Here are advantages to different locomotives (**= compoud locomotive): *4000 class 4-8-8-4 "Big Boy": Length-132' 9" (longest steam locomotive); Power (cyl. hp.)-10,000@70mph (most of any st. loco.), 5,200@20mph. *H-8 class 2-6-6-6: Power (hp.)-7,500@40mph; weight-724,500-778,500 pounds (exact weight unknown; possibly heaviest steam locomotive when tenderless) *800 class/AE class 2-10-10-2**: Tractive Effort (starting)- 176,600 pounds, most of any steam locomotive; only successful st. loco. with more than 16 driving wheels. *AC series 4-8-8-2 "Cab-Forward': best visibility of any steam locomotive; no smoke can get to cab. Z-5 class 2-8-8-4 "Yellow Stone": Most grate area, evaporative heating surface, and super heating surface of any steam locomotive. Add any others that you think are important.
Hands down the finest articulateds were the N&W Y6b and Class A. They did well holding off those boxes with internal combustion engines.
One aspect I like, is listening to sound from an articulated. Especially when easing along at a low speed. The uneven exhaust barking is fascinating to hear. Boxcab E50
Garratts are also articulateds A different type of articulateds is the Garratt type. Its advantages are lower boiler positioning and reduced overhangs in curves. The Australian AD60 (built by Beyer-Peacock in the UK) is standard gauge and weighs about 263 tons. See also: Garratt for originals and models. The attached picture is from the site given above. It shows a double-header.
How about Erie's try at a 2-8-8-8-2? http://www.dself.dsl.pipex.com/MUSEUM/LOCOLOCO/triplex/triplex.htm I've actually seen one of these done in HO, quite the attention getter!
I have wondered if the Triplex concept wasn't a dead end. In later years, various "advanced steam" designs incorporated improved exhaust systems and steam passages, not to mention new boiler and firebox designs. Several changes increased steam-raising ability, and that might have solved the main problem with the triplex.
