MY FINISHED MODEL Robert Stirling's Famous Hot Ait Engine

[Trevor]

Well I finally got to make my replica (or as near to) of Robert Stirling's Model of the Hot Air Engine.
I bought a copy of the book by James G.Rizzo of the two engines presented to the Glasgow & Edinburgh Universities.
I didn't have money to make the turned down legs and foraged these from an old chair. I used stainless Steel drink container for the displacer cylinder and Stainless shell for the water cooler. This was all soldered using standard lead solder. All the other gear was what I could find around the second hand shops and markets. The rest of the wood was done with pine and use of a good rasp - Yes - I am hopeless with wood work.

It may not look as glamorous as the original models, but - who cares! I am happy and over the moon with the results and it works quite well. It does not rev out, and runs slowly so you can see the cranks working which gives the model that glamorous look.
I found I had to use a 3:1 ratio for the piston to work and I used leather washers as per instruction but found these were a bit tight and changed to a nylon piston with a soft 'O' ring. Made a one hell of a lot of difference.

Anyway - Here is the results
Trevor

[Ian S C]

Trevor,that looks like a very nice model. A number of years ago the plans for that motor appeared in "Model Engineer". The actual motor is at the museum in Glasgow.
Ian S C

[Trevor]

HI Ian
Thanks. I saw a picture of the one in Glasgow assuming it was the one with the water cooler. I couldn't even find a cast iron pulley and had to use an aluminium one. I think I will need to add some more weight to it so it will turn over a bit easier.

I am now working on a large LTD Engine using a model solar hot water system for the heating end - I will post some pics as I start the venture.
Trev

[Ian S C]

I think what I would do with that flywheel is wind some copper wire in the grove until nearly full, then use some body filler to bring it up to flush, smooth it off, then paint it. You would be surprised how little flywheel is needed to get one of these things running. One of my bigger motors will run with out its FW, very fast, and little power. With a large diameter FW less weight is needed.
Ian S C

[cbstirling2]

A YouTube video available? Looks awesome by the way.
As a test, maybe put a bead of playdough in the groove? I wonder if it would run faster or slower...

I didn't realize solder sticks to stainless...

[thanh-cuibap]

Hi Trevor !
Very nice model , Waiting for pictures finish and video

[Trevor]

HI Ian - I like the idea of winding copper wire around the rim and then using bog to finish it. I may very well give this a go as the alloy one is much lighter than the cast one they show. I see CB came up with another good idea of using playdough and that may even work. CB if you are reading this, Yes, there is a special flux which you can solder most ferrous metal and non ferrous metals to stainless steel. You can get it mostly at welding supplies etc.
Ian one other question if you don't mind. In your model using the bell crank - does this crank have to be equal length between the pivot points.

Trevor

Videos will come much leter

[Ian S C]

On the motor with the bell crank/Ross Yoke is symmetrical, as the motor is an ALPHA type, with equal bore and stroke in both the hot and cold cylinders. This type of linkage can be used in a GAMMER motor, and if the bores are the same the yoke is made with a ratio of 1.5 (displacer): 1 (power piston).
With a leather cup washer, a reasonably light leather should be used, and the edges feathered off to a thin edge. One place to get leather that may do the job is the tongue of a pair of lace up shoes (probably a warn out pair), old hand bags are another source.
If you are really over enthusiastic (nuts), you can solder aluminium, although I doubt that a cast aluminium pulley could take solder.
Ian S C

[Trevor]

Thanks mate!