134 



NATURE 



\_Dec. lo, 



the centre of the crank axle is a spherical boss, on which 

 can swivel, but not turn freely in all directions, a large 

 double hollow chain wheel kept parallel to the driving 

 wheel by two idle rollers. As a matter of fact the crank 

 axle swivels within this chain wheel and the brackets 

 which support it being rigidly connected with the handle 

 bar serve to steer the machine. 



Tandem Bicyi/es. — At present there are only two makes 

 of tandem bicycle, each invented by Mr. Rucker. The 

 earlier one is constructed of two ordinary bicycle driving 

 wheels complete in their forks, which are then connected 

 by a backbone containing an axial joint. Each rider 

 drives, steers, and balances on his own wheel independ- 

 ently of the other, but of course the rear must follow 

 within a foot or so the path of the one in front. Although 

 this machine is very fast, lighter than two ordinary bicycles, 

 and almost entirely free from vibrations, there is an ele- 

 ment of danger about it that militates against its general 

 use, inasmuch as it demands to a certain extent a unity 

 of thought and action on the part of both riders. 



A very satisfactory tandem has been arranged by the 

 author, a modification of this, in which the rear wheel is 

 replaced by the driving wheels of an ordinary Humber 

 tricycle, the connecting bar of course being modified to 

 suit the altered conditions. The later tandem bicycle 

 eclipses the earlier ; it is probably the fastest machine 

 in existence. It is constructed on the lines of a 

 dwarf geared bicycle. The seat for the front rider i; 

 mounted immediately over the centre of the driving wheel, 

 while the rear rider who alone steers and manages the 

 machine is about midway between the two wheels. 

 Divided pedal axes are mounted fore and aft of the centre 

 of the driving wheel. The weight of this bicycle is only 

 55 lbs. ; it is therefore the lightest machine yet made to 

 carry two riders. 



O/fo Bicycle. — This peculiar machine, which is due 

 to the brother of the inventor of the gas engine known 

 by the same name, is almost more nearly allied to 

 a tricycle than to a bicycle proper, but as it has only 

 two wheels and consequently requires the balance to 

 be still maintained by the rider, it is rightly called a 

 bicycle. The wheels are the same size, and are here 

 mounted loose on the same axle, parallel to each other 

 and both of them are drivers. The rider sits between 

 them and works a continuous pedal crank-axle, the posi- 

 tion of which when he is seated is below and slightly in 

 front of the a.xle carrying the driving wheels. The crank 

 axle is connected with the driving wheels by endless steel 

 bands passing round plain pulleys on the ends of the 

 crank-axle and on each wheel. The bands are kept 

 taut by tightening springs, and the machine is steered by 

 slacking one or other of them, which causes the corre- 

 sponding driving wheel to lose motion, and therefore the 

 other wheel runs round it. If a very sharp turn has to 

 be made suddenly, a brake is applied to one wheel at the 

 same time that its driving band is slackened, which 

 causes the machine to turn round in a circle upon that 

 wheel as a centre. This machine having no small wheel 

 fore or aft, the rider, while steady sideways, has to 

 balance himself in the direction of his motion, which he 

 is enabled to do through the medium of the pedal crank 

 axle : by pressing on the forward pedal, if he is falling 

 forwards, he throws his weight backwards and conversely 

 by pressing on the rear pedal he throws his weight 

 forwards. To preserve him from actually capsizing back- 

 wards a safety tail projects behind the seat, which will 

 bear on the ground whenever the seat is tipped too far 

 back. 



Among the many beautiful features presented by this 

 raachhie the best seem to be : (l) the balance whereby 

 the rider is always in the best position to utilise his 

 strength and weight notwithstanding the various gra- 

 dients ; (2) the nicety by which it can be steered ; (3) its 

 tendency to run in a straight line without any effort on 



the part of the rider ; (4) its freedom from vibration ; 

 (5) the circumstance that it makes only two tracks. 



Tricycles 



The tricycle presents far greater difficulties than the 

 bicycle. It is necessary that each wheel shall be free to 

 move in its own direction independently of the imited 

 action of the other two. For running in a straight 

 line all three wheels must be parallel ; whiht for running 

 round a curve, one or more of the wheels must be turned 

 until the centre lines of the axles intersect in plane, their 

 point of intersection being the centre of the path described. 

 Besides being independent in direction of running, each 

 wheel must also be capable of revolving at a greater or 

 less speed than the others. It is also essential that only 

 so much of the rider's weight shall be borne by the 

 steering wheel or wheels as is necessary to ensure their 

 proper action. Owing to the variety of ways in which 

 these principles can be carried out practically, it is 

 easy to account for the variety of tricycles constructed. 



.Single-dnving Tricycle. — The simplest form of tricycle 

 is that with only one driving wheel, either or both of the 

 others being used for steering. The single driving rear- 

 steerer is now practically obsolete. 



Covcntty Rotary Tricycle. — Another single driver, 

 known as the " Coventry rotary," has the large driving- 

 wheel on one side, and two small steering wheels on the 

 opposite side, arranged to turn together in contrary direc- 

 tions for steering. The double steering counteracts the 

 evil of one-sided driving. Though one of the first machines 

 introduced it is still largely in use, its advantages being 

 that it is simple, it makes only two tracks, and it is narrow 

 enough to pass through an ordinary doorway ; this, how- 

 ever, diminishes its natural stability. 



Front Steering Tricycle. — .\ single driving machine of 

 this class exists which is steered by the two front wheels, 

 and driven by the rear wheel, but there is not sufficient 

 weight on the driving wheel. 



Double-driving Tricycles. — In these the two driving 

 wheels are always placed parallel and opposite to one 

 another, with the steering wheel in front or behind, and 

 generally central. It is sometimes placed on one side 

 when the tricycle makes only two tracks. There are 

 two methods of double-driving : firstly, by clutch-action ; 

 secondly, by differential or balance gear. 



Doitble-driiing by Clutch Action. — In this plan the two 

 driving wheels are locked to their axle only when the 

 machine is being driven forwards in a straight line, but in 

 running round a curve the outer wheel overruns the 

 clutch and the inner wheel alone drives. In the Bourdon 

 Clutch, which is most generally used, a disk has its edge 

 cut away so as to form three or more inclined planes. In 

 each of the spaces between these recesses and an outer 

 ring is a hard steel roller, which jams when the clutch 

 drives the wheel, but which does not hinder the wheel 

 from running ahead of the clutch. 



A clutch machine cannot, without extra gearing, be 

 driven backwards, nor can it be retarded except by the 

 action of the brake. On the other hand the free pedal is 

 a convenience. Various attempts have been made to 

 construct a clutch which shall drive either way, but 

 hitherto without success, in consequence of the loss of 

 time between the forward and the backward grip. The 

 author of the paper is now at work on this problem. 



Double Driving by Differential or Balance-Gear.— This 

 other mode of double driving, so called because the power 

 is divided or balanced between the two driving wheels, 

 depends on the action of an epicyclic train, in which the 

 two primary wheels are connected with the driving wheels 

 of the tricycle, while the arm or train which connects them 

 is driven. The simplest form invented by Starley consists 

 of three bevel wheels. Here the arm or axis of the 

 middle one being carried round, drives the other two and 



