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Old Jan 03, 2013, 04:43 PM
J. Craig
Jacksonville, FL
Joined Jan 2011
6 Posts
Have you tried an extra head gasket or two? Have you re-set the piston ball & socket? Clean roughen & a little JB Weld on that spot for good measure. One summer, I flew an R/C flying wing on a 2 oz tank all summer long on a gal of fuel. (Many recommend Sig Champion 35% Nitro fuel) Finally had to change the plug. Never a problem. Loved the fine threaded needle valves. If one of these do not work I am clueless. Has someone changed the cylinder or crankshaft timing?
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Old Jan 04, 2013, 12:02 PM
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United States, SC, Columbia
Joined May 2010
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I used two head gaskets, considering my fuel was under 25% nitro. I never did try three. And I am using a KK needle valve and have tried two different ones. My venturi was fairly conservatively bored at .130" I bored it more to .145" and it didn't help. The ball socket has almost no play. As far as I can see, the piston crown is right at the deck height at TDC so I don't think the timing was altered. All I can figure is the crankcase has a friction problem when it gets hot. It definitely looks as if it's had a thrown rod in its past.

It's in the engine drawer now and I'll get back to it later. The Li'l Satan is all back together with a really nice running Tee Dee and ready to fly. I bought some Sig 35 as well as some fresh Glowplugboy fuel too.

Thanks for the input. Welcome to RCGroups.
Rusty
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Old Jan 04, 2013, 02:26 PM
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United States, OR, Albany
Joined Jun 2007
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Rusty,

For my TD crankcases, I use a small dab of regular old style crest tooth paste on the crankshaft, insert in back into the case and use a drill to spin the crank a little. Wash it out with water and reassemble. The fit should allow just a little blow by to lube the crank bearing when running.

George
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Old Jan 04, 2013, 03:59 PM
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Quote:
Originally Posted by GeorgeG97322 View Post
Rusty,

For my TD crankcases, I use a small dab of regular old style crest tooth paste on the crankshaft, insert in back into the case and use a drill to spin the crank a little. Wash it out with water and reassemble. The fit should allow just a little blow by to lube the crank bearing when running.

George
I think I'll do that when I get back to this engine. Give it a little nosebleed. I hate having a Tee Dee that I can't use.
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Old Jan 04, 2013, 08:36 PM
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Rusty,

Here's the best advice...

George
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Old Jan 04, 2013, 11:36 PM
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United States, SC, Columbia
Joined May 2010
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Thanks George, I've got that in my Tee Dee tuning folder. Good stuff.
Those one blade props are not something i ever imagined before I found out about speed planes. They just look so wrong. I might try to make one someday... after I get a flak jacket and a riot helmet.
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Old Jan 05, 2013, 12:09 AM
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Poteau, OK
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George: Can you please post the rest of the article?
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Old Jan 05, 2013, 01:04 AM
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E One -6

E One -7

Tee Dee Info (Kluse)
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Old Jan 05, 2013, 10:22 AM
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Poteau, OK
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Thanks Rusty!
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Old Jan 05, 2013, 01:32 PM
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Knowledgeable people say not to lap Cox crankshafts in place, but rather to polish them out of the engine. Lapping in place destroys the hardened surface of the case, and leads to rapid wear, so it is said.
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Old Jan 05, 2013, 01:40 PM
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United States, OR, Albany
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Jim, I agree with your comment about causing wear to the hardended surface, however, if the engine is run at higher temp's such as high nitro and propyline oxcide the case needs a little bit of clearance.

My main speed engine lasted about 20 years of moderate flying (First on a profile proto speed ship, then as a combat engine) until the crankshaft broke in two. It was a bored out crank, center hole was 0.20" dia., and an electric or mechanical starter was always used.

Never broke a rod or crank with a starter... just FYI

George
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Old Jan 05, 2013, 11:23 PM
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I don't run screaming speeds like combat pilots do, but I fly fast control line sport, as fast as I can handle at my advanced age of diminishing coordination. I launch them at 18-20k rpm depending on the prop and fly full bore, so probably hitting 22k in the air, I would guess. With all the engines I've rebuilt, I polish the crank bearings with 1000 grit paper wet with 10w oil, and not overly aggressively. I've recently been told by a couple of others to lap the crank in the case too. As yet I haven't tried it.

For lack of any other ideas with the engine that this thread is mostly about, it might be worth a try. If the case is slightly out of true, it could be seizing when it gets hot. That fits with the pattern of slowing at half of a tank and I rich it up, it cools off and then it goes back to full speed. Then repeats that behavior through the rest of the run.

I was thinking of taking Bare's advice and swapping that crankcase with my one Medallion. It has a slit SPI cylinder/piston, but it still runs a few RPMs slower than the TD, and might not have the same trouble. If the Tee Dee has this problem after that, it could be the piston/cylinder; I never did try swapping that out. But it's a loose one with no varnish, so I don't really suspect it. I'd have to buy a new one to try because I'm not cannibalizing the new Li'l Satan engine. I wanna fly the damn thing!
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Old Jan 06, 2013, 12:14 AM
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United States, OR, Albany
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Rusty, 22k rpm is about all you can get out of a fairly stock TD. The 1/2A engines used by the combat guys today rev a lot higher and are not cox engines. Its been a while sense I have had my medalion apart, I know the crank is different, but try it with your TD parts and see what it does. Have you lapped the backplate opening on the case yet. Often leaks ocure between the case and backplate. I also lap both ends of the plastic venturi body too.

George
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Old Jan 06, 2013, 04:35 AM
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Australia, VIC
Joined Dec 2011
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Hmmmmm , lapping a crank into the case ?

Oil + Braso [ polish ] use a motor tool [ Dremel style ] , if you wish to polish ?
Goes against the grain with the crank - by all polish the crank , but the case ?
See all those tiny imperfections trap oil [ lubrication ] and also = less surface area ..

Lap a crank into a case = less imperfection for oil , more surface area ..
By all means polish the crank - reduce dia by a few microns .. Smother crank is good ..

Ahhh well , we all have our own ideas !
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Old Jan 06, 2013, 11:24 AM
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Canada, ON, Cottam
Joined Jan 2012
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I go along with your idea Old 4570. Polish the crank (and crankpin) I have had too many reedies that won't run a tank because of wear on the crank/crankcase. The seal goes and it just won't run right, up, down, up, down. I havent worn out anything else but the reedies on the plain bearing motors yet, maybe the carb up front lubes better. Even LA type motors never seem to wear on the crank with any bad effect. I use 60,000 grit sandpaper, and no I don't know where to get any more. Some KK cranks were chromed back in the day.
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