Dreams of Quadraplexes

Four Locomotives in One

With A Little On Quintuplexes...

Updated: 7 Sept 2015

Another Quad pic

The Baldwin Quadraplex.
The Baldwin Quintuplex.
The Beyer Peacock Quadraplex
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None of the locomotives on this page were ever built. They are, however, all believed to have been be serious projects rather than flights of fantasy.
One quadruplex was built, however, a Belgian loco with two Franco-Crosti boilers. See here.

In 1915 Baldwin built three Triplex locomotives for the Erie Railroad, and another for the Virginian Railroad in 1916. See The Triplex for details. Initial results were apparently promising, for Baldwin laid plans to build an even more monstrous loco- a Quadraplex, or four engines in one. George Henderson was the designer, and was granted US patent 1,100,563 in June 1914. Apparently the Santa Fe Railroad was seriously interested for a while.

Above: The Baldwin 2-8-8-8-8-2 Quadraplex, from US patent 1,100,563

A machine of this length could not be built with a rigid boiler, so note the bellows connection in the middle. This notion was not specific to the Quadruplex- see Flexible Mallets for another example. In engineering terms, this sort of technique is called "Asking For Trouble". There were two separate boilers, one on each side of the bellows joint.

The locomotive was a compound, with cylinders operating at only two pressures; the HP cylinders 7 on the drawing above were fed from the forward boiler and worked at high pressure, a horizontal pipe taking the exhaust from 7 to 8 which worked at low pressure. HP cylinders 9 were fed from the rear boiler and exhausted through another horizontal pipe to LP cylinders 10. (The designer very sensibly avoided the temptation to go for quadruple-expansion, as used in some marine steam engines) The draught was provided not by an exhaust steam blast, but by a steam-turbine driven fan driven 26 exhausting through the funnel 19. The exhaust steam from the LP cylinders went straight to atmosphere via the funnels 33 and 38.

Henderson recognised that forward vision wouldn't be too good if you had to squint along the length of such a boiler, so the loco was a cabforward design. The driver was to communicate with the fireman at the back by means of a voicepipe; it is difficult to see that working well with effectively four steam locomotives at once adding to the ambient noise.

The Baldwin Locomotive Company seriously intended to build this monster, but after it became clear that the Triplexes were failures there were (perhaps fortunately) no customers.

Above: A contemporary drawing of the Baldwin 2-8-8-8-8-2 Quadraplex. Taken from a book published in Santiago, Chile, in 1918. It is not just a copy of the patent drawing.

Left: An artist's impression of the 2-8-8-8-8-2 Baldwin Quadraplex

From Trains, date unknown.

Left: An artist's impression of the 2-8-8-8-8-2 Baldwin Quadraplex in action

The design was envisioned by George Henderson of the Baldwin Company in 1913.

From Trains, date unknown.


Henderson also proposed what he called a Quintuplex:

Above: An artist's impression of the 2-8-8-8-8-8-2 Baldwin Quintuplex proposal.

From Trains, date unknown.

Left: Artist's impression of the final development of these proposals: a 2-10-10-10-10-10-2 Baldwin Quintuplex in action!

From Trains, date unknown.

OK, back to sanity. (Relatively speaking)

Of all the deviations from convention, the Beyer-Garratt articulated loco was one of the most successful. In 1927 Beyer Peacock & Co produced this design for a 2-6-6-2 + 2-6-6-2 doubly-articulated quadraplex, which would have produced a starting tractive effort of more than 200,000 lbs.
It could be called a Mallett-Garrett, as each engine section has its front half pivoted at the rear and sliding at the front in the Mallett manner. This looks like a much more practical machine than the Baldwin above. It has been suggested that it was offered tongue-in-cheek, but it is hardly likely that Beyer Peacock would have gone to the trouble and expense of getting a patent unless they meant business.

Above: Side elevation of the Garrett quadraplex.

Above: Every home should have one; a rare image of the Garrett quadraplex. Convincing as it looks, this is just a contemporary drawing. Note smaller water tanks compared with the drawing above.

4' 8.5"
Grate area:
160 sq ft
Tractive force at 90% boiler pressure:
215,200 lbs
400 tons

Unfortunately there were no takers and none were built. Pity! I'd buy one.

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