Multiplex locomotive

[1][2][self-published source] The concept of the duplex locomotive originated in the early development of the compound locomotive, in which the high-pressure cylinders worked on drive wheels or drive wheel sets that were not coupled to those on which the low-pressure cylinders worked.

This concept was used most notably by the Baldwin Locomotive Works in North America in the early 1930s.

Articulated locomotives with two drive wheel sets were typically of the Mallet, the Garratt or the Meyer type.

All the triplex locomotives built were of the Mallet type, but with an extra set of driving wheels under the tender.

They could only be used as slow pushers because of the enormous tractive effort was too much for the car couplings to withstand and the boiler did not produce enough steam to operate the locomotives at higher speeds.

There was a project by Baldwin Locomotive Works and one by Beyer, Peacock & Company for the United States, both of which were never realised.

The company presented the design to the Atchison, Topeka, & Santa Fe Railway (AT&SF), which showed some interest in the project.

The middle section, with two engines with four wheels each, carried the two steam boilers, which operated at 14 bar.

The total weight of the three-part locomotive was given as 230 t (according to other sources 248 t), the adhesion mass as 164 t.[9] In the middle section were two identical cabs, which were used depending on the direction of travel, as the 29 m (31 m according to other sources) long locomotive could not use turntables due to its length.

The sheer size of the locomotives caused problems with stabling, the large number of coupling wheels, cylinders and seals on the movable connections between the preheaters and the main boilers were additional maintenance problems, apart from the fact that the locomotive required two firemen instead of one.

[11] The starting tractive force of 200,000 pounds-force (890 kN) of the 460-ton locomotive would probably have been at the limit of the couplers in use at the time.

Like a Garratt locomotive, it had a centre frame with boiler, firebox and cab, which sat on two subframes at each end.

[7][8][14] An even larger 2-10-10-10-10-10-2 variant appeared as an artist's impression in the August 1951 issue of Trains magazine.