Above: right side view
Below: left side view

ENGINE NO. NINE DATA

Cylinders: 1
Type: Horizontal Stirling Cycle (external heat application)
Bore: 1.0”
Stroke: 1.625
Displacement: 1.28 cu in
Est. Max. RPM: 2,000
Est. Horsepower: 0.2

BUILDER'S NOTES

Background -- The Stirling or Hot Air Engine was patented in 1816 by Robert Stirling, a Scottish clergyman. He called it a "heat economizer." I purchased the drawings from Coles Power Models and built the unit from their drawings. The basic idea is that Stirlings are supposed to convert any temperature difference directly into movement. While there have been successful engines of this type, they always have some inherent difficulty, such as being quite large and heavy for the power they generate. Every now and then someone re-discovers the Sterling principle and while they have their uses, they don't really compete with internal combustion engines.

Construction -- The construction of this model was pretty straight forward but had to be pretty precise. It was fun to build and makes a great display model.

Operation -- This model was a non-operator: zero RPM. The energy source was heat applied (via a torch) to what looks like an exhaust pipe in the photos. You could see it trying, but I could never quite get it to turn the crank. Quite disappointing. The basic problem seemed to be that there was not enough contrast between the cooling section and the heated section. Coles models gave a hint of this when they suggested the engine could be modified by pressurizing the air chamber to increase efficiency. Makes me think they couldn't get it to work either. Well, you win some and you lose some. So much for hot air.