rebuilt ours using a rebuild kit available through our
local BMW motorcycle dealer. It is very simple to do and it is very
doubtful that you would need it honed - just clean it up with a very fine
silica paper. If you need a complete new cylinder, check with Grob and if
the price seems high, have your local BMW dealer try to order one for you.
They may not be able to get one though given teh age and the fact that it
may not be a BMW part. Most BMW's of the era had square reservoirs on them
and not the round type used in the Grob. This particular Magura may have
actually been from a dirt bike since Magura master cylinders were used by
many manufacturers.

I had to laugh the first time I saw it in the Grob! I imagined a bunch of
German engineers leaned over the glider with slide rules and calipers trying
to design the ultimate brake cylinder when some apprentice walks in holding
the master cylinder he just took off his motorcycle in the parking lot! I
also laughed when these same engineers evenually threw up their hands and
used the brake disc and caliper off a Cessna!!! (Ahhh, the myth of German
enginering prowess exposed!!!)

Bleeding is best done from the caliper by forcing the fluid up. It is
nearly impossible to "pump" out the air bubbles from the top. I learned of
the problems bleeding these Magura cylinders from a motorcycle tech site on
the net. Here's a cheap, easy and effective tool to use. Get a hand pump
like used on a soap dispenser (or go all out and buy a similar plastic hand
pump sold at a marina as a tool for adding oil to the lower case of a marine
outboard motor) and attach a piece of hose from the spout to the caliper
bleed nipple. Screw it on to the plastic brake fluid bottle (fit seems to
be universal) and start pumping. After only a few strokes, the job is done.
You just have to wrap some paper towel around the open reservoir to catch
the excess or use a syringe to draw it off as the level goes up. (Forget
using the syringe from the bottom. It is not as easy as the hand pump since
the back pressure makes it hard to operate.)

After resurfacing the pads and disc as well as the cylinder rebuild, our
Grob now stops like a lawn dart.


"Buck Wild" wrote in message
om...
Ray Lovinggood wrote in message
...
Our club's G-103 Acro needs a new brake master cylinder.
We can probably get one from Grob in Ohio within several
weeks, but we would like to get one sooner.

Does anyone, anywhere, have a master cylinder they
would sell us? Then, we would pay overnight freight
to our club's location in North Carolina, USA.

Please contact me at:

Thanks,
Ray Lovinggood
Carrboro, North Carolina, USA

Ray, that master cylinder is from a BMW motorcycle. It's the front
brake cyl with the hand lever cut short. Im sure you can get it
cheaper than from Grob if you check cycle salvage places.
-Dan