50+AirYears

Tight engine? Slow break-in? That first 15BB took almost 10 sessions to get it loose enough to spin with a Sullivan starter. I was cutting fingers and gloves on the prop, it was so tight. I had to use a plastic screwdriver handle to flip the thing. But, by the second day, it would run out a tank of fuel every time. About 22 minutes on 4 ounces. Put out it's best using an 8.5-4.5 wood prop. At least that was the prop that flew the plane the best.

WhiteRook

My Feedback: (38)

i have 2 fox 45's , one is the old shinny case version, both have great compression, but the carbs dont work at all in transition. should i replace them with E Z carbs or perrys?

thanks

dan

RaceCity

Typhoon...how much prop are you using on those old .45's? The older vintage "B" frame .40's and .45's were arguably VERY overcarbureted using a carb bore similar to that of the .60 size engines. This, combined with a too-big prop and one could imagine some transition problems arising. Overbore carbs are great if top end is the only objective.

The carb from a current .45/.46 should work well provided it's properly tuned.

NM2K

My Feedback: (14)

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I talked with Duke about this some years ago. He said to let the engine rev up and then it would carburet properly. A 10x6 is all you need on a Fox .40 or .45. Larger than that and the carb is too large. Remember, these are old paradigm engines and were made long before anyone used an 11x6 or larger on a .40 to .45 sized glow two-stroke. An alternative might be an 11x5. Also, those old large crankcase .40 - .45 engines were made to run on Missile Mist and they will run rich in the midrange if ran on lower nitro fuel. Small prop and a bit of nitro couldn't hurt. They are going to be powerful, but LOUD.

WhiteRook

My Feedback: (38)

i ran a 10-6, but with5% nitro, i just couldn't get them to idle, mabey it was the nitro content.

one of em fired right up, and it hadn't been run in years. paradigm? what does this term mean?

thanks

NM2K

My Feedback: (14)

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Paradigm (paradygm - old spelling) refers to a "world view" which incorporates science, sociology, etc. Back in the old days, we used to scream the dickens out of engines, thinking that we were getting the most out of them that way. Duke went along with that line of thinking and equipped his engines with oversize carbs before the Japanese, and later the Chinese, caught on to it. Problem is, the Chinese are still fitting their engines with oversize carbs, but most noise conscious users have swung the other way and are using larger props for efficiency and lower sound production. The Chinese need to bring their thinking into the current paradigm (larger props, less noise).

The Fox engines can also benefit from glow plug experimentation. If you want to burn 5% in them, you might profit from using a hotter glow plug (Fox Miracle Plug or an OS #3).

50+AirYears

There was also a series of carb that required the idle to be set first, then the high end. I never had any problem once I found this out. Even set up a couple others' 45s this way. Always ran 10-6, 10-7, or 11-5 props. Also, I've always added several ounces of castor oil to the fuel I've used, which was usually a 10% or 15% nitro.

Typhoonfury, maybe you could richen the top end a bit, then go to set the idle to it's best point, then adjust the high end? Also, sometimes placing a bit of fuel line over the idle and high end needles might help if there is some looseness on the threads giving a bit of an air leak.

http://www.flitelinesolutions.com/ez.html carries a huge amount of info about the Fox engine line.

If a number of the magazine reviewers call a 2300 RPM idle very good, what would they call the 1950 rpm idles I've gotten from the 45s?

NM2K

My Feedback: (14)

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You are absolutely right. How could I have forgotten about this? <G>

These carbs were made during the Seventies mostly. They had cast-in carb nipples mostly (tapered the wrong way for retaining fuel line).

If you didn't set the low speed first and get that squared away, you could diddle with the high speed needle until the cows came home and the engine would never run right.

stg61abc

Hey folks, i also have a Fox, a .35 stunt shiny case from around 78. it´s still flying in my sport c/l aircraft very well !

loughbd

I have a dozen or so Foxes, mostly 35's and 36's. Combat and Rat Race engines. Newest was purchased in 1976, a 36X. After Johnson quit the engine business in the middle 60's, Super Tigre and Fox were the only good C/L engines for combat. Super Tigre G21/35 was choice one, then Fox. I ran a Fox 36X about a year ago, 104 DB. Too loud to use anywhere near people. Subpiston induction so you can't use a muffler. Now they all sit in boxes in the basement.

Dr Nitro

Correction, the Mecoa is made in china too. The Thunder Tiger is made in Taiwan (OK, not mainland china, but free china).

I have always like the Fox engines, once a bit of a learning curve is achieved, and some quality break in time, you have great running and reliable engines.
I have a pair of 50's that have been on a twin with absoutly zero deadsticks. My 74's are plenty stronger than my ST 75's and approach the power of the ST 90.

They are good engines and have gotten much better over the years. Well worth the money.

Sport_Pilot

Actually you can use it. If the subinduction is not too much then use a very unrestrictive muffler. It will not have the same power but it will run. Or you can shim the sleeve. It will have less compression and more radical timing, so this may or not work depending on the amount you have to shim. As I recall the ST G21/35 combat will work with a muffler.

j.duncker

My Feedback: (2)

There is a memory from the past! A Fox 36X combat special on a 9x7 at ?????? RPM. I used to do demos and shows. It was a real attention getter in a Splinter.

It was Loooooouuuuud.

loughbd

The 36X was not sold as a combat special. The combat special was a different engine. I have several of each. There were also a couple different Fox combat specials. Side exhaust and rear exhaust.

Sure you can use a muffler on a sub induction engine but as the incoming charge is diluted with exhaust power will be way down so what's the point? The super Tigre G21/35 and G21/29's had sub induction porting too. At least the early ones did. Same problem. Why use an engine way down on power when you can use a muffled modern engine that will produce more power with it's muffler.

Sort of like removing two spark plug wires on a V8. It will run but power will be way down.

If you shim the cylinder so it sits higher so the bottom of the piston is not exposed you will lower the compression.

buzzard bait

I have two 15 RC Foxes with the slant plug and the MKX carb. I think this type was only made for a short time in the early 80s. The carb looks just like the one on my later 15BBRC. I got them both used, and have fired up the more worn of the two. Compression is very strong; in fact, it is stronger than the less worn engine, which leads me to suspect that the head shim was taken out of the more worn engine and not taken out of the other. Both engines hold compression extremely well at TDC.

I had some trouble getting it to keep running and to idle and transition. I used an 8 x 4 prop and 15% nitro with extra castor. I probably need to spend more time adjusting the two needles, but I also wondered if I should put a pressure nipple on the muffler to get some pressure in the tank?

These little guys weigh slightly less than an OS 10 FP (stock mufflers on each), but the Fox clearly puts out way more power. I think these old engines must have a very good power/weight ratio even by modern standards.

Too bad they're such noisy suckers!

Jim

NM2K

My Feedback: (14)

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Are you certain about that, loughbd? I'm not, so I'm not saying you are wrong, but the idea of making a needle bearing engine just for sport flying seems kind of out there. Yet, Duke specialized in being out there at times.

Later, the 36X nomenclature appeared to be reused for a different line of engines. IIRC, some even had round intake venturies.

The one that I had (1965/66) had a square intake and allegedly sported needle bearings. I never had mine apart.

loughbd

The 1961 35X had needle bearings front and rear. The 1963 35X had a needle bearing in the rear only. The 1964 36X had needle bearings. The 1965 36X had ball bearings. The 36X was designed for combat use but never called a combat special. OS made an old 50 with a needle front bearing and it was a sport engine.

The first Fox "combat special was the 1956 "35" combat special. Then the 1958 "35" combat series II. Then the 1960 series III combat special. The next was th 1974 Combat "36" special MkII

All Fox combat specials were called combat specials. The 36X wasn't. Doesn't mean they weren't used in Combat because they were. That's what I used them for.

Johnson made a combat special, the JCS, and it was sold as a combat special. He also made a ball bearing engine, the JBB, which was an excellent combat engine. That was my preferred combat engine in the 60's. It wasn't a combat special though.

Super Tigre G21/29's and 35's were great combat engines but not sold as combat specials.

Again, no Fox 36X was sold as a "combat special".

Short quick history of Fox combat engines

NM2K

My Feedback: (14)

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What you are saying rings true.

I bought a used Johnson .29 at B&B Hobbies in Glendale, AZ back in 1966. It ran right along with the .35's at our field. A very impressive running engine.

loughbd

The Johnson 29R was a hot rat race engine. Very powerful and one flip starting. The Johnson R/C was just the JBB with a Johnson automix carb. That was the first mixture control carb. The barrel moved in and out controling the mixture at idle like most modern carbs. Ol' Hi was way ahead if his time. Too bad he quit making engines and got into slot cars. The automix carb really revolutionized radio Control engines.

SDM

My Feedback: (9)

My list of Fox motors as follows...

74 on a Sig 4* 60
45 GP Corsair
40 bb ABC delux Sig Kougar
40 bb standard
25 bb still in pieces after a big crash but fixable someday
15 bb
15 baffle that has been rebuilt by Fox and waiting assignment
Great engines and super good service ...[8D]
Sam

Sport_Pilot

Power won't be down near as much as you seem to think. Subinduction occures near top dead center when most of the induction through the carb is done. Also the exhaust from the prior cycle has been disipated in the muffler So there is not that much back pressure left. With a very simple muffler on a G21 ST 35 combat, the power was still above most sport .35 engines.

loughbd

First off I have tried it and it DOES knock the power way down. Almost 1000rpm in Fox 36X and even more in a Johnson BB. The exhaust is under pressure (remember muffler pressure?) and that pressure is always there and the gas is forced into the case by that pressure and there is a pretty good vacuum in the case from the induction. That vacuum is what made sub piston induction work in the first place. A shot of air was pulled in under the piston at TDC. Both lead to a fair amount of contamination of the incoming charge. Like I said, I have done it.

50+AirYears

Somewhere in my files I may have an article from I think Riley Wooten on how he modified the 36X to get speeds consistently over 100 or 125 mph for combat. Both the 36Xs I have have the needle bearings. They wee pretty easy to implement.

loughbd

The article was by Larry Scarzini and it was in the July 1964 Model Airplane News. The article was about a combat airplane called the Blitz. The engine was a first model 36X with a rear roller bearing rear and a plain bushing for the front bearing. The secret was the crankshaft. It had a special shaft made by Duke Fox called a stroker shaft. The previous shafts had weak spots and broke under high nitro use. Fox had just released BLAST fuel which was 50% nitro methane. The orginal shafts couldn't handle it and broke. There were a few other mods to the engine but mostly the shaft and rod. The airplane would do 120mph without a streamer on Blast and about 110 on lower nitro fuel.

I did the mod on one of my 36X ball bearings and it would scream on a trimmed wooden 8x8. Didn't use it too much. Blast cost a fortune ($1.25 a pint) and paper route earnings couldn't handle the load. I flew the plane once in a while to impress my friends. The rod finally let go and that solved that. I still have what's left of the engine. Got too old to compete in AMA combat. The kids beat the pants off me.

Here's a little note for all those guys that think a wet front end from a leaking front bearing is bad. Part of the mod was to run several scratches down the bore of the plain bearing so lubrication could get to the front end. It doesn't cause an air leak as stated in another thread. The crankcase preasure forces the oil forward and out the front of the engine. Standard trick in old plain bearing racing engines.

CapnJack

Hey Any suggestions on what brand fuel to run with Fox Engines?