No Start - Voltage Drop While Cranking

[Jim]

Yes indeed Brother. I'd use a bore gauge or snap gauges and mic to verify that, if the engine has hours and low compression. I am sure that they are bored without taper, obviously. Equally sure that they are tapered after they're old and tired...just like all piston engines. I have honed cylinders to take out taper...takes all day, and usually you have to 10 over what you started with. They wear at the hot end, less so at the oily end that's cooler. Thanks.

Best!

Since I used to work on engines that were indeed taper bored from the factory, thought I'd point out that the XS's ain't one of 'em.

 

[arcticXS]

Since I used to work on engines that were indeed taper bored from the factory, thought I'd point out that the XS's ain't one of 'em.

Aircraft piston engines?

 

[Paul Sutton]

Why tapered?

 

[40north]

Why tapered?

I can't say, but I can propose two thoughts.

One, a cylinder may be a cylinder cold, but it's a sort of conical form when it operates hot. So if an engineer wanted to have a bore that was actually cylindrical in dynamic operation...

Two, I suppose it's a realbitch to bore a cold conical bore...modern tooling makes it less difficult? I'd say the final form would be via honing ?

Since rings compress and expand in a tapered bore, per since steam engines and Watt, and since they have inertia, at high speed there's a limit - ergo a cylinder that's straight when hot would permit higher revs... The alloy of the pistons and the design of the pistons can in normal engines, significantly compensate for the upper cylinder expansion, but this tends to tighten the fit at the oily end of the stroke, so that approach has some limits, and the rings in any case still have to slide in and out to conform...maybe that's a factor...

I'm only speculating. Is there a real engineer out there, an actually informed cat? I'd guess that a websearch might be productive. I find that yandex is often useful to compare the results ya git v goggle or duckduck

Best!

 

[Jim]

Aircraft piston engines?

Why tapered?

Yes, some of the Lycoming's.... and P&W's iirc. Think there was also a model of the Franklin that used taper. It wasn't much... about 5 thou as I remember.
The heads and cylinders were all one piece... actually they were two pieces, joined at the factory into one piece. You couldn't take 'em apart after that.

The reason.... most of the heat is concentrated in the head and the top part of the cylinder. Remember, these are air cooled engines. Anyway.... that's where most of the expansion was, up by the head. Once the engine was up to normal operating temperature, the taper went away.... it was a straight bore, until it cooled down again and the taper returned.

 

[Paul Sutton]

Maybe just tapered when bored but close to conical cylinderical once the head is shrunk on? Where is Jim?

Edit: Meant to say cylinderical, not conical.

 

[Paul Sutton]

We just crossed wires. Jim is back!

 

[40north]

Yes, some of the Lycoming's.... and P&W's iirc. Think there was also a model of the Franklin that used taper. It wasn't much... about 5 thou as I remember.
The heads and cylinders were all one piece... actually they were two pieces, joined at the factory into one piece. You couldn't take 'em apart after that.

The reason.... most of the heat is concentrated in the head and the top part of the cylinder. Remember, these are air cooled engines. Anyway.... that's where most of the expansion was, up by the head. Once the engine was up to normal operating temperature, the taper went away.... it was a straight bore, until it cooled down again and the taper returned.

are those engines radials? opposed" I'm not an aircraft fella...

 

[Jim]

Got curious so I looked it up. The Lycoming OHM doesn't say how much the taper is, just gives ring gap specs.
Funny, airplane companies cant use normal terminology like the rest of us... .... they didn't call 'em tapered cylinders.... they were called "choke barrels."

For some reason I now find that hilarious.