Dec. 24, 1885] 



NA TURE 



177 



CYCLES 



Variable Speed-gear 



FIVE methods have been employed for making the 

 speed of the wheels variable with respect to the 

 pedal crank-axle whilst the tricycle is in motion, so as to 

 vary the power to suit the nature of the road. 



(i) A set of change wheels may be thrown in and out 

 of action as desired. 



(3) An epicyclic train may be used which for one speed 

 is locked together and moves as a single piece, and is set 

 in motion for the other speed. The well-known crypto- 

 dynamic two-speed-gearing was figured and described. 

 In this an internally toothed wheel is keyed to the crank- 

 axle. Connecting this and a loose pinion on the axle are 

 four live pinions, the axles of which are attached to the 

 chain-wheel. The internal wheel is fitted with a clutch, 

 by which it can either be held stationary or keyed to the 

 chain-wheel ; when keyed to the latter the gear moves 

 as one piece, and the higher speed is employed ; when 

 held stationary the live pinions roll round the centre 

 wheel so that the chain-wheel travels less fast than the 

 crank-axle, and then the greater power is obtained. This 

 change can be eftected by a striking lever. 



(3) A third plan is to use two sets of chain-wheels and 

 chains, either of which can be connected or disconnected 

 at pleasure. 



(4) Expanding chain-wheels can be used. Generally 

 one only is employed and an idle pulley is provided for 

 taking up the slack of the chain. A specimen was ex- 

 hibited in which the pitch of the teeth is never altered. 



(5) Another method of obtaining increased power is to 

 use cranks with a variable throw. A diagram was shown 

 of such a crank which could be changed in length by 

 preventing it from rising by pressure when at the bottom 

 of the throw ; for at that time only is it free to turn on an 

 eccentric, being locked by pawls and a gravitating bolt at 

 any other position. 



Position of Rider. — In every machine there is a certain 

 position for the rider's seat, in respect both to the a.xle of 

 the driving-wheel and to the crank-axle, which, on the 

 level, will enable the rider to work to the greatest advan- 

 tage. In ascending a hill the rider requires to be moved 

 more forward, but he is in reality put further back, and 

 the reverse is true when descending a hill. The most 

 perfect contrivance for this purpose is the swing frame, 

 which has been applied by Mr. Warner Jones to the 

 Devon tricycle. The saddle and crank-axle are on the 

 same frame, which is capable of rocking about the main 

 axle and of being locked in various positions. By such 

 means a rider is enabled to ascend a hill without leaning 

 forward in the usual manner. A modification of the 

 same arrangement by Mr. Griffiths was referred to. 



Another method of varying the position depends on 

 the use of a sliding base to the saddle-spring, which may 

 be actuated by a lever and locked in one of three 

 positions. 



Hand-power Tricycles. — A few machines driven by the 

 arms instead of by the legs have been made, but from the 

 greater weakness of the arms they cannot compete with 

 ordinary cycles, but are suitable only in special cases. 

 Two machines, the Velociman and Oarsman were de- 

 scribed. In the Velociman a pair of hand-levers are con- 

 nected to the cranks of a second axle, which drives the 

 main axle by a chain as usual, differential gear being 

 employed to actuate the wheels. The rear steering-wheel 

 is actuated by a lever carrying a cushion, which can be 

 moved by inclining the body. In the Oarsman the action 

 is similar to rowing. The rider sits on a sliding or a 

 rocking seat, and pulls a cross-bar which is attached to a 

 pair of driving ends which pass over pulleys connected 

 with the driving wheels by clutches. During the return 

 stroke the pulleys have their motion reversed by a spring. 



^ Continued from p. 135. 



Sociable Tricycles.— Oi tricycles for two riders those in 

 which the riders sit side by side are called Sociables, and 

 those in which one is in fiont of the other, Tandems. 

 The Sociable is merely an enlargement of the single 

 form with some part in duplicate. Some can be con- 

 verted into a single machine. In the Coventry rotary 

 Sociable, since four wheels are on the ground, a joint has 

 to be introduced to allow for the inequalities of the 

 surface. In this machine each rider drives the wheel on 

 his side only. An ordinary front-steering pattern of cori- 

 vertible tricycle was figured, in which, when one wheel is 

 removed from the single form a second half-frame can be 

 bolted on, while the axle of the added part is fitted^ where 

 the wheel was removed, and the crank-axle of the'added 

 part is bolted to the crank-axle of the single part ; thus the 

 two riders drive through the same chain the box of the 

 differential gear which drives each wheel equally. 



Tandem Tricycles. — In these there is more scope for 

 variety, and the different machines may be classed as 

 follows : — 



(i) The ordinary front or rear-steering tricycle in which 

 the wheel-base is extended, so that the riders may be 

 seated fore and aft of the differential-geared driving-axle 

 without destroying the balance of the machine. 



(2) The Humber tandem, in which the extra rider is 

 seated in front of the driving-axle, but as nearly over it 

 as possible, and communicates motion to it in a similar 

 manner to the rear rider, who is seated further back than 

 in the single machine so as to counterbalance the extra 

 weight in front. 



(3) A machine in which an auxiliary trailing frame is 

 fixed in the rear of an ordinary front-steering tricycle. 

 In order that the trailing frame may rise and fall with the 

 inequalities of the road, and may follow properly when the 

 machine is running round a curve, it is necessary for it to 

 have both a transverse and a vertical joint between the 

 two frames. A figure was given of a trailing frame with 

 a chain to drive its own wheel which could be clamped 

 to the back of any front-steering tricycle. With this 

 arrangement there is no necessity to take off a chain 

 when detaching. A special detachable chain for con- 

 vertible tandems was shown. 



Carrier Tricycles.- 'Wi^ most useful kind of tricycle of 

 all is that for carrying a burden. First the " Coventry 

 Chair" was exhibited. This consists of a Bath-chair in 

 which the large wheels are driven by a rider at the back 

 in the same way as the wheels of a tricycle. The driver 

 also controls the steering and manipulates the brake. 

 The passenger sits in a comfortable wicker chair. 

 Though these machines cannot be driven with the free- 

 dom of an ordinary tricycle, yet when their weight and 

 the fact that there is a passenger on board is considered, 

 they travel with marvellous ease. Examples of journeys 

 made were given. 



Of goods carriers there are a large number of makes, 

 but there is nothing in their construction to call for 

 special comment ; their success depends chiefly on the 

 load being balanced as much as possible on the driving 

 wheels. They are largely used by the Post Office for the 

 parcels post, for the delivery of letters in rural districts. 

 They are also largely used by newspaper offices for the 

 distribution of papers, and by tradesmen for the delivery 

 of goods. 



Arrangement of Driving (J(?ar.— Tricycles driven by 

 rotary action may be subdivided according as the differen- 

 tial gear-box is in the centre or on one side, and according 

 as the driving chain is in the centre or on one side. 



In side-driving tricycles the loop frame is generally 

 employed and the gear-box may be either at the centre or 

 the side. 



In central-driving tricycles the frame is usually of the 

 T pattern. Here again the gear-box may be either at 

 the centre or the side. Theoretically there is an advan- 

 tage in the central position of the gear-box, as the friction 



