INNER
CORE
CORE
CORE
NUT
TIP
TIP
CASING
NUT
FERRULE
FERRULE
ASf06083
Figure 6-83.--Speedometer and tachometer drive shaft.
tachometer may be driven either by a flexible shaft or
(frequently on the same instrument) records distance
by electrical means. The type that uses a flexible shaft is
traveled. The speedometer may be driven either by a
driven, through the shaft, from the vehicle generator,
flexible shaft or by electrical input. The type that uses a
camshaft, or distributor shaft. The tachometer driven by
flexible shaft has a set of gears in the vehicle
electrical means is comprised of two separate units, a
transmission. This set of gears drives the flexible shaft,
generator (or transmitter) and an indicator, con-
and the flexible shaft, in turn, drives the rotating part of
nected by electrical wires. Many tachometers are
the speedometer and the gears of the odometer. The
self-contained units operated by voltages from the
gears are designed for the particular vehicle model and
negative side of the ignition coil. An hour meter is often
take into consideration the tire size and rear axle ratio.
incorporated in the tachometer to record operating
The flexible shaft consists of an outer casing and an
time.
inner drive core (fig. 6-83). The speedometer driven by
electrical means is comprised of two separate units, a
Even though the internal parts of the various
generator (or transmitter) and an indicator, connected
instruments differ in construction and appearance, they
by electrical wires.
all incorporate the same basic components and operate
on the same principles.
The tachometer (fig. 6-82, view B) is ordinarily
used to indicate vehicle engine speed. It is similar to the
SPEED INDICATOR.--The speed-indicating
speedometer, except that the face dial indicates
portion of a speedometer (fig. 6-84) or tachometer of
revolutions per minute instead of miles per hour. The
MAGNET
FIELD
PLATE
SPEED
HAIRSPRING
CUP
ASf06084
Figure 6-84.--Sectional view of indicating portion of the speedometer.
6-68
