Why did steam tractors die out

If someone could figure out a way to capture all of the heat energy of internal or external combustion and turn it into work, they would really have something. But even the most efficient intercooled turbo diesels still waste much of the energy in the fuel out the exhaust and through the cooling system. Gas engines are even less efficient and most steam designs only use a very small fraction of the fuel's energy.

I am amazed at the improvements in fuel economy in modern cars. But this improvement comes at a high cost: the high tech electronic controls cost a lot of money and it is not possible for the backyard mechanic to fix, or even find lots of the problems that come up.

Back when gas was 25 cents and fuel oil was a dime, poor fuel efficiency helped doom the steamer. Railroads figured this out very quickly in the late 40's. With gas and fuel oil rapidly approaching $2 the argument is now even more compelling!

You are also correct about efficiencies of combined cycle central station plants. However these plants are fiendishly complex, and must operate at extreme temperatures/pressures to achieve this level of efficiency (= extremely high cost!). And they require careful operation and maintenance to sustain this efficiency. Contrast that to a reciprocating, non-condensing steam engine fed saturated steam from a hand-fired 125 psi boiler, filled with dirty pond water, and operated by an "engineer" who has at best only a rudimentary understanding of the thermodynamics of efficient steam plant operation. These would be fairly typical steam tractor operating conditions – and do not favor fuel efficiency!

Another problem with steamers: The consequences of inattentive operation. If steamer is not properly maintained and operated, a boiler explosion is a real threat. And explosion will destroy the machine (and it's operator!) and usually results in dramatic collateral damage as well. (Witness the tragedy involving a steamer at a show in Marion OH a couple years ago.) Compare that to the consequences of an inattentive operation of an internal combustion tractor. Generally the worst that will happen here is the tractor simply quits running, and perhaps a few expensive parts must be replaced. Insurance companies would throw a fit and terminate farm coverage quickly if every farm were to have steamer or two on the premises!

Bottom line is I like the look, sound and smell of a steamer as much as anyone. However is the agricultural steam engine is a technology whose time has clearly passed!