FAST AND HEAVY RAILWAY SERVICE. 245 
We will assume a three-car train, motor car and two regular 
coaches weighing complete with passengers r14otons. This 
demands no special construction; in fact the less departure 
from the usual form and appearance of cars the better with 
respect to securing traffic. 
It is worth while, however, to give the locomotive a 
head in the form of a parabolic wedge, which is slightly 
better than the wedge of Fig. 127, to vestibule the cars 
snugly, and to build the cars as free from pro’ections as is 
consistent with usual models. 
With these precautions the total equivalent sectional 
area could easily be kept within 100 sq. ft. Nearly all of 
this, too, can gain advantage from shaping. For the rela- 
tive resistance of wedge and plane Fig. 127 gives accurate 
values, while the close agreement of the experiments based 
on normal surface attests their general accuracy. Adding 
one-third to the wedge value for 100 miles per hour to take 
account of plane and irregular surfaces, we have a total 
atmospheric resistance of ten pounds per _square foot. 
The track resistance we will assume at eight pounds per 
ton since this value is quite attainable at high speed on a 
good track, and furthermore was used in computing the 
points shown on Fig 127 sothat if eight poundsis too low, 
the air resistances are too high. We may now compute the 
total train resistance as follows: 
140 tons at 8 lbs., 1120 lbs. 
100 sq. ft. at 101bs., 1000 1bs. 
Total drawbar pull, 2120 lbs. 
At 100 miles per hour, 8800 ft. per minute, this means 565 
mechanical horse power developed by the motors. This 
power would be raised to about 1300 h. p. in taking a one 
per cent grade at the same speed. At 125 miles per hour, 
the assumed maximum, the air resistance would rise to 
about thirteen pounds per square foot and the horse power 
to 733. Even if through increased speed and headwind 
the air resistance were doubled, the mnecessary output 
would still be below 1000 h. p. We may safely assume