In some they are made of lined and soft rubber, the hard forming the wearing surface and the soft the abutting surface or cushion. The tire is generally fixed to the rim by being cemented in it. A wire. however, has been passed along the center of the tire, the two ends secured together by a right and left handed nut. Various sections of rims have also been used for holding the tire without extra neous aid. It is questionable, though. whether there is not a want of cohesion between the rim and the tire in this method.
The tangentially arranged spokes were adopted be cause of a certain amount of windage which takes place before the Dower is transmitted to the rim through the spokes. In the tangentially arranged spokes they are generally arranged in pairs, each pair being threaded through a hole in the flange of the hub, with their outer or free ends fixed to the rim by lock-nuts or nipples. One of the recent forms of tangential spokes is to use single instead of pairs of spokes threaded through trans verse holes in the hub, and Iwilt to run off al right angles to the hole, and thus form a kind of hook. The spoke-ends are also headed, to prevent them from pulling through the holes, and secured to the rim by nipples or lock-nuts.
Another form of spoke is the corrugated or crimped spoke, corrugated throughout its entire length, which gives :t certain amount of elasticity to the wheel.
The bearings of the wheels are now invariably made with anti-friction halls interposed be tween the moving parts. :Many have thought that this method of easing the runmng parts was an invention which cause in with the improved bicycle. but such anti-friction halls and rollers had been proposed and described for use with axles as far hack as the year 1781% and other patents for similar emit rivanees were granted in 1701 and in 1704, One of the successful kind of ball-bearings is that known as the " hearing, in whip]] the adjustment is concentric, so that the bearing remains perfectly true after adjust ment. In another form, shlAyn in Pig.:;, there are two facing cones. only one of whit+ is moved in adjusting to take up the side-play or check. One enterprising gentleman by care 1 ful experiment found that 12 balls in it hearing lost together gr. in weight in running 1,000 or only gr. per ball, equaling an actual surface wear of only 158000 The frame, of a bicycle is generally constructed of weblless steel tube. and consists of two
essem nil parts, 1 he front fork tlaibackbone.
In order to give strength to the fork, to enable it to resist the torsional strain pro (Need by the rider's pulling upon the steering-handles, it is generally drawn and tapered into an oval section, while the backbone is of circular section, although somewhat, tapered toward the point where it is usually brazed to the backbone. This latter is bent and blocked into shape from a blank of sheet-steel, the sides being usually of a half-round section. Frequently, however, the back fork is simply a prolongation of the backbone proper. The front fork is made rigid hetween the axle mid front end of the backbone.
Bearing in mind that the front wheel is the steering-wheel, and that this is carried in the vertical front fork, the method of mounting and controlling the wheel must be considered.
At the top of the fork is a socket or head pivotally connected by a short spindle with the front end of the backbone, coned bearings being provided at each end of the spindle. A trans verse bar having handles at both ends, and fixed upon the head just mentioned. serves to con trol the and affords also a steadiment for the rider. A brake-handle is pivoted to the handle-bar in such way as to be easily grasped by the rider without releasing Ids hold on the bar. The brake now almost invariably used on ordinary bicycles is termed a "spoon brake," and consists of a spoon-lever so pivoted in the head as to be easily brought to hear upon the circumference I if the driving-wheel. The leverage is so arranged that great power is obtained, and care must be, exercised in applying it so as to prevent sudden stoppage, which results in the rider being thrown off.
The saddle is of leather, and in some of the most popular types of machine is made detach able from its frame or support, which is mounted upon the backbone close behind the front fork, so that the rider's feet may conveniently reach the pedals. Different forms of steel springs are used in making up the saddle-frame, and these have an adjustable tension for riders of different weights. Devices. for adjusting the saddle fore and aft and for altering the pitch of the seat are also mow invariably employed.