80 ARMATURE CONSTRUCTION 



is used for the space block. As will be seen in both cases, small 

 pieces of the lamination are nicked out in the plate and turned up 

 at right angles. 



Fig. 83 is an interesting method used by Messrs Vickers, 

 Sons & Maxim, which may be also seen by a close examination of 

 Fig. 85, Chap. V. 



The lower the speed, the smaller the diameter, and the greater 

 the length, the more important does it become to give careful 

 attention to the details of the design of the ventilating scheme 

 and the construction of the spacing pieces. 



Where spacing fingers of the types shown in Figs. 78, 79, and 

 80 are employed, it is a good plan to standardise the width of 

 ventilating duct to be used on all machines, or else adopt one 

 uniform width for small machines and another for large machines. 

 This permits of the spacing fingers being manufactured and 

 stocked in large quantities. The width of duct employed should 

 not be less than 10 miu., nor exceed 20 mm. 



