Motors and Motor-Driving/Chapter 11

by Alfred Charles William Harmsworth

CHAPTER XI

TYRES

By C. L. Freeston

It is a curious paradox, but none the less true, that while the public has still to be converted to a more widespread appreciation of the efficiency of the mechanical motor, to the automobilist himself the problem of the day, and of many days yet to come, is how to find a perfect tyre. Excellent motors have been in use for years—in fact, it may be said that in actual practice the engine is the least likely portion of the car to fail; and though improvements have been effected, and others will yet be introduced in this and other parts of the machine, to the gratification of every driver, he would willingly resign them all and use, say, a Daimler motor of 1896, if only he could be ensured entire immunity from tyre troubles. No one is exempt from this apparently chronic obstacle to pleasurable driving; the novice with his first car experiences sundry mechanical difficulties which the experienced hand may avoid, or quickly conquer if they occur, but every automobilist alike is a prey to the inconvenience of punctures, and the expense of upkeep of a costly and too easily perishable tyre equipment.

Arguing from the analogy of the cycle, in respect of which the use of the pneumatic tyre has been so signal a success, the average reader may find it difficult to understand why the motor-car tyre should not be just as satisfactory, provided that its substance be increased in converse ratio to the weight it has to carry and the work it has to do. This, however, is unfortunately the crux of the whole matter. Various factors enter into the situation which are virtually unknown in the case of the ordinary cycle. The motor-car not only surpasses in speed the greatest efforts of the cyclist, but also maintains a high momentum for protracted periods; hence overheating is one factor, not to mention others, which is present in the motor-tyre, but which in cycling is only known to the Alpine rider who 'coasts' for twenty miles or more with the brakes on all the time. The motor-car, too, must be driven through everything, including long patches of 'new metal,' and must take its grip on bad surfaces as well as good; the cyclist, on the other hand, can often pick his way, and, if not, can get down and push his mount, the tyres thus making a rolling contact only instead of sustaining the driving friction which does all the harm.

With all its drawbacks, however, the pneumatic tyre is almost indispensable for most types of motor-carriage. In speed, in comfort, in saving the mechanism from pronounced concussion, and in facility of steering, there is no question as to the superiority of the air chamber as compared with solid rubber. The curious fact, moreover, remains that in the very circumstances which emphasise the weak points of the pneumatic tyre the solid would be even worse. High speed and a heavy car form a combination which tests the pneumatic tyre severely, but the solid tyre in like circumstances can with difficulty be kept on the wheel at all. At high speed, again, the pneumatic tyre is particularly liable to puncture; but the very fact of the tremendous speed necessitates the rejection of the solid, because the comfort of the passengers, the conservation of the mechanism from jar, and the ease and safety of the steering become more than ever important.

It is a melancholy fact that our French neighbours have all along been even more ahead of this country in regard to the manufacture of motor-tyres than of motor-cars themselves. This circumstance for years pressed very hardly on the English amateur. In 1901, however, the Dunlop Company permitted the tyre which was most favourably known abroad, i.e. the Michelin, to be imported into the United Kingdom under licence, as the 'Clipper-Michelin,' and it at once became the standard type of pneumatic tyre among British users.

THE CHOICE OF A TYRE

Assuming that the reader is purchasing a car for the first time, he may reasonably specify the fitting of Clipper-Michelin tyres and leave experimenting, if so inclined, until a later date. This type of tyre is taken as a standard for purposes of description and illustration of the processes of repair.^[1] Several items, however, require previous consideration. It is more than likely that though the right make of tyre be chosen the novice may go wrong as to certain points of detail. In the first place it is of the highest importance that the diameters should be correctly apportioned to the weight, and secondly, whatever the size of cover, that it should be of the correct degree of substance. Thirdly, it is advantageous that all the wheels should be of equal size.

As regards diameters, it may be stated that the Michelin tyre is made in various sizes, ranging from fifty-five to one hundred and twenty millimetres, or two and a half inches to four and three-quarter inches. The tendency of makers is to fit too small a diameter, and in most cases it is safe to ask for one size larger than that which is offered. In the 'Guide Michelin,' however, a complete table is provided in which the suitable diameters for given weights are specified, together with the degree of inflation to be allowed, and these data should be studied with due care. The 'Guide,' a most useful volume of 575 pages, is included with the Michelin repair outfits, or may be obtained gratuitously from the firm. With regard to substance, the covers are of three types, the léger, the renforcé, and the extra-fort. The first-named may be discarded altogether, the second fitted to the front wheels if the car be very light, while the third should invariably be chosen for the driving wheels, and preferably for the front as well. It is well to bear in mind that the average English road is not as good as the average French road, and to make allowances accordingly.

REPAIRS

The repair of a Michelin motor-tyre approximates to that of an ordinary cycle-tyre with beaded edges, save that much greater resistance has to be overcome in the former type owing to its substance, while the winged nuts add one new feature of complication. On the other hand the motorist has full access to the wheel, and has no fork-blades to impede his operations. While it is probable that most automobilists will have previously become acquainted with a cycle-tyre, it is desirable to describe the repair processes throughout.

It is essential that a satisfactory repair outfit should be obtained at the outset, and nothing on the market can be compared with the Michelin nécessaire de voiture, which is worth buying if only for the special levers it contains, apart from the

Fig. 1

excellence of the tackle generally. One of the levers (see fig. 1) has three projections intended for use with covers of 65, 90, and 120 millimetres respectively; the other lever has a hook which comes in handily when replacing a large cover (see fig. 13). The larger the tyre the more essential are the levers; a new cover is also much stiffer than one that has been used for a considerable time. In the case of a small or medium-sized tyre, not too new a very strong pair of hands may render the levers superfluous.

When the driver has reason to suppose, from the bumping of the car on one side, that a tyre is punctured he should stop at once to examine. It is of the highest importance that a tyre should not be ridden deflated, but it is not always easy to detect the fact of a puncture at once in a back tyre, when the road is itself bumpy. In a four-seated car the rear passengers should glance occasionally at the driving-wheel tyres out of consideration for the driver, and if either of them be splayed at the point of contact with the road he should be apprised of the fact at once.

If he decide, upon dismounting, that the tyre is punctured, and not merely short of inflation, the car should be jacked up so as to permit free movement of the wheel. The tyre should then be cleaned, the best article for the purpose being a brush with wire bristles; the type is known as a 'jeweller's scratchbrush.' Loose dirt should also be wiped from the spokes. If these precautions be neglected every movement of the wheel Fig. 2 will cause particles of dirt to fall into the hollow of the cover, whence they must be removed at all costs. If a cloth be damped with water or petrol the dirt will cling to it readily, and can be quickly wiped away.

To Remove the Tube.—To remove the airchamber tor examination the valve cap should be unscrewed and inverted, the pin being then pressed into the valve stem so as to push away the needle (see fig. 2). Deflation may be expedited by loosening the large nut and pulling out the plug, especial care being taken not to lose the little needle with its shell-shaped head. Then unscrew the winged nuts almost as far as they will turn without detaching them from the bolts, and push the latter upwards until the nuts meet the rim.

The beaded edge of the tyre should then be forced inwards all round the rim by the left hand, the right hand assisting the operation by inserting the point of one of the levers. Then moisten the blade of each lever to make it glide more easily on the rubber. Take hold of the cover, as in fig. 3, with the left hand, at a point between two winged nuts, and not near the valve. Push forwards with the palm of the hand and the thumb, and simultaneously, having inserted a lever, work it downwards with a laterally oscillating movement until it assumes the position shown in fig. 3. Depress the haft until the blade is horizontal, and then slowly work the point again

Fig. 3

Fig. 4

with a sideway oscillation, until the opposite edge is reached, as in fig. 4. Still holding this lever firmly, insert the other at a point from ten to fourteen inches away, according to the size of the wheel; roundly speaking, the distance between the levers should be a third of the diameter of the rim. Avoid, however, placing either lever near the valve or one of the winged nuts.

Having worked the second lever forwards in like manner to the first (see fig. 5) depress the hands towards the hub (see fig. 6). This should bring the beaded edge right over the rim; if the movement fails the levers are too far apart, or if the edge comes over but slips back again they are too close. The remainder of the cover may be detached with the hands alone in the case of a voiturette tyre, but otherwise the right-hand lever must be re-inserted six inches further down, and again depressed, the process being repeated until detachment is complete. Care should be taken that the winged nuts remain flush with the rim throughout.

If a single lever only be available the removal of a cover requires more strength and more dexterity. The left hand should

Fig. 5

Fig. 6

press the cover outwardly as much as possible, the point of the lever should be insinuated between the beaded edge and the rim, but not beneath the air-chamber, and the position shown in fig. 7 should be attained, by pulling the cover forward with

Fig. 7

Fig. 8

the left hand and depressing the lever with the right. Avoid the position shown in fig. 8. Slide the lever, which should be moistened, between the rim and the beaded edge, and as the latter is progressively unhooked press downwards on the cover, as in fig. 9, to prevent any slipping back. The case or otherwise of the removal with one lever depends upon the size and age of the tyre; two levers are in most eases to be preferred.

To save time on the road it is usual to remove the air-chamber bodily and replace it with a new one, deferring the repairing of the puncture to a more convenient occasion. In this case the valve should be loosened by unscrewing the large nut and rubber washer, and pushing the stem upwards until it leaves the rim. The air-tube should then be detached all round with the fingers, great care being exercised lest the rubber be adhering to the lining of the cover, owing to an insufficiency of chalk having been employed when the tube was last fixed, and also lest, as is very probable, the nail, flint, or Fig. 9 other puncturing instrument, be still lodged within the cover, in which case ungentle handling may tear the tube. If the cause of the puncture be found, or even if there be a visible cut right through the cover, the corresponding spot on the tube should be determined, when a hole will probably disclose itself if the rubber be slightly stretched. The puncture should at once be marked with a coloured Fig. 9 pencil, whether the tube is to be repaired forthwith or not. Then remove the nail, or other cause of damage, from the cover without fail.

If no spare tube be available, and the one in situ must be mended there and then, it is not necessary to loosen the valve in the first instance, as the puncture will probably be easy to locate, and may be at such a distance from the valve as to render a repair feasible without removing the entire tube. If the valve has to be detached, however, and the cover is of 90 mm. diameter or more, the lever with three projections should be employed, as in fig. 10, to hold up the cover.

To Repair a Puncture.— This process is simple. Select a patch from the repair-box, of small size if the puncture be a mere perforation, but larger if the tube be cut. Clean the tube round the hole with glass-paper or petrol, brush dry, and then apply solution, over a space somewhat larger than the patch. Next cover the patch with solution also, on the side that is not bevelled. In each case the solution should be thinly and evenly spread, not in clots. Wait until all traces of moisture have disappeared—a point of paramount importance and then fix the patch upon the tube, pressing the surfaces firmly together. There should be no ambiguity about the adhesion; the patch will stick like a leech at once if the solution has been thinly applied and sufficient time—from five to ten minutes— allowed for it to dry.

To Repair the Cover.—Before replacing either a new or repaired tube the cover should be attended to. If the hole or cut be very small, it will suffice to plug it with cotton wadding, soaked in solution, to prevent the ingress of water or dirt; the possibility of the air-chamber, however, under strong inflation, forcing its way into the aperture and bursting must be borne in mind, and when doubt exists as to the safe course to follow an oblong patch of canvas should be applied instead. The lining of the cover should be cleaned with glass-paper and solution spread on the fabric and on the canvas patch, as described above in the case of the air-tube. Apply a liberal dose of powdered chalk to the patch when fixed.

Replacing the Tube.—Considerable care is requisite when inserting an air-chamber. It should first be plentifully chalked, and a handful of chalk should also be placed in the well of the cover, and distributed by revolving the wheel two or three times. The opposing surfaces are thus well lubricated, and the possibility reduced to a minimum of nipping the tube, a factor which M. Michelin has declared to be the cause of fifty-one per cent of the injuries to air-chambers. Ensure that the tube is entirely deflated before replacing; to effect this it must be rolled upon itself and all the air squeezed forwards towards the valve, all the parts of which must previously have been detached excepting the plate and nut at the base of the stem. Before replacing the tube, see Fig. 10 that the overlap at the join is facing towards the back of the car, and not forwards. Then push the stem through the rim, meanwhile holding up the cover as in fig. 10. Place the rubber washer and large nut on the stem, but do not screw right home. The tube should then be passed round the bed of the rim, without any twist, and without being slack at one point and stretched at another.

Now insert the remaining parts of the valve, except the cap, and inflate slightly, just sufficiently to make the air-chamber round, but without the least stretching of the rubber. Then pass the hand all round, between the tube and cover, to make sure that no creases remain.

To Replace the Cover. Unscrew the rim nuts sufficiently to allow the valve to be pushed upwards, and the beaded edge to pass into its place. Force as much of the cover into

Fig. 11

Fig. 12

position as is possible by pressure from the hands, and then insert the lever as in fig. 11, and by lateral oscillation work the remainder into the hook of the rim. If the cover assumes the position seen in fig. 12 replacement will be difficult. In that case fix the lever with a single prong in the position shown in fig 13, and depress the other lever. Then bring the levers towards each other, and push the cover along the inclined plane formed by the lower lever, as in fig. 14. Withdraw the upper lever, and, by raising the other lever, force the cover into the rim, afterwards tucking the edge beneath the hook by reiterated pressure from the point.

As each bolt is reached it should be pushed upwards as far as it will go when the winged nut is unscrewed to the last limit, and when the cover is in position all the way round these bolts should be worked up and down to determine whether the tube be nipped. The movement will, in that event, release the tube, and the bolt should come back much as the key of a pianoforte after pressure from the finger. If the bolt cannot be pushed upwards the beaded edge is not accurately bedded.

Fig. 13

Fig. 14

It now remains to ensure that the air-chamber is nowhere nipped. Seize the cover with both hands, and with the thumbs force the beaded edge towards the centre of the rim. Make the circuit of the tyre in this way, and if the red tube be nowhere visible it is not nipped, but if it project at any point it must be pushed inwards with the lever.

The tyre may now be inflated, care being taken, in order to avoid wasted effort, that there is no leakage between the nozzle of the pump and the milled cap into which it is screwed, or between the latter and the rubber pipe, or between the nozzle and the valve. After inflation see that the valve nut and the winged nuts are tight to the rim, or wet will penetrate to the tyre.

To Change a Cover.—Remove the inner tube, then detach the winged nuts and take out the bolts. Pass a lever not only under the detached edge of the cover but also beneath the one opposite, as in fig. 14. Depress the lever, and pull the cover forwards. As soon as about eight inches of cover have been levered off, the rest can be removed with the hands.

Replacing a Cover.—In this operation the beaded edge on the far side must first be fixed, care being taken to have the notch exactly opposite the valve hole, and that the cover does not pucker in one part and stretch in another. Insert the bolts in turn, holding up the cover as in fig. 10. Then replace the air-chamber as ante.

Bursts.—Bursts of the air-chamber, if not more than four or five inches long, may be repaired in the same way as a puncture, using a very wide patch, however, and affixing it with extreme care. A large burst in the outer cover may be temporarily repaired by solutioning to the lining a specially stout patch made of two thicknesses of canvas with an insertion of vellum. The cover may also require to be laced up with a large bandage of leather. As soon as possible, however, the tyre should be sent to the factory.

GENERAL HINTS

Watch the winged nuts, and keep them always tightly screwed to the rims.

Wash the tyres occasionally with petrol, and examine for cuts. If deep, insert a piece of rubber and fix with solution. If the cuts have gone completely through, plug with cotton wool, and reline the cover with canvas where required. The older the tyre the more carefully must it be watched, and probable bursts prevented by interior reinforcements.

Never drive with a tyre deflated.

Scrupulously keep all wet from percolating into any part of the tyre. Whenever necessary re-enamel the rim and spoke-heads.

Also keep oil away from the tyres, or it will rot them.

Do not be afraid to pump the tyres hard, especially if carrying a full load. They should never splay more than half an inch.

Never let the car rest on deflated tyres.

In the case of wire wheels, make sure that the spoke-heads are properly covered by the tape.

Test spare tubes by inflation in water, for possible minute leakages.

Do not, however, construe air-bubbles from the valve as a sign of permanent leakage. The needle of the Michelin valve does not fit absolutely tight under the light inflation of an unprotected tube, but under full inflation in the cover may be air-proof. A good plan when tube-testing is to stop this slight leakage by moistening the needle in the mouth.

Keep all spare tubes completely deflated and away from the light. Brown paper is a good preservative. Do not wrap up two tubes together, or the pins may cause punctures.

Always carry at least two spare tubes when driving, and more if the wheels are unequal in size. Spare covers should also be carried when those in use are much worn.

Never start a journey without a pump, a lifting jack, and a fully furnished repair box. See, also, that the pump nozzle has not become detached from its socket.

At every stopping-place it is worth while to examine the covers, in case nails or flints have become embedded in the tread.

When a nail cannot be found, in case of puncture, the cover should be carefully examined for possible flints or pins.

Be sure that the wheels are strictly parallel to each other. To determine whether a tyre is fully inflated, stand on the step and oscillate the car; the expansion of the tyre at its lowest point should be inconsiderable.

The Michelin 'cradle,' or metal nail-catcher, is a useful device to attach to the back wheels, as it may strike off nails before they have had time to work their way through the tread.

To reduce the probability of puncture in patches of loose stones, let the car run as much as possible by gravity, and not by driving friction.

OTHER TYRES

Various attempts have been made to produce efficient tyres for motor-cars without infringement of the Dunlop patents. At present (1902) there is only a restricted experience to call upon in respect of these new types, but the appended enumeration of their leading features is based upon personal investigations among actual users.

The Collier.—As will be seen from the sectional illustration (fig. 15), this type is provided with an unusually stout tread, Fig. 15 and is made in very large diameters. The mode of fastening is by vertical bolts passing through a horizontal flange of metal which is shrunk on to each side of the wooden felloe. The upper ends of the bolts are ringed, and receive a wire which passes all round the bead of the cover, on each side of the wheel alike. To remove the tyre when deflated it is only necessary to unscrew the locking nuts outside the flange, and, as the wire threaded through the rings is not endless, the bolts can be pushed inwards and the edge of the cover lifted without difficulty, especially as it only engages with a flat surface, and not the tuned edge of a rim of the ordinary pattern. The cost of the Collier is about 25 per cent in excess of ordinary types. Not only is excellent rubber employed, however, but the system of moulding is such that even on a heavy car the tyres show fewer cuts than solids. I have seen a set of Colliers on a 27-cwt. car that had been driven 2,300 miles over bad roads, and even the covers of the driving wheels were quite smooth and unimpaired. The maximum speed of this car was 25 miles an hour; experience is wanting as to what results would follow the use of these tyres on a high-powered vehicle, both as regards wear on the tread and the strength of the attachment.

The Goodyear.—Bolts are also employed, but in a different way, in the Goodyear (fig. 16), a tyre of American origin. They are passed horizontally, to the number of sixteen, through Fig. 16 vertical flanges of metal and the intervening wooden felloe. The base of the tyre is thus held by the pressure from the flanges and that of inflation also. Access to the air-chamber is gained by removing the locking nuts and detaching one flange bodily. The cover can then be pulled off its flat bed without any particular difficulty. One of the good points of the Goodyear is that it cannot come off the rim if deflated, nor will it 'creep,' as strands of contracting wires inserted through the base make the circumference constant. To prevent overheating at high speed the Fig. 17 fabric has an insertion of asbestos. The Goodyear is very well spoken of by those who have tried it up to now.

The New York.—Another American tyre is the New York (fig. 17). Unlike the foregoing it is of the single tube variety. It is made in light and heavy patterns, the one illustrated being intended for cars weighing over a ton. Owing to the uniform thickness of the walls the tyre can be ridden deflated without material damage. It is fastened to the rim both by vertical and horizontal bolts.

 

NON-SLIPPING TYRES

A tyre which has become popular in France for town and winter work is the Gallus. Its use in England is impracticable for the present, both by reason of patent rights and the fact that it contravenes the stipulations of the Local Government Board as to projections being 'of the same material as that of the tyre itself, or of some other soft and elastic material.' The Gallus, nevertheless, possesses several interesting features, and Fig. 18 may ultimately find its way into the United Kingdom. From fig. 18 it will be noticed that the tread is covered with parallel armatures of metal set in close series. Except for remotely possible penetrations between the plates the cover is unpuncturable; but the Gallus is chiefly valued in Paris because of its non-slipping properties. It is employed even on 20-h.-p. cars, and within the speed limitations imposed by town use the armatures do not easily become detached.

Curiously enough, only one Gallus cover is fitted to each car, namely, on the near side driving wheel, the object being to prevent the skid towards the gutter to which a car is liable on greasy thoroughfares. In this country, of course, where the rule of the road is reversed, the safety tyre would need to be used on the off side. The Gallus is somewhat more expensive than the ordinary cover; it is also slower, and on hard surfaces is more vibratory; on snow, too, it is ineffective as a non-slipper, owing to the clogging of the apertures. Nevertheless, its advantages are held to outweigh these disadvantages, and during last winter it was largely adopted by leading chauffeurs in Paris.

The Falconnet.—A method of wiring the tread of a pneumatic tyre in order to prevent non-slipping was introduced in 1901 by the Falconnet Perodeaud Co., of Choisy-le-Roi. As will be seen by fig. 19, the cover is full of closely set strands of Fig. 19 crimped wire, the points of which project slightly above the tread, and thus present a rough surface to the road. It is claimed that not only is side-slipping prevented, but that the cover is also more durable and less susceptible to punctures. As to its behaviour at high speed no evidence is available.

The Wilkinson.—At the Wilkinson Tyre Manufactory, Huddersfield, is made a somewhat similar tread, which can be solutioned on to any cover. The wires in this case, however, are straight, not crimped, and are less numerous; they are also stronger individually, and project further. The tread is made in three sections, and as the wires are worn down the rubber of the external section can be pulled away, the process being repeated after further wear. On light cars there is evidence to show that this tread is satisfactory, and really prevents skidding, even in bad grease, but it has not yet been tried on fast and heavy cars.

SOLID TYRES

The fact that solid tyres are considerably cheaper than pneumatics, and, of course, immune from puncture troubles, causes many automobilists to make experiments in that direction. As mentioned at the outset, however, the solid tyre is most conspicuously wanting under the very conditions when the pneumatic may seem least desirable, but is really the superior type. The problem is curiously complex. On a light, slow car, of the old Benz type, solids may safely be used; on a light, fast car the mechanism will suffer and the passengers' comfort be affected. With a heavy car the need for solids becomes greater so far as punctures are concerned, but again the demands of the car itself and the passengers assert themselves in converse ratio. What really kills the solid tyre, however, is speed, pure and simple, quite apart from the car or the passengers. Beyond a certain maximum rate of progression several factors combine to cause the solid tyre to leave the rim. The heat due to road friction, the pressure arising from the weight of the car, and the combination of centrifugal force with the weight of the tyre itself—much greater than that of a pneumatic—all create expansion and make the tyre rise from its bed and at times fly off bodily. A tendency to creep in the rim is also caused by the non-absorbent qualities of the solid as compared with the pneumatic tyre.

Given a combination of a heavy touring car with moderate speed, the use of solid tyres is practicable; and with a very heavy car, but of low speed, they may also be reasonably employed. But when the speed exceeds twenty miles an hour the solid tyre is inadvisable for more reasons than one, whatever the weight of the vehicle itself.

Of late a tendency has declared itself to effect a compromise on large cars of fair speed by fitting solid tyres to the driving wheels and pneumatics to the front. This method ensures facility of steering, and immunity from road shocks to the engine, and by the aid of long French springs the comfort of the passengers may be preserved, provided that the car is 'nursed' over specially rough surfaces. Even this compromise, however, has its limitations, and does not appear desirable for high-powered cars, unless the power is only used to the full on up gradients and considerably throttled Fig. 20 down on level roads.

The types of solid tyre in use are not numerous. Perhaps the best known is the Clincher. The Sirdar and Capon Heaton are also favourably known. A tyre that has also been tried by a few British automobilists is the Falconnet (fig. 20), which is provided with a core of spongy rubber, and is thus somewhat less harsh than the entirely solid patterns. Experience has shown, however, that the security of this tyre at speeds in excess of sixteen miles an hour is a doubtful quantity. The tyre shows a tendency to become detached from its bolts, and as it is very heavy it is likely to be lifted off by centrifugal force.

In the case of solid tyres the chief essential is that a gap of a quarter of an inch should be left between the ends, to allow of expansion under heat or pressure. If this gap becomes closed in time one end of the tyre should be cut away. If the tyre be a close fit at the outset it will creep on the rim, crack at the sides, and be liable to fly off at any but slow speeds.

1. Figures 1 to 16 have been selected by permission from the excellent Guide Michelin and redrawn, in some cases with slight emendations.