CYCLING AND MOTORING.

Taranaki Daily News, 19 May 1916, Page 7

CYCLING AND MOTORING.

VKWS AND NOTES. _ The New Mouth Wales police authorities have issued instructions that action is to be taken against any record-breakers committing a breach of the traliic laws of the State by driving to the danger of other users of the road on the overland route. This means that aspirants after either the existing motor-car or motorcycle records will have to exercise great care, or they are likely to fall foul with the New South Wales police. In the not very far distant past many motor-car manufacturers gave but casual attention to the balancing of their engines, trusting to the vibrations of the road to disguise those dues to the engine, or divert attention from the en-gine-builder to the road-builder or the tyre-maker. Great improvements have been made, however, for it has been realised that proper balancing means much to the efficiency and life of the entire machine, as well as increased comfort to the user, and the advent of the multi-cylinder engines has brought the subject still closer to the designer. There is still much that can be done in the way of balancing moving parts and eliminating vibrations, and engineers are giving the subject careful study, although the frequent changes of model delays the •results.

It is well known that after a long and fast run the tyres of a motor-car are found to be very hot, and many have supposed this is the result of the friction of the tyre on the road. Such is, however, not the case, at least as to the greater portion of the heat. The real cause of heating is the internal friction of the tyre itself, for as the tjrre is being constantly deflected by contact with the road, the various plies, or layers, which compose the tyre, db not act uniformly, and consequently there is mere or less motion between them, which results in friction and heat. The greater the change in shape in the tyre as it comes in contact with the road the greater will be the friction. Of course the harder the tyre is pimaped, the less will be the deflection; but it is evident that while a perfectly rigid tyre would generate but little heat, it would fail in giving easy riding, so we must put up with some heating and consequent wear of the tyre. The subject is one that is being successfully studied by tyre manufacturers.

Perfect gear changing is a difficult art. Only a small minority of motorists acquire it to perfection. A contemporary thinks that the problem is not insuperable, and mentions various attempts to solve it, such as the adoption of electrical devices, some simple form of mechanical device, or the adoption of electrical transmission, which is already being used in several cases and possesses the great advantage of flexibility. There are many, however, who would regret the passing of the present gear-box system, for when machiaery is over simplified, so that it becomes almost automatic, interest is apt to be lost to a considerable extent. The skill and attention needed in making a quick, clean change is a pleasure in itself, though it must be admitted that the proportion of those who can accemplis-h the movement so that there is no grinding or grating is comparatively few, and from this point of view no doubt a practical method of preventing the gears being damaged would be welcomed by the majority. The electrical gear change is not, however, likely to fill the bill, for here also a certain amount of skill would be needed. Possibly electric transmission may solve the problem. Time alone will tell.

The amount of petrol that will pass through a comparatively small hole in the spirit tank or its connections must he experienced to be realised to the full. Petrol is a most penetrative spirit, and it 'Will find its way through the smallest aperture, and oven through what does not appear to the eye to be an aperture. In these days of high-priced spirit one cannot afford to allow the fluid to run to waste, and apart from that fact there is always the fire risk to be considered. The only manner in which a leak in the tank or connections can be permanently fixed is by the aid of solder, but it is not every one who can use a soldering iron, nor is there always one available. The method of temporarily stopping a leak that is usually recommended is to apply soap, but this is far from satisfactory, even where the leakage is very slight. Plasticine is also recommended for the purpose, and as the substance is now widely used by children for modelling, a little of it will readily be found in most houses. A writer ,in a contemporary tells that he staunched a leak in this way, and did (10 miles over bad roads after making the repair and 40 miles on the following day, and at the end of the run he found that the plasticine was quite solid and difficult to remove.

The frequency with which little. difficulties crop up in respect to the relationship of gear and crank-length seem to suggest that something is wrong with the method of expressing the gear of a bicycle (says Cycling). For example, hero is a recent enquiry: "My machine is geared to 7l 1 / 2 (4fi and 18 teeth), with 7iii cranks. If I replace the latter with fl'/jin cranks, wliat gear shall I then have—os or thereabout?" There is a double-barrelled misconception here, for not only does an alteration 'of crank length always leave the gear unchanged, but the effect of the reduction prop'osed in this case would be equivalent to raising the gear, not lowering it. Let us I have a clear understanding about this. I When we say that a bicycle is geargd to 7S, we mean that evorr revolution of the pedals carries us just as far as if wo were astride a big wheel, ungeared, of 7Sin diameter; one revolution will only take it along the road one-third the distance covered by a revolution of a 78in wheel. To compensate for this we use gearing, the large chain wheel being three times the size of the small one (i.e., 48 and 10 teetli respectively). Thus one revolution of the pedals drives the road wheel round exactly three times, so that we have the equivalent of a 78in wheel, and we express this as "a gear of 78." Now it will bo seen at once that the length of the cranks never enters inl'o the calculation at all, and the only way to alter the gear is to vary the size of one of the chain wheels or of the road wheel. In the above case, the gear of 71'/;, will remain 71% whether one uses Oin or 12jn cranks. Nevertheless one cannot entirely divorce the two considerations, because gear and crank length are interdependent in their effect, even though they are unrelated in the formula by which gear is ascertained and expressed.