Re: Garratt Design - and the Americanization thereof ...

Doug,

Adding length to the K-37 boiler will do little to add to steam production but will make operation through curves that much more difficult. As you said, a larger diameter boiler would be needed.

Quoting from A.E.Durrant's Garratt Locomotives of the World "As for the boiler, again, not being over the wheels or chassis, the size is restricted only by the loading gauge, a limit seldom reached, and in particular, the firebox can be made of adequate depth, and having slung under it an ample ashpan. The firebox can be a simple rectangular box, there is no need to provide an expensive combustion chamber of complicated shape as the deep firebox provides all the volume required for combustion."



Compare the drawing of a South African 42"gauge GMA 4-8-2+2-8-4 Garratt with your proposed double K-37. The boiler is relatively short and fat and the firebox is deep. The GMA would be rated at about 65,500 lb TE if calculated at 85%, close to the output of two K-37's. If the driver diameter is reduced to the same 44" as the K-36's and K-37's, the TE rises to 80,000lbs!

Also of interest, the maximum axle loading for a K-36 is 36,000 pounds. Assuming that the axle loading for the GMA is in imperial (2240lbs) tons, the maximum axle loading for the GMA is 35,168. As long as clearances weren't a problem, a 3 foot gauge GMA equivalent would be able to operated on the D&RGW narrow gauge main lines.

Michael Allen