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model steam engine: Comments on the design I have in mind?

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bogstandard:
Nick,

The main body and the sliding plate could be machined as one unit, totally flat.

The spring loaded side plate, is also finely machined on the sliding plate side. This would make it into a very close tolerance fit. Allowing it to be easily redressed in the case of wear. Just remachine the two sets, and away you go again.
I would have the swivel spindle to have a couple of thou clearance in its bearing hole, basically to allow a bit of auto levelling float.

I wouldn't use perspex, because you need the rigidity and hardness of metal to keep the pressure integrity. Plastic would very easily score and allow leakage.

But again, with this type of engine, you can't beat a poppet valve and sliding piston auto exhaust. I am no super expert on them, but they are dead easy to make, and work faultlessly.

See the C-o-C for details of how I made the head valve. The poppet valve can be mounted almost anywhere, as long as it is fired by the cam as fast as possible. The air should just make a very quick pulse, and timed to fire just as the piston has gone over TDC, and finish well before the piston reaches BDC.

I can show you the build up of the poppet valve itself if you need it. Everything is really easy to make.


John

NickG:
Thanks for that John, what is the purpose of the hole at the bottom of the stroke? Is that just to relieve the initial pressure when the piston starts to move back on it's exhaust stroke?

Cheers,

Nick

ps I think I had a look at Chuck's single which has this sort of valve arrangement?

bogstandard:
Nick,

Yes, the hole is to release any residual pressure by the time the piston has reached BDC.

It was Chuck who showed me this design, I just made the poppet valve remote instead of being connected to the head.

As I said before, if I want to make something, I will use other peoples ideas, but one thing I usually do is to give them credit for it in either my post or video. Everyone should get recognition for their efforts.

John

HS93:
these may help with basic steam engine working,

Peter   :ddb:

NickG:
That's a good illustration of the slide valve engine and no doubt people starting out will find it useful on here.  :clap:

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