Old stock production engines with tapered bore

balogh Sun May 30, 2021 1:05 pm

Bought a couple of decently used red postage stamp backplate reedies with thin wall No.1 cylinders over the past 2 years off of feebay. They must have served their prior owners until their host COX planes were damaged beyond repair, and then have been sitting around for decades in drawers..all have very good compression, and when equipped with a turbo plug adaptor head, turn the COX 5x3 safety tip black propeller 21k on the bench when fed with 20% nitro in the fuel..

Based on their component details I traced them back to the mid 60-s with the help of COX Engine Handbook of Dan Sitter.

When dismantling them on arrival from the seller for a check and clean up, most turn out to have tapered bore with the piston moving up to the TDC only...hmmm... A nice surprise and makes me wonder, how come, when only old stock TeeDees were known to have tapered bore.......???

This one just joined the fleet, was a piece of gunk on arrival,

Old stock production engines with tapered bore Screen37

...and was given the right cleaning, additional parts and care it deserves.

Old stock production engines with tapered bore 16223911

aspeed Sun May 30, 2021 5:28 pm

I was under the impression that they were all tapered until at least the time that the step in the bottom of the cylinder was still there.

balogh Sun May 30, 2021 5:40 pm

Yes, all those No 1 thin wall cylinders I managed to disassemble seem to have tapered bore.Some remain stuck in the crankcase and I do not want to force them therefore cannot check if tgey have tapered bore, but very likely they do.

I have stepped wall No.1 cylinders but they are no tapered bore ones. I think COX may have given up tapered bore in No.1 after the thin wall changed to stepped wall. The No4 and 5 stepped wall cylinders of TeeDee-s continued with taper bore for some time, but e.g. my later production TeeDees with thick wall cylinder do not have tapered bore at all.

aspeed Sun May 30, 2021 5:48 pm

Probably the era when the original tooling was sold off was the time when the ability of the tapered bore went away. There was a time when the nose of the crankcase went from a thin radius to a larger diameter, and then was no radius at all. Maybe at the last phase the taper was lost. IDK. I stopped buying new ones around that time.

iamplanecrazy2 Mon May 31, 2021 10:56 am

Great job, I like the Goldberg mount.

coxaddict Tue Jun 01, 2021 12:20 am

All the thin wall cylinders that Iv'e come across have tapered bores, including the no. 2 marked cylinders. That's why some no. 2 cylinder equipped engines turn surprising rpm numbers.

balogh Tue Jun 01, 2021 12:28 am

Thanks. A hidden value of all those old stock engines that even the cylinder identification table misses.

crankbndr Wed Jun 02, 2021 12:15 pm

The Killer Bee and Venom had taper in 1995, the latest I know so they had the ability then. Then Estes crash and burn in 96.

Scotland421 Sat Jun 05, 2021 6:25 pm

In the 60's all of Cox screw machines were fresh and they were very accurate. They used TCC (temperature control) their steel and aluminum stock was stored in the same temperature as the machine shop. Santa Anna was a good location with very constant temps throughout the year...kept air conditioning costs constant.

balogh Sun Jun 06, 2021 1:28 am

Yes the heydays of COX...unbelievably high production quality in engines that were supposed to be thrown aside after a few flights of their host planes..

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Old stock production engines with tapered bore

Old stock production engines with tapered bore

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Re: Old stock production engines with tapered bore

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Re: Old stock production engines with tapered bore

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