There's a cutaway drawing and pictures of a Deltic delta-formed 2-cycle opposed-piston diesel engine at
http://fastjeff57.tripod.com/Scroll down or use page finder to "deltic." This engine was used in both locomotives and marine work. It was supposedly easy to maintain.
That site, called "My Longtime Romance with Engines by N. Jeffrey Perry--Motorhead for Life " is rife with fascinating engines, big, small, aircraft, automotive, marine and shows what is supposedly the biggest engine in the world.
Once, by the RR tracks behind my little farm I found a huge chunk of machined graphite which must have been one of the brushes for either the generator or the motor of a diesel electric locomotive. I surmise that during a maintenance operation, someone parked it on the frame of the loco and it happened to fall out right there. The chunk was obviously machined and shaped and was about 3" or 4" in two dimensions.
On another branch track near the farm, I watched a diesel electric pulling a bunch of coal cars when it started up, and the wheels slipped on the track, just like the "torquey" steam locos, and when I looked later, you could see where the wheels had dug a slight concave in the tracks. Must have been a new engineer or something. I was about 150 yards away when the idling sound changed to a big roar and an enormous puff of black smoke came out of it while the wheels spun.
I was amazed. I knew the torque on a steam engine was basically the same whether it was running or sitting there at zero RPM*, but I didn't realize that diesel electrics could generate that kind of torque on startup, too. Made sense when I thought about it a while, since the torque curve on a parallel-wired electric motor is pretty flat up until the back-EMF approaches the applied EMF. (Did I get that right? Or was that on a series-wound motor...? It's been a long time since I dealt with that stuff.)
Terry, 230RN
* You;ve seen that in movies, I'm sure, where the camera's on the wheels and the engineer applies steam, and suddenly the wheels spin and the train goes CHUFFCHUFFCHUFF...Chuff... Chuff... chuff and starts to move. The chuff is the exhaust steam from each stroke blasting up the stack to increase the draught on the firebox.
Torque's basically the same whether it's moving or not? Sure. You put 250psi of steam on a 12" diameter piston, and the thrust on the connecting rod is 28,274.33 pounds at Top Dead Center whether the piston is moving away at that instant or not. Changes through the rotational cycle, of course