Gamma Stirling Engine

Hi all,

I have started work on my first stirling engine. This one is a simple demonstration unit as per: Stirling '60' - YouTube

If this goes well then I might make a bigger one. I would like to be able to drive it from solar power via a satellite dish.

I have a set of full plans for this engine. In addition to the brass I already have I have ordered some additional supplies.

Today I made the first part. It is just a simple mounting post for the flywheel bearing.

So far so good, but there are still a few challenges.

  • I need some perlitic iron for the displacer bearing. No idea where to get that from. I could substitute it with brass…
  • I need to cut a thin 1.6mm slit 9mm deep. Might need a slitting saw for that?
  • and I need to cut the test tube down to size.

Should be fun!


I watched the video you linked. It looks cool and like scifi magic. What why do you want to make one? What caught you passion in this direction?

I wanted to build a machining project, but didn’t want to do a steam engine. This looks like something that could be semi-useful. :slight_smile:

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Sounds boss. Spam us with project piccies. Even the blue prints look boss!! :grinning:

A couple more parts made.

Those are the Main Shaft Bearing Housing and the Main Shaft.

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I managed to cut down a test tube.

I’ll make a couple more spares, while have it setup.

The method that I used is to make a jig that will let me slowly cut it using a dremel with a diamond cutting wheel. I cut it about 1mm long. I then re-adjust the jig so I can face it slightly to get the worst of the roughness off. I then spend a quality hour grinding it down using 400 git wet and dry.

Few more parts made

I decided to re-make the bearing housing to fit different bearings. The part on the left is unfinished, as I need to machine it using the rotary table. Many thanks to Dave for the excellent idea of making the 20mm cylinder on the bottom. This will register in the central precision bore of the rotary table and will mean I only need one small clamp to hold it down. But I will need to make some T nuts for the rotary table.

Have made the crank. This was a cool part to make as I got to use the rotary table. However I first had to make all the clamping hardware.

Next job is the flywheel.

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Work on the flywheel has started.

Trepanning the face was fiddly using the tools I had, but I got it done (not as neatly as I’d like). A DRO on the lathe would make life much easier…

Operation 2 is to mill out the cutouts using the rotary table. Operation 3 will be back on the lathe to finish off the back side.

Spent some quality time on the rotary table today.

Now I need to turn the other side…

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Nice work

Work on the flywheel continues…

I made this trepanning tool from an old end mill.

And used it to cut away the other side of the flywheel.

Still some deburring and tidying up, but it does run true!

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For the various linkages I need to drill 1.2mm holes. This is a bit of a worry as that is not necessarily an easier thing to do. Drills this size need to be spun FAST and are very easy to break!

I did consider using my cheap set of PCB drills, but these require an intermediate chuck as they won’t fit in a mill collet or its drill chuck. But the main problem with this will be excessive runout as the intermediate chuck is cheap and not well built.

Instead I got a couple of sets of carbide (supposedly) PCB drills with a 3mm shank. These fit nicely in the smallest mill collet. In fact they only have 0.04mm runout, which we call in the trade “good enough”!

So after a bit of setup I was able to quite easily drill the hole.

And the 1.2mm wire fits in perfectly.

Luckily the drill is only just long enough to make it through.


Next on the agenda is the Power Piston and Cylinder. I started with the cylinder.

The one on the right is the first one I did. It has 2 problems:

  1. The fin spacing is all over the place. I used the saddle handwheel to space them; that was a mistake.
  2. The 5mm reamed bore is not parallel. This is partly because of the poor quality reamer and the fact that I don’t have a floating reamer holder.

The one on the left is the better version. I used a dial gauge to space the fins better. For the bore I pilot drilled then drilled to 4.8mm. When reaming I located the reamer at the start of the hole then tightened the chuck. This seamed to align it better and it is much closer to being parallel. Still not sure if it is parallel enough though.

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Another part made.

This is the main support post. It is the first part I used the slitting saw on. I am now a big fan of slitting saws. They do a very clean job!


The tumbler plate and the power piston con-rod are now done.

The tumbler plate was made on HILDI

Then finished on the mill.

Here are all the pieces on a temporary mount.

The flywheel has also has had some polishing ready for nickel plating.


Nickel plating of the flywheel is (hopefully) complete. I think I got a good coverage. Luckily rust will tell me what I missed. :slight_smile: