grob main wheel and brake disk

[Scott Williams]

does anyone know the Parker/Cleveland part number for the brake Disk
used on a Grob Twin II fixed gear which used a Cleveland caliper? Glider made about 1981.
I'm aware of the Dot 3/4 compatible O-ring used in the caliper.

Thanks,
Scott

[mark...@comcast.net]

I had ours off of the club twin II recently and took a photo of the data plate. Here is the info on ours -
Model - 40-97A
Size. - 6.00 - 6
Static rating 2500 ( I assume this is pounds!)
Wgt. 5.8. ( again, assume pounds)

On the backside of the disk there are numbers following numbers stamped into it -- 26A 233
Ours accepts the 6.00 x 6 tire.

Hope,this helps, Mark Guay

[mark...@comcast.net]

My bad - numbers off of the data plate refer to the wheel hub. The 26A 233 number were stamped into the bachdide of the brake disk/rotor and the only identifying information on it.

[Scott Williams]

after a couple hours on the computer, I found a listing on an archived Cleveland
application chart, seems to call out;
disk, #164-02601
caliper, #30-63A, But the O-rings have to be changed out to dot 3-4 compatible rings.
linings#066-10500
wheel, #40-97A

thanks,
Scott

[Scott Williams]

On Tuesday, July 17, 2018 at 10:38:55 AM UTC-5, Scott Williams wrote:

Further a Cleveland/parker part # for a chrome disc is 126-12601

[Scott Williams]

On Tuesday, July 17, 2018 at 10:38:55 AM UTC-5, Scott Williams wrote:

Even further,
you need an EPDM #224 o ring, for dot 3-4 compatibility, hardness shore 70
and the torque plate number might be Cleveland 075-03700

[Charlie M. (UH & 002 owner/pilot)]

OK, my bad, looking to learn......what was the original hydraulic system? If mineral oil, I can see the O-ring swap, otherwise, I "believe" ANY DOT fluid works in ANY system (other than DOT 5 which REALLY SUCKS WATER OUT OF THE AIR).
So, you can run ANY DOT brake fluid in any DOT system, DOT 5 just means a lot more fluid changes.
So, DOT 1-4 and DOT 5.1 are all compatible.

Again, just asking for my edumafication as well as others (misspelling intentional).

[jamesb...@comcast.net]

On Friday, July 20, 2018 at 2:49:20 PM UTC-4, Charlie M. (UH & 002 owner/pilot) wrote:
> DOT 5 which REALLY SUCKS WATER OUT OF THE AIR).

Are you sure about this? Sounds like you are, but DOT 5 brake
fluid is silicone based, isn't it? Hydrophobic, as I read it.
Silicone brake fluid is a favorite with some antique car owners,
since it doesn't absorb water, which rusts the interior of the
brake system. I've got it in my old cars. It has other problems,
like being harder to bleed, though.

Or I could be completely wrong again.

Jim Beckman

[Scott Williams]

On Tuesday, July 17, 2018 at 10:38:55 AM UTC-5, Scott Williams wrote:

Well,
to the best of my knowledge, and the Grob 103 twin II manual, and service bulletin OSB 315-17, .
the master cylinder was a modified Magura motorcycle part, which might have been original equipment on BMWs, maybe a R100? which uses dot 3 fluid.
The original equipment caliper is a Cleveland/Parker Hannifin 30-63A, which has a Buna-N O ring( MS28775-224) for use with petroleum based aircraft hydraulic fluid,
I think it was easier and cheaper to change the caliper O ring than to change the master cylinder seals.
The "O ring swap" I mentioned was intended to ensure caliper O ring compatibility with the Brake fluid indicated in the flight manual.( dot 3)
If someone simply replaced either the caliper or just the O ring with the Cleveland called out part number, this would result in the Cleveland O ring swelling over time. That is something you don't want in a caliper.
The ID label on our Grob 103 caliper should be labeled "DOT 3" but is not (Yet).
Larry Suter, on rec aviation Jan. 6th 2015 started a thread that covered it better than I.
If I'm incorrect, please post.
Thanks,
Scott

[Charlie M. (UH & 002 owner/pilot)]

Ummmm....yes, I am very happy with my post.
Pretty much ANY DOT fluid is cross compatible EXCEPT DOT 5.
DOT 5 "will work", but it is even MORE water hungry than others. I do not believe it is a seal issue, it is water absorption issue. Thus, race cars is fine, other uses, sucks.

Now, mineral based fluids vs. DOT fluids is a different matter. Thus my question.

Oh, and to accentuate this, if you have an old system that uses DOT 1, using DOT 1-4 AND 5.1 is fine.

Yes, I made a bold statement, I will do my best to provide GOOD relevant links to prove, not just me stating it. Say, within 24hrs?

[jamesb...@comcast.net]

On Friday, July 20, 2018 at 4:55:41 PM UTC-4, Charlie M. (UH & 002 owner/pilot) wrote:
>
> DOT 5 "will work", but it is even MORE water hungry than others.

> Yes, I made a bold statement, I will do my best to provide GOOD relevant links to prove, not just me stating it. Say, within 24hrs?

Any progress on this question? Every source I've seen
says something like "Unlike polyethylene glycol based fluids,
Dot 5 is hydrophobic." My first reaction was that the stuff
must act like a rabid raccoon, so I had to look the word up,
but I think it means the fluid has no affinity for water.

At least, that's the way I understand it.

Jim Beckman

[Charlie Quebec]

Quit so, normal brake fluids are hygroscopic, and easily absorb water, which then causes vapour issues in the lines when heated, allowing it to be compressed.
Sounds to me like dot5 is a better option.

[jamesb...@comcast.net]

On Tuesday, July 24, 2018 at 11:07:52 AM UTC-4, Charlie Quebec wrote:
> Quit so, normal brake fluids are hygroscopic, and easily absorb water, which then causes vapour issues in the lines when heated, allowing it to be compressed.
> Sounds to me like dot5 is a better option.

I've forgotten if this was the original problem or not, but I've been through the whole process of rebuilding the hydraulic brake system on a Grob 103. Complications arise because Grob used an off-the-shelf master cylinder derived from a motorcycle application. That requires a different type of fluid than the usual hydraulic fluid used in aircraft brakes, and expected by the Cleveland wheel cylinder O-ring. One of us went to a mechanic that works on power planes, and he handed us an O-ring based on the Cleveland part number. Then I went to a real glider mechanic, and he threw that one away, because it wasn't going to be compatible. I think we got some help from Robert(?) Mudd, and once you know the material you're looking for, McMaster has them cheap (but you probably have to buy at least 25 to get 1). Unfortunately I've forgotten when that material was, but I could look around in my spare parts box, if it's important to anybody.

I got the master cylinder overhaul parts from a company that supplies parts for old BMW (Oilheads?) motorcycles.

Jim Beckman

[Scott Williams]

On Tuesday, July 17, 2018 at 10:38:55 AM UTC-5, Scott Williams wrote:

if anyone wants a new rubber diaphragm for the round cap, it is BMW motorcycle part number
32 72 1 238 387

good lift,
Scott

[eaachap...@gmail.com]

James,
Our aircraft mechanic put aviation brake fluid into our Grob brake and all the seals swelled up and are no good. Do you recall which master cylinder rebuild kit you used?
Thanks,
Chris

[Scott Williams]

On Tuesday, July 17, 2018 at 10:38:55 AM UTC-5, Scott Williams wrote:

Check and measure the master cylinder bore size, compare the pictures to your component piston and spring. try here,
https://www.beemerboneyard.com/mamacykifr3.html
good luck