Hudson 63 1936, Mechanical Procedure Manual

Page: 120 / 333

MECHANICAL PROCEDURE MANUAL
SECTION 9
Page 3
Printed in U. S. A. ISSUED MAY, 1937
AUTOMATIC CLUTCH
AUTOMATIC CLUTCH CONTROL
The principle of operation of the Automatic Clutch Mecha-
nism used on all Hudson and Terraplane models is the same,
however, there are detail changes which have been made to time
the engagement more accurately with the throttle operation. In
the 1937 models an electric control is incorporated to eliminate
coasting in high gear when the foot is taken from the accelerator
pedal.
AUTOMATIC CLUTCH OPERATIONS
Disengagemen t
When the cut off plunger (10) Figure 901, which is operated
by the dash control is pulled out, vacuum from the engine intake
manifold is admitted to the accelerator plunger (11) which
controls the vacuum to the power cylinder.
When the plunger is pulled out (accelerator pedal released) the
vacuum enters the front of the power cylinder so that the piston
(3 is moved forward and air enters the rear of the power cylinder
through the atmospheric check valve (6) and the air by pass (1).
The forward movement of the piston disengages the clutch.
Engagement
The accelerator plunger moves in when the accelerator pedal
is depressed, moving the radial slot (14) away from the vacuum
port, cutting off the vacuum to the power cylinder and bringing
the longitudinal slot (15) in line with the port so that air can enter
the front of the power cylinder.
The air entering the front of the cylinder permits the clutch
springs to pull the piston backward forcing air out of the rear of
the cylinder through the air by pass (1) in the piston rod (2). It
will be noted that the air by pass extends only to within about
1-1/2" of the piston so that it is closed as soon as its inner end
enters the piston rod seal (4) in the cylinder head.
Up to this point the piston is allowed to move rapidly to bring
the clutch plates to the point where they are just ready to begin
to engage.
Now since the air by pass (1) is closed and the atmospheric
check valve (6) is held against its seat by air pressure from inside
the cylinder, the only means of escape for the air is through the
bleed line leading from the front of the cylinder to the cushion
control or pendulum valve (19).
When the car is at rest or accelerating normally the pendulum
(14) hangs straight down and holds the cushion control valve
radial slot in line with the ports so that air can pass through to a
port communicating with the cylinder in which the accelerator
plunger (11) operates. The air passes from this port into the
taper slot (16) and escapes. The further the accelerator plunger
is pushed in, the deeper the portion of the taper slot in commu-
nication with the air port so that the rate of air bleed is in-
creased as the throttle is opened giving slow clutch
engagement on low throttle and rapid engagement on open
throttle.
If the engagement is too rapid on open throttle tending to
jerk the car, the pendulum swings backward partially or com-
pletely closing the air bleed and arresting the clutch engage-
ment and insuring a smooth get away.
Details of Control
A comparison of the earlier design shown in Figure 901
with the 1937 design shown in Figure 903 will show the detail
differences in the control valves and particularly the air filter
in the 1937 design which prevents dirt entering the vacuum
chamber during engagement of the clutch.
The solenoid cut off valve is also clearly shown in Figure
903.
Adjustment
There are three major adjustments which must always be
performed in the following order.
1. Piston Rod Length.
2. Throttle Rod Lash.
3. Cushion Control Valve Spring Pressure.
Purpose of Adjustments
1. The piston rod length is important as the inner end of the air
by-pass (1) must enter the piston seal (4) just as the clutch plates
are about to engage and arrest the fast motion of engagement of
the clutch. If the piston rod is too long the clutch will grab and
tend to stall the engine. If too short, the engagement will be slow
and the engine will race before the clutch engages. The piston rod
length must be adjusted occasionally to compensate for clutch
facing wear.
2. The Throttle Rod Lash (lost motion) has a two-fold purpose:
First, it permits moving the accelerator plunger in to the point of
cutting off the vacuum from the intake manifold so that the clutch
may be brought up to the point of engagement before the throttle
starts to open and the engine speeds up. Second, it makes it
possible to drive the car even at idle speed without the clutch
disengaging.
Too little lash will cause the engine to speed up before the
clutch engages and will also make it impossible to drive the car at
idle speed.