Evening star. [volume] (Washington, D.C.) 1854-1972, 1897-07-17

in view. Il the propelfng power tair) can
be controlled to the same extent as steam.
This remains to be proved.
IN any system. occasional complete
o or OF machinery are expected. In
all other systems there is q sufYicient re-
serve power In each motor to tow a dis
aoied motor from any point on the route
back TO the power house. Mr.. McFar-
IN the motors in question is too small TO
tainty.
Fitness for the work.-rhis includes the
question OF speed. power to overcome
grades. curves. etc: convenience of loca-
tion or power plant. and economic suita-
hiiity. The first two requisites can be met
IL the motors can Toe supplied with air I'm
quantity and at pressures sufficient for the
work The tests show that a car I'm work
ing order. supplied with sufficient air at a.
proper pressure. can carry the required
load up the worst grades the road, and
can attain the requisite speed.
IL has not been shown, however that
,railers can he used with these motors.
AS trafffc increases. trailers play n most
important part in the reduction OF operat-
Ing expenses. and. I'm fact may be con-
s'dered necessity. especially where un-
usual transportation demands must be met
on special occasions.
System the Least Flexible.
The air motor system seems the least
flexible OF systems as to the arrangement
"a h' l'oWtT pid.lt- ne SnOrtneSS OF DOS
sible run requires recharging stations at
points on the line which cannot be chang
ed 10 any material extent. The companies
row propose either to establish three pow
er plant houses OF to establish one main
power house. with two sulst tons supplied
with air from the main station through
pipes laid under the streets but each hav-
ing a reheating plant. Neither alternative
IL advantageous 10 the city. The latter is
by Tar the more Objectionable besides be-
ing OF doubtful practicablity
,r There remains the economic problem.
mere are thirty-one miles of tracks In
me combined systems. For a portion OF
the routes they pass through the busiest
parts OF the city. No system should be in
PRODUCED which does not give a sure prou,-
Use or commercial success. The needs
OF the District are too great to per-
INIT the risk of commercial failure and OF
me conseQut mt breakdown OF the adopted
system.
The use of compressed air as n rno,iye
power Is not new. The real problem In
viewed In its application to street cars is
hcw 10 store supply sufficient for a pro-
iohseu run withou: recharging Given A
supply OF air under pressure the main loss
OF energy in its use. I'm a well-designed ma
crime, crises from the cold of exhaustion
anu leakage. and these causes of loss he
CO me create; as the pressure under which
the ar Is stored and used Is increased
ordinarily air for running machinery is
delivered at pressures of less than l,,
PtuS per square men. In the motors in
question. In order to provide supply suf,i-
cieht Tor pro longed run the reservoirs
d.e charged with air at a pressure of mor.
.taii -.vo pounds per square inch. From
the AR passes through valve de-
Ssncu "a fcuuoe the pressure to 200 hounds
ana thence il goes to The machinery being
power.
1T is the necessity for these great pres
suies that make the motors To a large do
gree experimental. ana this is proved hy
'he very great air consumption per mile
as detailed in Mr. McFarlands report. II
..is ieihase ana loss is so great with new
machinery, run under the CONDITION of n
uiai "TRIP. what Will il Ice when the valves
ana packing become worn? No data are
presented and none could be obtained. in
me tests noSsihl" 10 make, to show what
would he the effects of wear, nor how
much repair is required.
MI. McFarland's report shows thar The
alI motor system proposed is not econom!-
cai as a machine. TIE average horse. mower
required TO be developed rer car from The
approximate estimate he makes uhe only
es.iinate possible with the informa lion at
taihabe) Il from about 43.7 TO It.4 The
average horse power per car to be .leN,l-
oped IN an electric line varies from ~ 10
-. This would show in part the reason
why the operating expenses per car mile
should be relatively IA cents and . cents
ior the TWO classes of motors, as mentioned
IN MI. Emack's report.
Earnings and ENpenses
ITO keep road solvent the earnings must
De suficient to meet the operating expenses
plus the Interest the bonded indebted
ness. Thus, in two systems "A cheap plant
with large operating expenses may Ice less
economical than a more expensive plant
with small operating expenses
Taking Mr.. Emacks figures of the cost
OF equipping the roads with the air motor
sy stem and with the underground electric
system, respectively, We have the following
Cost of Two Systcms.
Air motor
Cost Of Interest Operating
eqnillnient. at pc enpJnses Total
Sas..4 40 Sal .2G0lo $3.50 102 s331 .1e 10
Underground Electric
Cost Of Interest Operating
equipment. pc ,xpaps.s Total
81 ,443.UHo Slol .0l0uo S2a5 I37 s3.m; az 90
difference ia favor of underground cleo
trio system. S,5,2l5.l0
THE above figures not claimed 10 he
accurate. Accurate figures are not attain
able.
I'm conclusion. II would seem that the
air motor system possesses many good
qualities. but that as yet il is experimental
Being experimental, good policy would
seem 10 forbid its installation on so large
a scale as the equipment of the Ecking.on
and Soldiers Home and Belt railways
would require.
1.-The system may be in all respects n
proper and satisfactory motive power for
the speedy and convenient propulsion of
street cars but satisfactory evidence that
is hnG mt