WHEELS AND PINIONS. 



When a large wheel works in the teeth of a much smaller one, 

 which is a very frequent case in all species of wheelwork, the 

 smaller wheel is called for distinction a PINION, and its teeth are 

 called LEAVES. 



24. The method of manufacturing the pinions and smaller 

 wheels used in watch and clockwork is very ingenious. A rod of 

 wire, the diameter of which a little exceeds that of the wheel or 

 pinion to be made, is drawn through an aperture cut in a steel plate, 

 having the exact form and magnitude of the wheel or pinion to be 

 formed. After being forced through this aperture by the ordinary 

 process of wire-drawing, it is converted into a fluted wire, the 

 ridges of the fluting corresponding exactly in form and magnitude 

 to the edge of the aperture, and therefore to the teeth or leaves of 

 the pinion or wheel. 



This fluted wire, called pinion wire, is then cut by a cutter, 

 adapted to the purpose, into thin slices, at right angles to its length. 

 Each slice is a perfect wheel, or pinion ; and it is evident that all 

 of them must be absolutely identical in form and magnitude. 



Such a wire-drawing plate, with apertures of different forms and 

 sizes, is represented in fig. 6. 



Fig. 6. 



*.* * 



Fig. 7. 



25. Two wheels of unequal magnitude, working one in the 

 other, are represented in fig. 7. It will be easily perceived, that 

 in this case their motions must be in 

 contrary directions. Thus, if the 

 wheel A move in the direction of the 

 hand of a watch, the wheel B must 

 move in the contrary direction. 



Also, the rate at which they revolve 

 on their axles will be in the inverse 

 proportion of the number of their 



teeth. Thus, if the wheel B have fifty teeth, while the wheel A 

 has only ten, it is evident that one revolution of B must be 

 accompanied by five revolutions of A, since an equal number of 

 teeth of each wheel must necessarily pass the point of contact c 

 in the same time. 



Now, in clock and watchwork, one of the objects to be attained 

 is to cause certain wheels to revolve in a given numerical pro- 

 portion to others. Thus, that upon the axis of which the seconds 

 c 2 19 



