The Washington herald., 1919-10-26
H0TCHKISSD DRIVE.
.IsLITTLEkN0WN
Propulsiive Power Through
Springs and Not By
Radius Rods.

To tn average motor car owner the
term "Hotchkiss drive" means prac'
tically nothing. In fact. majority
OF them probably consider that this
indefinite something Is some type OF
arrangement OF geogs for driving the
rear wheels. Thiso nethod of drive is
becoming such &redominant factor
in the field of au<D4nobile design thai
even the car owner should under.
stand its meaning and we shall try
to outline 1t briefly.
Let us say in the beginning that
Hotchkiss drive Is not part of the
mechanism. 1t is a principle and not
a mechanical unit. Indeed II may be
described as a method of eliminating
certain parts from the cars mocha
nism. by making the springs serve
a double purpose. To do this the
springs naturally have to be strength
ened, but the gain Is obvious In sim
plicity of design, which is one OF the
principal aims of modern motor car
engineering.
This method of driving was first dis.
covered by an American back about
1902. but 1t did not make any definite
appeal to our engineers, so he took II
to France. where 1t won instant recog-
milton and has been used in French
design ever since. Now it has come
back to the land of its birth, brough,
here by cars imported from Europe
and 1t is now used on more than three.
fifths of the cars built in this country,
The simplest way to explain Hotch'
kiss drive is to say that the propulsive
power of the car is transmitted
through the springs instead Of by rad
ius rods. as used to be the rule. Fur
ther. the rear springs are called upor
to take part of the torque or twist Of
the whole rear axle assembly.
The rear axle unit is peculiarly liable
TO twisting, because OF its position and
also because of its functions. Let u:
-cxplain that when the car is being
driven straight ahead there is a GER
tain amount Of twisting in the real
axle, whenever the rate of speed is
altered. A somewhat different action
is set up when the brakes are applied
and the car is stopped. In this case
the wheels are suddenly stopped. while
the body of the car tends to continue
on in the direction it has been pur-
suing. This is simply the operation
of what is known as the law of inertia
which we need not investigate further
here. On the other hand, when the
car is started the axle has tendency
to twist forward and in cases where
the springs are unusually flexible this
movement can actually be observed
when the car is getting under way.
With the Hotchkiss drive pripciple
employed all these various twisting
tendencies are taken care of by the
10 IaGoriha6 q q
absorbing these torque movements
Then after the car is actually in mo-
ton the rear axle keeps the rest OF
the vehicle going by pushing 1t. You
see the driving wheels are on the
rear axle and these must supply the
impetus that propels the whole car.
on the springs.
The reader scarcely needs to be
told that to bear all this burden the
springs must he well designed and
constructed. The usual practice In
designing springs for Hotchkiss drire
is to make the main leaf. which is
the keystone of the arch. larger than
would otherwise be the case and also
naturally to make il of the best
available materials. The finest grades
OF alloy steel go into the making of
springs today. and no part of the
mechanism has demanded more care
full thought on the part Of our en-
Eineers and designers. AS a rule cas-
tellated nuts are usually employed
on the spring clips. the nuts being
firmly secured by cotter pins. Two
clips are generally considered enough
to distribute the twist or torque to
the spring as a whole, thereby taking
some Of the burden off the central
leaf
The car owner whose vehicle en-
bodies Hotchkiss drive should be more
careful than usual to give the spring
assembly the inspection and attention
1t needs. The clips must be kept
snugly in place. If the spring clips
become loosened the driving force may
easily break some part of the spring
the resistive power of which ha:
been weakened. 1t is the old provert
of united we stand. divided We fall. u
All the spring leaves together car
carry the load but separately they are
not strong enough.
In addition to keeping the clip.
snugly drawn up the shackle bolts OF
the springs should be systematically
fabricated. Two or three times a sea