BHN - RETNURN “CIRCULT, 53
ceeded by the trolley and feeder copper,-raising the ratio to
equality. A double track, of course, improves matters. We
may tabulate these results somewhat as follows, calling Rt
the track resistance and R the overhead resistance.
Rt— 110 .2R. Exceedingly good track and very
light load.
N .2to .3R. Good track and moderate load.
R — 4to .6 R. Tair track, moderatedoad,
R! == 2to .3 R. Exceptional track and large sys-
tem.
R — 140 7 R. Good frack, large systetn.
Rt = .7to 1.0 R. Poor track, large system.
In cases now somewhat exceptional the track resist-
ance may exceed the overhead resistance considerably. The
Drop-Volts
Return circuit Street Railway Journal,
F1c. 36.
assumption now frequently made, that the track resistance
is one-quarter that of the overhead system really repre-
sents a better state of things than usually exists. To
justify it requires the combination of continuous rail or
exceptionally perfect bonding, with conditions of load that
do not require large feeder capacity. Under the ordinary
conditions R!=.4R is probably nearer the truth. The
proportion between R and R? has, of course, a very im-
portant bearing on the design of the overhead system. If
the return circuit had no resistance then the entire drop