Evening star. [volume] (Washington, D.C.) 1854-1972, 1897-07-03
W. F. Mcfarland Rsoites His Expe-
riences With Them.
he REACHES A FAVORABLE FINDING
TabuIated Statements of the Last
Two Public Tests.
MANY DIFFICULTIES YET


Engineer Commissioner of the District of
Columbia who verbally Instructed June
0 to investigate and report upon the per-
fCrmance of tte air motor cars Nos. 91 and
4n1. used on the line of The lexington and
Soldiers Home Railway Company, has
submitted to the Engineer Commissioner
three reports, under dates of June a. &c
and -. 1897. Mr.. Mcfarland says that
both cars are of the same size, being the
ordinary closed type, mounted On standard
trucks, furnished with hand brakes, and
having seating capaci:y.of thirty persons.
Except III the matter of reheating the .lr
and introducing moisture into the cyin-
ders, the rSotors on the said cars are the
same The motors compound, each
consisting of two horizontal cylinders, with
double acting pistons, controlled by piston
valves
He describes ve-y closely the character
Of the mechanism by which the cars are
propelled and controlled, stating that the
conpre: sea air. at an initial pressure from
2."D to 1850 pounds per square inch, is
stored in seamless steel bottles. each hav-
ing a capacity of one and one-fifth cubic
feet, which are placed under the seats in
the ear and also under the floor and plat
form Mr.. Mcfarland, after describing the
heating of the air, the number of bottles
used on each car, and the manner of their
connection with the propelling mechanism,
gives full history of the way both cars
worked on each trip he made upon them,
ard then proceeds to report upon the re-
suits attained, stating. follows, in re-
lation to No. 81:
The Results.
"As far as speed. carrying capacity and
freedom from arrangement of machinery
are concerned this car appears to me to
be satisfactory over the route on which It
has been The consumption of air is
yery large NOT less than
claimed good practice by the builders
and limits the length of run, even under
favorable circumstances, to not more than
six miles.
The Objectionable features. from the
passengers point of view, are the fire pot
ard stove pipe, which have been abolished
In the later car; vibration caused by i'm
perfectly balanced crank disks on the en-
gines mot at all serious). and a disagree
able odor. probably caused by gases from
the fire pot and burnt oil from the re-
heating coils The sound of the air ex-
hausting from the low-pressure motor is
quite noticeable in starting and in ascend
ing grades"
on ear No. 400 Mr. Mcfarland saws:
THE working of this car is In all re-
spects better than that of No. 91. though
the consumption of air is still excessive;
in this connection il Is but fair TO call at
tontion to the fact that the s-foot wheel
base on both these cars Is by means
adapted to the curves on which they are
obliged to run; the fianges of the wheels
absorbing large amount of power 1t
should also be mentioned that the steam
pressure at present available for heating
the tank is only ao pounds whereas that
contemplated in permanent plant Is 100
pounds. giving difference in temperature
of about 80 F.. and a probable gain in
leEEth of run of 10 per cent.
This car" he says, has made continu-
runs of eight and eight and a half
miles on one change of air as reported
above. over the heaviest grades on the
system, but carried TO passengers and
made few stops. 1t climbed the grade at
9th street and Louisiana avenue at slow
speed, and would, in my opinion have
rounded the curve at 5th street without
difficulty had the wheel base been ada pied
to the track: 1t has taken this grade three
times at full speed, but carried no pas
sengers; headway was well maintained to
the top Of the HILL
Question of Safety.
Under the head of safety Mr.. Mcfarland
continues:
While the rupture Of a bottle under
pressure is not impossible, 1t is certainly
improbable; the maximum pressure on
bottles Will always occur at the charging
points. with a steadily decreasing pressure
to the end of the run.
In the matter of laying pipes to carry
ar under pressure from the central power
station TO the recharging points there
should be no serious difficulty in making
them perfectly safe under the pressure
used; it would. of course, be quite neces-
sary to protect them from corrosion
should the pipes be laid as much as four
1eet below the surface, il is not probable
lhat even Ill case of rupture any serious
damage would result. An objectionab bic
feature would seem to be the necessI.v
for having high pressure steam boiler
at each recharging point, for the purpose
OF reEeating the tank water.
The OILY alternative to conduits would
he so or more isolated power stations. AT
~hlSh TIE engines would probably have to
De run non-condensing at a considerable
increase IN cost of maintenance
in my opinion the type of motor under
consideration mounted on a car havine
wheels and wheel base adapted. as far as
nay be possible. to the tracks on which II
Is 10 run and with possibly slightly larger
o'thiSteT OF cylinders, is suitable for the
service desired. "'
some Plans Developed
Regarding the compressor, Mr.. MacFar-
land says:
The compressor used for experimental
purposes is q small four-step, belt-driven
affair. with inter-coolers. AMI answers fairly
well for the purpose Intended
ne general plan OF "a power plant and
oondults, as outlined by Superintendent
ICdd OF the lexington road, consists of a
central power station in the neiahborhooJ
OF 10th and II streets southwest fitted
WITH compound condencing engines This
location is chosen TO permit the use OF
'-'N' '&tti III tIIC cO0uenSOrS and would
heSessitale the use of at least two lines
OF pipe, one TO the vicinity Of 7th and p
streets northwest. and enc 10 18th and d
streets northeast"
Supplemental Reports.
There are Two supplemental reports OF
further performances Of car No 400 In tn,
first OF these. dated June 28, Mr.. McFar
land. among other things, says:
This car made the trip from 4th and 7
streets northeast to the Center Market. I,
Brookland. and back to the power house a
fth and I streets under the following con
ditions: Left ith and T streets at 8:4l o. m
June -, carrying twenty passengers; ma d.
eighteen full stops, evenly distributed owe
the route. between 4th and T streets anS
the Center Market. one of these stops beinJ
MADE on the Louisiana avenue tangent be
tween 9TH and 9Th streets; Center Marke
reached at 1903 pm: twenty-five passenger
were on board In descending the 9Th stree
hill.
Left Center Market for return run a
600 pm. carrying twenty-one passengers
made full stop at 9th and G streets, ant
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