Minimum steam space between the piston and cylinder head
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Minimum steam space between the piston and cylinder head
I picked up an locomotive project to finish. Upon inspection I find there is only about .075" clearance between the pistons and the heads of the cylinder. This engine is using 2" dia. Allen Model Cylinders. Is this clearance adequate steam space for proper operation?
Rob
Rob
Re: Minimum steam space between the piston and cylinder head
As long as functioning cylinder cocks are in place, minimum space is better for operation.
~RN
~RN
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Re: Minimum steam space between the piston and cylinder head
I looked up what is on the Allen Model prints. They have 0.093 nominal clearance when you do the math. I found the heads are machined a little thicker where they pilot into the cylinders than the print dimensions show. So I will correct them to the print dimensions.
These cylinders do not have the ports machined in for the drains either, so another task to add to the to do list.
Rob
These cylinders do not have the ports machined in for the drains either, so another task to add to the to do list.
Rob
- Bill Shields
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Re: Minimum steam space between the piston and cylinder head
as close as you can get without banging is just about right.
why waste space expanding steam unnecessarily?
why waste space expanding steam unnecessarily?
Too many things going on to bother listing them.
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Re: Minimum steam space between the piston and cylinder head
Another thing to consider is the holes running between the ports and the cylinder end, you don't want the boss on the cylinder head to choke them off. A small flat or cut-out on the boss can help with that, and it will not ruin the centering function of the boss.
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Re: Minimum steam space between the piston and cylinder head
One must be aware of wear that can occur on connecting rod and crosshead bushes. Too much, and the gap will close to the extent the piston may hit the cylinder cover ( I have seen this happen and destroy the cylinder casting). Yes small gap is good between piston head and cylinder cap, but take into account bush wear over time.
John Heald , New Zealand.
John Heald , New Zealand.
Re: Minimum steam space between the piston and cylinder head
I agree with Bills opinion, not like you have to worry about rod stretch/deflection or too high of a compression ratio with steam.
All my 200cc engine builds for my racing kart I shoot for .030" to allow for rod stretch, heat growth, and crank deflection.
All my 200cc engine builds for my racing kart I shoot for .030" to allow for rod stretch, heat growth, and crank deflection.
Re: Minimum steam space between the piston and cylinder head
So Robin....what’s the locomotive?
Keith
Keith
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Re: Minimum steam space between the piston and cylinder head
The locomotive is a 7 1/4 or 7/ 1/2 inch gauge 2-4-2 called Mini. It is around 2" scale. Balloon stack, old american 4-4-0 head light and pilot. Stevenson valve gear. 9" dia. drivers.
The valve gear linkage needs to be corrected, it assembled with set screws instead of silver soldered or pinned joints of rocker arms to shafts.
It was set up for 7 1/4 gauge. I am regauging it to 7 1/2 to run during the winter season in Florida.
I am doing a down to the frame disassembly to see if there is any thing else that needs correcting.
So far I machined the drain ports in the cylinders, honed the bores and added brass cylinder jackets. I also had the boiler steam dome corrected and dry pipe added to the boiler at welding shop.
The valve gear linkage needs to be corrected, it assembled with set screws instead of silver soldered or pinned joints of rocker arms to shafts.
It was set up for 7 1/4 gauge. I am regauging it to 7 1/2 to run during the winter season in Florida.
I am doing a down to the frame disassembly to see if there is any thing else that needs correcting.
So far I machined the drain ports in the cylinders, honed the bores and added brass cylinder jackets. I also had the boiler steam dome corrected and dry pipe added to the boiler at welding shop.
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Re: Minimum steam space between the piston and cylinder head
never mind, found in "Build Log"
steamer
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Re: Minimum steam space between the piston and cylinder head
Yes I started thread in Build Log for the regauaging and completion of the locomotive.
Rob
Rob