Why Brass

[modelbob]

The following info is from steamlocomotive.com, which is usually pretty accurate. Is it correct in this case?

In 1909, the Great Northern had installed 35 class M1, Mallets of an unusual wheel arrangement, 2-6-8-0, In 1924/5, the road rebuilt the class as simple engines, class M2. Not satisfied, the GN in 1925/6 proceeded to rebuild 22 of the M2 as a new, and very large 2-8-2, class O7. These locomotives took the GN into the field of truly giant 2-8-2s: 31 x 32 cylinders, 69 inch drivers, 210 psi, 268/348,000 lbs weight, 79,950 lbs tractive effort. Seemingly, the GN was not satisfied with the O7. New boilers were ordered from Baldwin and Alco, and the result was class O8 of 1945/6: 28 x 32 cylinders, 250 psi boilers, 69 inch drivers, weights 325/425,000 lbs, starting tractive effort 75,900 lbs. (In 1932, 3 earlier O8s had been built from scratch. They had 29 x 32 cylinders, 69 inch drivers, 250 psi boilers, weights of 280/367,000 lbs. Starting tractive effort was 78,000 lbs. In 1946, these three locomotives were rebuilt to conform to the 22 "new" O8s, thus making a class of 25. Also, over time, some if not all of the class were converted to oil burners.)

 

[jbaakko]

Wow, those buggers got rebuilt more times then an SD40-2!

 

[HaggisKennedy]

Yeah, pretty much. GN was good at building and rebuilding locomotives. The O-8 Mike was the largest Mike ever built. Somebody told me that the O-8 was comparable in size to the GTW's U3-b 4-8-4 Northerns, which are somewhat on the small size to begin with.

Here's another good rebuild, the GN N-3 class 2-8-8-0s. Also from steamlocomotive.com:

Delivered as N-1 compounds by Baldwin in 1912, these engines were simpled in the mid-1920s (N-2). Note that they still had the characteristic Belpaire firebox.

In the early 1940s they got new frames, nickel-steel boilers, and roller bearings as well as a larger grate; at that point they became N-3s.

http://www.greatnorthernempire.net/index2.htm?GNEGNPrototypeDrawingsSteam.htm (visited 7 Jan 2005) shows all of the numbers in the GN's locomotive diagram. A note says the boiler had a nominal pressure of 275 psi, but was lowered to 265 psi for working. A comparison with the N-1's factors shows what a huge increase in power these rebuilds represented.

The timing couldn't have been better, either. The first of the rebuilds (2024) was completed on 10 February 1940, the last (2009) wrapping up almost exactly 2 years later on 12 Feb 1942. Thus the greater horsepower was available in time for the Great Northern's World War II traffic spike. Virtually all of the class was retired in 1955.

They started at 93,000lbs of tractive effort, but the N-3s were up to 118,400lbs by 1941.

Kennedy