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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238
first with the one-half area shoes demonstrated the effect of shoe tem-
perature which was offsetting the probable tendency of the better bear-
ing area condition originally secured as a result of the reduced warping
effect.
Flanged Shoes.
450. The advantage of an increased bearing area was demon-
strated beyond question by the fact that the use of flanged brake shoes
after being worn to a satisfactory bearing resulted invariably in a
shorter stop than under similar conditions with unflanged shoes. The
shortest stops made in the entire series of tests were with flanged brake
shoes and their use shortened the stop approximately 12 per cent, as
compared with the best similar tests in which unflanged shoes were
used under similar conditions. This comparison is illustrated graph-
ically in Fig. 116. A discussion of the performance of flanged versus
plain shoes will be found in Par. 533.
MACHINE TESTS.
451. Up to the time of these tests there was no definite laboratory
test information which would apply to the particular braking conditions
under investigation, especially with reference to the actual brake shoe
performance as distinguished from the brake rigging performance.
452. To supplement the road tests, a series of laboratory tests
was carried out on the brake shoe testing machine of the American
Brake Shoe and Foundry Company, at Mahwah, N. J.
453. The shoes used in the laboratory tests were selected from the
group of shoes provided for the road tests so that as far as uniformity
of shoe metal is concerned the laboratory test results would be com-
parable with the results of the road tests. The schedule of the tests
was devised to develop information concerning the following:—
(A) The effect of bearing area upon the mean coefficient of
friction.
(B) The effect of temperature upon the mean coefficient of fric-
tion.
(C) The effect of width and length of shoe upon the mean co-
efficient of friction on the basis of equal bearing areas.
(D) Variation in the mean coefficient of friction through a range
of speeds at constant braking power.
(E) Variation in the mean coefficient of friction through a range
of braking powers at constant speed.
(F) The effect of clasp and standard brake conditions on the
mean coefficient of friction at constant speed with various braking
powers and at constant braking power with various speeds.