CH. Ill TAPER AXLE 33 



any movement tending to unscrew one will screw 

 up the other. Outside of the nuts there is a small 

 pin passing through the reduced end of the axle, 

 which pin is prevented from coming out by the cap 

 covering it. This cap screws into the box, and con- 

 sequently into the hub, and not on the axle ; it 

 turns, therefore, with the wheel. The cap holds 

 about half a pint of oil which slowly finds its way 

 along the arm through shallow grooves made for 

 the purpose. The outward pressure of the wheel is 

 not taken directly by the back of the nut, but by a 

 loose collar, called the collet, which is behind the 

 nut, and prevented from turning by being fitted to 

 a fiat place worked on that part of the axle. 



The thrust in the other direction is against an 

 enlargement of the arm, a leather washer being 

 put there to regulate the play of the wheel. This 

 washer also prevents the oil from oozing out at the 

 back of the wheel, and the dirty oil accumulates in 

 a recess in the box, made for the purpose. 



It will be noticed that both these arms are cylin- 

 drical and not tapered ; the fit is therefore made by 

 the maker and is not adjustable. 



The point at which an axle-arm is most liable to 

 break, is at its back end, owing to the leverage of 

 the wheel being the greatest there, and the diam- 

 eter at that point must be made proportionate to the 



mechanical processes were not so far advanced as at present, should 

 have been so perfect that little improvement has been made upon it 

 in a hundred years. 



