All About Engines

The Petrol Motor 219 rather larger in size are necessary. The power is communicated to the rear axle by various mechanisms which it would be out of place to describe here, but which are, nevertheless, of first-rate importance in considering the car as a whole. It is in this sphere, perhaps, that the greatest difference between a good and a bad car is to be found. So far as engines are concerned, the chief variations occur in the general arrangement. Thus the cylinders may be cast singly or in pairs or in fours. The valves may be in the ends of the cylinders or in combustion chambers at the side. In the Lanchester engine, for example, they are operated by flat “ leaf ” springs which press upon the ends of the valve spindles just as one might do with the end of the finger ; and this engine also has a wick carburettor in which the petrol vapour is drawn through wicks dipping into a reservoir. In some cases the water circulates natur- ally, and in others it is driven round by a pump. Where extreme lightness is required the crank case may be made of aluminium alloy, and the pistons, instead of being made of cast iron, may be of steel, or even of aluminium alloy. Apart from excellence of material, accuracy of workmanship, and perfect lit, the most essential condition of satisfactory working —and this is true of any kind of high-speed engine —is that all rubbing surfaces should be flooded with oil. It must never be forgotten that in a space of, say 2 feet by 2 feet by 1 foot, energy is being liberated at the rate of 20 horse-power—that is to say, work is being done at the rate of 660,000 ft.-lb. per minute.