DIRECT-CURRENT DYNAMOS AND MOTORS. 127 
95. 
The weight of the shaft, bearings, and bed (or supporting 
brackets) depends upon the type and arrangement of the 
machine, and varies so widely for different designs of 
machines that no definite rule for estimating its amount 
can be given. 
To compute the weights of the various parts, multiply their 
solid contents, in cubic inches, by .28, in case of wrought 
tron or cast steel; by .26, in case of cast tron; by .32, 
for copper; and by .30, for brass. 
Example of Determining Weight-Efficiency.— 
Find the weight-efficiency of the toothed-armature 
shunt-wound four-pole dynamo shown in Fig. 26, page 
77. 
Solution.—The weights of the various parts of this dy- 
namo are as follows: 
Yoke, 274" external diameter, 224” internal diameter, 
8” breadth: 
[ 274" : = eae | AE BR AA eae ae 440 Ibs. 
4 cores, 63" diameter, 4” long: 
eee XX BBS eal. t ese 155 
Polepieces and core-seats on yoke, approximately, 75 “ 
Magnet winding (see page 111), 148 lbs., or round: 150 * 
Armature. Core, 12” external diameter; 6$” in- 
ternal diameter; 10$” long; slots, 1’’ deep. 
Provided that the entire height of the slots is occu- 
pied by the winding, the dimensions of the wound 
armature are: External diameter 12”, internal 
diameter 4%”, length 124”; and its weight is, 
practically: 
[i2yZ - (48)"F | Ph M28 Ss e535)... yusx 800). 
The total weight of the armature core and wind- 
