O-ring Sizes: Scott Master Cylinders

lwford

lwford

New member
I have STC from Webers for Cleveland wheels and brakes SA294GL This is a standard for Cessna 120 thru 182. This has been installed on the crate in 1981 after a runway excursion. It is everything but the master cylinders so begins my story. I thought I knew everything about the crate as I have been married to it for 11 years. I have been having to add fluid to the left master since last Annual so this year June Annual I attack. I set the parking brake and left it overnight sure enough there is a puddle of 5606 on top of the left master. The masters are Goodrich 87-87 circa 1957. The last time they were addressed was 1973. I pull the left out and the shaft is slighly bent the O rings are shot. I pull the right and find that the shaft had been busted and welded a real surprize to me and you are not taking it apart due to the weld. Tryed to find shafts HA HA got to be kidding nowhere on the Internet was I successful. Of course you can get used POS from the (W) junk people. I ended up having 2 shafts custom made by a friend who is a master machinest. If anyone wants a copy of the STC and parts pic and breakdown, let me know as the Clevelands are top shelf.
Lynn the crate (my wife calls herJezebell) I wonder why??? :D
 
I'm glad to see you got an airplane! Mine is still not flying but I now have wings on it and gear under it and the engine is running. Maybe I'll get a flight on her this year. If I don't get frustrated again and run her through a brush chipper...
These master cylinders use standard size o-rings so getting the proper size is only a matter of taking the cylinder parts down to an accessory shop or aircraft parts house and finding the o-rings that fit. Be sure to change the little tiny o-ring or stat-o-seal washer on the shaft under the piston. lots of people don't know it's there and it can cause all kinds of leak backs and problems like you're having. You have to remove the piston from the shaft to find it, if you haven't already. The piston is held on by a tiny snap ring and a spring. Be careful not to lose these! They'll fly away into oblivion and they're so small you'll never find them unless you're real lucky. The seal in there will be either a tiny o-ring or a stat-o-seal which is a washer with a tiny o-ring bonded into it.
Don't try to use automotive o-rings on airplanes. It is very important that aircraft o-rings are installed! Automotive Buna-N o-rings are often metric sized making them unsuitable for U.S.-built aircraft. The o-rings should be of a part number MS28775-XXX. The -XXX will be numbers that reflect the sizes. I can't remember the sizes but only one size will fit properly so when you find it you'll know! You may also see MS28778-XXX o-rings but these are skinnier and are intended for use under fittings and jam nuts. They will leak if they are installed where an MS28775 o-ring is supposed to go. Try to size them using the MS numbering system. The old AN6227 and AN6230 o-ring sizes kind of overlap what is separate in the MS system so sizing o-rings by AN part numbers can be confusing. Both AN and MS sizes are the same. There are no "AN-only" or "MS-only" sizes.
Also check the shaft for damage and wear. Very often moisture will collect on top of brake master cylinders in aircraft that sit for long periods of time in leaky hangars and this will corrode the shaft right at the o-ring. Corrosion pits can damage the o-ring when the pedal is operated. Some corrosion can be cleaned and polished and the cylinder saved but it may still seep a little over time.
Good Luck!
Rogers Hunter
 
copy and paste link below for o-ring info. Regarding Scott 4000...have you tried to get a parts drwg or illustrated parts list?


http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CEIQFjAC&url=http%3A%2F%2Fwww.gen-aircraft-hardware.com%2Famelia%2Fdetails.asp%3Fstore%3D%26id%3D504%26TName_HID%3Dsubcat&ei=I3C-UZ32K8vvrAGAxYDgDw&usg=AFQjCNGqZ9xaFg_mek4pTX67jyh6RHrJ6g&sig2=xIlGyTvXqgOgH6UEQQWhhA&bvm=bv.47883778,d.aWM
 
blimpy said:
The franklin is such a simple and straight forward engine.. and yet so many "mechanics" run the other way when you
mention one. It's nuts. Look at all the voluminous change and variation that car mechanics have to deal with...
yet the A&P's go appoplectic and pissy... maybe that's what a and p means. ( sorry guys).
Click to expand...

Try being an A&P having to adhere to the regs, face exposure to liabilities, and deal with owners who think their plane is special.
Franks are no less complex than Lycs or Conts. pistons, rods, cranks, bearings, cases, mags, generators, starters,... same stuff. And like the others, Franks have their quirks but to the average mechanic today they are rarely seen. To expect a shop today to smile and greet you with open arms is foolish. They don't have any experience with them, don't know their quirks, have zero support in the system and no resources available (just because you know about Susan at A-1 doesn't mean they do). In order to help you they are going to have to take extra time and effort (which of course you'll object to the extra charges) and won't make any money on you.
So, why bother? It isn't begin angry or "pissy", they have to make an income too.
Think your auto mechanic is the god-of-wrenches? Drive your Tucker in there and expect them to diagnose your rough-running engine. Make sure you use the guy who spent 3 years of college on his own dime getting the required education, then took 6 federal exams to get certified just so they could apprentice. I'm sure you'll expect that same guy to be able to fix your brakes, find the short that keeps blowing your brake-light fuse and do your body work too while he's waiting for your new rings to arrive. (oh wait, those guys don't actually work on engine internals anymore huh?). Surely he wont mind signing his name to your life-long record taking responsibility..
Don't get me wrong, I love the Franks, owned and fed one for 16+ years, still work with three others (two on Stinsons, one on a Hiller) - nice smooth running (albeit thirsty) engine. Eisemann mags, SPA carbs.. easy-peasy IF you have the time, inclination, and experience to know how to deal with them or, if you know someone that does. Don't expect every corner shop at the airport to help you with it, they don't need you.

Bill Monroe A&P/IA, DER, AS degrees in Aviation Maintenance and Airport Management, past adjunct professor San Diego Miramar Part 147 Aviation Maintenance School, former Stinson Owner and now proud to own a Bellanca 14-19-3.
 
No truer words spoken. Find a guy or become the guy for the Franklins. I take care of a Stinson and without Susan it would be at the junk people. Lynn the crate :!:
 
Blimpy, have you contacted Don Green yet? His company makes and sells Bodel brakes and he should know all about the masters, and probably what cleveland masters are the same overall length and throw. He is listed in the Contact.___Good luck____Grant.
 
Larry, call me, you have my number. If you get my answering machine leave me a mailing address , and I will mail you some scotts that are not bent. I have a box full of masters(most unidentifiable), but I know I have extra scotts._____Grant.
 
Larry, I lied!, after going through a box of almost 2 dozen masters, I could not find a single Scott that was not bent or rusted. I have sent you some Wheeler Dealer(yes that is the name) masters that are a latter version of the Firestone/Bodel brakes that are already approved on our planes. I believe these are about half way between the Scotts and the Cleavelands, as far as volume and pressure goes. Jim Green should have any parts needed. If you dont like dealing with 337s and kissing the FAAs backside, you might consider going with Bodels, since they are(I believe) just a log book sign off. They are good brakes, but just a little more complicated than Cleavelands.I would be curious at the pressure that the WD masters give in your test, compared to the Scotts? Good Luck with it.____Grant.
 
I have seen no comments about Bodell (Jim Green) going bankrupt, but I might have missed it. They are actually reasonably common brakes, and work very well. The # for Jim Green should be in the Bellanca Contact. The pedals I sent were from your comment on a welded pedal. I sent two different ones because another of Bellanca oddities is that the bolts that hold the brake pedals in are different in some planes than others. Some are drilled fore and aft , and some are drilled athwartship. I dont know if that changed at some seriel number or why they changed, but I have run across it before. Keep us all posted as to how this all goes? I am real curious how a pressure test (and maybe a volume comparison) compares between the Scotts and the Bodells?____Grant.
 
Jim & Madelyn Greene
Skybound Mfg.
770-446-6797
greenejames@bellsouth.net

Jim & Madelyn have been Club members for about 10 years and would be more than glad to help. They said they would be at AirVenture this year.
 
Larry, to my understanding, the Bodell brakes are a continuation of the Firestone brakes which I believe are in our type certificate. I am remodeling my house right now, so I cant find any paper work. The Firestones have gone through a number of name changes over the years. Firestone/Adams/Wheeler Dealer/ Bodell and maybe one other. They are all the same brake and I think all parts are interchangeable. Check with Jim Green on that. I think the Wheeler Dealer masters will work with your present brakes, but a pressure comparison and volume test would be a good idea. I am sure they will work with Bodells. My thoughts were that the WD masters would safely get you through until you decide what to do about changing brakes. Take one apart and compare the piston size. I will telephone you tonight.____Grant.
 
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