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Some Useful Traction Engine Terms Explained

Regulator. This controls the amount of steam allowed into the cylinder and so the speed of the engine. It is operated by a lever at the drivers position.

Reversing Lever. The setting of this determines the position in which the steam enters the cylinder so that the engine can be driven forwards or in reverse.

Injector System. A simple device which enables the pressure of the steam in the boiler to create a vacuum to raise water from an inbuilt tank or from an outside source and then increase that pressure sufficiently to force the drawn up water into the boiler, to keep it topped up.

Fusible Plug. This a brass screw plug with a lead filled centre fitted into the top of the firebox. It is a safety device to protect against over-heating should the water level fall below a certain limit. If this happens the lead centre melts out allowing steam to rush into the firebox extinguishing the fire.

Flywheel. Fitted to the crankshaft and is generally quite heavy, it keeps the engine turning over quite smoothly. Often it has a wide rim to take a driving belt which would power attached equipment.

N.H.P. (Nominal Horse Power). This is quoted for most traction engines but is only a fraction of the true horse power. It is of the order of 8-10 times greater.

S.C.C. (Single Crank Compound). Only a single crank on the crankshaft giving two power strokes per revolution.

D.C.C (Double Crank Compound). They have a separate connecting rod from each cylinder. The crankshaft has two cranks set at 90o to each other giving four power strokes each revolution.

Priming. A term used to describe the emission of water as well as the exhausted steam from the chimney. It is generally caused by an over-filled boiler.

Crosshead. The link between the piston rod and the connecting rod. Also keeps the piston rod in line.

Safety Valve. Usually fitted to the top of the cylinder block. It is pre-set to a safe working pressure for that engine. Should that pressure be exceeded it will operate and allow the excess steam to escape.

Strakes. Plates that are fitted to the rear wheels of an traction engine to give it grip.

Spuds. These can be fitted to the rear wheels of an engine to give it extra grip in the mud.

Spud pan. Generally fitted to the front axle to carry the spuds when not in use.

Perch Bracket. Fitted to the smoke box and carries the front axle.

Driving Pins. These connect the rear wheels to the axle. The drive to these wheels is removed if the pins are withdrawn enabling the axle to be used as a winch if fitted with a winding drum.