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Wagon Wheel Stirling Engine - Part 3

Nigel Taylor

I drilled 8 off 3mm diameter holes around the rim of the fan and in these pushed the small magnets, alternating the magnetic poles. I placed a small amount of superglue in the holes afterwards to seal the magnets in place.

With 32 magnets around the rim of the flywheel and 8 magnets on the fan the gear ratio is 4:1

I always order my magnets from: Abel Magnets (

I clamped the main bearing plates together and drilled them through with a 25mm fast wood bit.

The holes ended up pretty clean and aligned - lucky really.

I machined a bottom bearing holder from aluminium. This shows it in place although not fixed as yet.

There are three holes for fixings which I think I'm going to need as the magnetic coupling does apply quite a lot of side force to the flywheel.

The ball races were sealed, but I removed the covers and washed them out and then applied some very thin oil.

The main bearings are 22mm OD, 8mm ID and 7mm thick.

The crank was machined to fit the ball races and to be a push fit through the flywheel (10mm diameter at this point).

The flange is still plain at this point with no holes for fixings, I will drill three holes for fixing the flywheel.

This shows the crank in place in the frame without the upper bearing.

The upper bearing is then placed on the crank.

Again I removed the bearing seals.

The upper bearing housing then fits on from above.

Again note the holes for three fixings, I may drill these slightly larger and use bolts and captive nuts. Ordered bolts from:

You can see that I made a 20mm hole through this housing so that you can clearly see the brass cage of the ballrace.

I machined a brass hub with ball races in each end and then a spigot for this to sit on.

The base of the spigot was glued to a strip of wood and then this glued to the main frame.

You can see the cross-bracing that supports the fan.

This shows the crankshaft fitted into the flywheel.

In reality you have to assemble the crankshaft and flywheel in the frame.

The flywheel assembled in the frame.

As yet the main bearings are not fixed and there is no upper support for the fan.

The glue had not set at this point on the support braces for the fan hence the clips.

The following video shows the fan turning at 4 times the speed of the flywheel via the magnetic coupling/gears. As the bearings are not fixed and there is no upper fan support the motion is a bit hit and miss. I'll record another video of it running once the bearings are fixed.

Back to Part 1, Part 2 to read how it started, on to Part 4.

If you have made a similar engine and would like to share your experience we would love to hear from you - ed.