234 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
or grooves for gripping, the more smoothly the trolley will 
run and the better the general contact. A plain round 
wire would be the best if it could be clamped so as not to 
produce projections to cause trouble at high speed. Of 
the two pioneer heavy service roads, one, the Nantasket, 
uses the two-lobed trolley wire shown in Fig. 120, weigh- 
ing one pound per linear foot, the other, the Mt. Holly 
branch of the Pennsylvania Railroad, took for its rather 
lighter service a No. oo plain wire. 
T'o get a clear idea of the power requirements on this 
class of road let us assume a fairly simple case and work 
out the feeder system. Let A B (Fig. 121) be a straight sub- 
urban system, 50,000 ft. (nearly 1o miles) in length, with 
no grades steeper than 14 per cent, double tracked 
throughout with stations, say, every sooo ft. ILet the 
power station be at C, the middle point, which would gen- 
  
  
  
  
  
  
  
  
  
  
  
  
  
900000 ¢. m. 900000 c. m. 
750000 c. m. 750000 c. m., 
efasfaauele]eae) : 1l|i[|l[ 
A a b c a elelar 0 h i 748 
|__\ ; Y Street Ry.Journal 
FIG. I2I. 
erally be as convenient as anywhere. We will assume 
trains to be run on ten minutes’ headway, and to make the 
round trip in an hour. During the busy hours, 7-10 A. M. 
and 4-7 p.M., the trains should consist of motor car and two 
trailers, at other times of motor car and a single trailer. 
Certain trains would probably have to carry three trailers. 
From 8 p.M. on, and before 7 A.M. twenty minute headway 
would be sufficient. During the busy hours there would 
then be twelve trains in service, six of them heavily 
loaded, and each a three-car train. From the rush hours 
on the number of trains would be the same as before, until 
8 p.M., after which six trains would suffice. 
From these data we may calculate the power which 
would have to be delivered. As in other railway work the 
feeding system 1is really determined by the conditions of 
maximum load. ‘This would usually fall between 8 and g