SECTION M THE BRAKING SYSTEM
GENERAL DESCRIPTION
The braking system consists of four Dunlop calliper type disc brakes hydraulically controlled by means
of a foot-operated master cylinder
Steel pipe lines, unions, and flexible hoses convey the hydraulic pressure from the master cylinder to
each. wheel cylinder.
The cable-actuated hand brake mechanism is entirely separate in operation from the hydraulic system
and operates on the rear wheels only. Each brake consists of two carriers to which friction pads are
riveted. The carriers are mounted on the top of the rear callipers, one each side of the disc, by means
of hinge bolts.
BRAKE UNITS
Each wheel brake unit comprises a hub-mounted disc rotating with the wheel and a braking unit rigidly
attached to the axle at the rear and to the swivel pin at the front. The brake unit consists of a calliper
which straddles the disc and houses a pair of rectangular friction pad assemblies. Cylinder blocks
bolted to the outer faces of each calliper accommodate piston assemblies keyed to the friction pad and
securing plate assemblies. A spigot formed on the outer face of each piston locates in the bore of a
backing plate with an integral boss grooved to accommodate the collar of a flexible rubber dust seal.
When the piston is assembled to the cylinder block the seal engages a lip on the block face and so
protects the assembly from intrusion of moisture and foreign matter. The central blind bore of the
piston inner face accommodates the end of a retractor pin and its friction bush. A piston seal is located
between the piston inner face and a plate secured to the piston by peen-locked screws. The piston
assembly when pressed into the cylinder bore locates on the retractor pin assembly, which is peened
into the base of the cylinder bore. This assembly comprises a retractor stop bush, two spring washers,
a dished cap, and the retractor pin; it functions as a return spring and maintains the brake-off working
clearance of approximately .008 to .010 in. (.203 to .254 mm.) between the pads and the disc
throughout the life of the pads.
MASTER CYLINDER
The components of the master cylinder are housed within the bore of a cylinder body with an integral
reservoir. The reservoir is fitted with a detachable cover which incorporates the filler orifice and is
secured by means of six bolts and spring washers. A fluid-tight joint is maintained by a cork gasket
between the cover and reservoir faces. The enclosed end of the cylinder is bored to provide
communication between the reservoir and the cylinder; a housing for an outlet connection is provided
by an internally threaded boss integral with the cylinder. Formed around the opposite end of the
cylinder is a flange with two holes for the master cylinder attachment bolts. In the unloaded condition a
spring-loaded piston carrying a rubber 'O' ring in a groove is held against the underside of a dished
washer retained by a circlip at the head of the cylinder. A hemispherically ended push-rod seats in a
similarly formed recess at the head of the piston. The head of the master cylinder is shrouded by a
rubber dust excluder, the lip of which seats in a groove in the cylinder body.
A cylindrical spring support is fitted around the inner end of the piston and a small drilling in the end of
the support is engaged by the stem of a valve. The larger diameter head of the valve is in a central
blind bore in the piston. The valve passes through the bore of a vented spring support and protrudes
into the fluid passage which communicates with the reservoir. Interposed between the spring support
and an integral flange formed on the valve is a small coiled spring. A rubber seal is fitted between the
end of the cylinder body and the underside of the valve flange. This assembly forms a recuperation
valve which controls fluid flow to and from the reservoir.
When the foot pedal is in the off' position the master, cylinder is fully extended and the valve. is held
clear of the base of the cylinder by the action of the main spring. In this condition the master cylinder is
in fluid communication with the reservoir, thus permitting recuperation of any fluid loss sustained,
particularly during the priming and bleeding operation of the brake system.
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General