Potty Popcorn Engine

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Stilldrillin:
"Thats that one done".

And very well done it is, too! :clap: :thumbup:

David D

saw:
Thank you for nice picture and good description, I always learn something from you. :bow:

AndyB:
Hi Stew (and everyone else) :wave:

Another stupid question I'm afraid :doh:...how do you calculate the eccentric offset please? Is it half the total slide movement? I'm sure there is more to it than that as the ports have to be covered/uncovered correctly.

I really like what you are doing and am thinking about a recycle version, made out of scrap, such as an old cistern weight for the flywheel, the base from an aluminium casting from a load of scrapped office furniture at work, this sort of thing. I just love some of the steampunk stuff, and I have an idea that I could make your engine in the same vein.

Many thanks

Andy (getting brave now :lol: :lol: :lol: :lol: :lol:)

sbwhart:
Hi Andy

Theirs no such thing as a stupid question, it's the smart honest thing to ask a question.

The off set is half the total slide movement as you said.

To work the valve spacing out I use this method, I took it from one of tubal Cains books, I've used it for three engines now and found it works well on air running model engine, steam running engines are a bit different as it all depends what you're doing with them as you want to use the steam as efficient as posable, and people will have different ideas on the best design, personally for a model I think they overcomplicate the issue.

For the width of the valve ports a rule of thumb:-for the inlet about 1/10 the dia of the cylinder and for the exhaust 1/4 the dia of the cylinder, I try to go to the nearest standard cutter size, for the web between the ports equals the width of the inlet port.

Hope this makes sense

That steam punk job sounds interesting, I always try and make an engine from material I have in my stash.

Stew

kvom:
For a previous build (paddleducks engine) I followed Bogs' method on the piston, in that it was roughed, then loctited to the rod, and then faced and turned to final diameter with the rod chucked in the lathe. This ensured that the piston rod and piston were concentric. Did you find that machining them separately is accurate enough? or perhaps the packing gland provides any needed adjustment.

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