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Antique Gas Engine Discussion

Tappered Cylinders


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  #1  
Old 06-22-2005, 07:26:06 PM
Chuck Parcher (Ks.) Chuck Parcher (Ks.) is offline
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Default Tappered Cylinders

I must have missed somewhere during my early years why cylinders are tappered. Then when I use logic to try to understand the concept I really get baffeled. Logic tells me i want as much compression as i can get, so if I use a cylinder where the taper is closest to the head the compression ratio would increase as the piston comes up on compression stroke. There only a couple of ideas that could explain the reason and i'm not sure either one is correct.

Perhaps if the taper was closest to the head the heat generated at ignition might expand the piston and the cyl. causing a problem. or if the taper was away from the head i helps to hold the gasses pushing down the piston on the power stroke. I DON"T KNOW does anyone know that could explain this tapering purpose I a taper really nessessary at all??????????????

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Chuck
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Old 06-22-2005, 07:34:34 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Tappered Cylinders

Cylinders are uaually bored straight, taper is a result of wear. Wear is usually worse at the top of the cylinder because of compression expanding rings, dirt, and fuel washing oil away. I think the little model airplane engines use a cylinder tapered to the top, thes engines don't use rings, rely on precision machining and oil for a seal.
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Old 06-22-2005, 10:05:07 PM
Havvey Havvey is offline
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Default Re: Tappered Cylinders

i think jb is correct but taperd heads build compression thats the advantage of an overhead vs a flat head the taper is generly from wear.
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Old 06-22-2005, 10:46:31 PM
Bill Brock Bill Brock is offline
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Default Re: Tappered Cylinders

Hi Chuck, The taper at the top of the cylinder is called choke. An engine with straight bored cylinders will expand more at the top due to combustion heat and actually flare out a few thousands and lose compression/leak past rings. A cylinder thats tapered in a few thousands at the top will be straight when hot resulting in less leakage and better compression. This system is used a lot on air cooled aircraft engines because air cooled engines have higher cylinder temperatures.
Bill
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