"Me" wrote in message
Actually here in the USA most of the Mine Trains are electric with
Induction motors, and Solidstate FreqDrives that have no brushes or
Sparkpoints that aren't covered by Flame Supperssion Barriers....
Flame Suppresion Technology has been in our mines since the 1920's
when they were mostly electrified. A few are diesel-electric, and a
few more Propane-electric, but being a retired Powderman, I has some
small experience in the Industry, and have NEVER seen an Air Powered
Mine trains using air motors were extensively used in Belgium, France and
Germany. In the 1930s the Germans had a diesel/air hybrid loco, that gave
very good economy. I don't know why it was dropped.
Air is being looked into as a hybrid for vehicles. It makes sense to use air
for brake regeneration and starting, as air is free. No expensive batteries
and it can be used all in the one engine, as the UCLA/Ford project and the
MDI aircar in France does.
Improve the IC engine and matters are even more efficient. Revetec are to
bring to market, so they say, an IC engine using cams instead of a
crankshaft that improves efficiency by about 90%, so they say.
This cam arrangement can be used in any engine,
using any fuel, that uses a crankshaft.