Fox Plain bearing engines as pushers or with starters

[Bob Reeves]

OK never had a pusher other than a Dumas Swamp Buggy with a Fox 25 back in the 70's but I do have a present problem using a starter on a large case 70's Fox 40. This engine is in my Balloon bust airplane and gets flown by 3 or more pilots once a year at the Tulsa contest. It usually will not hot start so out comes the starter and it gets hit 6 or 7 times before it's all over or the poor thing is in more than one piece.

The problem is the aluminum prop drive washer is being pushed against the aluminum case with the starter.. Not a good combination aluminum on aluminum. The starter is wearing a grove in the back of the drive washer and expect it to start giving me big problems in the near future. Thought about trying to find a thrust washer but the keys on the crank that mate with the drive washer kinda prevents any kind of washer that would fit and stay centered. Also I can see score marks on the back plate where the crank is obviously being pushed against the back plate.

I know the real answer is to quit using a starter but that would be trading allot of fun flying for prop flipping in the heat of competition.. I would think the Fox 35 being built the same way would suffer the same fate..

Anyone have any ideas?

[Russell Shaffer]

Actually, I do.  An aluminum starting pulley like OK used to sell for their .049's.  I have several in use and they work pretty well.  I don't have a picture loaded at the moment, but I can send one.  The largest engine with a pulley is a Veco 45 that is a great runner, but worn enough that it is hard to start by flipping.  Usually will go with one pull on the starter cord.  When you pull the handle, the engine turns over real fast about 10 times. 

[Phil Bare]

Bob, I am not experienced with the large case .40 so can not really say much other then what I know and have experienced with the stunt .35 and it may or may not apply to your engine. On the stunt .35 with the stock back plate, the distance from the back end of the crank pin to the inner surface of the back plate is considerabl more then the distance from the back side of the prop drive washer to the front of the crank case/main bushing end. As a result, the back side of the thrust washer riding on the front of the main bushing provides the exact same thrust surface as is available on the other end between the crank and main bushing. On the stunt .35, I use the steel prop drive washer......I do not know if there is a steel drive washer available for your particular engine, if so, it might be worth obtaining one to use with your electric starting. I normaly do not use an electric starter on anything as a normal routine, although I do have one and use it once in awhile on a stubborn engine...   Regards, Phil

[Herman Green]

I bought 2 or 3 of those large case plain bearing Foxes back when they were fairly new on the market.  They came with aluminum drive washers, but the instructions had a note on them that said if you plan on using a starter, order a steel drive washer from Fox.  I bought a couple of them.  Fox probably still has them.

Herman

[Keith Spriggs]

As I recall you do some machining work. Perhaps you could machine a steel or brass washer to go between the drive washer and the crankcase. This should also stop the crankshaft from rubbing on the back plate. Teflon is another possibility for the washer.

[Paul Smith]

I would like to agree with you, but the last time I backed your position I was called an idiot.

See the topic "A+B+C = something or other".

[Marvin Denny]

  Bob,  Is the engine you are referencing the old George aldrich designed 40  or the later Schneurle ported  with six bolt back plate one?
 Youy might try using some JB Weld and attaching a brass plate shim to the front of the case for the thrust washer to rub against.  If it is the older GMA design, I have a thrust washer for it.

  Bigiron

[Bob Reeves]

Thanks for the ideas gang...

Hi Marvin, was hoping you would jump in,it's the old GMA design. The problem I see with a thrust washer, if the center hole is large enough or machined to go past the keys on the crank it will flop around once it gets past them. If you make it thick enough to grab the keys the drive washer won't fit properly. Also congratulations on you anniversary tell Rea Pat and I said hi...

Hi Keith, ya I do a little machining but am far from being a "Machinist". Could probably make one out of brass but was thinking some sort of hardened steel would be what is needed, it would have to be close to the same thickness as the FP thrust washers which are pretty thin. Would be afraid brass wouldn't last very long.

Tom martin from our club said he had a few different Fox steel drive washers.. next time he comes over we are going to see if he has one that will fit. If Tom has one we are home free I think? Of course sometimes my thinking is muddied.

[Bob Reeves]

Actually, I do.  An aluminum starting pulley like OK used to sell for their .049's.  I have several in use and they work pretty well.  I don't have a picture loaded at the moment, but I can send one.  The largest engine with a pulley is a Veco 45 that is a great runner, but worn enough that it is hard to start by flipping.  Usually will go with one pull on the starter cord.  When you pull the handle, the engine turns over real fast about 10 times. 

Good idea for a profile but this is a full fuselage fully cowled engine.. No place to put a pully but I like the idea.

[Marvin Denny]

  Bob, That is why I recommended to stick the brass shim onto the front of the case with JB Weld instesd of putting it onto the thrust washer.  I will check and see if any of my thrust washers are steel too.

  Bigiron

[Richard Grogan]

Good idea for a profile but this is a full fuselage fully cowled engine.. No place to put a pully but I like the idea.

Hi Bob,
You ought to check with Billy G. I bet he can help you out no matter which way you wanna go...
RG

[Phil Bare]

Bob, if you put a prop on the engine and tighten it up you will see that the prop drive washer is botomed out on the front of the crank. You can take a feeler gauge and determin the clearence between the prop drive washer and the front of the crank case/main bushing, that thickness, minus a couple thousanths is what the brass washer needs to be. The I.D. of the washer needs to be a fit on the O.D. of the crank. There is no need to capture the washer between the prop drive washer and the front of the crank, matter of fact, doing so would move the prop drive washer forward by the thickness of the washer and would do nothing to (take up the slack) so to speak. If the brass washer is a tight fit on the O.D. of the crank, it will spin with the prop drive washer and will be lubed by any blow by from the mail bushing and should last a good long time as well as solving the electric starting concerns..Regards, Phil

[Marvin Denny]

  The Fox stunt 35 won't suffer as much as the old 40 as the stunt 35 has a full length bronze bushing for the thrust washer to work against  whereas the 40 is aluminum up front..

  Bigiron

[Phil Bare]

Thanks Bigiron, I was thinking in terms of Stunt .35 and a full length bushing. Do you think that the brass washer idea would help? Seems to me that it would be far better then aluminum against aluminum huh??  Phil

[Bill Mohrbacher]

I just ran in to the engine room and tried a STEEL thrust washer from one of the "big block" 40/45s (the ones with the bolt on venturi), the small block 40s, the series 5 29/36/40s, and the 19/25 bushing engines.  NONE fit the Aldrich 40!  Marvin has some good ideas.

[Marvin Denny]

  Bob, I checked all of my extra Thrust washers for the GMA 40 and all are aluminum four flat cast finish and two slick shiney finish.
  my suggestion is to cut a hole in a piece of brass shim stock  very slightly larger than the front hole in the case,  The OD of the shim is not critical as long as it is as large or larger than the OD of the case shaft housing.  Clean the shim  very clean and the front of the case housing also.  Put a thin coating of JB  (or conley) Weld on the case and push the  shim washer down firmly on to the end of the case. Put some vaseline on the crank shaft and install the shaft backwards into the case hole and rubber band it so that it FIRMLY presses against the shim.  This will insure that the shim is flat and square with the front of the case.  After cureing, pull the shaft out and clean any flash from inside the case hole and outside of the shaft.
  If you do not wish to disassemble the engine,  do the same operation of applying the adhesive with the shaft in place, but BE SURE that the shim is up OVER the end of the shaft, and use the thrust washer  to press against the shim stock washer.
  By putting the shim on the case rather than the thrust washer, you do not have to worry about any off balance situation.
 Added by edit---  If you wish,  give me a call    (316)838-8494

  Bigiron

[Bob Reeves]

Thanks Marvin, am pretty sure I understand, if I run into a problem I'll call..

Should have asked this question a weak earlier as I did have the engine apart installing a crank case pressure nipple for a smoke system.