Hydralic Brakes Flashcards
What characteristics dose brake fluid have to do?
Low viscosity Compatibility with rubber components Must not chemically react with the rubber seals and metals High boiling point Low freezing point Fluid compatibility Resistance to chemical ageing
Main disadvantage fo brake fluid?
It’s hygroscopic. This means that is absorbs moisture from the air
What enables free play to be set between push rod and master cylinder?
Adjustable push rod
Why is free play important?
Without free play the brakes may not release fully
Why is a check valve fitted to a basic single piston barrel type master cylinder?
To allow florid in both directions depending on wether the brakes are applied or released
What is the biggest disadvantage of a single piston barrel type master cylinder?
And how do you prevent this?
If there was a break in the brake pipe, braking ability will be lost
To prevent this the braking system was designed know as a divided line braking circuit
What are the 3 commonly used divides?
Front/rear split
X split
L split
How dose the pressure differential warning indicator work?
When the pressure between the two lines of a split systems is unequal
Pressure drops on line A, allowing side B to push piston across. Raising the ball to activate the sensor
What are the characteristics of brake pipes?
Narrow bore
Usually made of steel
Seamless to cope with operational pressures
2 common types of wheel cylinders?
A double acting type
A single acting type
Say information about a double acting type?
Bolted to the backplate
Used on a leading/trailing show set up
Only one required
Contains 2 pistons that move outwards when pressurised
Hydraulic fluid comes in and pushed the pistons out
Say information about a single acting cylinder?
Bolted to backplate
Used in a twin leading shoe set up
Contains single piston that is pushed out by hydraulic pressure
What is the purpose of the show adjusters?
And why is it needed
To ensure that shoes sit as close to drum without binding so that minimum pedal movement is required to apply brakes
When friction lining wears due to use
When sitting up brakes after they have been worked
What are the 3 designs of shoe adjusters?
Snail cam
Wedge and tappets
Screwed plug type
What are the 2 main variants of automatic adjusters?
One that works off the foot brake
One that works off the handbrake
Why are brake pad and discs for favourable for heat reduction?
Hot spot it localised
Larger area is exposed to the atmosphere - improving heat dissipation
What are the 2 types of brake pad and discs?
Solid or vented type
How does the vented type brake disc dissipate heat?
Directs air through the centre of the disc
Increases the surface area exposed to the atmosphere
What does the groove in the brake pad allow?
Dust to escape
What do some pads incorporate?
Wear indicator that illuminates a light in the cab
Where are the pads housed?
Brake callipers
What does the seal between the piston and cylinder do?
Prevents brake fluid leaking passed the piston
What does the dust shield do?
Prevents an ingress of dirt and water
Which could damage or corrode the pistons or cylinder
What is the area behind the piston known as?
Fluid chamber
