Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1917-08-12
S|MPL|F|ED. LESSONS ON
PROPER CARE OF AUTOS
Driving Mechanism Of Motor Car
Given Close Study and Explained
by Times-Dispatcll Expert.
GRowL SHOWS BAD SETTING
Indicates That Adjustment Of Bevel
Gear and Pinion in Rear Housing
Needs Attention to Prevent Break
ing-Questions and Answers.
LESSON NO. 81.
The Final Drive.

Copyright. 1917. by Frederick c.
Guerrlich.)
The driving mechanism of an auto
mobile located in the rear axle housing
Is termed the final drive. 1t comprises
a device for transmitting the power OF
the propeller shaft to the driving axles
OIL the rear wheels. which are at right
angles to the propeller shaft: and q
device. called the diferential. which
takes care OF driving the rear wheels
at tho different speeds they must re-
FoiVe when the car is making turn.
Probably the least perfected and
most unsatisfactory mechanism OF tho
entire car Is the device used for chang
Ing the direction OF the drive Of the
propeller shaft to the right angle OF tho
driving axles. In practically all pleas
ure cars this is accomplished by the
use OF bowel gear and pinion, while
In trucks, worm and worm gear are
much used.
Unless tho bevel gear and pinion arc
set just right, there Will be hum
ming" or growing" sound In the rear
axle. while II they are set improperly
to any extent they will almost surely
break.
The adjusting Of the driving pinion.
as bevel pinion is called, is, therefore, q
Job which should only be done by an
expert mechanic who has had expert
encc In this work.
When bad growing" noise comes
from the rear axle housing, the adj
1ustment Of the pnion should imme-
d!ately be looked TO. as the ''growl"
is an indication that the pinion and
gear are not set up properly.
Let US see what the bevel gear and
pinion are: why their proper adjust
ment Is 80 important. and how they arc
adjusted.
bevel gear is one used for driving
from one shaft TO another. when these
M rD1n
other. While the universal joint will
also do this. 1t can only be used when
the shafts are at but a slight angle.
so that they are bat comparatively
little out OF a straight line, while the
bevel gear can be used for driving at
any predetermined angle.
Figure ] shows u part OF a bevel
gear and its bevel driving gear, or
as the small driving gear Is termed,
pinion. a glance will show how. when
the pinton rcvolves on It's axis, It will
make the large gear revolve on It's
axis. which axis In this case Is at a
right angle TO that OF the pinion.
BY studying the gear you will OBJ
serve that because the timer ,,s .Sion of
the teeth are in 4 circle whose diameter
Is smaller than that Of the circle on
which the outer portion OF the teeth
are. that the teeth are tapered, being
wider on the outside. az as a. than on
the inSide. as at B. The Same is true
OF the spaces between tho teeth, they
also being wider on tn outside than
on the Inside. AS the teeth of the
pinion must just fit into the spaces OF
the gear. and as tho pinion spaces must
just nt the gear teeth, the spaces and
teeth OF the pinion viii also be
tapered.
1t is because the teeth are tapered
that such care must be taken In set
ting the gear and pinion.
ODyiDuSly ifSfhe piDiop ,yera cot 80
far to the right. the wide portion Of its
teeth would have to get into the mar