Muffler for Fox!

With the fears of case distortion when bolting a muffler to Fox/McCoy's etc - why hasn't anyone produced one that bolts to the exhaust stack?

>With the fears of case distortion when bolting a muffler to
>Fox/McCoy's etc - why hasn't anyone produced one that bolts
>to the exhaust stack?
>
>Tony

I am not sure what you are asking, Tony, but there are all sorts of variations. I have some adapters, for instance, that bolt to the center hole of the McCoy RedHead (for those cases that had the center hole) and then a "normal" muffler can be bolted on in a normal way. Same for the Super Tigre engines. Fox had some over/under holes in early muffler models and you can get mufflers to mount here if you wish. I never found the over/under mount very satisfactory although it gave the ability to mount it from the exhaust side if that was important.

Is this what you are asking.

With the fears of case distortion when bolting a muffler to Fox/McCoy's etc - why hasn't anyone produced one that bolts to the exhaust stack?
Tony

Actually, at least one is produced although it was not intended to be used in this manner.

If one begins with a newer Fox 35 case, one which has muffler mounting lugs beefed up and extending to face of exhaust port, it is a simple matter to sleeve down the existing holes, tap for 4-40 machine screws and attach an RSM tongue muffler to engine from the exhaust side.

I have used hard 1/8" diameter copper tubing installed in case lugs with JB Weld, tapping tubing the next day. Yes, inside diameter of the tubing is a bit larger than desired for a 4-40 fastener; but it still works fine, I've never had a failure.

This is a good trick, not only to reduce the possibility of squeezing the light-case Fox 35 out of round, but eliminates the need for extra holes in cowling in some installations.

Full credit to Don McClave for the idea.

As a side note, and pointing out that I have always been aware of the potential for pushing Fox 35 internals around when tightening down the muffler attachment bolts, one time several years ago I was flying one of my Smoothies and for some reason had to remove the engine. With it all buttoned back up I started the Fox and after just a few moments shut it back down. It just did not sound right, did not needle properly. This was not apparent to any of those standing around; and I'm not sure if it would have been apparent to me if a day had passed between working on the engine and running it.

That the piston/cylinder set could easily have been ruined for contest flying, made slightly soft for even sport flying, has never been forgotten.

If it is an old Fox without muffler provisions, a strap on goes around easily, without obstructions.

Don't worry about it. You can tighten it down pretty hard, and nothing will happen. I suppose the pressure is evenly distributed, sort of.

Fox Stunts are like mules or camels. You can abuse them, and they keep on keeping on.

They are so low stressed, to start out with.

You use a radiator clamp for your strap. Nice chrome one if you prefer.

Currell,

If you are talking about Fox 35s which are expected to perform at peak and be used for contest work, I could not disagree more. While I didn't say so in my preceding post, I can show you--with a tach--the effect on a running Fox 35 from loosening and (over-) tightening muffler attachment screws. And this would be on an approved sort of installation, screws running through bosses on Fox 35 case and into stock, RSM tongue, Adamisin tube-type muffler, etc.

Given the huge leverage advantage of a screw squeezing closed a hose clamp wrapped around a Fox 35 cylinder I could demonstrate a **substantial** loss of rpm. Without the use of a tach...

If, however, you are talking about a Fox 35 which is already kinda beat up, is used only for very casual sport flying, you're probably right, even though I don't own a Fox 35 so trashy I would treat it in this manner.

DD: As usual, your standards are much higher than mine.

Or, maybe I can't put as much ##### behind the strap screwdriver as some. So this keeps the Fox and me out of trouble. Maybe.

Currell (losing muscle mass in Michigan)

Len has some kind of filter (#### ad nauseaum) for a word that rhymes with mass, and is synonymous with donkey. Or mule.

One can do much the same thing when heads are removed and reinstalled. On Fox 35's with a good fit, I always remove the plug and tighten and loosen head bolts to get the least amount of drag. If the bolts are just tightened down you can almost lock up the piston some where towards the top of stroke.

>Len has some kind of filter (#### ad nauseaum) for a word
>that rhymes with mass, and is synonymous with donkey. Or
>mule.
>
>Currell

BUZZZZZ

"What is #####"
I'll take Stunt Shorts for $500 Alex

Scott(I got one!)Riese

This is what I mean:

My BiSlob needed a light muffler. I also wanted to use one of my old Stupid-Slow motors that had the lugs removed. This is what I came up with. Planning on using aluminum 4-40 screws so the muffler can break away when/if I stuff the BiSlob. Weight less screws is 8.8 grams. Waiting for better weather to see how well it works.
Pat MacKenzie

Hi Pat,
"How you do that?"
Must be nice to be able to machine parts like that, BEAUTIFUL!
I want one, please, can I have one?????
Bill <><

ME TOO!!

pat how big are the holes looks like 14 drilled, is that right iam makeing one something like it only im useing thin brass to strap it on with. ill let you know how it works.

14 holes .074". Here is the part drawing, along with one for a "normal" tongue.
The "normal" one was borrowed from a friend. I can't recall the brand, but it was labeled as FOX .35, OS 40/46. I couldn't get it to fit either motor, since the mounting hole spacing was >1.375".
Pat MacKenzie

I thought that using the over/under lugs distorted the case worse than the 'ears' type!

Tony,
that is of course entirely possible. As I said, I have yet to test this out.
The best solution would be to use the newer case where the outside lugs have been extended to the muffler face. I did that for the Fox in my Chipmunk. Bought a new case and used the old guts.
In this case I wanted to use an old motor and needed a light muffler. A hose clamp could have been used to hold it on. I resorted to that before when the old style lugs broke and it worked fine, but surely that is worse than using the over/under mounts.
Both surfaces are pretty flat. The screw bosses are flush with the face of the exhaust. The tongue itself is quite thin walled, so it should be more flexible than the case.

My guess is that this is not as good as using a new style case, but
less likely to distort the case than either the wrap-around clamp or the old style "ears".
Once the weather improves, I will be able to see how well it works.

Pat MacKenzie