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Engine basics => Engine set up tips => Topic started by: FLOYD CARTER on December 05, 2020, 01:14:48 PM
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I have this old Fox sand cast engine. There are no markings on it. Is there any way to know if it is a 29 or a 35?
I don't want to remove the cyl head to measure it.
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I have no other Foxies to look at.
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Based on this link, it looks like a 51 Fox, no mention of a .29 that year.
50 and 52 there are .29s mentioned, and they are both marked as .29, which is typically what Fox did.
http://foxmodelmotors.com/engines/35/35-history.htm
This would suggest that yours is a .35.
NVA looks aftermarket, perhaps Enya?
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I am not sure, but others may know for sure, did they make the sand cast engine in a .29 displacement? I don't recall ever hearing discussion about the sand cast engine in that size.
That is one thing sad about loosing Stuka Stunt in that some one posted photos in a long thread about all the different versions and itwerations f the Fox .35 and .29 at one time.
Type at you later,
Dan McEntee
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Anderson's shows the 29/35 sandcast started in 1949 with 2 bolt backplate and 4 bolt head. Markings were on the exhaust stack...but Fox is known for marking lugs or having no marks at all. The 3 bolt backplate with 4 bolt head was only in 1951 for 29/35. The 3 bolt backplate and 6 bolt head started in 1952 as a new design. Anderson's may be right or wrong but that's what he published in the 2nd addition.
I suppose a really good machinist (who have mostly evaporated off the face of the planet) could measure bore through the exhaust if taking the head off isn't an option.
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Anderson's shows the 29/35 sandcast started in 1949 with 2 bolt backplate and 4 bolt head. Markings were on the exhaust stack...but Fox is known for marking lugs or having no marks at all. The 3 bolt backplate with 4 bolt head was only in 1951 for 29/35. The 3 bolt backplate and 6 bolt head started in 1952 as a new design. Anderson's may be right or wrong but that's what he published in the 2nd addition.
I suppose a really good machinist (who have mostly evaporated off the face of the planet) could measure bore through the exhaust if taking the head off isn't an option.
How? You probably couldn't get a telescoping gauge through the exhaust port, and everything else (like a tri-mic) would have to go through the top. Maybe you could make a telescoping gauge.
A good machinist would just take the head off, although Floyd's concern is legitimate, if it is working, you *don't want to take it apart* or even tighten up a loose screw.
Brett
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You could use a depth gauge with a small diameter probe on the end. With the piston up measure to the side of the piston, then to the far side of the bore with the piston down.
The baffle would make things a bit tricky, but with a bit of fiddling (small bend in the rod to clear it) it should be possible.
The motor would need to be fixtured to something as well, but that would be fairly simple.
You don't need to be too accurate, .8" versus something like .73" should be easy to measure.
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How? Micro tools like Starrett made...simple sliding vernier depth gauge, small hole gauges, inside vernier calipers, telescoping, inside radius gauges. All of these were made in micro sizes and would easily fit the exhaust...and even smaller areas. The trick is finding a machinist who knows this stuff and has the tools. You could also use a common 1/2 protractor and add a measuring rule on center to fit inside the exhaust to do it...swing both ways and measure the delta (using marks on the protractor) after removing the rule.
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Hal DeBolt told me that the only motor he ever had in the All American Sr was a Fox .29. That was 1950.
Ed
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OK. My thanks to everyone. It really doesn't matter if it is 29 or 35. Long ago I gave up on small planes. All mine are now running with .60's (well maybe a ST 51 also)
I last flew Fox engines in 1952 in the USAF. The hot setup was a sandcast Fox and the Sterling Yak or P-51. We flew on the beach in Gulfport, MS. If sand got into the engines on a landing, we had to quit flying.
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or go the other way ,make it the size of a 29 and see if it is loose inside
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Look into the exhaust. The thickness of the liner visible will look like about 3/32" on the .29 and less than 1/16' on the .35.
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Hi Floyd,
According to Tim Dannels Model Engine Encyclopedia, The 1950 (two bolt backplate) and 1951
( 3 bolt backplate) .29 sized engines had 29 stamped on the front of the exhaust stack.
The 1952 Fox .29 had 29 stamped in the raised circle on the bypass.
So, If there is no marking on the exhaust stack, it is a .35.
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Thanks, De. I knew there had to be some Foxie experts out there.