UK Railways Experimental & Prototype Decapod

photo; Great Eastern Railway

The Great Eastern 3 cylinder decapod, designed by James Holden
built to demonstrate that a steam locomotive could accelerate a 300ton train from a stand to 30mph in 30seconds.
3 cylinders were used because there was insufficient room for 2 cylinders large enough to develope the required tractive effort without going up to a higher boiler pressue
Even so it still had to have a pressure of 250lb to achive the required result.
After many trials and tests the loco proved succesful but was found to be too heavy for some bridges on the system and after a brief carrier was converted to a 0-8-0 freight loco.
Weight in running order; 70tons
Driving wheel dia; 5' 4"
Cylinders; (3) 18½" x 24"
Boiler length; 15' 6"
Boiler dia; (inside) 5' 3"
Tubes: 395 x 1.3/4" dia
Heating surface; 2,873.3 sq. ft.
Fire box heating surface; 131.7sq.ft.

There were three seperate grates annd ash pans, one on each side outside the frames and a third between, giving a aggregate area of 42sq. ft.
The trailing drivers were given a side play of ½", the coupling rods being fitted with ball and socket joints. As the cranks of the three cylinders were set at 120 degrees in relation to each other, perfect balancing of the reciprocating parts was secured.
In order to minimise the drivers slipping, compressed air sanders were fitted.
James Holden pictured with his loco

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