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model steam engine: Comments on the design I have in mind?
jonogt:
OK i think i see what you guys are saying. I modified my sketch a little...
It doesn't show any actual valve action plans, but is that the sequence of airflow that I need?
I looked at some of the plans and pictures on the links, but I understand things a lot better if I draw them myself, so thanks again for the comments
bogstandard:
Slightly wrong Jon,
On the fourth pic, you need to have the inlet swapped over to an exhaust valve, as the returning piston is trying to compress the air above it.
There are two ways to counteract it. If you go the way of a poppet head valve, like I did and have an auto exhaust valve built in to relieve the pressure, then it will work fine, or the other way is to have a large flywheel mass to get over the air compression until the inlet valves fire again.
John S built one like that, which used a stiker pin on the top of the piston to open the inlet valve. But really that system is only used for fast running engines, they need the inertia of the flywheel to keep running.
I think I still have a few plans on that engine knocking about, so if you are really interested, something can be arranged.
John
jonogt:
So in my design, once the piston gets to the top of the stroke, exhausts, and starts moving back to the bottom, even though the built up pressure is gone, the air in the cylinder is still enough to drag down the kinetic energy? So when its returning to the bottom of the stroke, there needs to be an exhaust opening so that the piston can freely move and push all the air out... correct? If so, I guess that explains why the inlet and exhaust are usually right next to eachother, because the exhaust needs to be inside the cylinder-piston volume.
Do I have it figured out now?
Divided he ad:
Hi Jon,
I don't want to let you think I have much knowledge here so I'll let you in on a secret I look at when I am having trouble getting my head around these types of issues....
Take a look through the various engine types here.... http://www.keveney.com/Engines.html There's bound to be something that can help your design?
Most anything we could think of has been done before by many different men... This is just a helpfull jogger as to how many of the designs work.
Hope it helps?
Ralph.
jonogt:
Hey thanks for dropping in Ralph. Sorry for flaking out on you a few months ago when we were chatting via PM... I'm way too easily distracted, really in most elements of my life.
I actually found that site last night a short while after I posted, and the animations help tremendously. I'm currently finishing up a different project... a desk w/keyboard tray sized for sitting cross-legged at floor level. Its made of steel tubing, angle, flat bar, and the surfaces will be flat plate. I'll be taking photos of it when its done and i'll be sure to post em then. After that's all finished I'll start working on plans for this engine.
thanks again,
-Jon
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