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HINTS ON MAINTENANCE._

10th October 1922
Page 32
Page 33
Page 32, 10th October 1922 — HINTS ON MAINTENANCE._
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How to Get the Best Out of a Vehicle, to Secure Reliability and to Avoid Trouble.

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, and the matter should be written with a view to the disclosure of workshop and garage practice in the maintenance of a vehicle—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., dealing with letters froni our driVer and mechanic readers. Communications should be addressed to "The Editor, The Commercia I Motor, 7-15, Ilosebery Avenue, London, E.C.1."

274.—A Method of Cushioning the Body on a Ford Ton Truck.

The Ford ton truck when laden is fairly well sprung, but a good deal of vibration is experienced when the Vehicle is run light, with the result that the body suffers accordingly. This question of hard riding when the vehicle is unladen. is, as a matter of fact, a source of considerable trouble on most commercial vehicles, and a method of alleviating it to a certain extent is by fitting rubber blocks or buffers between the cross beams supporting the body and the chassis.

In the case of the Ford, the cross beams are usu-, ally carried on angle brackets, in which event the rubber buffers are inserted between the beams and these brackets. Even comparatively thin buffers make quite an appreciable difference to the riding, as they absorb the small vibrations which are not taken up by the springs. The idea is very simple, but in actual practicesatisfactory results have been attained.

275.—Precautions to be Taken when Fitting Aluminium Pistons.

Aluminium pistons must always be handled with clean hands, and when. on the bench they should be 'placed on a piece of paper ; the object of this precaution is to ensure freedom from grit. There should he no sharp edges at the piston-ring slots ; in fact., a fine radius is best, so that if abrasion occurs the burrs will not lock the rings in their grooves. The rings should have ample clearance in the grooves (about .003 in. is satisfactory), otherwise, owing to the great expansion of aluminium, they will be held fast in one position, also distortion of the grooves may be caused.

The gudgeon pin should be a pdsh fit in the piston bosses ; a tight fit will cause distortion of the piston, for the reason that the pin does not expand at the same rate as the piston; therefore, as the piston becomes hot, it creeps out along, the pini and when the engine is stoppeil for a long time the piston contracts, gripping the pm at the bosses, owing to the fact that aluminium is.able to dissipate heat very rapidly ; also the piston has its surface in contact with the cylinder walls, whilst the gudgeon pin is more or less isolated.

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276.—The Care and Adjustment of Cone . Clutches.

The majority of motor vehicles now on the market are fitted with clutches of the cone type. These are simple in -construction,. cheap, and reliable, but require occasional attention if they are to retain their efficiency.

All clutch troubles may be placed under one of the following headings:—(1) Fierce clutch ; (2) slipping clutch; (3) spinning clutch. •

A fierce clutch will entail excessive wear of tyres. straining of transmission, and discomfort to the mupants of the vehicle, or possible damage to fragile goods if these are carried, and should, therefore,-be instantly remedied.

If leather is used as the friction material, examine this ; if dry and hard, roughen the surface slightly and dress with neat's-foot or castor oil. The operation will be facilitated if the ciuteh is wedged out by placing a piece of wood between' the front seat and the pedal.

In the case of the friction material being either leather or asbestos, the heads of the rivets by meansof which the material is attached to the cone may be projecting slightly, and if so they should be punched down below the surface If the clutch has recently been dismantled, the trouble may be due to excessive pressure of the clutch spring, which. should be adjusted.

A slipping dutch ma' he due to oil or grease on -the leather, to remove a-ny excess of which wash with paraffin and dress with neat's-foot or castor oil.

Slipping may also be, caused by a worn friction material, which should be replaced by new, preferably obtained from the makers of the vehicle, who usually have spare pieces made up, drilled and countersunk ready for fitting to the cone. In order to renew the material, the clutch must be dismantled, when the old covering can be removed and the new_ . one attached by copper rivets.

When reassembling, some difficulty may he found in replacing the clutch spring, but this can often be overcome if the spring be compressed in a vice, and wired in this position. The spring can then be re placed, and the thrust bearing secured with compara tive ease, after -which the wire should be cut and 2arcfully removed.

The spring tension should then he correctly adjusted and the linkage between the pedal and the operating fork so arranged that some movement of the pedal is made before the clutch commences to be withdrawn.

It will sometimes be found oil examining a 'clutch that has been slipping that a ridge has been worn on the material, whieh prevents the cone being forced home. The removal of the ridge-by means of a rasp will he found an efficient remedy.

If the leather or bonded asbestos is in good condition the trouble may he due to maladjustment of the pedal linkage or a weak clutch spring. The. remedy foi the former is 'obvious, and the latter can

soon be corrected if an adjustment is provided ; if not, an improvement can be effected by introducing a washer or washers behind the spring.

Most cars are provided with a stop, which acts as a brake and prevents the clutch continuing to spin when the pedal is depressed. This is to facilitate

gear-charging, and if it is found difficult to get a noiseless change, the 'cause may often be traced to a spinning clutch. The stop can be tested by depressing the clutch pedal, with the floorfiourds removed and the engine running, and, if inefficient, should be adjusted.

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