The Washington herald. [volume] (Washington, D.C.) 1906-1939, 1922-03-26
TENDENCY TOWARD
PROPELLER SHAFT
BRAKE INCREASING
Engineers Show Growing
Interest in Safer Brake
Method.

Typical practice An brakes Is to
use the Internal and expanding
types on the rear wheels. This has
no doubt been widely adopted be-
cause Of the simplicity Of the
linkage. due 20 the fact that the
brakes are both very close to the
rear wheels upon which they op-
crate, and because of the possibility
OF using a single drum. says a
writer in Motor World. Most en-
.sineers have been partial to the
wheel as being the proper place,
because it involves stress at the
least number Of parts and SO is con-
sidered safer. There are. however,
quite a'few who are considering
the propeller shaft, brake and one
newcomer into the ranks of manu-
facturers this year. the Duesenberg,
employs fonr-wheel brakes which
are automatically operated.
Foot Brakes on Wheels.
There is very probably q tendency
toward the Installation of the foot
or service brake on the rear wheel,
and the hand brake on the trans
mission or propeller shaft. This
has the advantage of providing two
absolutely independent brake drums.
so that in case one breaks it does
not affect the other, and further
more. puts into the hands OF the
driver a very powerful emergency
braking system. Because OF the To-
cation on the propeller shaft the
brake has the benefit of the reduc-
ton through the rear driving sys-
TEN and also OF the equalization
secured by the differentisl gears.
The propeller brake. however. has
its Disadvantages. Those most fire.
auently cited against II are the
tendency to chatter, the excessive
stresses which must be impaired to
the universal joints and rear axle
parts, and also the dificulty of dis
sipating the tremendous amount OF
heat absorbed by the small brake
drum. Naturally, the size Of the
brake drum is quite limited because
Of the location of the propeller
shaft Immediately under the floor
boards of the car. In spite of these
objections. however. by properly
designing the brake. IL has been
found to give very satisfactory
usage. particularly on the hand
brake installation. 1t is to be found
on THE Maxwell. Duesenberg, Rick =
enbacker. westcott and several 9TH
er passenger cars, and in the trucS
field is common.
wrapping Band Type.
Most of the real wheel brakes are
of the wrapping band type. because
in the wrapping principle a maxi :
mum amount of brake resistance is
secured by the action of the brake
wrapping itself up in the band.
Brake squealing Is largely due to
the concentration OF the braking
pressure. These high spots or con-
tracing points. being highly stress
ed, cause a chatter which sets up
vibration. giving the noise.
An Improvement which has been
made this year Is the increasing of
the strength in the releasing mech
anism on some OF the brakes. Brake
drag Is oten due to insufficient
strength of the releasing mechan-
ism or the releasing principles Of
the brake may not be adequate to
insure a proper release of the brake
bands from the drum when the
brake pedal is released by the drI-
yer.
Brake-actuating means are so well
known that there is not much need
for going into them in detail. Cen
orally, on the external contracting
type. there Is a pivot anchor direct
ly opposite the contracting mechan-
ism. The brake segments are formed
with eyes for the anchorage joints
or the steel bands have a fitting
which Is riveted to them to serve
the same purpose. The brake support
consists of a bracelet secured to the
rear axle or to the radius rod. The
contracting mechanism is nearly al
ways a floating bell crank lever to
the short arm of which one end OF
the brake band il connected by
means of a riveted bracket. while the
other end of the band connects
through a short link to the fulcrum
of the bell crank. The operating
rod is connected TO the long arm of
the bell crank. The short link is
bCu " lhc NHC IlCC Gnu VI NhS
brake band and passes through the
fulcrum pin. the bell crank being
forked at the lower end. A butterfly
nut Is screwed over the end of the
link and provides a convenient ad-
justment.
Locking the Adjustment.
The adjustment Is locked by the
spring surrounding the link. which
forces the arms of the bell crank
over the flat end of the wing
nut, thus preventing: it from
turning. The coil springs at the
same time help release the
band when the pressure is taken
off the brake lever. This
method. while offering a simple apd
efficient means of applying the
brakes. has also the advantage of
providing simple adjustment
means. This is general practice on
American cars.
The internal expanding brakes
are generally either cam or toggle
expanded. Practice on this point is
about evenly divided. Considering
the cam type, the internal shoes are
pivoted opposite the expanding
point. An expanding cam is placed
between the two fat surfaces or is