24 
DIRECT-CURRENT DYNAMCS AND MOTORS. 
TABLE 12. 
DRUM-ARMATURE DIMENSIONS. 
High Speed. Medium Speed. Low Speed. 
R. p.m.| Dia. | Length. / K. W.|R.p.m |Dia. |Length. |K. W. Bato Length. 
2400 | 2,5;| 4 56] 1800 | 58 | 23 
2400 | 28 5 .75 | 1900 | 58 28 1.5 | 1200 | 64 84 
2100 335 64 1.875] 1700 | 64 8+ 2.62] 1°50 | 73 4e 
1900 | 4 8 | 8.75 | 1600] 72 | 48 | 8.75] 950] 84] 54 
1800 | 543} 92 | 5.62 | 1850 | 84] 52 ey 850194] 54 
1700 | 5z| 10 | 7.5 | 3250] 9 64 17.5] 70 |10h | 6 
1600163} 12 |11.25| 1150 |103 | 6 {ti.25] 650/118] 68 
1500 | 62} 184 |15 1050 |:18 ; 6% |15 600 113 8 
1400 | 72} 15 22.5 $75 j13 8 22.6 | 5675 [15 84 
1300 | 88 | 164 |30 950 |182 | 8% 130 B10 {15 8} 
1200 | 93) 18 87.5 900 15 84 [87.5 650 116 Y- 
1000 |114,| 203 | 45 850 |153 | 8} 
800 |164 9 
700 j122 244 
650 |168 | 25 
450 (232 | 263 
450 |23% | 3844 
It will be noted in Tables 141 and 12, where machines of 
different manufacturers are placed side by side, that the 
armature dimensions of dynamos for similar output and 
speed in some instances vary greatly from one another, 
which goes to show that a wide range is given to the 
judgment of the designer in assuming the variable quan- 
tities such as peripheral speed, shape-ratios, etc. Yor in- 
stance, in Table 11 two 390 K. W. 150 revolution arm- 
atures are given, the first having a diameter of 57 inches 
and a length of 19 inches, while the second has a diame- 
ter of 68 inches anda length of l14inches. The peripheral 
velocity in the first machine is v = pal S 7 X 150 = 2240 
feet p. min., whilein the second itis 88 7 x 150 = 2670 
feet p. min. The length is 4%, or 4 of the diameter in 
the first armature, anl }4, or about § of the diameter in 
the second armature, 
