Gallery, Projects and General > How do I??

Dimensions for slow runner

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rleete:
I'm starting on plans for a small horizontal mill engine.  Double acting, single cylinder with a spool type valve.  I'd like it to tick over nice and slowly.  Something that runs on just a few PSI.  Obviously, good fits are critical for reduced friction, and a large (somewhat oversized?) flywheel will help.

My question is, what is better for a slow running engine?  Long or short stroke, large or narrow bore?  Is is a ratio?  I'd like to keep the bore down under 1", if that helps.

Darren:
I believe low RPM like a long stroke, nice long burn to make it efficient....

What do ya mean you want steam.... :lol:

Bernd:
Roger,

I'd think about incorporating ball bearings in the moving parts. Just for a challenge of course.  :)

I also think long stroke and large bore. Think of the big diesel engines that run at low rpm.

Bernd

rleete:
Darren, is there any rule of thumb on that?  i.e. is "long stroke" double the bore?  Tripple?  More?

Bernd, already planned on bearings, just because i happen to have some I rescued from the scrap bin.

John Hill:
I do not know if low RPM likes a long stroke but it is certainly true that high RPM calls for a short stroke!

Everyday internal combustion engines for cars etc became 'square' (stroke=bore) about 60 years ago most nowadays would be stroke less than bore (I think) however I recently read that stationery steam engines were typically stroke=bore x 3.

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