I went to the Old Thresher's Reunionin Iowa, in 2002. It was fascinating.
People came from hundreds (if not thousands) of miles away with huge, heavy old machines on trailers to display them at this event. And besides that, the above event takes place at a museum of agricultural technology which contains a nearly unbeatable display of old technology.
The first thing I saw was the display of old internal combustion engines. If you want to see how they built them in the old days, before things like fuel injection or the throttle, go no farther. The most impressive thing I saw in that area was an engine the size of a Ford Excursion...and it was rated at 20 horsepower.
The steam tractor displays were equally impressive. The actual prime mover of the typical steam tractor is a double-acting steam cylinder about eight inches across with a stroke of roughly four feet or so. This was capable of generating around sixty horsepower; but all these tractors moved no faster than a brisk walk due to massive gear reduction. Where a modern diesel tractor may produce hundreds of horsepower, the available tractive effort is not necessarily that much greater than that of the steam tractors. Steam power produces prodigious amounts of torque, and torque is what actually moves the machinery.
The primary advantage of internal combustion, over steam power, is efficiency. The most efficient steam engine ever devised was not more than around 10% efficient at best. Internal combustion engines do slightly less than double that, around 18%. It's why cars have to have radiators; about 80% of the energy produced by the combustion of the fuel is wasted as heat. Most of it goes out the tailpipe, but some is captured by the engine block and must be carried away by coolant. Still, 18% is better than 10%--and as I said, 10% is optimistic.
Of course there are many other factors, such as the fact that internal combustion is vastly more convenient than steam power; you can shut the engine off when you don't need it, and need not bring a tank of water to boiling before the thing will move under its own power. Besides, the throttle is a lot more responsive.
The actual museum was also full of interesting things. The most memorable was a dragline engine, a gigantic two cylinder, two-stroke diesel engine, vintage 1925. The particulars:
Weight: 16 tons
Displacement: 5300 CID
(I mentioned it on the Fiero Forum: The biggest internal combustion engine I have ever seen )
I calculated its torque output at its redline: 2300 lb-ft of torque.
They run it every so often, and it's just amazing to see this enormous engine in operation.
Overall the museum itself, in Mt. Pleasant, Iowa, is well worth visiting. But add the annual Old Thresher's Reunion to the mix, and those of us who like machinery will just be in heaven.
It took me a day to see a lot of it, and still I think I didn't see it all.