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Old May 29, 2015, 04:14 PM
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Cox Tee Dee .049/.051 Engines

Just curious, I have a few (brand new) Cox Tee Dee .049 and .051 engines. I've noticed that each engine cylinder position varies in regards to how the exhaust ports are positioned relative to the crankcase. Some cylinders are positioned such that the exhaust ports are in-line in a fore to aft relationship with the crankcase. Others cylinders are positioned in a side-to-side relationship with the crankcase. Is this just a random thing? Due to how each cylinder threaded base affixes itself to the crankcase once tightened?

But it seems like each engine I come across the cylinder exhaust ports are either forward/backward relationship to the crankcase, or almost perfectly side-to-side relationship to the crankcase (90 degrees rotationally, one way or the other).
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Old May 29, 2015, 04:49 PM
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It is random.
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Old May 29, 2015, 05:01 PM
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Chalk it up to manufacturing tolerances. Years ago, an outfit named Kustom Kraftsmanship used to make and sell very thin cylinder shins so you could adjust the exhaust position and/or exhaust timing.
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Old May 29, 2015, 05:16 PM
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That is a problem with engines that use a threaded cylinder system. Where you screw in the cylinder into the crankcase. In the past they used to use shims with some brands to get it to have the exhaust port come out on the side. But with Cox engines they didn't worry about it or bother. Since they made engines my the millions, it wasn't a item to be concerned with. It didn't normally hurt the performance of the engines any either. But the racing folks would shim the cylinder to get the exhaust ports angled just right to eek out that little extra bit of performance.
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Old May 29, 2015, 05:49 PM
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thanks for your comments. That's what I figured. I've played with several (and I mean several) Cox .049 variants (mostly Baby Bee) as a kid/teenager, and I sort of remember that reality then (ie. cylinder threads yielding random positioning of exhaust ports).

It's been years for me, I've recently purchased these (vintage) Tee Dee engines, and it sort of got my curiosity
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Old May 29, 2015, 09:42 PM
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The only Cox that had the screw threads matched to the cylinder was the Tee Dee 15 Special Mk2 which had a single exhaust port and that faced to the LH side. It's also the only Cox that used a normal conrod/wristpin.
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Old May 30, 2015, 01:06 AM
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I flew 1/2 A speed and never shimmed the cylinder in my TD 049's. They all ran about the same. Cox machining was so good you could by pistons and cylinder separately. Their machining tolerances were 25 millionths of an inch. The 15 MkII is the most powerful 15 I ever owned. Look what they sell for today.
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Old May 30, 2015, 08:11 AM
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Is the Mk 2 faster than the Conquest? I was under the impression that was the best they ever offered. Mine is pretty good. I think about 19,500 RPM with my standard testing prop of Master Airscrew 7-5 prop on 10% fuel. For a time it was my fastest .15, but with some fiddling on others, that changed. I haven't played with the Conquest yet, and don't have the Mk 2 TD. If they are $$, it is doubtful that I will. I think I have enough, as the wife reminds me all the time.
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Old May 30, 2015, 09:56 AM
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Conquest makes more power than the Special Mk2.
Until the rod lets go........
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Old May 30, 2015, 04:32 PM
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The conquest was originally made by K&B. Couldn't compete with a MkII Have them both. Well I don't have the MkII anymore. It was stolen when I lived in Hawaii along with several other valuable today engines.

You never saw a Conquest in Class A U/C speed. The MkII was a a top Speed engine in that class.
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Old May 30, 2015, 05:10 PM
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Quote:
Originally Posted by datsunguy View Post
The conquest was originally made by K&B. Couldn't compete with a MkII Have them both. Well I don't have the MkII anymore. It was stolen when I lived in Hawaii along with several other valuable today engines.

You never saw a Conquest in Class A U/C speed. The MkII was a a top Speed engine in that class.
the conquest was made by cox before K&B took the design over. and it came out a decade after MkII production ended. i really doubt it was weaker unless you're talking about one of the mild ported versions. the design was copied from the rossi and a lot of parts interchange. the MVVS 2.5 that came later was also the same basic design with a fatter crank. with the right head button and porting it will spank them all.
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Old May 30, 2015, 08:28 PM
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I think around 1982 one of the guys on our team used the Conquest. I think he got the motors as a sponsored perk or something. I think his results were similar to the Rossi which was king at the time. Maybe 150 mph? I would have to look it up. My Conquest is 500 rpm better than the example of a pylon Rossi that I have. I never tried a piped Conquest. Now I am afraid of busting it. Can't seem to get parts from MECOA for it.
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Old May 31, 2015, 12:12 AM
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i wonder if a piston/cylinder set from one of the many .15 car engines would fit?
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Old May 31, 2015, 08:55 AM
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Or a rod? I think the Rossi rod was used in some other motors like the Ucktam and Supertiger X .15. I don't know about the new stuff. Just to keep on topic, shims were used to get the TD ports lined up to be fore and aft, so the wind would blow through and clear the exhaust. I think it would affect the bypass and exhaust total timing favourably too. if higher revs are the goal.
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Old May 31, 2015, 10:25 AM
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Lots of guys put Rossi piston/liners into the Conquests.
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