178 



N^ rURE 



[Da. 24, 1885 



due to the bearings is equally distributed between the two 

 wheels, whereas with side-gear one wheel only is retarded 

 by this friction, but practically the difference is inappreci- 

 able. In central-driving machines the bearings must be 

 so distributed as to prevent the main axle from bending 

 under the pull of the driving-chain. The advantages of 

 the T frame are its simpUcity and lightness and the 

 possibility of using adjustable cranks. 



Widlli. — As the width of a tricycle varies between 

 thirty-six and thirty-nine inches — excepting the Coventry 

 Rotary, which from its special design can be made as 

 narrow as twenty-seven inches — many arrangements have 

 been devised for temporarily reducing the width, so as to 

 enable a machine to pass through an ordinary doorway. 

 Two plans only call for special notice, namely, folding 

 frames and telescopic frames. A folding frame, when one 

 or more pins are removed, can be folded up, but can still 

 be wheeled along. In telescopic frames, which are always 

 used with central-gearing, the frame and the axle on one 

 side of the machine are made telescopic, so that by 

 slackening a nut the parts slide over one another. A 

 telescopic axle was shown. 



Weight of Tricycle. — The proportionate weight of the 

 several parts of a loop-frame front-steering tricycle were 

 given. 



Component Parts of Cycles 

 Of the component parts of modern cycles the following 

 alone call for special notice : wheels,' bearings, frame, 

 steering-gear, brake and pedals. 



Suspension wheels, the first great improvement in cycle 

 construction, are made with either solid or hollow rims, the 

 latter being the lightest and strongest. In an ordinary 

 wheel the spokes are radial ; they are threaded through 

 holes in the rim, and screwed into the edge of the flanges 

 of the hub, being butt-ended or enlarged where the thread 

 is cut upon them. The section of the rims is crescent- 

 shaped. Hollow rims are made either from a tube by 

 rolling it to form, or out of a single strip of steel plate 

 bent to the desired section, in which case the edges lap 

 over one another and are brazed together ; or out of two 

 or more strips of metal bent to form and brazed or 

 sweated together. 



Round rubber tyres are used, but with surfaces some- 

 times corrugated longitudinally, which gives a better hold 

 on the road. The outer surface of the tyres is sometimes 

 made of harder rubber to diminish the wear, w^hile the 

 elasticity of the inner and softer rubber saves the jolting 

 of hard rubber alone. Tyres are usually fixed by cement, 

 which when properly done is suflicient, but a wire passing 

 through the centre of the tyre is used by some. 



Tangent spokes are employed to give extra torsional 

 rigidity to the wheel. The spokes, instead of being 

 radial leave the hub nearly at a tangent alternately in 

 opposite directions ; sometimes a single piece of wire is 

 threaded through the flange and the two ends made fast 

 to the rim by nuts, but in that case they invariably give 

 way first at the point of the double bend. Headed 

 spokes passing transversely through the edge of the 

 flange are now used. 



One of the latest innovations in the construction of 

 wheels consists in corrugating the spokes throughout 

 their entire length, which gives a certain amount of 

 elasticity to the wheel. At first sight it would appear 

 that these corrugations should seriously diminish the 

 lateral stability of the wheel ; but as far as experience 

 shows such is not the case. As, however, wheels so con- 

 structed have not been very long in use, it remains to be 

 seen whether they will stand the wear and tear of the 

 road. 



Bearings. — The bearings of the wheels are now almost 

 without exception made with anti-friction balls interposed 

 between the moving parts. The most approved kind is 

 that known as the vEoIus, which can be adjusted concen- 

 trically. The balls lie round a groove on a collar on the 



axle, on the two sides of which they bear. They are en- 

 closed within a concentric casing composed of two pieces, 

 one of which screws within the other. Each of these 

 has a hollow conical surface, between which the balls are 

 free to run. One piece can be screwed in until there is 

 as little shake as may be desired, and it may then be 

 locked in position by a small toothed bracket. A diagram 

 was given showing the section of the usual small wheel 

 bearing also capable of concentric adjustment. The 

 results of the experiments made by Mr. Boys on the 

 wear of balls in ball bearings were given. He found that 

 in running 1000 miles each ball lost in weight only 1/250 

 grain, which is equal to an actual surface wear of only 

 1/158,000 inch. 



FrcDiie. — The frames of both bicycles and tricycles are 

 largely constructed of weldless steel tube. In the bicycle 

 the front fork is made of tube tapered and worked into 

 an oval section so as to give the greatest possible strength 

 to withstand the severe torsional stress to which it is 

 subject. The back-bone is left round, but is tapered, 

 while the hind-wheel forks are usually made from a 

 stamping in sheet steel. 



The hollow framing of tricycles is usually circular, 

 having a diameter of from i to li in. and a thickness of 

 from o'o65 to 0095 inch. The large number of solid 

 parts necessary are usually made from wrought-iron or 

 steel stampings. Malleable-iron castings are also largely 

 used and are the cause of many of the breakdowns of 

 machines. Owing to the great expense of dies the 

 temptation to use these is strong. This expense, com- 

 bined with the fact that the patterns of tricycles at 

 present are frequently being changed, is the cause of the 

 present high price of first-class machines. 



Steering-gear. — The steering-gear may be dealt with 

 under two heads: (l) the method of mounting the 

 steering-wheel so that it may be turned for the purpose of 

 steering ; (2) the method of controlling the wheel. 



(i) The steering-wheel of all bicycles and of most 

 tricycles is mounted in a fork, at the top of which is a 

 " head" by which the fork is attached to the frame. In 

 the head is the joint to allow the steering-wheel to be 

 turned. The " Socket '' and the " Stanley " head were 

 described and a figure given of an improved " Stanley " 

 head in which, instead of cones, balls are used to allow 

 of free motion between the head and the central pin. A 

 figure was given of another form of Stanley head in 

 which a centra! pin is employed. 



The steering-wheels of tricycles are not always 

 mounted in forks. Among other methods that employed 

 in the " Quadrant " tricycle was described, and another 

 in which a large skeleton hub carries within it a small 

 head actuated by a lever from the outside. 



(2) On an ordinary bicycle the steering is controlled 

 simply by a handle bar rigidly fixed to the fork. 



Tricycles have their steering actuated usually by the 

 rack and pinion ; a handle-bar as used on a bicycle is also 

 employed either connected directly with the fork or 

 through levers. 



Owing to the sensitiveness of this mode of steering, 

 mechanism has been contrived which tends to keep the 

 steering wheel to a straight course. The most effectual 

 is that employed on the Humber make of front-steering 

 tricycle. A V-shapcd cam on the steering-rod lies in a 

 corresponding recess on the top of the socket of the 

 steering-spindle and is held down by a spring. When 

 the machine is steered the spring is compressed by the 

 action of the cam, and so it tends to bring the wheel back 

 to the straight line. 



Brake. — There are but two varieties of brake ; the 

 spoon- and the band-brake. The spoon-brake consists of 

 a spoon-shaped lever so pivoted that it can be pressed 

 against the tyre of the large wheel in the bicycle or the 

 two wheels of a tricycle. 



The l>and-brake, almost exclusively used on tricycles, 



