"Standard Class 4 Tank" by Henry Greenly

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2" GAUGE ~ 17/32" - 1' SCALE

The design exemplifies a type of tank engine introduced on British Railways in 1951 and is one recommended for modelling in 2-inch gauge or larger if desired. It is suitable for heavy duty on an outdoor model railway system. The weight on all six-coupled wheels should not be less than three-quarters of the total weight of the engine in working order. The tractive effort is 10 lb., and the engine is capable of hauling a load of 250 lb. on a level track.

The front and rear ends of the engine are guided by a swivelling bogie and pony truck respectively, and therefore the locomotive rides very well indeed on lines with sharp curves. The minimum radius recommended for 2-inch gauge is 10 feet (3 metres).


Cylinders. 5/8 -inch bore by 1 1/8-inch stroke. Two outside cylinders only inclined on a slope of 1 in 16 with the valve chests on top. Piston-valve or slide-valve cylinders may be fitted.

Valve Gear. Outside Walschaerts' designed to give a maximum cut-off of 85% of the stroke.

Slide Valves. Steam port opening 0.07 by inch wide. Exhaust port opening 0.14 by inch wide. Thickness of port bar 0.08 inch. Lap of valve 0.046 inch. Total valve travel 0.232 inch.

Coupled Wheels. 3-inch diameter on the tread and of a good close-grained cast iron. Wheels to be an even press fit on ground steel axles and keyed. The right-hand crank-pins to be a quartet turn in advance of the left-hand crank-pin (90). The axles to be 3/8-inch diameter and carried in gun-metal axle-boxes on underhung coil springs.

Bogie. As the trailing end of the engine overhangs the track a considerable amount when negotiating a sharp curve, the slot in the bogie stretcher must be wide enough to allow side play. of the central pin. Allow for a total movement of 3/8-inch. The bogie to be, equalized and sprung. Wheels 1 19/32-inch diameter.

Pony Truck. The wheels are 1 19/32-inch diameter! The truck is sprung and pivoted at a point 3-inches behind the axle.

Boiler. Locomotive type with narrow firebox. It may be designed and tested for a working pressure of 65 lb. per square inch on the gauge.

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This page was last changed on 06/05/2016