Grand Forks herald. [volume] (Grand Forks, N.D.) 1916-1955, 1919-03-10
DIFFERENTlAIS
ARE EXPLAINED
Present Type Contributes
Largely to Skidding,
Says Expert.

The motor vehicle Of today is COM
pa%ratively speaking, a highly organ
lied mechanical entity, made up OF
mechanical units that have beer de-
veloped to a greater or less condi-
ton of perfection. Many Of these
mechanical units or systems leave al
most nothing to be desired in point OF
efficiency. Others are only relatively
satisfactory n a few of them are so
backward in their course of evolution
that they might almost be termed
barbaric. Such a backward part is
the d~ifferential. The simple fact Of
the matter is that these relatively IN
developed units have served we'll
enough the purpose for which they
were installed and the engineers have
gone on to something more pressing.
However, there is little question that
after we have won the war and our
,sharpened wits are left free for
peaceful progress again, these various
backward members of the mechanism
will be improved past all knowledge.
The function Of the d%ifferential unit
is simply to compensate for necessary
differences in the speeds of the rear
wheels, under certain conditions of
operation. For instance where a a
is turning a corner, the outer wheel
must traverse a greater distance than
the inner wheel, which in a sense may
act as a pivot during this operation.
Now the differential is designed to
permit one wheel to turn more rapid
ly than the other under these cir
cumstances.
The ordinary bevel or spur gear
d~ifferential is simply. a combination
Or bevel or spur gear SO arranged as
to allow n wheel to turn independ-
emily of the other. This is accomplish
ed by using two axle shafts, one for
each wheel, the ends of these shafts
being geared indirectly to the driving.
bevel which in turn is operated by the
pinion at the end of the propeller
shaft. Pulling straight ahead and
pull equally and there is M differen-
tial action but the differential' turn
ing as a unit with the driving bowel or
ring gear. So soon as n wheel
leaves the ground due to a bump, or
as a corner is turned, or n wheel is
on slippery ground. the diferential
comes into action automatically. 1t
then transmits the greater power to
the wheel with the least traction. 1t
too efficient because it differentiates
for all differences instead of only, for
some.
The great fault of this ordinary
type of d%iffercntial is the fact that it
permits the wheel which is getting
the least traction to get the greater
part of the power. The commonest
illustration of this is the car with one
wheel stuck in a mud hole. That
wheel tends to slip and the differen-
tial allows it to absorb most Of the
power. with the result that it spins
uselessly in the slippery mud and the
car stays just where it is. II the
power were distributed equally to
both wheels, the car would readily
climb out of almost any hole it got
into. unless, Of course, neither wheel
could get traction.
Another condition which brings put
the inherent failure of the ordinary
differential is when the wheels of the
car bounce up in the air. In this case
the wheel which leaves the ground is
permitted to spin at high speed, with
the result that when it strikes the
earth again the tire receives a scrap
ing blow that is not very different
from fling off part of the tire tread.
Further, the present type Of differ
entail contributes largely to skdding,
sometimes become tragedy. When
the brakes are applied on a slippery
pavement, it is the usual thing for one
wheel to hold. while the other re-
wolves. If each wheel had equal pow
err all the time, this tendency would
be largely obviated.
Naturally some attempts have been
d to improve on the commonly
accepted type Of differential. It can
not be said that at the present time
any Of these attempts has me with