Dynamometer for LSM series Stirling Engines

Dynamometers, which measure power output in controlled circumstances, are an essential tool used in the development of engines.

They conventionally do this by measuring torque and speed (RPM) – power equals torque times RPM times a constant.

This one measures torque using an eddy current brake- magnets rotating close to but not touching a copper ring.  The moving magnetic field generates currents in the copper ring which resist movement.  Energy is dissipated by heating – which is minor for the 300watts or so typically being measured in this case.

RPM is measured using an external rev counter and the scale is set to show Watts output at 300RPM which is in the range at which most LSM series engine develop maximum power.

Actual outputs for speeds other than 300 RPM are proportional- 200rpm will be 2/3rds of the shown power and so on.

It can be fitted to most LSM engines in this display. 

Peter Lynn for the Mahan Heritage Centre, August 2025