Dear all,

I'm out to build myself a Stirling engine, just to use the temperature difference between a coal fueled forge visavi the outside of the workshop.

The idea is to build a 2 cylinder engine, with one cylinder being mounted in close proximity to the firepot and the other cylinder on the outside, just to get as big a difference in temperature as possible.

After that then the idea is to have the crankshaft powering an alternator to be able to power a forge fan and some lights for the workshop.

So ideas are welcome regarding how to put together the cylinders, what's recommended to use as piston seals, etc etc.

Lynx, I commend you on the motivation and desire to build a Sterling.  I like your animation as it saves a secondary crank lobe.

Just recently I came across a crankshaft-less engine design which made me think "DUH" that would be so much more efficient than what we all have used for a century.  It is the free-piston engine. This is an introductory video:

free-piston range extender - Youtube

Here is an animation of one version of it for you:

free-piston engine design - Youtube

Here is a shop sized version:

free-piston engine by Robert Hunt - Youtube

Thanks for the reply Ken :thumbsup:
Interesting design no doubt, although it wouldn't serve my purpose of using difference in temperatures as means to get a mechanical movement (I.E getting a crank shaft to spin around as a result of said difference in temperatures, which is exactly the way Sterling engines work).

Quote from Lynx on November 23rd, 2018, 02:12 PM

Thanks for the reply Ken :thumbsup:
Interesting design no doubt, although it wouldn't serve my purpose of using difference in temperatures as means to get a mechanical movement (I.E getting a crank shaft to spin around as a result of said difference in temperatures, which is exactly the way Sterling engines work).

I don't see why not, unless you are set on using a rotary alternator.  The last video I posted above, should be fairly close to being adaptable for sterling engine use, and offers rotary output as well.  The whole point of showing this design is the efficiency improvements of NOT having a crankshaft to rotate. By using a linear alternator (simply a shaker flashlight generator - but bigger) you get your electric output (and at 24 KW output, the power / size ratio of the first unit is impressive).

But should you want to go big with a free-piston sterling, here is a big one:

1kW Stirling Free Piston Generator disassembling- Youtube

Here Robert Murray-Smith builds one in an hour.

Robert Murray-Smith free-piston sterling - Youtube

The particular engine you show in the animation is the "alpha" type which requires a sealed piston on the hot side. I think that the "beta" type has the advantage of using a loose-fitting "displacer" on the hot side.

Quote from kenssurplus on November 23rd, 2018, 05:51 PM

I don't see why not, unless you are set on using a rotary alternator.  The last video I posted above, should be fairly close to being adaptable for sterling engine use, and offers rotary output as well.  The whole point of showing this design is the efficiency improvements of NOT having a crankshaft to rotate. By using a linear alternator (simply a shaker flashlight generator - but bigger) you get your electric output (and at 24 KW output, the power / size ratio of the first unit is impressive).

But should you want to go big with a free-piston sterling, here is a big one:
https://www.youtube.com/watch?v=adLZIDxM8tQ]1kW

Here Robert Murray-Smith builds one in an hour.
https://www.youtube.com/watch?v=SJsuwIUb0wE]Robert Murray-Smith free-piston sterling - Youtube

Many thanks Ken, appreciate it :thumbsup2:

I love the Robert Murray-Smith engine, simplicity at it's best :-D