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

Seriously impressed by your demonstration here Philip.

As a guess, each of the first two engines is running somewhat slower than it otherwise would be, based on the exhaust back pressure caused by its follow on engine, as opposed to a free flowing exhaust. But you can hardly tell, as both the Jensen and the PMR seem to be running just fine. But having that Stuart ticking over nicely in third place, really tells the story of how expansive even low pressure steam really is!