THE SPRINGS. 



387 



in having the bolts run in a groove made in the surface 

 of the box, taking in one half the diameter of the bolts 

 This lessens the amount which is necessary to be cut from 

 the substance of the hub. 



The Half-Patent Axle is similar to the foregoing, 

 but does not retain the bolts and plate. The wheel k 

 gecured bj a nut upon the end of the axle. 



THE SPRINGS. 



These are of many kinds. The old spring (Fig. 72), 

 the cradle spring (Fig. 73), the elliptic spring, (Figs. 74 and 

 75), the shackle spring (Figs. 76 

 & 77), and the platform spring. 

 Thai in most common use, and 

 by far the best for ordinary pur- 

 poses, is the elliptic spring, of 

 which those shaped like Fig. 74 

 are better than those like Fig. 75. 

 It is of the first importance 

 that the springs should be of 

 the proper degree of 

 Btiffiiess required by the 

 weight of the carriage, 

 and the number of per- 

 sons they are intended 

 to bear ; if too stiff, they 

 will "ride hard" and 

 cause great discomfort ; 

 or if they are not stiff 

 enough they will col- 

 lapse or break. The 

 stiffness is regulated by ' 

 the thickness of the steel 

 used, the length of the fig. 75.-Eiiiptic spring-bad s 



