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What to Do in Emergencies.

20th August 1914, Page 35
20th August 1914
Page 35
Page 36
Page 35, 20th August 1914 — What to Do in Emergencies.
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During the present state of affairs, we shall substitute this new feature for our usual " Drivers' and Mechanics' Contributions"; these we shall reNuirie when more normal circumstances rule in our industry, We repeat our statement of last week, that we are desirous of assisting the "new man at 'he wheel," of whom there are many at the present time. Our usual "D, and M. " pages included many tips as to workshop procedure, etc. ; these we are temporarily dropping, whilst we are selecting more appropriate suggestions with care. Drivers and mechanics

may still send in contributions, which will be paid for at the usual rates.

Air Leakage through Worn Valve Guides.

On machines that have been in service for some considerable time it sometimes happens that the valve guides get badly worn, with the result that there is a leakage of air past the valve stems, arid the engine

cannot be throttled down satisfactorily for slow running. It means, of course, a costly job to take the cylinders out and rebush the valve guides, but an emergency repair can be effected as follows :— For each faulty guide a piece of soft. leather is procured and a hole is bored in it slightly smaller than the diameter of the valve stern. The leather is placed on the underface of the guide, after the manner shown in the accompanying illustration. Upon the insertion of the valve spring the leather will be kept in position, and in a very satisfactory manner air will be kept from leaking past the faulty guide. The repair is simple and effective, and it is surprising how long the leather washers will last. It is quite unnecessary, of course, to treat the exhaust valves in this manner.

A Quick Method of Removing Carbon Deposit.

The accumulation of carbon deposit in cylinders is a source of serious trouble in consequence of preignition being likely, not to mention the impossibility of the engine's being able to develop its maximum power. It is always a good plan to get rid of the carbon deposit hi its initial stages, and this can be readily accomplished by squirting a small quantity of denatured alcohol into the cylinders after the vehicle has been running for a few hours.

The engine should then be accelerated for a few minutes until it is presumed that the alcohol is burned out, when most of the deposited carbon will find its way out of the cylinders with the exhaust gases. It follows that if this is done periodically the engine will be kept in quite a clean condition.

A Tip for Studding and Tapping.

Tapping out by hand calls for a considerable amount of care, particularly in the initial stages of the oneration, it being most important that the tap should enter the workpiece quite perpendicularly. An effectual method by which this can be ensured is to screw a nut on the tap and run it down against the face of the workpiece. which, it is assumed, has been accurately faced. This will readily show how much the tap inclines, if at all. Should this be the case then work the wrench in order to bring the tap square again. Care must be taken to ensure that the nut does not lock itself when feeding in the tap ; should this occur, the latter must be reversed in order to effect a release.

Making Joints.

When a joint is broken it may sometimes happen that the gasket between the machined faces becomes destroyed ; the following tips should prove useful on such occasions.

Those joints which are required to be waterproof should be made of graphited asbestos which has previously been spread over with shellac. Care should be taken, however, that only a thin layer of shellac is provided, otherwise, when the bolts are tightened, the medium will be squeezed into the water circulation and thus cause trouble. In addition to the previous type of joint, shellac is very useful for making rubber connections, i.e., provided it be not required to break the connections very frequently. For inlet pipe facings graphited asbestos should be used, hut in this instance, without shellac.

For exhaust-pipe joints asbestos or sheet copper arid asbestos makes a satisfactory gasket.

Those joints between the engine crank chamber and the oil sump, gearbox and back-axle casing joints should be made up with drawing paper, or if this material is not procurable, brown paper serves the purpose very well. Either material should be covered with oil or grease before it is interposed between the surfaces.

When Gearwheels Break.

The actual fracture, of a gearwheel is nowadays an uncommon event, as they usually wear until the teeth are of no further use. However, now and then, owing perhaps to a defective hardening or some such fault, a gearwheel will split right across. The illustration shows a repair that can be effected in an instance of this kind.

A mild-steel disc is first turned to suit the web of the wheel, and this disc is bolted to the wheel in the manner shown. The gearwheels themselves are usually held by a number of small bolts. If this is the case these bolts, or some slightly longer, can be used to secure the disc. When holes have to be drilled it may he found necessary to soften the wheel. In this event it should be carefully case-hardened after the repair, or if made of hardening steel, hardened and tempered, as the case may be Gearwheel repairs are not limited to breakages of this description. To save money it is sometimes found possible to dovetail in a piece of steel and cut one or more teeth to replace those which have broken off. The accompanying illustration shows such a repair. The chief point to remember when fitting new teeth is to hold them very securely in position, otherwise, in the event of their working loose, the rest of the gears may be involved in the trouble.

Extracting a Broken Tap, To the inexperienced the breaking of a tap during operations generally presents difficulties in the matter of unscrewing the broken part of the tool from the workpiece. 1+1., ith a little care, however, the embedded portion of the tap can often be extracted by backing it out with a small nail-punch and hammer. Should this method fail, another tip is to procure a piece of mild-steel bar about the same diameter as the tap itself and drill out one end so that three or four prongs may be filed thereon according to the number of grooves in the tap. The projections are then inserted in the grooves, and it will generally be found that, upon unscrewing, the fractured tap will be released.

If both these methods prove unsuccessful there is nothing else to do but to resort to a drill, and it fellows that the broken tap must be softened before any drill will make headway. To soften the tap, it must be heated to a dull red and covered with dry lime or sawdust until cool. The drill is then sent into the centre part of the tap, and what is left after it has done its work is picked out with a small chisel. When it is not practicable to beat the part in a fire the services of a blow-lamp may prove useful.

It must, however, be borne in mind that the tap has to be softened before any part of it can be cut away. When using the drill turpentine or paraffin generally acts as a satisfactory lubricant.

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