Hi All,

On the Fox .35 40th Anniv. (and others I'm sure) the tiny ears at the rear of the crankcase for the muffler bolts are a source of failure at times.

I have heard of guys using JB Weld to attach brass tubes which extend to the front of the exhaust facing to help keep the ears from breaking off.

Anyone here who does that?  Please give specifics.  Any other "cures"?

    I haven't done that, but it appears to work. I have seen several crashes where this kept the engine alive, whereas the crashes without the tubes either broke the ears off, or broke the ears off AND took a chunk of the crankcase around it with it.

     I certainly wouldn't use the ears as they were originally made. Even if the tubes come loose, they relieve some of the clamping pressure that causes the ears to distort the case.

    The other alternative is to get a 50th Anniversary case, I think those came with the extension cast into the case just like a ST46.

     Brett

Thanks, guys.  I have seen the ears break simply running the engine. I am looking at a couple of Foxes I have that are good runners but have the tiny ears.  So I don't want them to break off or to have any distortion that could be caused by not having a solid mount.

BIG Bear
RNMM/AMM

<I have seen the ears break simply running the engine
Hmmm, i didn't know they were so fragile.
I'll have to do the same thing on my fox 40th anniversary also... since I REALLY DO crash all the time.
This is a good trick!
I think one best way to go about doing it is by mounting the muffler first, with the tubing. Maybe adding a little lubricant on the muffler so it won't stick?
-Daniel

Hi Daniel,

I did crash a model several years ago when the engine quit going vertical in the middle of the square 8's.  That engine was a Fox .35 40th Anniv.  Weirdly it hit so perfectly vertical that it didn't break the prop or the muffler mounts!

I understand that simply adding the tubes using regular JB Weld, and facing them down even with the exhaust facing is the "trick".  I would just like to hear it from some of the people who have actually done it.

I suspect that once I can physically fly again, there could be some incidents where terra firma is a factor again..........

Bill

I have done it Bill, and it works pretty well. I used brass tubing cut just a few thousands longer than the stack, and bolted the muffler on with wax paper between the muffler and the stack. Then used JB Weld to fill in and make it look much like the newer case. After it sets up at least 12 hours, I removed the muffler, packed paper towels in the exhaust, and filed it down flat. I have found that if you put the engine in the crockpot for cleaning it will soften the JB Weld and kind of eat into it. Otherwise it seems to work pretty well, and I have Foxes that have been flown for years without problems, although lately I have been flying mine without mufflers on most of them.

               I use the stock muffler on some of them. The tilt down blimp looking muffler is horrible. The exit is too small and the newer current ones available are smaller yet. The bigger problem is how it mates to the cylinder head. In the event of crash, the forward momentum with all that weight hanging below the stack typically results in not only the ears twisting and breaking, but the stack itself cracks off. Even though this mod would sufficiently replace a fractured ear, or even make the existing ears stay intact, the stack is still susceptible to breaking.Bottom line, don't crash.  The new case does alleviate that problem. I replaced some of my broken cases due to this fact. So one would think it should be a simple swap of a few parts and your back in business. Think again as a few things have taken place over the years. The muffler holes are close but the new ones do have a slightly different configuration and the length of the new case was slightly longer and the crank didn't protrude out the front enough. All is well now, but in my opinion, the new case certainly has benefits. Ken

Instead of using brass  tubes I use auto brake line tubing.  One side needs to be filed flat in order to work.

I did this a number of years ago with a 40th anniversary crankcase.  I scuffed up the sides of the crankcase with a Dremel, cleaned it thoroughly with solvent and JB welded aluminum tubes to the sides of the case.  I believe I mounted a muffler (to keep everything aligned) separated with wax paper or similar material to keep the JB Weld from adhering to the muffler.  I then lapped the whole face of the exhaust stack on a jointer surface with 600 paper.  It never failed.

Fred

Bill

My experience was that those little ears can cause the case to warp if the muffler mounting bolts were over tightened.  The muffler mounting face was possibly warped or somenthing but once I backed off the screws the the engine turned over freely again. 

This is an excellent solution. I have a brand new Double Star .60BB with the same type of ears as the older Fox. If I ever put it into service I will make use of this great mod.

The only way you will break DS 60 ears is grossly overtightening them.  The ears on my lite 60 have been fine for over 1000 flights.  My BB 60 went straight in to the asphault in my ill fated Avanti, and the ears held.  Then the BB 60 went straight in when my Trex folded up in flight, and the ears still held.  They don't need any help.

Bill,

Believe I wrote this up in SN over 10 yrs. ago. 


Ward-O

Hi Ward-O!

Then you are probably where I heard it from!   I intend to do it to two of my Fox .35.  I feel good that I will have no problems.

Bill