Cylinders .020 Pee Wee

MauricioB Fri Jan 12, 2018 8:47 am

I have a doubt, it is likely that the subject was already commented, but the truth is I do not know. My question is, why are the cylinders externally different? Is there a purpose? Huh...

Thank you!

AA thin wall

BB stepped wall

CC Smooth thick wall

Jason_WI Fri Jan 12, 2018 9:26 am

From the engine handbook.

1/2A Nut Fri Jan 12, 2018 9:35 am

A have never ran thick walled type, one came in the mail yesterday note there is are no slots for the
wrench to remove the cylinder. Forces you to use the exhaust slots to remove the cylinder.

I inspected the engine and oiled it up everything is in mint condition makes good compression.

Marleysky Fri Jan 12, 2018 10:09 am

Oh No! Don’t use the exhaust slots! You’ll put a “bur” on the cylinder ID that will render it useless.
Use a leather strap to wrap around the cylinder to remove.

1/2A Nut Fri Jan 12, 2018 10:18 am

I use the Cox wrench on the outside of the exhaust ports with the piston bdc. Has to be done snugged up and no slipping, If it does not come
loose with moderate force then I wait till the engine has just been ran and hot to loosen it up. But yes strap is best if you have one.

Small Cox Logo

MauricioB Fri Jan 12, 2018 3:09 pm

Jason_WI wrote:From the engine handbook.

Friend the manual that your samples refers to the engine .049, not to .020 .... I do not understand if you want to say that it is the same criterion.

What I am interested in knowing is that external difference in the .020 cylinder. I ask again, do you want to tell me that it is the same criterion as for the engine .049?

Jason_WI Fri Jan 12, 2018 5:54 pm

The engine handbook only has one section on the explanation of the reason for the stepped wall then to the transition to the full thick wall cylinder. It was a change in the honing tooling that drove the change from stepped to full wall thickness cylinders. The new honing machine did not require a step to be milled in. One would have to assume the same changes followed through with the .020 cylinder wall changes. Only a former employee or someone in the know would have the exact details on the .020 cylinder. I only posted what I had available.

MauricioB Sat Jan 13, 2018 4:02 am

Jason_WI wrote:The engine handbook only has one section on the explanation of the reason for the stepped wall then to the transition to the full thick wall cylinder. It was a change in the honing tooling that drove the change from stepped to full wall thickness cylinders. The new honing machine did not require a step to be milled in. One would have to assume the same changes followed through with the .020 cylinder wall changes. Only a former employee or someone in the know would have the exact details on the .020 cylinder. I only posted what I had available.

I understand friend that one takes deductions by default.
I thought for a moment that it was a matter of allanating as much as possible the engine and therefore there was the process of thin wall, then I read out that in some model accidents, the cylinders broke before a blow and maybe from there they thought about make them stronger
It is an interesting world the history of these engines, one imagines many things when in truth perhaps it was different projects based on different ideas ... Very Happy

balogh Sat Jan 13, 2018 5:48 am

Mauricio

I guess the evolution was:

1. Thin wall cylinder
2. Stepped wall cylinder to strengthen the exhaust area to prevent cylinders from cracking and/or for the honing tool
3. Thick wall cylinder.

I do not know when COX abandoned the tapered bore though. My TeeDee 020 and larger TD engines had tapered bore with almost all stepped wall cylinders but neither the replacement stepped walls sold as parts nor any of the thick wall cylinders had tapered bore.

All my TD010 engines have thin wall cylinders and some had tapered bore.

balogh Sat Jan 13, 2018 5:55 am

1/2A Nut wrote:I use the Cox wrench on the outside of the exhaust ports with the piston bdc. Has to be done snugged up and no slipping, If it does not come
loose with moderate force then I wait till the engine has just been ran and hot to loosen it up. But yes strap is best if you have one.

I wrap the wrench at the exhaust port area in multiple layers of scotch tape if I have to remove the cylinder with the wrench placed on the exhaust port. I never have managed to remove a cylinder with a leather strap wound aroun it though..what do I wrong?

MauricioB Sat Jan 13, 2018 5:56 am

balogh wrote:Mauricio

I guess the evolution was:

1. Thin wall cylinder
2. Stepped wall cylinder to strengthen the exhaust area to prevent cylinders from cracking and/or for the honing tool
3. Thick wall cylinder.

I do not know when COX abandoned the tapered bore though. My TeeDee 020 and larger TD engines had tapered bore with almost all stepped wall cylinders but neither the replacement stepped walls sold as parts nor any of the thick wall cylinders had tapered bore.

All my TD010 engines have thin wall cylinders and some had tapered bore.

Hello András, thank you for your contribution, it is possible that this has been the evolution path of the engines .... tell me your comments of: * Tapered Hole * ... what do you mean specifically? ... I do not understand, Sorry for not understanding your information Sad Goodbye

balogh Sat Jan 13, 2018 6:02 am

Tapered bore has a bit smaller diameter on cylinder and piston top where they are the hottest during operation in order to ensure tight fit and good compression even when hot. This is similar to the " pinch" other engines have at the top dead center for the same purpose.

You can check it by pushing the piston up the cylinder by hand. Tapered bore will stop the piston snug at the top dead center and you cannot push it further.

MauricioB Sat Jan 13, 2018 6:04 am

balogh wrote:Tapered bore has a bit smaller diameter on cylinder and piston top where they are the hottest during operation in order to ensure tight fit and good compression even when hot. This is similar to the " pinch" other engines have at the top dead center for the same purpose.

Ahhh yes !, now I understand, you mean the conical hole of the cylinder for the piston cylinder compression! Thumbs Up

balogh Sat Jan 13, 2018 6:10 am

Yes exactly. One if my TD051-s with tapered bore is past 300 hours runtime and it still has enough compression for hand starting. I am not sure if non-tapered cylinders will also retain compression so long due to the wear in operation.

MauricioB Sat Jan 13, 2018 6:19 am

balogh wrote:Yes exactly. One if my TD051-s with tapered bore is past 300 hours runtime and it still has enough compression for hand starting. I am not sure if non-tapered cylinders will also retain compression so long due to the wear in operation.

This engine is a clear example of a conical jacket...
....Have you ever tried an MVVS .49? just turn it around and you can not believe it !!

balogh Sat Jan 13, 2018 6:37 am

I have a NV061 that had some pinch on the top dead center but except for OS Max FS 056 4 strokers that have ringed pistons all my other engines are COX.

The MVVS engines are famous runners from I believe the former Czechoslovakia? Those and Hungarian Moki engines were the best competition engines from the Communist countries..Maybe Zeiss also from former East Germany..

1/2A Nut Sat Jan 13, 2018 7:32 am

I have some engines that have so much pinch at TDC a warming jacket needs / should
be used before starting them to avoid excess wear and strain.

I bought this for them:

Tested this one a GS Pro V12RR

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