• HINTS, ON MAINTENANCE.
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How to Get the Best Out of a Vehicle, to Secure Reliability and to Avoid Troubles.
CONTRIBUTIONS are invited for this page from , fleet managers, drivers, garage foremen and mechanics, works staff and draughtsmen, and will be paid for on a generous scale. Every system, make, and type of commercial motor vehicle will be dealt with, arid the matter should be written with a view to the disclosure of workshop and garage practice in the maintenance of a vehide—practices which, whilst they may be quite-normal, are peculiar to the particular vehicle and may not be generally known to those responsible for its running. Expedients and suggestions for overcoming roadside and other troubles are covered in the following page, headed "Roadside. and Garage." Communications should be addressed to "The Editor, The Commercial Motor, 7-15, Rosebery Avenue, London, RC. 1."
68.—The Steam Gauge.
The ordinary .steam gauge employed on ;a, steam wagon is quite a simple instrument and usually consists of a curved tube, generally elliptical in section. This tube is closed at one end and open at the other, where it communicates with the boiler pressure by means of a cock. The closed end of the tube is fastened to a sector provided, with teeth which mesh with those of a pinion on the same axis as the pointer on the face of the gauge. Under theipres• sure of the steam the tube tends to straighten itself, thus moving the sector and operating the pointer.
It is seldom that these gaugesgetout of order, but occasionally they are found to give readings of 30 lb. to 50 lb., either above or below the correct pressure. If a gauge registers over the correct figure, it means that the engine may be labouring, or, if under, the boiler may be working at too high it pressure, as the safety valve is usually kept in tune with the gauge ; therefore, it is as well toe,have the latter tested occasionally by the boiler inspector.
A simple way in which the driver may roughly test it himself is to havu the safety valve blowing ciff, to close the cock connecting the gauge to the boiler, and then to open it quickly. If the pointer moves quickly to the red mark it is probably correct, but if it is sluggish it usually requires attention.
69.—A.E.C. Gear Troubles.
The following hints dealing with the gearbox and its appurtenances, on the A.E.C. chassis, are the outcome of many years of experience in connection with the running of a large fleet of these vehicles and will therefore, probably prove of particular interest to users of this make of machine :— (1) After a, time the sphericaVbushes carrying the gear lever shaft are apt to wear in the bore. This may be cured by new ones, of course, but an economy may be effected by truing up the bore, makinrit little larger, and relininrit with white metal, subsequently re-boring it to the correct size. This method is particularly useful if the shaft, too, has worn and new standard bushes will not effect a complete cure. Moreover, it can be repeated again and again until the outside of the bush, toe, is worn and to such an extent as to necessitate renewal of the bushes.
(2) The change-speed arms sometimes work loose on the shaft, the extent of the play can be detected by moving the gear lever in each direction and at the same time noting the relative movement of the connections, shaft and levers. As a general rule a repair can be effected by fitting ne* keys and tightening the clamping bolts.
(3) The brackets which carry the above-named spherical bushes, when worn, allow excessive movement ei)f those bushes, and thus limit the effective movement of the selector rod so that the gears'clo not get quite home. The remedy iseto file the face of the top cap until a standard bush can just be moved when in position in the bracket, the calaand brackeObeing held in the vice. It is important to useaa, standard bush for this 'adjustment and not a worn one, as otherwise difficulty will arise when the time comes to fit a new standard bush.
(4) Whenever the fork connecting the hand lever to gearshaft lever wears to such an extent that sideplay develops, fit thin washers at each side of the fork taking care to maintain it in mid-position so that it . retain its correct place in the gate. (5) The locating plunger springs in the gearbox
sometimes break. When this occurs the gears are likely to slip out of place or proper engagement when under load. To extract a broken spring, disconnect the selector rod concerned and remove the striking fork belonging to it in the gearbox. The latter fits on a tapered portion of the spindle or rod and requires a smart blow to loosen it. When free, withdraw the selector rod and fit a, new spring. This operation can be carried out with the gearbox in position.
(6) A trouble which is difficult to locate, and fortunately is not of frequent occurrence, results from wear of the front suspension bolts of the gearbox, as shown in Fig. 5. When this occurs, the gearbox vibrates, while the lorry is running, to the full extent of the wear which has taken place ; so much so as sometimes to cause the gears to come out of engagement, if the wear has been excessive. The only satisfactory cure is to renew both eye-bolt and cross-bolt.. To fit these, withdraw the cross-bolt by taking off the
nut which is inside the gearbox and knocking the bolt through. Take off the nuts of the rear bolts—these are beneath the box, and lower the .gearbox, with the aid of a screw-jack, until the eye-bolt clears the boss on the gearbox. This can be done without disconnecting either the selector rods or universal joints.
Do not remove the rear bolts in the course of this operation ; they are useful to guide the box into position again when. the operation is completed; and, as a special note, do not forget to replace the -split pin on that part of the cross-bolt which is inside the gearbox or some real troubles will ensue"