THE UPKEEP OF STEAM WAGONS.
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No. 13.—Engine Overhaul and Repairs : Springs, Steering, Front Axle Forecarriage and Brake Gear.
Some drivers are disposed to think that springs require little or no attention. This is by no means the case. If left to themselves, they simply become hard and dead. The spring ends will wear grooves in the pads and so tend to become locked. The leaves of a spring are „ aontinually sliding slightly over one another, and therefore they require a certain amount of lubrication. From time to time the springs should be taken to pieces, the rust cleaned off and greased. Grease can also be inserted between the leaves without taking the springs apart, by using the simple tool illustrated in Fig. 56. Forcing the points between the leaves opens them slightly, and grease can • be introduced with a thin, flat piece of metal. By keeping the springs in good condition, the wheels are more likely to keep in contact with the ground, so that the tyre bill is reduced. • Spring pads should never be made of soft material ; • highly-tempered spring steel is .best. Failing this,
• however, deeply ease-harden the pads after they have been fitted in the housings. If a hind spring is damaged and has to be replaced, compare the camber of both springs, and if one side is lower than the other pack it up. On account of the camber of the road, it is sometimes an advantage if the left-hand side be slightly higher than the right, say, about
The front springs are invariably those requiring most attention. Being short and stiff, they are not so resilient as the hind springs. Consequently, they settle down and lose their camber. In some cases, where the spring has not received attention, it rides solid on the front axle. Extra life can be obtained if packings are placed between the spring pads and the axle, thus lifting the spring up.
The replacement of the front spring is greatly facilitoted. if the forecarria.ge pin is made with a long tapering end, instead of being cut off square (see Fig. 57). Owing to the side pressure on the spring when turning, the leaves are liable to become twisted. To remedy this, fit a new buckle to the spring. If any
of the leaves are found to be broken, new, ones can be fitted, thus saving the expense of a new spring.
Driving Axle. ,
If the ends of the axle or the bearing journals are badliscored, it is advisable to return them, taking off only sufficient to remove the score marks, and rebush the wheels and bearings to suit. In some cases where a wheel is keyed on the axle, the keyways will be found to have worn irregular, making it impossible to fit a new key. The best way to deal with this is to weld up the sides of the keyway 133i oxyacetylene and then recut them.
The axle bearings will most probably require new bushes to the top half : the bottom half is not bushed, as no pressure comes on this part. These bushes often wear badly on the side flanges, especially if no provision be made to keep dust out of the bearings. Too much side play causesa jerk and strain on the wheels and .springs, especially on a rough road.
If the same bolts are used for holding the two halves of the bearing and connecting the spring to the tap half, these bolts should be carefully examined. They have to withstand heavy and fluctuating stresses' and it is quite possible that one or more may be broken or badly strained. It is also a good plan to anneal the sound ones, for they may have become hard and brittle. If any part fixed on the axle has become
very slack, such as the lock i ing boss, t should be re
placed: a loose member on the driving axle is a serious risk.
Steerage, Front Axle and Forecarriage.
On account of the continu.
ous and alternating stresses to which it is subjected, and its exposed position, the steering gear wears very quickly. The backlash or lost motion of the steering wheel makes the steering of the wagon much more strenuous. Although most worm gears are covered in,
Fig. 58. the teeth wear and .become Tipped front axle. slack. The teeth of the worm wheel will be found to have worn more at one place. This can be remedied by refixing the chains on the shaft so that the -worm wheel is turned round 180 degrees, bringing the less worn teeth MO operation. Owing to the end piessure of the worm on its bearings, end play develops. This can be overcome by fitting a washer between the worm and its bearings.
These bearings will no doubt require rebushing, as will also the bear,ings of the chain shaft. Examine the chain shaft ends, and if they are worn eccentric, true them up and make the new bushes to suit. It is sometimes necessary to weld a new end on the spindle, where the worm is fitted, on account of the excessive wear at this part. A common defect of the forecarriage swivel is tipping of the axle due to wear of the faces, as shown in Fig. 58. Weld up the sides of the bracket and the faces of the axle by oxy-acetylene, and reshape them both to fit. It is important that the chains should be carefully examined, and if the links are worn badly
new chains should be fitted : never run any risk with these or the result may be disastrous. If new chains are not required, the old ones will most probably require tightening ; this can easily be done by cutting off a link at the front end of each chain adjoining the axle shackle and slipping the shackle through the next link.
The stay connecting the bottom of the foreearriage bracket to the front of the ftebox will no doubt be found to be slack. Close in the joints, reamer out the holes and fit larger size pins. Sometimes this stay is only held on the forecarriage bracket by a washer and split pin. This is not a very safe job, since the pin is liable to wear through and allow-the stay to drop off. A better way is to screw the end of the pin and fit a castle nut.
As the front axle is stationary, all the wear takes place on the underside, thus making the arms out of round. If the axle be parallel, one way to remedy this is to turn the axle over and refit the spring pads. But most axle arms are set down slightly to suit the camber of the road, so that ttie wheel tyres will get a bearing on their full width. In this case the arms should be re-turned and the wheels bushed to suit.
The axle collars are also subjected to a good deal of wear, owing to the side pressure on the wheels when turning. New collars should be fitted of greater Width to tike up the slackness.
In overhauling the brakes it is not only suffiaent to see that the brakes can be applied withoot the lever or screw nut reaching the' limit of its travel, far, in spite of this, the brakes may still remain inefficient. If, for instance, the lever (A) operating on the brake strap is inclined, as shown in Fig. 59, the leverage is reduced, and, consequently, less power is applied 'at the strap. To transmit maximum power, the lever (A) should be vertical when the brake is on ; in fact, it ought to be set inclining slightly in the opposite direction, to compensate for further wear_ The straps should be examined and relined if necessary. If they were originally fitted with wood blocks, line the new blocks with Foredo ; wood is apt to get hot arid char.
The drums, if worn badly, should also be returned. However, care must be taken to see that they are not worn too thin for this operation. A split drum is better than a solid one ; it is easier to replace if it breaks, while it is better able to withstand the stresses set up in tho material due to heating.
All Joints should be examined and closed in if too slack, and new pins fitted Where necessary. On the latest types of wagons fitted with brake drums on each driving wheel, if is. important to see that the compensating mechanism between the two drums is working properly. Directly a wheel skids, the braking effect ceases, and there is the danger of the wagon sliding sideways. It is important that no oil should drop on the drums from any other part of the mechanism. ilEPIUESTITS. (To be continued.)