Commercial Threewheelers at the Motorcycle Show
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OUTPUTS approaching 25 b.h.p. from • %.-/engines of no more than half a litre in capacity are by no means exceptional in the motorcycle field. Such a figure appears high to commercial-motor engineers, and the explanation is not entirely obvious.
Air cooling, light reciprocating parts, and the high speeds that the small cylinder dimensions permit, are all contributory factors to efficiency, but there is another point that must be considered. Three-wheelers and, sidecar outfits are the smallest types of vehicle in the commercial-motor range, and therefore mark the peak of power-toweight ratio; an analysis of present practice shows that the ratio rises in inverse proportion to weight.
It is this fact that is, Perhaps, the key to the situation. Conditions on the roads are the same for all vehicles, except in respect of speed limits; thus, the greater the power-to-weight ratio the shorter the periods of continuous running at full throttle.
A power unit that is never likely to be called upon to generate its full output for more than a matter of minutes can be built with a much narrower margin of safety than one that will regularly have to generate maximum torque for long periods without inter a42 mission, also many of the parts of which it is composed, particularly the bearings, can be more heavily stressed.
Thus, not only is the output per litre raised, . but also the power-to-weight ratio, so that we have within limits a. state of affairs that might be described as a " virtuous circle."
Wherein lies the benefit to the operator? Small efficient engines mean that first cost, fuel consumption and unladen weight are also smal:. In consequence, running costs and standing charges are light, whilst good engine performance makes possible highly efficient operation and quick service. There are numerous transport jobs that are served admirably by the type of machine in question, upon which the tax is only 24 per year. Although makers of light threewheelers and motorcycles and sidecars built for goods transport are fairly numerous, they are not fully represented at the Motor Cycle Show now being held at Olympia. There are on view, however, some interesting models.
Prominent among these are the latest streamline Handyvans made by the James Cycle Co., Ltd., Greet, Birmingham. There are three of these on view together with an open truck and a bare chassis to show constructional features. All are rated for 8-cwt. pay-loads but 12-cwt. models are available. Their prices range from £1041 10s.
A smaller three-wheeler is being exhibited by the Enfield Cycle Co., Ltd., Redditch. This concern is displaying an attractive dairyman's vehicle, a machine with a covered box body, and a chassis. No pay-load figure is quoted in this case, but box bodies having capacities of 131 cubic ft. and 9 cubic ft. are offered. Fully equipped, Royal Enfield carriers cost £49 15s.