MOTOR CYCLE 



MOTOR CYCLE 



of current reverses direction of 

 travel. The two serious obstacles 

 in the way of the electric car are 

 the cost and slowness of recharging 

 the batteries, and the limited 

 energy capacity of accumulators 

 relatively to their weight. 



Bibliography. The Complete Mo- 

 torist, A. B. Filson Young and W. 

 G. Aston, 8th ed. 1915 ; Motors and 

 Motoring, H. J. Spooner, 13th ed. 

 1919. Consult also The Car Road 

 Book and Guide, ed. Lord Mon- 

 tagu, The Motor Car Year Book, 

 and The Motoring Annual and Mo- 

 torist's Year Book. 



Motor Cycle. Broadly defined 

 as any power-driven two or three 

 wheeled vehicle. The definition 

 includes certain types of three- 

 wheeled cars, but the motor cycle 

 proper is a two-wheeled power- 

 driven vehicle, which may or may 

 not have attached to it a side- 

 car for the carrying of passengers, 

 etc. Nearly all such machines 

 are driven by one, two, three, or 

 four cylinder internal combustion 

 engines, the power being trans- 

 mitted by means of a belt or chain, 

 or the machine is shaft driven. 



Sir Thomas Parkyn exhibited 

 the first power-driven cycle in 1881 

 fitted with a steam engine, but it 

 was not till 1895 that any real 

 advance was made. In that year 

 the internal combustion engine was 

 adopted, though progress was slow 

 owing to the unreliability of igni- 

 tion and carburation. From 1907, 

 however, motor cycles made such 

 rapid strides that they have be- 

 come one of the most popular of all 

 power-driven vehicles. 



The h.p. of the motor cycle 

 varies from 1J up to 8 or 10. The 

 lightweight motor cycle is the most 

 popular solo machine, e.g. without 

 a sidecar attachment, and its en- 

 gine is usually 2J-3 h.p. Machines 

 of a greater h.p. are generally 

 classed as heavyweights. 



Compressed 



charge of gas 



(About to fire) 



Exhaust Port 



(dosed) 



Inlet Pan 

 (Open) 



Car 



[xhaust 



Motor Cycle. Diagrams of two- 

 stroke engine, showing working. 

 Top, cbaige about to be tired ; 

 bottom, exhaust gases escaping and 

 new charge entering cylinder. See 

 text 



For powers up to 4 h.p., single- 

 cylinder and twin-cylinder hori- 

 zontally opposed four-stroke en- 

 gines, and single-cylinder two- 

 stroke engines are used. High- 

 powered machines have twin- 

 cylinder V-type, twin-cylinder two- 

 stroke, or four-cylinder four- 

 stroke motors. The horizontal 

 " twin " engine, with both pistons 

 moving outwards and inwards 

 simultaneously, has proved excep- 

 tionally well suited for cycle pro- 



Carburetter 

 Control Levers 

 Carburetter \ 



pulsion. With but few exceptions, 

 motor cycle engines are air cooled, 



With the exception of light- 

 weights most motor cycles are pro- 

 vided with two, three, or multi- 

 ple-speed gears, or flexible gearing 

 transmission enabling them to be 

 driven with ease in traffic or up 

 hills. The gearing includes free 

 engine on each gear provided by 

 means of a clutch, hand or foot 

 controlled. The more powerful 

 machines are provided with a kick 

 starter enabling the engine to be 

 started with the least possible ex- 

 ertion, and a compression release 

 valve for the same purpose. The 

 supply of proper mixture of petrol, 

 benzol, etc., and air to the engine is 

 semi-automatic, making the con- 

 trol of the machine one of great 

 simplicity. The provision of wind 

 screens for passengers in sidecars, 

 special pillion seats on the carriers 

 of solo machines, dynamo electric 

 lighting, etc., have added to the 

 comfort of motor cycling. 



The principles of the two-stroke 

 engine, which is the most popular 

 type for light-weight motor-cycles, 

 are shown in diagrams in the next 

 column. 



The two-stroke engine is so 

 called because there is one power 

 impulse in every two strokes of the 

 piston-rod as compared with one 

 in four in the four-stroke engine. 



The upper diagram shows the en- 

 gine in section with the piston at the 

 top of its stroke, and the compressed 

 charge about to be fired. Exhaust 

 and transfer ports are closed, inlet 

 port open, the fresh gas flowing 

 into the crank-case and lower 

 cylinder. On the downward stroke 

 after the explosion the fresh gas 

 in the crank case and lower part of 

 the cylinder is compressed and 

 forced into the transfer way. 

 Igniiiun the piston falls, it passes 



/Control 



As 

 and 



Clutch , , 

 Silencer \ ^ V 



Crankcase 

 Motor Cycle. Diagram showing the principal parts of a modern twin-cylinder motor cycle 



