MOTORS & MOTORING

Dominion, Volume 14, Issue 124, 18 February 1921, Page 9

MOTORS & MOTORING

(By

"Clutch.”)

Motor-cycle Tyre Sizes, It is a very welcome sign that in many oases manufacturers are adopting largersized tyres as standard than have been previously favoured. As with cars so with motor-cycles, tyres are the most unreliable part of tho machine, and ninetenths of the trouble that the ordinary motorist suffers at the roadside is due to the tyres. In almost SH) per cent, of cases of tyro trouble tho cause can bo ultimately reduced to ono of two things —(a) the use of Undersized tyres, and (b) their inadequate inflation. The second of these is a thing over which the manufacturer of either cyclo or tyre has no control, lie canndt ensure that every user of his product will treat it properly, and of course abuse accounts for far more wear and deterioration than ordinary use. The first of these, however, in a thing for which the maker of a machine is alone responsible.

If a motor-cycle is turned out from its works with tyres of inadequate size, no care on tho part of the driver and no efforts on the part of the tyre manufacturer to produce wear-rosistingf articles can prove of avail. If the cycle manufacturer says that at tho present time production costs are so high that he must economise on his selling cost wherever reasonably possible, the answer lies in the fact that economy effected by a reduction of tyre sizes is not reasonable economy. It is far better to have an adequate sized tyre that will give a safe mileage of -1000 rathei' than an inadequate sized tyre that will be finished after 1500 miles.

Connected with the sanie subject is the interesting fact that British tyre manufacturers are showing a distinct leaning towards inch sizes, as contrasted with the millimetre sizes, which they have previously favoured for all tyres having .an effective diameter of more than 26 inches. The change, which is talcing place gradually but certainly, is one to be welcomed by the rider, for it is a fact of which no satisfactory explanation has yet been forthcoming that the tyre of which the size is expressed in inches is approximately of actually the same size as its nominal dimensions. With the millimetre-sized tyre this is not the case, and recently in England an enthusiastic motor-cycling "know-all" lost a bet because he wagered that a 2-6 x 21 inch cover was, smaller than a 700 x 88 mm. cover. It ought to have been, of course, but tho fact remains that it was not. Tyre Heating.

As every practical motorist knows l , a pneumatic tyro generates heat when running on the road, and, all other things being equal, tho faster the speed of the car the greater the heat generated. The generation of heat by a tyre, so far from . being a disadvantage, is, within limits/ rather a tribute to its shock-absorbing qualities The heat within the is not mainly generated by the actual friction with the road surface, which ac-_ counts for a relatively small proportion; what doeu cause heating is the constant flexion and recovery of the tyre -.walls in their , work of absorbing the shocks due to road inequalities. If the tyre did not possess those essential qualities of shock absorption there would be very little internal heating; but. of course, the car would' be very much more uncomfortable to ride in. The nearer a tyre approaches to the solid, the less heat there will be generated-/ Motor-Cycle Design. >

A plea is not infrequently raised for the introduction of new and more "scientifically” designed motor-cycles possessing features more akin to car practice, reduced to suitable proportions. In this connection science as an aid to design is not always apparent on the surface. There may quite easily be embodied in tho construction of a motor-cycle features which are the outcome of much careful investigation and elaborate tests, but which do not affect the outward appearance of the machine, in any detail and for the most part such features are concerned more with metallurgy than any other science. If the term is to ba construed as applying only to.design as such, the adoption of features not ordinarily found in ' a motor-cycle and so forth, then this may not be the time to look for any very startling’, departures from customary practice. The difficulties attending the manufacture are sufficiently pronounced as it is without seeking to increase them by processes aiming at revolutionising motor-cycle design. The general trend of opinion at the moment seems to lie in the direction of perpetuating models ,of established kinds catering for the many, who demand nothing more than a simple and straight-forward class of machine, rather than for the comparative few who clamour for what they term the "super” motor-cycle. Jottings.

Before the war the German-made magnetos practically held ittio European, market for this necessary fitment fqr cars, aeroplanes, motor-cycles, etc. With the advent of hostilities, England, France, and Italy were hard put for magnetos, which were essential in all branches of motor transport and aviation. To meet the shortage, several English concerns undertook the making of magnetos, and in tho latter stages of the war their efforts were such that they made better magnetos than any previously made and marketed by tho Germans. These manufacturers ia.ro now "up against” the cheaper-produced poet-war German magnetos, which arc being rushed into the English market at a price that English makers cannot approach. The position now is that the English magneto industry (practically a key one) is faced with disaster unless the English Government and tho English motor manufacturers stand by the British-made article. Owing to the depression in the American automobile trade, only one out, of every five tyre factories Ha working, and many of these are only operating up to about 20 per cent, of their maximum output. There hra about 2-10 tyre manufacturers in tl< United (States, as against forty only four years ago, and there has unquestionably been a serious* over-production of 'tyres in that country, resulting in a big slump. A recent test showed that to prevent excessive engine wearing, crank-case oil should bo changed at least every 1500 miles, preferably every 1000 miles. A new engine that was run 6000 miles with oil changed at proper intervals, upon being disassembled showed no signs of wear. The same engine, reassembled and run 6000 with old oil plus new oil as needed, upon inspection showed a wear of 0.15 inches. Motor manufacturers recommend, for better performance and longer life, that crank-cases be drained every thousand miles, the engine flushed with kerosene, and new oil added. The number of makes of electric vehicle produced in Great Britain is still small, but tho movement is nevertheless making appreciable progress. Interest in electric vehicles was stimulated during the war at the time when coal sup plies were comparatively plentiful, hut there was a marked shortage in petrol. The experience then gained by various municipalities and traders was on the whole vAy satisfactory, and, with tho difficulties in connection with liqud fuel supplies unlikely to be overcome in the near future, the demand for electric vans and lorries is likely to increase in all parts of tho Empire. Many of the American makers of wellknown cars are now limiting production to the demand. In Betroit alone- —the hub of automobile construction in the States—there was a drop of about 10 per cent, in production for September, as against the previous months output—or about 15 per cent, below the manufacturing schedules outlined at the beginning of the year. Lighting-up time: To-day, 6.52 p.m. Next Friday, 6.42 p.m.