# Steam Locomotive Construction and Maintenance/Chapter VI

CHAPTER VI
MACHINE SHOPS—AXLES AND WHEELS
Fig. 23.—Straight Axle.
Fig. 24.—Centre Driven Axle Lathe. By Messrs. Hulse & Co., Ltd. (Manchester).
Crank axles are turned in heavy lathes of the ordinary pattern, as the position of the crank webs does not allow of centre driving. The inside faces of the jaws of the crank webs are slotted out, or more usually milled out by a large revolving disc, into the periphery of which a number of cutters are inserted. A machine of this type is shown in Fig. 25. This has two centring headstocks at the back (one of which is hidden from view), in which the crank axle is held in special chucks, and there is also the revolving disc provided with cutters. The latter is slowly fed into the crank between the crank arms, and cuts these out to the dimensions required. This part of the work completed, the headstocks are set in motion to revolve the crank axle, which is set so that the crank pin is rounded by a cutting tool to a circular form. The axle is then turned round end to end in the centring headstocks and the other crank arms are milled out and the pin turned.
Fig. 25.—Crank Sweep Milling Machine. By Messrs. Craven Bros. (Manchester) Ltd.
Wheel Centres. The term “wheel centre” refers to that portion of the wheel which includes the central boss, and the spokes and rim, but does not include the axle or tyre. Wheel centres are now generally made of cast steel. They are turned outside, and also bored for the axles either in a wheel lathe, or—more conveniently—on the revolving table of a horizontal boring mill of the type shown in Fig. 26.
Fig. 26.—Horizontal Turning and Boring Mill. By Messrs. Craven Bros. (Manchester) Ltd.
Fig. 27.—Boring Tyres on Horizontal Boring Mill.
Tyres. The tyres, which come from the steel manufacturers, are rolled without weld. They are bored inside to an internal diameter slightly less than the outside diameter of the wheel centre, on to which they have to be shrunk, the allowance being about ¹⁄₁₀₀₀ of the diameter of the wheel centre. Formerly tyres were bored in a wheel lathe, but it is found much more convenient and expeditious to bore them on a boring and turning mill of the type shown in Fig. 26. The tyres are placed horizontally on a revolving table as shown in Fig. 27. The tool holders ​shown are special ones which allow several tools to be used at once.
After having been bored the tyres are placed on the floor inside a shallow pit, which has a circular gas ring round it, by which they are heated so that they expand. The wheel centre on the axle is then taken up by a crane and lowered into the tyre, which as it cools, shrinks and grips the wheel.
Figs. 28 and 29.—Tyre Fastenings.
Figs. 28 and 29 show the most usual methods of securing the tyres to the wheels. T is a section through the tyre, and W one through the rim of the wheel. In both examples, there is a lip A which prevents the tyre from sliding laterally over the wheel rim towards the inside of the rail. The flange F, which runs against the rail, prevents the tyre from sliding towards the outside. In Fig. 28 the tyre is secured by set screws S which pass through the rim of the wheel. Some engineers object to set screws, as the tyres tend to ​break across the holes. In the alternative construction, Fig. 29, the tyre is held by a retaining ring R, which is heated and driven into the recessed groove shown, and the lip B of the tyre is then hammered down all round the wheel on to the ring.
The outside crank pins, upon which work the coupling rods, and also the connecting rods of outside cylinder engines, are turned and then ground on a grinding machine, and pressed into the holes bored into the wheel boss to receive them. As the pin on one side of the engine has to be fixed at exactly 90° with the pin on the opposite side, the boring of the holes in the wheels is done on a special “quartering machine,” in which both holes are bored simultaneously in the opposite wheels. The arrangement of the machine is such that the 90° angle is automatically maintained.
Fig. 30.—Locomotive Driving Wheel Lathe. By Messrs. Craven Bros. (Manchester) Ltd.
Fig. 31–34.—Tyre Gauges.
is illustrated in Fig. 35. The wheels and axle rest in bearings supported by springs, and are driven at a speed corresponding to 60 m.p.h. by means of a 55 h.p. electric motor. The speed is registered by the counter on the wall at the back of the machine. The hand wheel actuates the brake blocks by means of a screw, so that the wheels can be stopped quickly when required after the current has been cut off. The excess or deficiency of balance, as found by the small weights attached during the test to secure steady running, is afterwards rectified in the balance weights. ​Axleboxes. The account of the work done in the wheel shop may conveniently include the axleboxes. These are most frequently machined in the general machine shop, but as they have to be fitted to the journals they are, in some modern works, machined in the wheel shop, where they are close to the wheels, and do not then require to be taken from one shop to another. An alternative method, used in other works, is to fit and bed the axleboxes on to a short “dummy” axle journal, kept in the machine shop for this purpose, the axleboxes then being taken straight to the erecting shop.
Axleboxes are either of gun-metal or of cast steel fitted with gun-metal bearings, the latter form being now more usual. The “brasses” which bear on the journals are provided with recesses, into which is run “white” or antifriction metal, consisting of about 80 per cent. of tin, 10 per cent. of copper, and 10 per cent. of antimony. This prevents the journal of the axle from being injured in case the bearing runs hot.
Fig. 35.—Wheel Balancing Machine. G.W.R. Swindon Works.