3. DEFINITION:
A type of brake, used in motor vehicles, in which the
braking force is transmitted from the brake pedal to the brakes
by a liquid under pressure
HISTORY:
Fred Duesenberg originated hydraulic brakes on his
1914 racing cars and Duesenberg was the first automotive
marque to use the technology on a passenger car in 1921. In
1918 Malcolm Lougheed (who later changed the spelling of his
name to Lockheed) developed a hydraulic brake system.
4. CLASIFICATIN OF BRAKES:
On the Basis of Method of Actuation
(a) Foot brake (also called service brake) operated by foot pedal.
(b) Hand brake – it is also called parking brake operated by hand.
On the Basis of Mode of Operation
(a) Mechanical brakes
(b) Hydraulic brakes
(c) Air brakes
(d) Vacuum brakes
(e) Electric brakes
On the Basis of Method of Application of Braking Contact
(a) Internally – expanding brakes
(b) Externally – contracting brakes.
5. PRINCIPLES OF HYDRAULIC BRAKING:
Hydraulic brakes work on the principle of Pascal’s
law which states that “pressure at a point in a fluid is equal
in all directions in space”.
According to this law when pressure is applied on a fluid
it travels equally in all directions so that uniform braking
action is applied on all four wheels.
9. • The master cylinder is the heart of the brake's hydraulic system.
• It converts the force exerted on the brake pedal into hydraulic pressure to apply
the brakes.
• Depressing the brake pedal moves a push rod in the master cylinder. Mounted on the
push rod are a pair of pistons (primary and secondary) in tandem (one after the other)
that exert force against the fluid in the master cylinder bore.
• The pressure created displaces fluid through the various brake circuits and lines to
each of the wheels and applies the brakes.
• Since brake fluid is incompressible it acts like a liquid linkage between the master
cylinder's pistons and the calipers and wheel cylinders.
11. • A wheel cylinder is a component in a drum brake system. It is located in
each wheel and is usually at the top, above the shoes.
• Its responsibility is to exert force onto the shoes so they can contact the drum and
stop the vehicle with friction.
13. • Brake shoes are made of two pieces of sheet steel welded together.
• The friction material is attached to the Lining table either by adhesive bonding or
riveting.
• The crescent shaped piece is called the Web and contains holes and slots in different
shapes for return springs.
• All the application force of the wheel cylinder is applied through the web to the lining
table and brake lining.
• Each brake assembly has two shoes, a primary and secondary. The primary shoe is
located toward the front of the vehicle and has the lining positioned differently than
the secondary shoe
15. • The brake drum is generally made of a special type of cast iron. It is positioned very
close to the brake shoe without actually touching it, and rotates with the wheel and
axle.
• As the lining is pushed against the inner surface of the drum, friction heat can reach
as high as 600 °F (316 °C). The brake drum must be:
• Accurately balanced.
• Sufficiently rigid.
• Resistant against wear.
• Highly heat-conductive.
• Lightweight.
16. BRAKE FLUID
Brake fluids are used to transfer force into pressure. It works
because liquids are incompressible.
• Brake fluid is subjected to very high temperatures they have high
boiling point
• brake fluid must maintain a constant viscosity under a wide range
of temperatures, including extreme cold
• Brakes fluids must not corrode the metals used inside
components such as calipers, master cylinders, etc.
• Most brake fluids used today are glycol-ether based, but mineral
oil and silicone (DOT 5) based fluids are also available.
17. OPERATION OF
A HYDRAULIC BRAKE SYSTEM
• as the brake pedal is pressed,
• a pushrod exerts force on the piston(s) in the master cylinder causing fluid from the
brake fluid reservoir to flow into a pressure chamber which results in an increase in
the pressure
• This forces fluid through the hydraulic lines toward calipers where it acts upon one
or two caliper pistons
• The brake caliper piston(s) then apply force to the brake pads. This causes them to be
pushed against the spinning rotor, and the friction between the pads and the rotor
causes a braking torque to be generated, slowing the vehicle.
18.
19. ADVANTAGES AND
DISADVANTAGES OF
HYDRAULIC BRAKES
• ADVANTAGES
I. Equal braking action on all wheels.
II. Increased braking force.
III. Simple in construction.
IV. Low wear rate of brake linings.
V. Flexibility of brake linings.
VI. Increased mechanical advantage
20. DISADVANTAGES
I. Whole braking system fails due to leakage of fluid from brake linings.
II. Presence of air inside the tubing's ruins the whole system.
