Lubrication

(By William Seddon, Turner, N.Z.R. Workshop, Petone)

The subject matter of this article is one that should appeal to all railway workers. It deals with a line of expenditure incalculable, owing to the frictional deterioration of component parts working upon a locomotive or other heavy type of rolling stock. Employees ought to derive some material benefit arising from the great economic savings accruing through the adoption of improved methods in various forms of lubrication. Wastage in this direction increases expenditure and, correspondingly, reduces profits which, in turn is detrimental to all concerned, for wages in any industry suffer, must suffer in consequence of any economic waste, whether through faulty lubrication or any other cause.

Lubricants are substances employed to reduce friction. Technically, “friction” may be described as the effect produced by two bodies sliding one upon the other which have upon their opposing surfaces minute asperities that interlock each other. The sliding movement which forcibly removes these minute irregularities, creates what we call friction. Friction is reduced when these asperities are small and lubrication is resorted to, to prevent that loss of power caused by motion under these conditions.

The lubricants chiefly used have a less co-officient of friction than the parts in contact. The term “co-efficient of friction” is an expression which indicates the proportion that resistance to sliding bears to the force which presses the surfaces together.

In a steam engine, where many parts are moving, a large amount of friction is produced, which tends to stop these parts, and would ultimately do so, were they not continually re-supplied with fresh motion obtained by the burning of fuels. Hence it is apparent that the engine has not only to overcome the resistance of the work to be done, but, also, the resistance created by its own parts. In other words, the amount of heat manifested in friction is the amount of extra heat that will have to be generated under the boiler, and the extra cost of working will be the cost of the fuel necessary to produce that heat. From observation we know that the tendency for a good many lubricants is to “gum”, or what might generally be called “oxidise.” This is chiefly caused by insufficient care in preparing the various forms of mixture.

The requisite for a good “locomotive grease” for high velocities is that it should be of a suitable consistency such that it will neither run away too rapidly nor be too stiff to cool the axles. It should also have lasting power, so that there may be as little increase of temperature as possible in the axles even at high speeds. It must be borne in mind that a careful analysis of locomotive grease is no test whatever of its practical value, which can be determined only by actual experiment.