Frequently asked questions for Braking System of an automobile

Q. 1. What is the purpose of brake shoe adjustor?

Ans. The purpose of adjustor is to compensate the wear of brake leather due to regular use of vehicle.

Q. 2. Define servo Brakes?

Ans. Mechanism which assist the driver’s effort for applying brakes is called servo mechanism. Servo means self energization. Servo Brakes generally used when vehicle load is above 3 tonnes.

Q. 3. What are different mechanism of Brake actuation.

Ans. Generally following are the actuation methods:

(a) Mechanical brakes

(b) Hydraulic brakes

(c) Electric brakes

(d) Vacuum brakes

(e) Air brakes.

Q. 4. What is fading of Brakes?

Ans. Fading of brakes means that friction is decreased between brake drum and brake lining due to regular use of brake.

Q. 5. What do you mean by bleeding of Brakes?

Ans. Bleeding means to drive out air from braking system. Because if air is entered into braking system their is no actuation of brakes.

Q. 6. What are the basic requirement for braking fluid?

Ans.

1. It should have high boiling temperature.

2. Viscosity of braking fluid should be less.

3. Brake fluid should not act as corrode agent to component which comes into contact.

Q. 7. Comparison between drum and disk brake.

Ans.

1. Drum brakes are heavier than disk brake.

2. Less fading of brake lining takes place in disk brake as compared to drum brakes.

3. In disk brakes uniform wear of friction lining as compared to drum brakes.

4. Disk brakes are more efficient than drum brakes.

 Q. 8. What is the locking of wheel during braking?

Ans. When the braking force is more than force of adhesion then wheel is stopped and start slipping on the road. The stopping of wheel by braking is called locking.

Q. 9. Which factors generally effect braking.

Ans.

1. Radius of brake drum and diameter of wheel.

2. Area of brake lining and amount of pressure applied.

3. Coefficient of friction.

Q. 10. Write few advantages of hydraulic system of braking.

Ans

1. There is less friction in hydraulic system of braking because there are less joints as compared to mechanical brakes.

2. System is self lubricating.

3. In hydraulic system equal pressure is in every circuit.

4. System is more flexible than mechanical system.

Q. 11. What is a leading shoe?

Ans. A leading shoe is that whose tip is dragged along the drum even when their is no brake force. Due to this reason leading shoe fade more than trailing shoe.

Q. 12. What is the function of brake value?

Ans. Function of the brake value is to control the intensity of the braking system in air brakes. It is operated by either foot treadle or by push rods linkage.

Q. 13. What do you understand by brake chamber?

Ans. It is a chamber installed on each wheel to connect pressure energy of compressed air into useful mechanical energy for proper application of brakes.

Q. 14. What are the trouble shooting in brake system?

Ans.

1. Loss of efficiency in braking:

(a) Brake lining does not work properly if oil is entered into brake drum.

(b) Due to defective master cylinder, which need overhauling.

(c) If air enters into braking system, braking application does not work properly.

(d) Brake lining are fade due to regular use or worn out friction lining.

2. Brakes overheating: Overheating of brakes occur while we drive a vehicle ascending down the hill or due to faulty binding material used for brakes binding.

Q. 15. Write short note on disc brake.

Ans. Disc brake consist of cast Iron disc bolted on the hole of wheel and it is housed in stationary housing called caliper. The caliper is connected to stationary part of the vehicle, like the stub axle and is cast in two parts, each part have a piston. In disc brake each piston and disc there is friction, pad held in position by retaining pairs, spring plate etc. There are passage for fluid to enter or leave each housing. This passage is also connected for bleeding when brakes are applied friction pads.

Q.16. What are the basic characteristics of brake fluid?

Ans.

1. Oil point: Due to high temperature during the braking applications brake

fluid should have high boiling point, to avoid vapour formation. Boiling point should be generally around 25O-3OOC.

2. Viscosity: Due to variations in weather conditions from very cold to hot it becomes imperative that the viscosity of the brake fluid should vary little with temperature to keep optimum flow conditions. So viscosity should be such that, flow occur in pipes easily without any temperature variations.

3. Lubrications properties : Brake fluid should have good lubrication properties so that proper lubrications of braking components (e.g. master cylinder) is done.

Q. 17. How can you classify the brakes ? Explain in details hydraulic brake system with neat diagram?

Ans. Brakes can be classified according to following considering the points:

(a) Purpose

(b) Location

(c) Construction

(d) Method of actuation

(e) Enter braking effort

(a) Purpose : Brakes can be applied to following ways to vehicle while in motion or in steady condition, mean during running condition if we applied brakes are called service brakes. But if we applied during parking or hold the vehicle in slop way are called packing brakes.

(b) Location : Brakes can be applied either at transmission or at the wheels. Wheel brakes are good in heat dissipation because energy wheel has separate brake drum which increases surface area and also quick heat dissipation. In automobiles wheel brakes are generally used.

(c) Construction : Generally two types of brakes are used. One is drum brakes and another is disk brakes.

(d) Method of actuation : Following are the ways of actuation.

(a) Mechanical brakes

(b) Hydraulic brakes

(c) Vacuum brakes

(d) Electric brakes

(e) Air brakes.

(e) Enter braking effort Some times due to heavy loaded vehicles are provided with outside power for application of brakes which are helpful for drivers to apply brakes are called servo brakes or power assisted brakes.

Hydraulic brakes : Most of the cars today use hydraulic brake system on all the wheels with additional hand brake to stop rear wheel movement. Main part of hydraulic system is a master cylinder which contains a braking fluid. It is well connected with four wheels by steels pipes, unions and flexible houses. Take the example of Ambassador car in which both front wheel has separate cylinders. On each brake shoe, whereas in rear wheels. There is only one cylinder which

operate both shoes. In hydraulic brake system is so designed that a small pressure of 50 kPa is maintained in all pipes times. So that cups of wheel cylinder are expanded always. This system prevents air entering into wheel cylinders while releasing the brake.

Master cylinder: It is called heart of hydraulic base system. It contains two main chambers, fluid reservoir and another is compression chamber in which piston operates. Fluid chamber which provides the fluid for braking when we apply the brakes with foot pedal. Fluid chamber compensate the fluid volume in pipeline due to any leakage or any temperature variation. To prevent leakage there are two rubber seals on both end of the piston in compression chamber. A rubber boot is provided at one end of push rod to present any dirt entering into cylinder. In brake line there is a fluid check value with rubber cup inside in the compression chamber, Main purpose of fluid check value is to maintained residual pressure in brake lines even when brakes are released. In primary seal side there are number of holes on the piston head. Two holes are connected to reservoir to the compression chamber. Size of smaller holes is about 7mm and it is also called compensation part/Byepars second hail is called recuperation port! intake. To keep fluid at atmospheric pressure their is a vent in the cap. When push rod is operated with links it actuate the piston and further pressure is directed toward pressure lines which apply brakes on the wheels when brakes pedal is released spring pressure in master cylinder push the piston in extreme position. This pressure of spring some times delay the return fluid from lines into compression chamber again. This condition cutes vacuum in compression chamber but is destroyed immediately by intake port in master cylinder which forces fluid into piston which deflects the rubber cup and enters the compression chamber destroying the vacuum.

Q. 18. What are the problems occurring in Braking system and what are their remedies?

Ans.

1. Brakes binding:

(a) To avoid brakes binding anchor pin should be lubricated at regular interval.

(b) Brake shoe retracting spring should be replaced with new one after regular interval.

(c) In hydraulic brakes by-pass port should be proper cleaned with compressed air and fresh fluid is filled in master cylinder, it should never be cleaned with wire drill.

(d) A hole on the master cylinder is to be cleaned.

(e) Brake shoe of vehicle for particular wheel may be adjusted so that dragging of vehicle is avoided.

2. Brake judder: It may take place due to wrong brake adjustment which may be corrected by proper fitting of brake lining by replacing old loose rivets with new one. In general conditions whole brake lining is replaced.

3. Hand brake Ineffective : This problem occurs when starching of operating cable is not properly adjusted. This arrangement comes with nut at one end which cause switching of wire.

4. Vehicle pulling one side:

(a) Some time dissimilar lining of brake shoe is fitted with different wheels. This problem is avoided by replacing with similar lining on all wheels.

(b) Some times dust enters into the brake drum, this also cause pulling of vehicle into one side. This problem is avoided by cleaning the drum.

(c) Some times oil or grease enters the brake drum which puts more load on clean linings. This problem is rectified by replacing greasy lining with dry lining.

5. Graffing brakes : When brakes are to sensitive, following types of problem occur due to reasons.

(a) Back plate may be loose, which should be tightened.

(b) Some time brake lining is greasy due to oil leakage should be replaced.

(c) If brake shoes- are not properly adjusted it should be adjusted after regular interval of time.

(d) Some time brake drum have a problem, it should be replaced with new brake drum.