Triplexes

[Leon Silverman]

The solution to low boiler horsepower is to have a deep firebox with a large grate area. This is why the the two wheel trailing truck was replaced by four and six-wheel trailing trucks. Unlike model engines, these rear trucks actually supported weight on real engines. The berkshires could not start a longer train than a mikado, but they could pull that same train faster due to the higher boiler horsepower available.
Having an engine with all driving wheels under it did not allow for a large firebox that could burn enough fuel to create the extra needed steam. Larter developments in steam locomotive design could not compensate for this. Witness the PRR Q-1 duplex design. This had the rear set of drivers powered by a steam chest that was in back of the drivers. The rear mounted steam chest restricted the size of firebox (and grate area)that the engine could carry. As a result, there was only one version of the Q-1 built. The 25 Q-2's that were built moved the rear steam chest to the front of the drivers (ala the T-1). This arrangement permitted the use of a large firebox. As a result, the Q-2 is reputed to be the highest horsepower RIGID framed steam engine ever built in America.

[CSSHEGEWISCH]

Where is Robert LeMassena when we need him? He would agree that the Triplexes basically had too much machinery and not enough boiler to be successful. George Henderson, who was the designer of the Triplexes, also held patents for quadruplexes and quintuplexes, which would probably have run out of steam before they even moved their own length.

The design modification which Pokemon suggests sounds like a Fairlie, but a most unusual Fairlie with boilers of different sizes.

[ragnar]

Had one of the Westside Models built H.O triplexs with three can motors, It at least lived up to its prototypes billing .....pulled every freight car i owned plus all of a friends, 175+

[West Coast S]

What killed the design was a grate area comparable with a small 2-8-0 coupled with a boiler that couldn't keep up with steam demands, all used saturated steam and no feedwater systems, so efficiency was nothing to brag about.

The tender drivers also had a tendency to slip as water and fuel were depleted from the tender, causing further firing problems and rod stress. I believe i've seen a in cab photo of a Triplex with duel fireboxes.

[Anonymous]

I was reading a steam engine book and it talked about these locomotives called "triplexes". It had a picture of one and talked about their failure on the Virginian line and Erie railroad. However, had they continued to research these locomotive, they may have become succesful. For example, they said that the reason they failed is that the boiler could not give enough power to the engine. I believe a solution would have been to have two throttles and a large boiler for the first two sets of driving wheel and a much smaller boiler for the last set of driving wheels. It might have been coal fired, but it would have to have two openings for the coal to go into instead of one. Later on, I believe they could have all been modified to be oil-fired and that would have made them much more succesful. If this had been, they would have been the most powerful locomotives ever made, probably even stronger that a big boy. BTW, a triplex had three sets of driving wheel(I forgot to add that at the beginning) They looked really cool in the picture.