Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Wow .... that's a lovely pair you have there!  ;c)

It is of course the available steam pressure/volume pairing that dictates the horsepower achieved in a rather direct proportion. So then, it is only to be determined what pressure and RPM regime the engine was designed to operate in, as to the power level it is supposed to be able to attain and provide.

@Stoker, thanks for the confirmation. Since the bore & stroke are almost the same as the Stuart 5A, then the main variables are the steam delivery pressure & the rpm. So, probably the Sipp is rated at a lower rpm & steam pressure; which is what it’s designed for.