CH. Ill 



CONED WHEEL 



41 



Fig. 21. 



it, since, owing to the clasp of the tire, the wheel 

 cannot be flattened out by a force acting on the in- 

 side end of the hub ; but it is correspondingly weak 

 in the opposite direction. Equal strength in both 

 directions can be secured by placing the 

 spokes alternately on both sides of a line 

 around the hub, as is done to an exagger- 

 ated extent in a bicycle wheel and to a 

 smaller extent in carriage wheels (Fig. 

 21). This ' stao-o-erinor ' or 'dodging,' of 

 the spokes also less weakens the hub. 



The best results would seem to be ob- 

 tained in heavy work, by using a parallel 

 axle, fitted by the best processes, set very nearly 

 level, with an almost vertical wheel having- but little 

 dish. 



II a wheel is dished and the axle so set as to 

 give a plumb bottom spoke, the tire, in order to fit 

 a flat road, must be horizontal cross- 

 wise at its bottom point, and must 

 therefore be a section of a cone, the 

 position of the apex of which will be 

 determined by the dip of the axle 

 (Fig. 22). If the tire is not so made 

 in the beginning it will finally wear 

 into that form. 



Now a cone, or a section of a cone, 

 will tend to roll in a circle, the centre 

 of which is the point at which the apex of the cone 

 would touch the ground, so that if the wheels of a 



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Fig. 22. 



