It is important to reference the image of the steam locomotive. To travel a distance it requires additional fuel. The fuel to weight ratio is very little. She requires just a few sticks of wood/calories per mile/km. It is the steam which is so efficient, and has proven to be so on boats.
But, the Rockefeller/Rothchilds said; these numbers are not good enough! To travel, you must use Gas, and Oil... "Our Oil!" ..."and Saudi Oil!" Some of us thought, huumm, if that is the case, I'd rather walk.
That's why I'm proud to see Try's bunch utilize a continuous, low-pressure compressed 'air motor.' It is superb for local travel, but the current range is not unlike an automobile. Air simply will not compress all that much.
This machine (link) requires 7lbs of -input pressure- to generate enormous -expansion- of water. This, in-turn, can drive a terrific turbine, at relatively low torque. Again, the MAIN issue is transferring the energy and overcoming the friction. The 'reciprocating' element, as I see it, can be moved upstream of that reaction, not downstream, thus the 'ram-pump' continuous pressure generator at the inlet. With this configuration, we also get the potential for enormous electric generation with a flywheel at the drive-stage which also serves as a gyro-stabilizer.
http://rexresearch.com/schaeffe/schaeffe.htm
Built of steel, I'm needing around 3,000lbs of vehicle weight. I don't mind this, provided the efficiency of the drive-trane, since it is inherently a -displacement- motor arrangement.