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Weyerhaeuser Timber 2-6-6-2ST

1928 7 produced
No. 106 Martin Hansen collection

The Weyerhaeuser Timber Co. was one of the American logging railroads which used Mallets instead of geared steam locomotives for their steep and winding lines. They hoped that these would be easier to maintain than a Shay, while having the same flexibility. Their first 2-6-6-2ST saddle tank locomotive No. 110 was delivered by Baldwin in 1928 for lines with grades between four and eight percent. It was oil fired for reduced fire risk when running in dry forests. The water tank was split into two parts which were located on sides of the boiler. In accordance with the original Mallet principle, it was a compound.

In the next year numbers 105 and 106 followed, but in contrast to the first one these had four cylinders of the same size. In other respects they were identical to 110, but heavier. In 1929, Baldwin delivered No. 111 that also worked with simple expansion, but had a much larger boiler. Some years later in 1936, Baldwin delivered three more which included the second No. 110, No. 112 and No. 9. These were again nearly identical to the first No. 110, but had larger cylinders.

111 was retired as the first one in 1947. It was sold to Canadian Forest Products and used on Vancouver Island until 1962. The others were used by Weyerhaeuser until the fifties and several were then sold to Rayonier, where they received an additional tender. The first 110 was restored between 1999 and 2001 and is today running on the Black Hill Central. The second 110 was sold to the California Western in 1967 to haul the Super Skunk tourist train. Later it came to the San Diego Railroad Museum.

The first No. 110, now running on the Black Hills Central

Technical data

General

Property 110/1 105, 106 111 110/2, 112, 9
Built 1928 1929 1936
Manufacturers Baldwin
Wheel arrangement 2-6-6-2ST (Mallet Mogul)
Gauge 1,435 mm (Standard gauge)

Dimensions and weights

Property 110/1 105, 106 111 110/2, 112, 9
Wheelbase 11.51 m
Service mass 100.7 t 111.6 t 119.7 t 112 t
Adhesion mass 83 t 94.3 t 99.8 t 95.3 t
Rigid wheelbase 2.44 m
Fuel capacity 4,542 l (oil)
Water capacity 12,113 l 9,464 l

Boiler

Property 110/1 105, 106 111 110/2, 112, 9
Grate area 2.434 m² 3.855 m² 2.434 m²
Firebox surface 11.892 m² 13.192 m² 11.892 m²
Tube heating surface 141.77 m² 200.485 m² 141.77 m²
Evaporative heating surface 153.662 m² 213.677 m² 153.662 m²
Superheater surface 33.259 m² 54.163 m² 33.259 m²
Total heating surface 186.9 m² 267.8 m² 186.9 m²

Power plant

Property 110/1 105, 106 111 110/2, 112, 9
Driver diameter 1,118 mm
Boiler pressure 13.8 bar 14.5 bar 13.8 bar
Expansion type compound simple expansion compound
Cylinders four, HP: 432 x 610 mm and LP: 660 x 610 mm four, 406 x 610 mm four, HP: 457 x 610 mm and LP: 711 x 610 mm

Power

Property 110/1 105, 106 111 110/2, 112, 9
Power source steam
Estimated power 820 kW (1,115 PS) 1,119 kW (1,521 PS) 820 kW (1,115 PS)
Starting effort 167.0 kN 211.2 kN 221.7 kN 189.1 kN
Starting effort simple 200.4 kN 227.0 kN

Calculated values

Property 110/1 105, 106 111 110/2, 112, 9
Factor of adhesion 1 : 4.88 1 : 4.38 1 : 4.41 1 : 4.94
Optimal speed 31 km/h 24 km/h 31 km/h 26 km/h
Power-to-weight ratio 8.1 kW/t 7.3 kW/t 9.3 kW/t 7.3 kW/t
Heating Surface Equivalent 279.6 m² 388.0 m² 279.6 m²
Cylinder volume/HSE 1 : 1,385.16 1 : 1,131.11 1 : 815.29 1 : 1,581.78
Adhesive weight/Total 1 : 1.21 1 : 1.18 1 : 1.20 1 : 1.18
Tractive force/Heating surface 1 : 18.66 1 : 23.60 1 : 17.29 1 : 21.13
Grate area/Heating surface 1 : 76.80 1 : 69.48 1 : 76.80
Firebox/Tube surface 1 : 11.92 1 : 15.20 1 : 11.92
Total/Superheater 1 : 4.62 1 : 3.95 1 : 4.62

Topics

  • steam locomotive
  • tank locomotive
  • Articulated
  • Mallet
  • freight
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Last changed: 03/2026

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