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Designing steam engines-oscillators specifically
Chuck in E. TN:
I am studying and experimenting with designing my own steam engine. I’’m starting with Oscillators. Specifically a double cylinder, double acting.
A member on another forum posted a link to an Ocillator simulator program, available here, that simulates simple single and double acting oscillator steam engines. It’s a neat program, and I learned a lot from it.
One thing that I haven’t been able to figure out is whether the piston should cover, not cover, or cover half the port openings at the top or bottom of it’s stroke. I assume(and you know what that does) it has something to do with timing and ‘cutoff’ in engines run on steam, but I don’t yet have a boiler, and will be running mine on compressed air.
The above mentioned simulator shows the piston covering half the port in one engine and not covering the ports I another. Can someone explain the difference or wherewithal of the piston covering, half covering, or not covering the ports?
chipenter:
I don't know about the piston covering half the port , but the port is cracked just before top dead centre called lead , to get more steam or air into the cylinder , you will also get more power if the sides of the ports are flat and lined up to the pivot point .
velocette:
Hi
As I see it this is not important and will attempt to explain.
The ports on an oscillator engine are closed when the engine is on TDC and will not open until the crank turns.
The angle before the ports are open depends on the length of the connecting rod. Short con rod less angle etc.
Do you need to reverse the crank rotation then the porting will need to be symetrical.
If not then the timing can be offset to admit Steam or Air at TDC and the exhaust to open earlier.
For maximum flow through the ports round ports are not the ideal shape. By careful marking out and shaping with the centre of the cylinder pivot used to align the flat sides of the ports.
vtsteam:
Chuck, can you give a link to that simulator so we can see what you're describing?
Chuck in E. TN:
Here's the link to the simulator. Note: it's for oscillator types only...
http://www.labbookpages.co.uk/metalwork/singleOsc.html
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