Featured Locomotive for December 2010

The 'Challenger' locomotive

This month we talk about 'Challenger' 4-6-6-4 Loco. The articulated design of locomotive, used in America & Europe, dates back to the 1870's. An invention of the Swiss engineer, Anatole Mallet. Numerous designs were used in America until 1914 when the US Railway Administration Board was set up to standardise the design of locomotives, in particular. The standard Mallet was 2-8-8-2 where the boiler is rigidly attached to the rear engine while the front engine is allowed to move sideways.

The 4-6-6-4 design dates from 1936 through to 1945. They were high speed locomotives, 70mph (110kph) and weighting in at 480 tonnes (481680kg). All up, 40% of the weight was in the 14 wheel tender, loco maximum tractive approx. 97350lbs.

Used mainly for freight, or sometimes as a passenger service, our example #5148 in Northern Pacific livery is shown hauling a passenger train. N.P. had 47 Challengers. The bulk of the locos were made by America Locomotive Co. (ALCO) 225 - Baldwin 27 - a successful class with 252 built.

The survivors of this class are Union Pacific #3985 in storage at Cheyenne, Wyoming and #3977 in North Platte, New England. While slightly smaller than 'Big Boy' and nearly 100 tonnes lighter its statistics are still impressive.

The Challenger Locomotive

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Challenger Statistics

Water capacity 25000 gallons (113500L)
Fuel Oil 6450gal (29283L)
Coal 32 tonnes (33000kg)
Driving wheels 69in (1755mm)
Boiler tubes 45 at 2.25ins (58mm) & 177 at 4ins (102mm)
Length 60.25ft (18.26m)
Boiler 95 inch diameter (2405mm) Pressure 280psi (1876kp)
Cylinder Bore 27 inches (533mm) Stroke 32 inches (812mm)

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