Brake Tests
År: 1913
Forlag: Pensylvania Railroad Company
Sted: Altoona, Penna.
Sider: 401
A Report Of A Series Of Road Tests Of Brakes On Passanger Equipment Cars Made At Absecon, New Jersey, In 1913
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244
The dynamometer spring was calibrated to register a vertical
deflection of 1 in. for each 1000 lb. pull of the brake shoe.
The length of stop or distance traveled at the periphery of
the test wheel is proportional to the horizontal distance measured
on the diagram. One inch travel of the paper corresponding to 72 ft.
travel at the periphery of a 36 in. test wheel.
The time pencil records the beats of a seconds’ pendulum, from
which record the speed in miles per hour is calculated.
For some of the diagrams two additional pencils were used, one
for recording data in connection with the sparks thrown off the
shoes and the other for data in connection with pyrometer records of
rise in shoe temperature.
H.—A speed indicator for showing the speed of the test wheel so
that the brake shoe could be applied at the predetermined speed.
EQUIVALENT WHEEL Load.
460. The area of the dynamometer card when measured to the
proper scale gives the amount of work done in making the stop. Ex-
pressed by formula this is as follows:
Work = Area of Diagram = Shoe Pull X Length of Stop = I
WV2
MV2 =.
2g
V being the velocity at the periphery of the test wheel and W the equiva-
lent wheel load. By obtaining the area of a large number of diagrams,
and taking the averages, the following values have been obtained for
the equivalent wheel load.
FLY Wheel Rings. Wheel Load 36 in. Wheel.
0 3360 lb.
1 5300 «
2 7220 «
2 0v 9400 «
4 11600 «
5 13700 «
6 15900 «
461. The corresponding car weights are obtained by multiplying
the wheel load by the number of wheels under the car for single shoe con-
ditions and by twice the number of wheels for clasp brake conditions.
462. The Mean Pull of the Shoe was obtained by dividing the area
of the dynamometer card by the length of the card measured from the
point of equivalent instantaneous application to the stop.
463. The Mean Coefficient of Friction is the quotient obtained by
dividing this mean pull of the shoe by the actual brake shoe pressure.
Method of Conducting Tests—MANIPULATION.
464. The tests of brake shoes made on the testing machine were
conducted under two different sets of conditions, namely, standard