STEERING GEARS, TYPE, CONSTRUCTION
OPERATION AND CARE
The steering mechanism used in automobile construction is arranged to
operate independent of the axle, or in other words the wheels turn on a
pivot, or knuckle, held between the yoked ends of the axle. A spindle
or axle extends outward from each steering knuckle to accommodate the
wheels. A set of short arms extend to rear of the steering knuckles; an
adjustable spacer bar, commonly called a tie or spread rod, serves as
the connection between the arms. The arms incline slightly toward each
other; which causes the inside wheel to turn on a shorter angle than
the outside wheel when turning a corner. Another steering arm carrying
a ball at the outer end, describes a half circle over the axle, and
is attached to either the spread rod arm or the steering knuckle. An
adjustable rod, or drag-link, carrying a ball socket at each end serves
as the connection between the steering arm extending from steering gear
and the half circle arm of the knuckle. To adjust wheels see chapter on
“Wheels and Axle Alignment.”
=Steering Gear Types.=--Three types of steering gears are commonly used
by automobile manufacturers. They are namely, the worm and sector, worm
and nut, and rack and pinion types.
Fig. 135 shows the construction and operation of the worm and sector
type. The lower end of the steering shaft carries a worm gear which
meshes with the sector gear supported by a separate shaft. The sector
has a ball arm extending downward, which moves in a forward and
backward direction when the steering shaft is turned.
[Illustration:
Steering Wheel
St. Column
Worm
Sector
Spark
Throttle
Frame
Fig. 135. Worm and Sector Steering Gear]
=Adjusting the Worm and Sector Type of Steering Gear.=--An eccentric
bushing is provided to take up play between the worm and sector. This
adjustment is made by driving the notched cone to the right to take out
play, and to the left to slack up or take out stiffness.
Fig. 136 shows the worm and nut type of steering gear. This type
of steering gear as well as the worm and sector, is called the
irreversible steering gear, which means that no reverse action takes
place, or is present at the steering wheel, should one of the front
wheels encounter a stone in the road, or drop into a deep rut. The
worm and nut type consists of a double armed and pivoted steering arm.
Each arm carries a ball. The drag link socket is attached to the ball
on the lower arm while the ball on the upper and shorter arm fits in a
socket in the nut through which the worm on the steering shaft passes.
This nut is threaded to fit the worm which passes through it and moves
up and down on the worm according to the direction which the steering
wheel is turned. The housing of this type of steering must be well
packed with a light cup or graphic grease to prevent the screw or worm
from binding, which will make steering difficult and tiresome.
[Illustration:
Steering Column
Worm Screw
Nut
Pivot
Frame
Drag Link
St. Arm
Fig. 136. Worm and Nut Type Steering Gear]
[Illustration:
Steering Shaft
Ball
Gear
Housing
Sliding tooth Shaft
Fig. 137. Rack and Pinion Type Steering Gear]
Fig. 137 shows the rack and pinion type of steering gear. This type of
steering gear is used on a few of the lighter weight cars and is not
as dependable owing to a reverse action through the steering mechanism
when an obstruction is encountered by one of the front wheels. This
type of steering device consists of a solid shaft with the steering
wheel keyed to the upper end.
A small spur gear is keyed and locked to the lower end, and meshes
with a horizontal toothed shaft which slides inside of a housing. The
connection between the steering gear and the steering knuckles is made
by a short rod or drag link carrying a split ball seat on each end.
One end of the drag link socket is fitted to a ball on the end of the
horizontal toothed shaft, while the socket on the other end is fitted
to a ball on the upper end of the bolt which connects the tie rod and
knuckle.
=Steering Gear Care.=--Steering gears should be closely adjusted. The
housing should be packed with a medium hard oil or graphite grease at
least once in every thousand miles that the car is driven. All bolts
and nuts connecting the different parts of the steering gear should be
regularly inspected and kept in a perfectly tight condition.
[Illustration: Fig. 138. Steering Wheel]
Fig. 138 shows the location of the spark and gas control levers which
usually operate on a quadrant on the upper side of the steering wheel.
The short lever always controls the spark, which may be advanced or
retarded by moving it. The long lever is attached to the carburetor,
and controls the speed of the motor by regulating the volume of gas
vapor supplied to the motor.