Gallery, Projects and General > Project Logs
Fixing the how NOT to make an engine
bogstandard:
You are quite right Eric.
When amateur machinists get to doing something wrong, they do it right, and everything ends up wrong. Work that out if you can.
I love doing things like this because it challenges you sometimes, trying to find ways to put it right and get the engine to work correctly afterwards.
I do these posts because a lot of the techniques can be used elsewhere, not just on this one engine. You just have to sift thru what is written to find them.
I think I have mentioned before, to make this engine from new would only take a couple of good workshop days, but to restore it, it has taken a lot longer.
Bogs
TFL45:
--- Quote from: bogstandard on July 30, 2009, 04:36:36 AM ---
Tim, you have it right, as long as the ports are all equal, it shouldn't matter which one you connect to. That works for both oscillators (wobblers) and piston valve engines, but not a slide valve.
Bogs
--- End quote ---
I agree John.... except when one doesn't know the basic operating principles of a slide valve engine and one goes to considerable pains to get the valve mechanism to fit just soooo.... Soon discovered the error of my ways but not before I tested with intake and exhaust reversed! Doubtless wouldn't work with any appreciable steam pressure, as the valve would lift off the face and/or bind, but made for a bit of a diversion while I re-read the plans! :scratch:
BTW - Great job on the refurb! :clap:
Floyd
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bogstandard:
Floyd,
A very nice engine indeed, maybe a little post by itself would be most appreciated by the membership, rather it being lost on the back end of this one.
But you did raise a very valid point about steam pressures.
The higher you go with the pressure, then the more inefficient an oscillator or piston valve will get. Whereas the higher you go with a slide valve, the more efficient it gets.
Just to explain a little.
If you put too much pressure into an oscillator, the port faces start to separate, and so you get inefficient running.
The same sort of thing happens with a piston valve, but at much higher pressures. Instead of blowing off the port faces, which it doesn't have, it starts to leak steam or air between the pressure and exhaust lines because of the very small shutoff and overlap timing of the piston valve.
With a slide valve, the pressure is actually acting against the valve plate, so the more pressure, the harder it seals.
Bogs
Bernd:
--- Quote from: bogstandard on August 01, 2009, 02:50:05 AM ---
If you put too much pressure into an oscillator, the port faces start to separate, and so you get inefficient running.
The same sort of thing happens with a slide valve, but at much higher pressures. Instead of blowing off the port faces, which it doesn't have, it starts to leak steam or air between the pressure and exhaust lines because of the very small shutoff and overlap timing of the piston valve.
With a slide valve, the pressure is actually acting against the valve plate, so the more pressure, the harder it seals.
Bogs
--- End quote ---
Bogs,
I'm a bit confused here. Easy to do on an early Sat. morning, but you are discribing both as a "slide valve".
bogstandard:
Sorry about the confusion Bernd, my context and mistake checker doesn't work early on a Saturday morning either. Not enough caffeine input.
It is now working, and it has put it right.
Bogs
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