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Old Dec 17, 2012, 09:09 PM
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Originally Posted by Gnu4FF View Post
Is the crease deep enough to cause an air leak in the case? That would mess with the transfer pressure.
I saw the crease when I first got the engine and inspected it under a magnifying lamp inside and out as closely as I could eyeball it, and didn't see any hairline cracks. The backplate threads in with no catches or tightness and the crank spins freely. After Christmas I can get it out to the field and try it with a different NVA and venturi and put the mystery to rest. If I can't get it to cooperate I'll pressure check it, just to be sure. I have another one with a brand new #4 cylinder/piston ready to steal its job.

Speaking of transfer, maybe it doesn't like running with the cylinder pointed straight up. I wonder if it would run any differently with the cylinder sideways. I only mounted it upright to protect the needle. I hadn't thought of transfer until you mentioned it. Every other one I run is sideways.
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Old Dec 20, 2012, 04:55 PM
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Troubleshooting the Satan's TD .049

Since this kind of turned into an engine troubleshooting thread I'll keep updating it.

Today I set up outside of the shop to experiment with it. I replaced the Kustom Kraftsmanship NVA with a known good one. I left everything else the same as when it flew last, including the 5.5x3 prop. I cranked it with the new NVA and it started fine, but soon needed adjusting to stay on peak. It was all over the place with the mixture adjustment. So, the NVA apparently wasn't the problem.

Next I removed the Cox #1702 Tee Dee head and installed a Galbreath/Nelson head. Cranked it again and it ran much better and faster holding about 19.3k rpm until a half tank when suddenly it needed richening slightly to keep it on peak. I was not using a fresh bladder, so maybe it was supplying uneven pressure. I ran 3 more tanks with identical results.

Next I put a MA 5x3 prop on it. I cranked and it ran and held 20k rpm for a half tank when again it needed a slight richening to keep on peak. Another identical 3 runs. So changing the head helped a lot. And the other prop was not causing the problem as one reply had suggested.

I need to make up some fresh bladders to test it again, and then if it still needs an adjustment at a half tank, the next thing I'll do is replace the carb body. It might have a bad fit causing a leak at a certain temperature. I have a new aluminum carb I can use. I don't have a laser temp reader, which would be a nice addition to my toolbox.

If all else fails, it's engine swap time, unless someone thinks of something else to try.

Rusty
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Old Dec 21, 2012, 11:00 AM
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Originally Posted by Jim Thomerson View Post
I have a TD 15 crankcase just like that; the result of a blown rod at high RPM. What you have there is a repaired and rebuilt engine.
Absolutely... likely from a broken crank event ? .. an expected failure with a TD once you get them running 25k rpms.
Clearly some previous owner had an event, with this rascal. Possibly a tiny crack opening up with heat and vibration? OR bent metal expanding under same?
Suspect that this motor (the case at least ) is now for the drawer.
Shame... but 'stuff' happens.
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Old Dec 21, 2012, 11:35 AM
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Absolutely... likely from a broken crank event ? .. an expected failure with a TD once you get them running 25k rpms.
Clearly some previous owner had an event, with this rascal. Possibly a tiny crack opening up with heat and vibration? OR bent metal expanding under same?
Suspect that this motor (the case at least ) is now for the drawer.
Shame... but 'stuff' happens.
Yeah, I hate that. It gets one more chance and then it becomes spare parts minus the case. Then I'll be down to two .049/.051 Tee Dees and a Medallion. There was a rumor that Bernie(Cox International) was considering making new ones, but I haven't asked him if there is any truth to it. I'd like to have a couple more for planes too light for a Norvel. I have three Big Mig .061s and a new MP Jet now. Some are still awaiting a ride.

I'll let y'all know how it runs with a new carb body. I might try running it on suction just for kicks too.
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Old Dec 21, 2012, 02:38 PM
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Lighter ??
If it's a serious consideration, hunt up a VA 049 ? a bit rare but perhaps possible.
Much Lighter than a TD and even Mo' Go than a Norvel
You 'could' run the damaged TD as a Medallion? Parts/engines on the shelf are just a waste imo :-)
Screw a black widow cyl /piston/plug on it and refit the OEM carb bits (no bladder) . With rpms in the sub 18K range there might not be issues..and it would still be quicker than a BW.
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Old Dec 21, 2012, 04:21 PM
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It may be varnished up too, They get that way quickly, especially if a lot of castor is in the fuel. It only takes a bit of Scotchbrite and some laquer thinner or acetone and a quick scrub of the inside of the cyl. It may be just a bit hot after it runs a while. There could be a lot of slop in the crank/crankcase making it leak air and being erratic too. I had seen a rod go right through the crankcase and soldered a patch on and it goes fine, Maybe I'll take some pic. but don't think that is a problem. I wouldn't put a single port cyl on anything unless it is just too fast for a certain plane. The TD cyl is the good one unless it is worn out completely, then they go faster(if you can start them)
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Old Dec 21, 2012, 08:08 PM
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Naaaah, new carb, fresh bladder, same thing. It's not varnished, in fact it's looser than I would like. It did run a couple of hundred RPMs faster, but it was 20 degrees colder outside too, so that probably explains that. I'll try what Bare says, turn the Tee Dee into a Medallion and visa versa. Worst case scenario; I'll then have a bum Medallion, which is better than a bum TD any day. My backup TD has a brand new #4 set and is raring to go, so it'll get the job.

Thanks everyone for helping make this an interesting thread. It started out as just another one of my videos and turned into a good discussion. At least now I know the Li'l Satan is capable of being ten times more fun than originally designed. Especially since it doesn't run out of gas every 90 seconds. The fun light stays lit for 4 minutes now. Next time I fly the Satan, I'll make a video and post it here. I promise a much more entertaining flight. When the plane is running right and I can trust it, I have some more tricks in my usual routine. I'm getting the hang of it.

Cheers,
Rusty
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Old Dec 22, 2012, 03:27 AM
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Hmmm , so it might be a compression ratio thing ..

Or not enough nitro ..

TD's were always sensitive to fuel [ My 09's were ]
+ If its too lose , it just might never run properly unless you jack up the nitro
A good TD would run well on 20% nitro [ Fits being good ]
But a lose one [ worn ] needed more nitro ..

I only ever played with the 09 Tee Dee's [ 1.5cc Half A ]
I stopped running TD's when the heads became scarce and expensive , I tried tapping the heads for a glow plug , but the power was gone [ glow plug mod just robbed power ] and you really needed to jack up the nitro to compensate

A lovely engine , aaah the good old days , cheap heads and cheaper Nitro !
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Old Dec 22, 2012, 06:57 AM
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Hmmm , so it might be a compression ratio thing ..

Or not enough nitro ..

TD's were always sensitive to fuel [ My 09's were ]
+ If its too lose , it just might never run properly unless you jack up the nitro
A good TD would run well on 20% nitro [ Fits being good ]
But a lose one [ worn ] needed more nitro ..

I only ever played with the 09 Tee Dee's [ 1.5cc Half A ]
I stopped running TD's when the heads became scarce and expensive , I tried tapping the heads for a glow plug , but the power was gone [ glow plug mod just robbed power ] and you really needed to jack up the nitro to compensate

A lovely engine , aaah the good old days , cheap heads and cheaper Nitro !
Well now, that's a good point. Its pattern of obstinance doesn't fit with what I'd expect, but maybe I'll put that new #4 set on it and give it a try. My nitro is about 22%. It was 24 until I added castor to it. I could try one shim in the head first too.

Fortunately new TD cylinders are plentiful now for $14.95 at Cox International. http://coxengines.ca/top-end/index2.html
I've had a couple in my wish list for a while now, maybe it's time to buy some. My other spare one is a brand new in-the-package Cox set.

I'll have to sneak time for the shop for the next couple of days since I have Christmas stuff on my extensive honey-do list.
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Old Dec 23, 2012, 01:07 PM
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erm.. those are twin slit cyls with the slit ground out and down? a wee bit for SPI
I'm thinking a diy TD lash up from an Estes cyl, which were known as 'less' accurate than earlier Cox production.
Find oem bits.. if needed and are seriously concerned.
Even the current 'foolish' collector prices are affordable :-)
In my experiences Cox cyls last a Looong time.. unless damaged.. and worn ones were best for max rpms. Some of us would even lap fresh cyls for a loose fit.
Having said that, try that 'suspect' cyl/piston in another engine to test it.. just to be sure.
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Old Dec 23, 2012, 02:03 PM
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That's right, Ronald Valentine modifies them for Bernie. They are each paired with a proper fitting piston, though not tapered. Cox started making the slit cylinders long before Estes. The design was good. Cox found the single boost flute accompanying each bypass port performed better than the earlier type with 2 flutes on each side like the Tee Dee #4. Given a choice I'd take the old #4, but there's no meaningful performance difference between them and Bernie's.
Don't worry, I'm not throwing the loose one away. If it's that bad I'll find a piston that fits.
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Old Dec 23, 2012, 10:50 PM
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Got the camera out today. Repaired crankcase on a TD where the rod went through, and an Arden .099 that someone brazed. I just got the Arden at a swap meet because it was older than me. The guy said it worked but I never tried it. The TD is ok but I use better ones. I put a cylinder on it for amusement.
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Old Dec 23, 2012, 11:27 PM
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Wow, that's a couple of old beaters.
I got my spare Tee Dee out for inspection today. Tore it down to check it out. It's perfect, the crank looks like new with no bearing side play, so the crankcase must be a low miler. The cylinder and piston are brand new, straight out of a sealed Cox package with a nice pinch at the top, so it should run like a brand new Tee Dee. I'll put it on the test stand and give the new cylinder a proper run-in before I mount it on the Li'l Satan. I'll worry about that other cranky old engine later.

I am looking forward to getting out to fly it again. The holidays are putting a cramp in my hobby time though.
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Old Dec 24, 2012, 11:13 AM
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That's right, Ronald Valentine modifies them for Bernie. They are each paired with a proper fitting piston, though not tapered. Cox started making the slit cylinders long before Estes. The design was good. Cox found the single boost flute accompanying each bypass port performed better than the earlier type with 2 flutes on each side like the Tee Dee #4..
Interesting, didn't know that's were the grinding was done.
Does then beg the question as to Why remove the slit ?
If the 2 slits is 'better' or even equal ? why grind it out and subsequently burring the bore? Then having to lap to remove it, further messing tolerances. Odd indeed.
Spi could be achieved by shortening the piston, if grinding was indicated, a less invasive widening of the lower slit could also serve..
Regards of pedigree, imo it's still not something I'd be paying $ for.
Hopefully you won't have to either :-)
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Old Dec 24, 2012, 09:07 PM
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Interesting, didn't know that's were the grinding was done.
Does then beg the question as to Why remove the slit ?
If the 2 slits is 'better' or even equal ? why grind it out and subsequently burring the bore? Then having to lap to remove it, further messing tolerances. Odd indeed.
Spi could be achieved by shortening the piston, if grinding was indicated, a less invasive widening of the lower slit could also serve..
Regards of pedigree, imo it's still not something I'd be paying $ for.
Hopefully you won't have to either :-)
Removing the slit reduces exhaust restriction and helps it breath. Valentine is also lowering the exhaust port bottoms for SPI with a regular piston. The slit is not part of a performance mod, it was a lawsuit reduction mod because people were obviously getting more stupid and burning their fingers and starting fires.

The new bypass porting was a performance boost. And SPI was then a higher performance option achieved only by making shorter piston skirts. Cox quit lowering the exhaust ports at that time, so all engines had the same cylinder and the high perf ones had the short piston type of SPI. It was advertised as a lightened piston too, probably because it sounded good. But anything lighter in an engine's rotating assembly is usually considered good. However It's conceivable to me that the old way with a regular heavier piston might develop more torque. That's arguable. Given a choice, I'd pick the old type SPI with the regular piston.

But I have an engine that says I'm wrong about the torque idea. I built an engine from assorted parts with a Killer Bee venturi and a plain Babe Bee crank. It has slit exhaust and an SPI piston. And it's the only engine that jerks my plastic PT-19 straight off the ground with no roll. It kicks all of my Black Widows' asses. They all have the old #1 cylinder set.

And if you try putting a short piston in an old SPI cylinder it falls on its face; too much SPI.
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