Usually the slower the better .
High speed if under generator load .
When repair one usually a quick sprint then forever slow .
I like the Stuart sun just turning over but boy can it speed as it was designed to .
Cheers
Dennis
Would you run your car engine at full speed in neutral ?.....Allan...
I only have mobile engines, no static ones. Some Mamods won't run particularly slowly but I always run them as slowly as practicable, the others certainly run slowly. I'm not a fan of a mobile running around at scale speed of 200mph whilst throwing oil around (and more importantly, away from where it should be). I try and work engines with some load to pull, to slow them down (if there's no throttle, like most Mamods) or I'll run them on a whiff of burner. Looks much more realistic to me but each to their own.
I have run engines flat out a) to see what they're capable of or b) to maximise power - such as for running a generator.
Locomotives at realistic scale speeds, usually as slow as possible.
Would you run your car engine at full speed in neutral ?.....Allan...
Only if I was 16 years old and I'd stolen it.
I've abused my Olds a time or two... 
I don't see any issues with it Nick ...what have you done to it....its hard to tell ?
A homemade El Camino?
A Woodchero?
For some reason, most people try to get their engines to run as slowly as possible, and that certainly works with things like beam engines and large mill engines, which never did run quickly in their full-sized incarnations.
Personally, I vary the speed during each run. I become bored easily....
I've abused my Olds a time or two...
Looks like my daily driver....
Many engines in my stable have no throttle, so speed can only be controlled by using a variac on an electric, or building a smaller fire on the flame fired models. I almost always work at keeping my engines running well under max rpm, but just every once in awhile I like to take a Jensen 35 or 70, or a Mamod Minor out for a spin!
