loco-info.com - Great Northern (US) class L-3

flickr/Twin Ports Rail History

In order to prevent individual chassis groups from slipping on slow freight trains, the Great Northern ordered a Mallet with unequal axle distribution. The front group consisted of a leading axle and three driving axles, while the rear group consisted of four driving axles. After ten locomotives from 1909, another 25 followed, which had a significantly larger tube heating area. Under the new scheme, they were designated class M-1.

They were converted to simple expansion to save complexity from 1926 and were designated class M-2. The rear cylinders remained slightly larger in order to be able to convert enough power for the additional driving axle. The existing feedwater heater was also removed. The locomotives had a choppy running that made speeds over 25 mph (40 km/h) difficult to run. 22 were scrapped from 1929 and their parts used for new O-7 class Mikados, while the remaining 13 partially survived until 1954.

Variant	first series	second series	rebuilt M-2

General
Built	1909	1910	1926-1928
Manufacturer	Baldwin		Great Northern
Wheel arr.	2-6-8-0
Gauge	4 ft 8 1/2 in (Standard gauge)

Dimensions and Weights
Wheelbase	43 ft 11 in
Rigid wheelbase	12 ft 6 in		15 ft
Total wheelbase	76 ft 2 1/2 in		85 ft 5 in
Service weight	368,700 lbs		403,000 lbs
Adhesive weight	350,000 lbs		384,000 lbs
Total weight	522,800 lbs		583,000 lbs
Axle load	51,400 lbs	50,000 lbs	56,000 lbs
Water capacity	8,000 us gal		10,000 us gal
Fuel capacity	26,000 lbs (coal)		4,500 us gal (oil)

Boiler
Grate area	78 sq ft
Firebox area	225 sq ft		258 sq ft
Tube heating area	3,059 sq ft	3,525 sq ft	4,982 sq ft
Evaporative heating area	3,284 sq ft	3,750 sq ft	5,240 sq ft
Superheater area	480 sq ft	579 sq ft	1,490 sq ft
Total heating area	3,764 sq ft	4,329 sq ft	6,730 sq ft

Variant	first series	second series	rebuilt M-2

Power Plant
Driver diameter	55 in
Boiler pressure	200 psi	210 psi
Expansion type	compound	simple
Cylinders	four, HP: 23 x 32 in and LP: 35 x 32 in	four, front: 22 x 32 in rear: 23 1/2 x 32 in

Power
Power source	steam
Estimated power	2,350 hp (1,752 kW)	2,500 hp (1,864 kW)	2,900 hp (2,163 kW)
Starting effort	73,085 lbf		107,620 lbf
with start valve	87,702 lbf

Calculated Values
Factor of adhesion	1 : 3.99		1 : 3.57
Optimal speed	20 mph	22 mph	18 mph
Power-to-weight ratio	0.0064 hp/lb	0.0068 hp/lb	0.0072 hp/lb
Heating Area Equivalent	5,369 sq ft	6,033 sq ft	9,510 sq ft
Cylinder volume/HAE	1 : 1885.05	1 : 1677.58	1 : 1064.23
Adhesive weight/Total	1 : 1.05
Tractive force/Heating area	1 : 5238.08	1 : 4554.44	1 : 3594.94
Grate area/Heating area	1 : 45.37	1 : 52.62	1 : 82.98
Firebox/Tube area	1 : 15.73	1 : 18.24	1 : 25.09
Total/Superheater	1 : 6.84	1 : 6.48	1 : 3.52
HP/LP cylinders	1 : 2.32

steam locomotive

freight

Mallet

Articulated

last changed: 03/2023

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