Steam Locomotive Construction and Maintenance/Chapter I

by E. L. Ahrons

STEAM LOCOMOTIVE
CONSTRUCTION
AND MAINTENANCE

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CHAPTER I

GENERAL CONSIDERATIONS AFFECTING METHODS OF CONSTRUCTION

A large volume would be required to deal fully with the manufacture of the many different parts of a locomotive and to describe the various processes in the foundries, smithy and forge, boiler-shop, machine shop, and erecting shops. Moreover the methods of construction of the various parts differ considerably in a small works, where perhaps only one or two engines are built at a time, from those in a large works, where from a dozen to fifty engines of the same class may be built to a single order. In the first case the methods and machines of an ordinary well equipped engineering shop would be used to a large extent, but in the second case there are employed special templates, “jigs,” fixtures, and above all, special machinery adapted for certain definite operations. The cost of such special machinery and appliances requires a large

Fig. 1.—Diagram Illustrating the Manufacture of Locomotive Engine and Tender.

capital outlay, which could not profitably be expended by a small works. It pays to make the necessary special time and labour-saving tools and appliances only when several similar engines are built together, or, as in many railway works, when much of the “motion work” and other parts of one class of engine are interchangeable with those of another class. Naturally when the conditions are such that a large number of similar engines can be constructed together with the help of special tools and “jigs,” the cost per locomotive is very considerably reduced. An isolated engine of a new design is necessarily expensive, but it generally pays a railway company to build such an engine, so that it can be tested thoroughly, and the necessary modifications and alterations made before placing a large order.

Progress of Work through the Workshops. A general idea of the order in which work passes through the various shops may be gained from Fig. 1, beginning with the raw materials. The latter term may and generally does include a considerable quantity of semi-finished material. Steel castings, axles, and tyres may be mentioned specially in this connection. One or two locomotive works, both of the railway companies and private firms, make their own steel castings, but generally these are purchased from outside manufacturers. The same applies to rough forged axles. Tyres are, in most cases, rolled at the mills of the steel makers who make a speciality of such work.

The diagram Fig. 1 explains itself, but there are considerable variations in the practice at different works. For instance, boiler mounting work is frequently done in an annexe of the boiler shop itself. Of general machine shops there are frequently two or even three, one or two being devoted to the large machines employed upon the heavier parts, and another to the smaller machines for small pieces and repetition work. The diagram does not show the route taken by every part which goes to form the locomotive. To do this would be impossible. For instance, the firebox of a locomotive boiler is stayed with a large number of screwed steel and copper stays. In the latest practice these are screwed in machines which are placed in a convenient bay in the boiler shop itself, but it is more often the case that they are made in one of the machine shops, from which they go to the boiler shop. There are frequently many such cross paths for various details, and to show these would make the diagram unnecessarily complicated. Certain materials coming from the manufacturers have also been omitted, such as the asbestos mattresses or magnesia blocks used for boiler covering, or lagging as it is termed. These are taken from the stores direct to the erecting shop, where the boiler is lagged during the later stages of the erection of the engines.

One department, not shown on the diagram, must be mentioned briefly. This is the template shop, in which thin sheets of metal are cut out to the finished shapes of the different parts of the boiler and engine details in accordance with the drawings. These templates are sent to the forge, boiler and machine shops, where they are laid upon the corresponding parts being manufactured, instead of marking off the latter to measurements by rule. Much time is saved by the use of the templates.

Stores and Costing Accounts All raw materials, or semi-manufactured parts such as steel castings, are received from the makers into the general stores. The works manager issues the necessary orders to the stores for such materials or articles, which are sent to the various shops in which they are required. The cost of these is debited to the particular order, say for ten locomotives, for which they are to be used, each order receiving an order number, against which everything is charged that is required for that particular lot of engines, until they are completed. The cost of labour is determined by means of daily time sheets, on which the number of hours taken by each workman is entered against the order on which he has been engaged. Finally an overall charge is added for general expenses which include rent, rates, taxes, management, unskilled labour, drawing office expenses, power, lighting and depreciation of plant. This charge usually takes the form of a fixed percentage either of the total cost of materials and skilled labour combined, or of the cost of skilled labour alone, generally the latter. The combined total gives the cost of the engines built to the particular order under consideration, which divided by the number of locomotives, gives the cost per engine.

Before the war the cost of an average mainline engine and tender, when say ten were constructed together, would vary roughly from about £2,500 to £3,700 at the works, according to the size of the engine, and the fluctuating prices of materials. Post-war conditions have caused these costs to be from 3½ to 4 times the above amounts.