The reference for locomotives and railcars
Baltimore & Ohio class O “Old Maude”
class DD1
United States | 1904 | only one produced
Locomotive Magazine, October 1904

The name “Old Maude” refers to a mule in a comic, but also the first large Mallet in the USA built for standard gauge. Its job was as a helper for heavy trains on inclines, what didn't require high speeds. This meant that she did not require any carrying axles, meaning that all six axles were available for traction. The top speed of 21 mph or 34 km/h was completely sufficient for her tasks. Although the locomotive, which was initially designated class O and later renamed DD1, did not have any sisters, it remained in service until 1938.

Axle config0-6-6-0 (Erie (Mallet)) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase30 ft 8 in
Fixed wheelbase10 ft
Service weight334,565 lbs
Adhesive weight334,565 lbs
Axle load477,565 lbs
Water capacity7,000 us gal
Fuel capacity26,000 lbs (coal)
Power sourcesteam
Estimated power2,000 hp (1,491 kW)
Optimal speed19 mph
Top speed21 mph
Starting effort65,664 lbf
with start valve78,797 lbf
Power Plant
Driver diameter56 in
Boiler pressure235 psi
Expansion typecompound
Cylindersfour, HP: 20 x 32 in
and LP: 32 x 32 in
Grate area72.2 sq ft
Firebox area219.4 sq ft
Tube heating area5,366.6 sq ft
Evaporative heating area5,586 sq ft
Total heating area5,586 sq ft
Calculated Values
steam locomotive
last changed: 02/2024

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