Help Me Identify This Engine, Please

[Rick Campbell]

A bit of a different looking Fox 35. I'd like to be able to describe it correctly before attempting to sell it. Thanks!

[Robert Zambelli]

Appears to be an early Fox Combat Special with a rather odd cylinder head.

[C.T. Schaefer]

sold as  .35 R/C.

[Mark Gerber]

Hi Rick,

Yes, it's a Fox 35RC.  I inherited one from my uncle who taught me to fly control line.  They came with a rotating exhaust baffle that was used to throttle the engine.  My uncle flew his on a Veco Tomahawk.  He used a 3rd line (string) to control the throttle.  Eventually, he removed the baffle and flew it like a regular control line engine.  The 2nd photo shows my uncle's mounted on a Tomahawk replica I built.

Mark Gerber

[Steve Lotz]

How well does it do on that plane? Did Fox drop the compression on that engine?

[Mark Gerber]

I haven't run this one and it's been 60 years since as a young teenager I saw my uncle fly it on his Veco Tomahawk.  Twenty years ago, I built my own Tomahawk, cleaned and mounted the 35RC on it and keep it for the memories.  It was quite a few years before I was able to identify it by seeing one on eBay.  My recollection as a kid was it seemed to run fine, but I don't know how it compares to the standard Fox 35.  I haven't taken the head off either.  I suppose I should be curious why the glow plug was moved off-center.

Mark Gerber

[Dan McEntee]

I haven't run this one and it's been 60 years since as a young teenager I saw my uncle fly it on his Veco Tomahawk.  Twenty years ago, I built my own Tomahawk, cleaned and mounted the 35RC on it and keep it for the memories.  It was quite a few years before I was able to identify it by seeing one on eBay.  My recollection as a kid was it seemed to run fine, but I don't know how it compares to the standard Fox 35.  I haven't taken the head off either.  I suppose I should be curious why the glow plug was moved off-center.

Mark Gerber

     Yes !!! The glow plug location is curious!! Of the few hemi head configurations that people seem interested in, there was the Tom Muggleston blue head ( I think) that was one piece and had a rear angled plug. I don't knw if anything has ever been written up on this. The other accessory heads have the plug angled in from the exhaust side, opposite the baffle. Is this .35R/C engine a flat top or baffle piston? You should be able to see through the exhaust.
 Type at you later,
   Dan McEntee

[Mark Gerber]

Now you got me curious too.  Does this piston flange match the Fox 35?  Was the offset glow plug was done to help the idle with the baffle?

Mark Gerber

[Paul Wescott]

     Yes !!! The glow plug location is curious!! Of the few hemi head configurations that people seem interested in, there was the Tom Muggleston blue head ( I think) that was one piece and had a rear angled plug. I don't knw if anything has ever been written up on this. The other accessory heads have the plug angled in from the exhaust side, opposite the baffle.
Dan McEntee

You nailed it Dan.  Tom Muggleton has been coming to our club meetings the last 6 months or so, but I haven’t seen him out at the Whittier Narrows flying field.  He reported at the first meeting he came back to that he is no longer machining anything.  Pity.

[Paul Wescott]

Now you got me curious too.  Does this piston flange match the Fox 35?  Was the offset glow plug was done to help the idle with the baffle?

Mark Gerber

I have heard it said that the guy assembling thousands of Fox motors would sometimes get bored and put the piston and head in/on backwards, and they ran the same.  Maybe one of the engine experts can say for sure: Does the baffle go towards the exhaust, or towards the intake?
 

[Mark Gerber]

I stumbled across this review of the 35RC in the October 1958 Model Airplane News.  Enjoy!

Mark Gerber

[Steve Lotz]

The plug to the rear was an effort to keep it hot at idle from what I've read.

[Dave Hull]

Tom has been out flying a number of times at the Basin the last 3-4 months. Usually assisting with engines, sometimes test flying. He came to the picnic and helped out. He likes his burgers WELL done!

All of the baffle-piston engines I have seen locate the baffle opposite the exhaust port and toward the bypass. If you wanted to test for the performance difference you would have to account for additional variables of that testing. You can't just turn the piston and head around and run the same parts and expect a valid test. And it is not worth to me to break in a new engine with the "guts backwards." And even if you did, do you have an objective way to test the performance of your two different configurations? You'd properly need a dyno test stand. I sometimes wish I'd bought the one Jed was selling...but didn't.

Dave

[Dan McEntee]

I have heard it said that the guy assembling thousands of Fox motors would sometimes get bored and put the piston and head in/on backwards, and they ran the same.  Maybe one of the engine experts can say for sure: Does the baffle go towards the exhaust, or towards the intake?

   I have never done it on purpose, but I have read on here and on Stuka Stunt about people experiencing previously owned engines not starting, not starting easily, or not running correctly and upon inspection find the piston installed backwards. Think about what it's job is. If the baffle is on the wrong side of the cylinder it will at least interfere with the exhaust cycle. The baffle is off set by quite a bit on a Fox .35 Stunt and if this is any where hear that it pretty much blocks off a lot of the exhaust opening. I'll bet a search of the forums history would turn up something on i t.
   Type at you later,
    Dan McEntee

[Dave Hull]

The usual issue with an improperly assembled engine that won't at more than a stumble is that the liner is in backwards. That changes the intake and exhaust timing. I suspect that rotating the piston would be a much less impactful error--unless the head is not rotated as well....

[BillLee]

The usual issue with an improperly assembled engine that won't at more than a stumble is that the liner is in backwards. That changes the intake and exhaust timing. I suspect that rotating the piston would be a much less impactful error--unless the head is not rotated as well....

Oh! Yes, that would be more "impactful"! :-)

[Rick Campbell]

Thank you all. I appreciate your help in putting a back story to this curiosity!

[Andre Ming]

Back sometime in 1970 during my first stint at Fox Mfg, Duke was sitting at his work desk, which at the time was next to my work station, and he was working on a project engine of some sort. (Memory jog, I THINK I recall he was working on the tall case Stunt 40.) As I went about my work (honing cylinders and fitting pistons/sleeves) I would glance his way and watch him as he would measure this, check that, etc. Soon he reassembled the engine... then commenced to flip it to check compression...

With an embarrassed look on his face he stuck out his tongue in a "DUH!" expression, then he looked my way and laughingly said "I put the head on backwards!"

(FWIW: Putting the head on backwards on most, if not all, offset baffled engines will result in the baffle hitting the head.)

I got a kick out of it, too.


Andre