Stirling Engine models

Stirling Engine model (click to enlarge)

The website Ministeam has an absolutely wonderful collection of steam engine models, steam cars,  a steam powered robot, devices -- Ferris wheels and the like -- to be powered by steam, suitcase train sets,  a working 23,000 rpm jet engine model and more.

To the point of this post, they also have a large number of Stirling Engine models. Above is a picture of one of their models -- click on it to see a larger view to examine its beautiful, retro-looking industrial design. Then go to the Bohm Stirling Engine section of their catalog and check out their full line. They also have videos there (they require written permission to use so I haven't embedded any -- it oddly fitting that a steam engine store wouldn't understand viral marketing on the internet).

Source: Wikipedia

Although I had heard of Stirling Engines, I didn't know how they worked. Stirling Engines have two cylinders with a contained fluid system. Heat is applied to expand the fluid and force the power cylinder forward. This will cause the expansion cylinder to retract and draw the fluild into a cooling chamber. The cooler fluid will the cause the power cylinder to be drawn back. Rinse, wash and repeat. To the right is an animated gif showing the cycle of a Stirling Engine.

Stirling Engines were popular during the 19th Century, but electric motors eventually replaced them. You can read more about them, and see more animated diagrams of their different configurations, at the Stirling Engine Wikipedia page. 

The models at Ministeam are a bit pricey, but if you search Google you can find cheaper ones, although they don't look nearly as good as the Bohm Stirling Engine models.