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[quote]QUOTE: Originally posted by Mikeygaw ok... here we go.... what's the difference between articulated and non-articulated steam locomotives? [/quote] Hi, Mikey! Here is how I understand it, but don't take any of it for granted: Articulated steamers have two (or more - Erie and Virginian railroads had locomotives with three) sets of cylinders+driving wheels, or two or more engines. The front engine is not rigidly fixed to the locomotive, its rear end is hinged approximately between the rear engine's cylinders, so it can swing under the boiler in order to enable the locomotive to negotiate curves etc. There are two types of articulated locomotives in the U.S. that I know of, the simple articulated, and the Mallett type. The Mallett articulateds can easily be spotted by giant front cylinders. Their front or low-pressure cylinders are approx. 50% larger than the rear or the high-pressure ones. That's because the steam from the boiler is fed to the rear cylinders first, and the rear cylinders exhaust it into the front cylinders via large steam pipes. The steam loses some of the pressure and heat in the process, and that's why the front or low-pressure cylinders are so large - to make better use of the remaining steam energy. The cylinders of simple articulateds are all of the same size and they all get high pressure steam directly from the boiler. I think I remember a sentence from a 1979 Model Railroader: "All Malletts are articulated, but not all articulateds are Malletts." I think the Beyer-Garrat locomotives also fall into the category of articulateds. They were mostly used in Africa. They also have two engines which are both hinged to a frame that carries the boiler and the cab of the locomotive and I think one of the engine carries the water tank above it, and the other carries the fuel (coal or oil). Interesting machines, and most of them narrow (1076 mm) gauge. Non-articulated steamers can have more than two cylinders, too - those are called compound locomotives. Their third (or third and fourth) cylinders are concealed inside the frame, under the boiler. Complicated maintenance. Another type, the Pennsylvania Railroad's T-1 Duplex steamers (4-4-4-4), had two sets of (outside placed) cylinders+drivers in a rigid frame, so they weren't articulated. I think the S-1 or what their name was (4-4-6-4), the PRR giants, were also rigid-frame locos. Have fun, Oliver
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