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Fox stunt .40 - anyone used one?

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Fox stunt .40 - anyone used one?

Old 09-19-2007, 08:50 PM
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Default Fox stunt .40 - anyone used one?

Not the newer 6 bolt backplate, this is 4 bolt with a tall smallish venturi. Good? Bad? Never saw one in 30 years, but I have access to a brand new one.
Old 09-20-2007, 05:12 PM
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Default RE: Fox stunt .40 - anyone used one?

Cutaway,

Was this the first Schneurle 40, from about 1970, with an aluminum cuff/spacer between the lower case and head, or an earlier baffle piston 40?

I have no personal experience using it but a friend, back then, liked the hefty 40 I describe - if he could get the head on straight. Torquing was a bit more demanding, with that sorta soft aluminum cooling-fin stack in the middle of things...

Interested to see what you've turned up, here...
Old 09-20-2007, 09:10 PM
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Default RE: Fox stunt .40 - anyone used one?

Looks like an ordinary loop scavenged design. More cooling fins on the head/cylinder than a stunt .35, but other than that not a whole lot bigger package. The venturi is smallish diameter but long like a McCoy.
Old 09-21-2007, 07:53 PM
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Default RE: Fox stunt .40 - anyone used one?

Cutaway,

I recall that engine, vaguely, from the mid- or late-60's. The Army sent me odd places in those days, so only intermittent opportunities... Did try to keep up with the magazine coverage, but again, only sporadically.

Couple of 'environmental factors' that may apply... Those were the days when our younger people seemed to have two main hobbies: slot cars and political protest. AMA's total membership dropped to less than 20,000, if I recall right, in a few of those years. The hard core cadre among us who were able to keep active had certain preferences for and against particular products and manufacturers - and Fox, Mfg., didn't always package lovely sculptures the way K&B, ENYA and OS did. Their QC varied from tolerable to somewhat less than.

So, for timing, reputation, snootiness, and whatever, there didn't seem to be many using your particular engine at that time. It might be fine, given what we now understand about how to make engines run, the need for ample castor for iron in steel piston/cyl engines, and the variety of props we can check to see what makes it happiest. As iron pistons are heavier than the modern aluminum alloy pistons, the older engines are likely to shake a bit more. They did then, and we've become spoiled, since then.

Still, given proper (oilier) fuel and moderate stress operation (at its happiest RPM range, that should be ample power, btw) iron in steel engines last very well, and are dependable and tolerant of conditions.
Old 09-22-2007, 04:46 PM
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Default RE: Fox stunt .40 - anyone used one?


ORIGINAL: cutaway

Not the newer 6 bolt backplate, this is 4 bolt with a tall smallish venturi. Good? Bad? Never saw one in 30 years, but I have access to a brand new one.

This is the George Aldridge designed fox 40 "big case" I have one, they take a long time to break in. It is powerfull, and I need to find a muffler for it. They run a little fast, but great for a sport model. Problem is the mouinting patern fits nearly nothing modern.

Old 09-23-2007, 05:45 PM
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Default RE: Fox stunt .40 - anyone used one?

I got hold of this beast today - you're right, the mounting pattern is VERY long on each side. Its also locked up solid since its been sitting on a shelf in its box for probably 40 years and the factory test pop oil is completely solidified, so its going to need some soaking and prodding with a heat gun to loosen it up.

Looks like a pretty stout engine though. No instruction sheet in the box. How did you break yours in? I'm thinking something light like a 9x4 for running on the stand and I just mixed up a batch of ~26-30% oil 10% nitro fuel.
Old 09-26-2007, 04:43 PM
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Default RE: Fox stunt .40 - anyone used one?

uliner and cutaway...

One of the Alrdich/? designed Fox 40s was a hefty sandcast, rear exhaust, schneurle. The cooling fins on the upper part of the casting were very shallow. Great engine in some ways, but never caught on. Heard it wasn't as powerful as several of the other 40's of its era. It may also have come in a 36 size, with an optional muffler that fit between the mounts, behind the engine...

That was a schneurle layout - flat top piston, no fence baffle. So was the "first" Fox schneurle, another 40, had a smooth, drop-in sleeve, cooled by an aluminum cuff between the head and the lower crankcase. The lower case only came up as high as the top of the exhaust stack. This one had a VERY long mount bolt spacing, fore and aft, too.

I do believe there was a CL version of the baffle piston Fox RC 40 of the late 60's. It looked more like a round venturii Combat Special than the 35 Stunt, and did have many more head fins, as did the Combat Specials. If I recall, the venturii stack had a short section right at the opening which rolled out like a very short trumpet bell. Again, the age was not supportive of some engines gaining a reputation, either way.

Most Fox engines I've used and seen gave good service at the cost of some time and effort when they were new. Other engines don't need as much TLC at the beginning, and are/were usually much prettier to look upon.
Old 10-07-2007, 10:33 AM
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Default RE: Fox stunt .40 - anyone used one?


ORIGINAL: cutaway

Not the newer 6 bolt backplate, this is 4 bolt with a tall smallish venturi. Good? Bad? Never saw one in 30 years, but I have access to a brand new one.
Sorry to be so late in this thread, however I will say this. Back in the late '60s and very early '70s when I was very active in CL stunt, after leaving the USAF, I owned one of those Fox .40 Stunt engines. At the time I was using mostly Fox .35s and for competition, a GA rebuilt ST .40 which was a superior Stunt engine.

Using Fox Superfuel, 29% castor oil 5% nitro fuel I ran the engine for a couple tanks just to get a feel for it. I used a fat 11-5 cut to 10-5 for break-in. Then it went onto a Midwest 48" w-s profile stunt model -- ME 109 -- for over 3 hours of constant flying over a couple weeks. It then went into one of my original stunters and was flown in competition for several years until I became completelyinto RC after '73

The Fox 40 was equal to the Super Tiger in every respect. It started the first flip if I obtained the "bump" then flipped. It had plenty power and I still have one NIB if I should again take up CL.

Incidentally, I used OS and ENYA CL needle valve assemblies with the single hole facing STRAIGHT BACK. This technique takes care of many problems that CL Stunt pilots manufacture for themselves.
Old 10-07-2007, 11:09 AM
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Default RE: Fox stunt .40 - anyone used one?

cutaway,

Generally, using a smallish prop, high castor content (~28%) using short runs on a bench for heat cycling are a good way to go on iron/steel engines.

Start rich, run for one or two minutes, shut it down by pulling fuel line or use small tank...don't flood it to stop it. Let it cool to air temperature, then do it again. Every other run, turn the needle in a few clicks. If during any run it starts to sag, shut it down, let it cool, and start it again a few clicks richer.

Once it runs near peak without sagging, run it in a plane for final break-in. Flying some lazy eights will run it between rich and lean for the final heat cycles.

Is this the only way? Of course not. But it is a way to break it in without risk of running over-heating.

Good luck.

George
Old 11-11-2007, 08:19 PM
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Default RE: Fox stunt .40 - anyone used one?

Try this link and see if this is the 40 you have, there are also reviews for a couple other of Duke's .40 CL engines on this site.

http://www.the.elmores.btinternet.co...ox_40_am0.html
Old 11-11-2007, 08:52 PM
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Default RE: Fox stunt .40 - anyone used one?

That's a much older one based on the Rocket case.

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