How do I decide what sort of engine to make next?

[John Hill]

It is time to be thinking of the next 'project' which will likely be an engine of some sort.

My little 'nutating engine' looks good on the shelf but next time I will be trying for something bigger, bigger because working tiny does not fit my style and makes the job harder. Maybe in the future I will work smaller, meanwhile I am thinking of a single cylinder engine of about 50mm or more bore, I more-or-less have the basic layout firm in my mind except for the top end of the cylinder which is where everything happens.

So, it could be a double acting steam/air engine but how much air would I need to drive something of that size? 

Maybe a Stirling or a flame licker, are the proportions close enough that I could make any of the three types for the same basic crank and cylinder?  Thinking is if the flame licker does not work I could add a displacer and call it a Stirling  or I could add the valve gear and convert to air/steam.

OK, OK, I know I am the one who must find the answers but thats where I am right now.

[bogstandard]

John,

Flame lickers are a pig to get running, and I personally wouldn't do one until you have a couple of basic piston and cylinder engines under your belt. The tolerances and friction reduction is the killer, and it is also the same for a Sterling type engine.

I designed and built a modular engine a while back (I am just going thru a blinging exercise on it to get it to showing standard).

The basic layout leaves it open to fitting almost any type of air control to it, I chose to go with a poppet valve and a floating piston in the cylinder head.
This is a rather old and well seen vid of it in it's basic operating mode.

The construction of it is shown here.

http://www.homemodelenginemachinist.com/index.php?topic=612.0

John

BTW, once you get over 1/2" diameter on the piston, you are starting to get into the realms of a normal air compressor rather than say an airbrush or larger fishtank one.

[John Hill]

Very interesting video John and a nice write up on the build which I learned a lot from. Thanks.

One thing for sure this next project of mine will be a design that is refined as build progresses, I will start with some basic ideas and a layout which will be heavily influenced by what can be found under the bench.  It will be difficult to match the connecting rod you have from the shop of B&B!

Poppet valves for a steam engine have stimulated the gray matter...