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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295
(c) With plain solid shoes the durability will be increased 41.1
per cent, under clasp brake conditions as compared with
that under single shoe conditions. (Par. 543-B.)
(d) With plain slotted shoes the durability will be increased
33.5 per cent, under clasp-brake conditions as compared
with that under single-shoe conditions. (Par. 543-C.)
(e) The advantage of clasp brakes over single-shoe brakes may
be summed up as follows:
First.—The clasp-brake shoe has but one-half the wheel load
and consequently one-half as much energy to absorb.
Second.—The clasp-brake shoe is working at only one-half the
shoe pressure at which the standard shoe must work
under the same braking power.
Third.—The available area for the same amount of energy to
be absorbed is double. (Par. 537.)
(f) A comparison of the values of mean coefficient of friction
for standard and for clasp-brake conditions indicates a
decided advantage for the clasp brake throughout the
entire range of braking powers. The gain in favor of the
clasp brake with slotted shoes amounts to about 40 per
cent, at a braking power of 180 per cent., and 100 per cent,
at a braking power of 40 per cent., an average gain for the
whole range of braking powers of about 70 per cent.
(Par. 535.)
(g) The generation of the retarding forces and consequent
absorption of the energy of the moving train is dependent
upon but a very small quantity of brake shoe metal.
(Par. 509.)
(h) The actual bearing area rather than the total face area of
the shoe is the important factor in brake shoe perform-
ance. (Par. 449.)
(i) The magnitude of the bearing area changes throughout the
stop and is greatest near the end of the stop. (Par. 498.)
(j) The bearing area shifts continuously from one portion of
the surface to another during the stop. (Par. 510.)
(k) The principal factor in producing high friction for any
given braking condition is the frequent shifting of the
bearing area from the heated to the cooler spots over the
face of the shoe. (Par. 513.)
(l) Slotted shoes are more flexible than solid shoes and the
bearing area shifts more readily than in the case of solid
shoes. (Par. 514-B.) •
(m) With shoes of the same type and of approximately the
same hardness, the wear per unit of work done is less
with the slotted shoe than with the solid shoe. The
stops with slotted shoes were always shorter and the