combatpigg

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Many years ago an Old Timers gave me a pair of ST .15s.
Some years after that another Old Timer handed me a collection of spare ST.15 parts ..[mostly what looked like used junk]
I've had a good deal of fun with these engines...running them in "as is" condition.
Many years have passed and I recently decided to run 1 of them again but it wasn't ready to run
The bearings were rusted, the prop driver collet was slipping and causing a bind against the front bearing and the P/L was not good enough to carry the mail like it should.
New bearings were easy enough to find.
In the stash of used parts was a brand new prop driver [!] and this was all it took to fix the slipping collet problem.
In the stash of used parts is also 4 old piston / liner sets.
I figure there was a 1% chance that any of them would be worth trying...but the first one I tried appears to have some pop.
I'll know by tomorrow if it is a runner or not.
Here's the plane I built for this project...34 inch span, 340 sq inches and it weighs just under a pound.
I flew it today with the ST.15 on back plate pressure and even though the engine was tired the combination shows signs of being pretty sporty.
One other problem besides the low compression is quite a lot of fuel is coming out the front bearing.
I have the hole in the spray bar pointing to the front of the engine, it might be smart to aim the discharge downward..?

aspeed

Plane looks like the old F2Ds from about 1980. I just gave one away to an old flying buddy. He asked about the old G15 that we used for goodyear racing back in the day. Seems to be missing a backplate and prop driver and is sitting on the bench. More searching. Don't want to give away a Rossi. Waiting for your video on this plane.

combatpigg

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YEP....I did a search for F2D designs and saw a photo of this one so I copied it...[except I was too lazy to make foam leading edges]
It ran so so today with a 7 x 5 APC and a 6,5 x 5 APC but the engine sags when doing tight turns.
The engine is throwing some fuel out the front bearing.
Here's a look at how it's going so far....

J330

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Back in my C/L days, that was my favorite engine. I flew mine on a Magician .15. 6X6 prop was hard to come by. Using a pen bladder was a good combination.
https://www.ebay.com/itm/134003444437

combatpigg

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The Magician is a good looking plane..!
https://aerofred.com/details.php?image_id=98061

speedracerntrixie

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Spitting fuel out the front bearing is usually a worn case, too much clearance between the case and crank. Not much you can do about it.

combatpigg

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One of the Fox Combat Specials had shallow spiral groove on the crank journal between the front bearing and the intake port. It looked like it was done by hand.

I think this was done to control fuel spitting ...?

Either that or it was done to provide fuel to the front bearing...?

There is a crank case leakage test that a small engine repair guy showed me to quickly diagnose crankcase pressure leakage.
He did this test to evaluate used weed eater, leaf blower and chainsaw engines.
He had plates he could attach to the intake and exhaust port. Either plate could be used as a "block off" or as a place to introduce air pressure. He would dunk the engines in a bucket full of water and look for bubbles coming out the crankcase. This was where you would have to know how much "test air pressure " and how much leakage is enough or too much.