Interestingly the steam engine itself is a very efficent drive.
The attribute of steam to expand like nearly no other gas without a chemical burning reaction makes the drive effective. Good locos are constructed to go with steam expansion, not just with steam filling.
Powerplants use steam turbines, because no other medium offers the attributes to carry the energy efficiently.
With the volume, the fact of beeing stationary, a highly detailed optimizing of mechanics and steamflow gives such plants an efficiency of 70-80 %
The problem with railroads is, that u need power 1.) mobile and 2.) with very changing effort.
That was always a problem and is till now. Not just with steamers. The only reason of creating a diesel-electric loco is the fact that the diesel can start from "0" velocity. Electric drives are good to controll. The efficiency of a diese-electric loco is bad comparing to a hydraulic geared one.
Diesels have a bit better efficiency than petrol-engines, but that was never the fact why they were used.
To give another example that may relativate the 11-13 % of a steamer is to take an average otto-engine of a average mass-producted car in the 1990´s. The efficiency is just about 30-32 % on the engine, and only 20-23% at the wheels.
So, the steam engines ARE not that bad.
There are several things to look at:
Heatloss IS a major problem, but not just in the exhaust! Bad isolation of the boiler and the way how the coal-energy is changed into water-stroed energy is ineffective. Surely the whole construction isnt capable to save heat in exhaust. Therefore some cunstructions tried to change this and use more of the heat. Think about overheated steam and double-heaters like the franco-crosti-construction.
Another, also mentioned main matter is the mass that has to be moved. Neither the heavy boiler nor the knietic losses on piston, steering and rods are useful for an effective drive.
The need of changing interatomic-energy in heat by burning, takeing this heat and store it in water, making it to steam by taking it out of storage and then change it first into kinetic linear energy in the pistons and then kinetic spinning energy with the rods is a very long way to go and therefore filled with losses.
The fact that this has to be mobile on a frame and wheels doesnt make it better.
the German 52 8055 was modernized by the Ing. Roger Waller from Swizzerland.
With this project he proved that with some changes on an old steamer, u can make it much more effective.
Really modern steamers are a bit better, because they have a better harmony with the new effords and techniques used nowadays.
How far he brought the efficiency til now i do not know.
So, when steamers died, there were some trys to rescue them....but in most cases, u need 2 man personal and the whole, free-running and just slighty-lubricated, mass-moving piston-drive is no construction to go into a future.
All efforts to hold the steam on the rails came too late and therefore were done just "half-hearted".
It was -to go further- that miserable wars that always cut down all efforts to bring the steamers a future:
not the efficiency was a question. Not the amount of burned coal. Not the costs of crew.
The only things that were interesting was: simplicity in construction and operation. To have as many locos as possible, easy to repair and made of less material.
They just had to move.
Reliable.
When the war was over, there was a bunch of those simple locos, and when they were used down, the time of steam was over.
In the 1920´s we had much more elegant and effective locos then in the 1950´s.
long posting...sorry
Frank
