Hello Simon,
I do appreciate that the model wheels would be doing the same RPM as the full size loco, so are you saying that for a scale 90MPH that the loco / train would have to do 55.7Meters per Minute? Or approx. 165' in a minute.
looking at the drawings of the forward turbine it's not that big (long), only say 3' then you would have the drive gear on the end as well. So to produce the H.P. it must have been a very good power plant.
For some reason I had always thought that the turbines were between the frames, not just the gearbox.
OzzyO.
No it isn't and like wise they look small to me, but a browse of rail mounted turbines in genereal shows them to be rather small units globally.
If you think about a normal steam engine, the piston is actually quite small as well, take 19" in diameter and a 20" stroke, physically it's even smaller than a turbine, of course a four cylinder loco has four of these to help it along, but overall it's not a big surface area when you think about it.
Where the turbine gets it's power from is clearly the gearbox, a small low power high rpm unit coupled to a large high ratio gearbox can do an awful lot of work, think mountain bikes, I've seen people cycle easily up grades you'd struggle to walk!
Mick D