128 
DIRECT-CURRENT DYNAMOS AND MOTORS. 
ing is herecomputed approximately by considering 
the wound armature as a hollow cylinder of iron. 
A more accurate method is to find the exact 
weight of the armature core, by deducting from 
the core, with the slots considered as solid, the 
weight of the iron in the slots, and adding to it 
the weight of the winding obtained by Par. 38 
and Table 13. 
Bedplate, Journals, and Shaft (estimated)....... 800 lbs. 
Aggregate weight of principal parts.......... 1950 Ibs. 
Allowance for accessory parts (15% of above 
Figure). 3 ina aes oe fy eke eee meee B00) 5 
Total weight of machine.............-. ey .. 2250 lbs. 
The output of the above dynamo is 125 volts and 240 
amperes (see page 88), or 30 kilowatts; hence the weight- 
efficiency: 
30,000 
Wt. Bf. = 
This being a very high weight-efficiency for a dynamo of 
the given size and speed, it follows that the machine is 
economically designed, and would, when built, compare 
favorably, as to lightness and cost, with existing ma- 
chines, 
= 13.3 watts per pound. 
Printed in U.S.A, 
