Unit - 5

General braking requirement

Q1) Write note on general braking system.

A1)

Requirement of braking system:

i) The brakes must the strong enough to stop the vehicle within a minimum distance in an emergency. But this should also be consistent with safety.
ii) The brakes must have good antifade characteristics i.e, their effectiveness should not decrease with constant, prolonged application e.g while descending hills. This requirements demands that coding of the brakes should be very efficient

Disc Brake:

Friction pads are flat.

Friction surface directly exposed to air cooling.

More efficiency.

Light in weight.

Better & anti fade characteristics

Frictional area of pad is less.

Drum Brake:

Friction lining are curved shape.

Friction occur internally & heat dissipate by conduction & convection.

Loss of efficiency.

Heavier in weight.

Poor anti fade characteristics.

Frictional area of pad is made.

Brakes are required to forestall the automobile inside the smallest viable distance & that is performed via way of means of changing the kinetic power of the automobile into the warmth power that is dissipated into the atmosphere.

Q2) What are the requirements of steering?

A2)

Requirement of steerage.

• The steerage mechanism need to be very accurate & smooth to handle.
• The attempt required to influence need to be minimal & need to now no longer be tiresome to the driver.
• The steerage mechanism need to additionally offer stability.
• This means that the automobile need to will be inclined to go back to its instantly beforehand function after turning.

Q3) What are the types of steering?

A3)

Types of steerage:

i) Power Steering: - It includes ah engine pushed oil pump with the with the reservoir manipulate valve & gift floor which help steerage attempt.

Ii). Adjustable Steering: - In this steerage wheel can modify the steerage perspective at convenient & circulate the wheel in preference function.

Iii) Collapsible steerage: - It is an power soaking up steerage offer protection via way of means of collapsing throughout effect shape the front cease crash. This carries with ball bearing outfitted among over lapping tube.

Iv) Center factor steerage - The association of the wheel, the front axle & stub axle. When the axis of wheel, King pin axis & vertical axis are hobby at identical factor on the identical time the street wheel makes touch with the ground. Then the development is known as nook factors steerage.

Q4) Explain elementary theory of shoe brake.

A4)

• The drum kind brake includes inner semicircular footwear, which might be covered with friction cloth matching to the inner rubbing face of the drum. The footwear are equipped on a lower back plate, additionally called a torque plate, among a pivot anchor or wedge kind abutment on the decrease shoe cease and on the higher shoe pinnacle cease via way of means of both a cam or hydraulic piston kind expander.
• During clockwise rotation of the drum, the higher guidelines of the footwear are driven aside via way of means of the expander pressure, Fe, and a ordinary inward response pressure, N, supplied via way of means of the drum, resists any shoe expansion.
• Consequently the drum slid over the shoe linings and a tangential frictional pressure Ft = iN is produced among every pair of rubbing surfaces. The friction pressure or drag at the proper hand shoe has a tendency to transport withinside the identical path because the shoe tip pressure Fe, which produces it.
• Accordingly this allows to tug the shoe onto the drum, in order that the shoe tip pressure is raised successfully above that of the unique expander pressure. This growth in shoe tip pressure above the enter expander pressure is named as fine servo, and footwear that offer this self-energizing or servo motion are called main footwear.

Q5) Write note on weight transfer.

A5)

Weight switch and cargo switch are expressions used fairly confusingly to explain awesome effects: the alternate in load borne with the aid of using one of a kind wheels of even flawlessly inflexible automobiles at some stage in acceleration the alternate in middle of mass (CoM) place relative to the wheels due to suspension compliance or shipment transferring or sloshing

In the car industry, weight switch usually refers back to the alternate in load borne with the aid of using one of a kind wheels at some stage in acceleration.

This might be greater nicely called load switch, and this is the expression used withinside the motorbike industry, whilst weight switch on motorcycles, to a lesser quantity on vehicles, and load motion on both is because of a alternate withinside the CoM place relative to the wheels. This article makes use of this latter pair of definitions. The important forces that boost up a car arise on the tires' touch patches.

Often that is interpreted with the aid of using the informal observer as a pitching or rolling movement of the automobiles frame. A flawlessly inflexible car, without suspension that might now no longer show off pitching or rolling of the frame, nonetheless undergoes load switch.

Q6) What is mean lining pressure?

A6)

Brake linings are composed of a extraordinarily gentle however hard and heat-resistant fabric with a excessive coefficient of dynamic friction (and preferably an same coefficient of static friction) generally established to a stable steel backing the use of excessive-temperature adhesives or rivets. The whole assembly (along with lining and backing) is then regularly referred to as a brake pad or brake shoe.

This approach that a pressure of one thousand Newtons at the pad will provide a ensuing brake pressure near four hundred Newtons. There are a few racing pads which have a completely excessive μ of 0.fifty five to 0.sixty two with incredible excessive-temperature behaviour.

These pads have excessive iron content material and could typically outperform some other pad used with iron discs. Though those excessive μ pads put on themselves and the discs down extra quickly, they're though a terrific fee powerful opportunity to extra exclusive/luxurious substances.

Q7) Explain heat generation.

A7)

Governing equations in disk brake machine: caliper meeting and Fig. 1b the schematic form of the disk and the pad in sliding touch is proven. As it's far proven disk is like an annulus and pad is sort of a partial annulus. The brake machine clamps the pads thru the caliper meeting through brake fluid stress withinside the cylinders.

Rotary movement of the disk reasons a sliding touch among the disk and the pad and generates warmth. For calculation of warmth era because of friction, price of dissipated warmth thru friction need to be taken into account. This is all to do with the calculation of friction pressure and price of labor performed through friction pressure.

For calculation of friction pressure, the stress distribution on the touch floor of the disk and the pad need to be determined. Here, sorts of stress distribution are taken into accounts:

Uniform pressure distribution: When the pad is new and short enough the pressure is distributed uniformly in the contact area that is:

p = pmax(1)

Uniform wear: After several braking action when the pad is rundown this type of pressure distribution is taken into account because work done by friction force grows when the radial distance increases and eventually the farther radial position is more encountered to wear and the assumption of uniform pressure distribution is no longer dominant.

Q8) What is heat generation due to friction?

A8)

Heat generation due to friction: In the contact area of brake components; the pads and the disk; heat is generated due to friction. For calculation of heat generation at the interface of these two sliding bodies’ two methods is suggested:

•At the basis of law of conservation of energy the kinetic energy of the vehicle during motion is equal to the dissipated heat after vehicle stop

•By knowing the friction coefficient, pressure distribution at the contact area, geometric characteristics of the pad and the disk, relative sliding velocity and duration of braking action one can calculate the heat generated due to friction

Q9) Explain pneumatic braking system.

A9)

In easy terms, Brakes are the element in any automobile which assist in lowering the velocity or preventing the automobile.

To observe the brakes, we must both press a pedal or pull a lever. But just assume how this transmission of pressure occurs from pedal/lever to brakes placed at wheels?

To obtain this we've got exclusive systems (Pneumatic/Air Brake) to select from relying at the requirement:

Mechanical –

Wherein metallic cables can be accountable to use the brakes at wheels, the instant you pull the brake lever.

Ex – Parking brakes of a vehicle or Rear drum brake of a motorcycle is normally operated via. Cables.

Hydraulic –

Hydraulic oil is accountable to by skip at the motive force carried out pressure via. Pedal or lever to the brake piston which in flip applies the brake on wheels.

Ex – Normal Braking gadget of a vehicle or a Disc Brake on a motorcycle.

Pneumatic –

As the phrase speaks for itself, it operates via. Air. Braking gadget preserve a excessive stress air interior it and second motive force applies brake, stress with inside the line begins off evolved dropping. This effects in making use of brakes on wheels. It will sound a piece peculiar however that is the way it works.

Q10) Explain working of pneumatic brake.

A10)

Working of Pneumatic Brake:

• Pneumatic or Air brakes perform on compressed air.
• Entire braking machine pipeline is first of all charged up with compressed air to hold gold standard stress.
• Moment motive force applies pressure on brake pedal, air stress drop initiates via. Motive force’s brake valve.
• Compressed air from auxiliary cylinder rushes in to the brake cylinder inflicting brake to get engaged.
• This is how pneumatic brakes paintings in actual time operation of brake pedal through motive force.
• This is how Parking Brake works in pneumatic braking machine of heavy vehicle.

Q11) Explain hydraulic braking system.

A11)

Hydraulic brakes use the incompressible fluid houses to actuate a braking mechanism and offer the braking components (discs, drums, pads, etc.) with pressure to interact and do away with strength from a transferring machine. Brakes fluctuate from one to the subsequent with inside the manner they interact, operate, and perform. The hydraulic fluid via hydraulic traces and forces the brake cylinders to move, actuating the braking device. Braking structures can variety in length from an easy hand lever operated brake on a snowmobile to complex, energy assisted structures.

Specifications

Performance specs to don't forget whilst choosing a hydraulic brake include, however aren't confined to:

• Torque Rating— the most torque score for the brake ought to same or exceed the application's requirement.
• Power— the most electricity score for the brake.
• Speed— the most rotary velocity score. This specification applies handiest to rotary brakes.
• Maximum Pressure— the most stress for a hydraulic brake. Shaft
• Configuration—Brake can be established in-line, parallel, or proper angle.

Q12) What are types of hydraulic brakes?

A12)

Energy may be eliminated via way of means of a brake in numerous ways. Here are a few distinct methods to braking:

Band

Band brakes are the handiest sort of brake. They have a metallic band covered with warmth- and wear-resistant friction material.

Drum

Drum brakes press footwear towards a spinning surface. They are regularly used on car rear wheels.

Disc

Disc brakes have brake pads, a calliper, and a rotor. During operation, the brake pads are squeezed towards the rotor. Disc brakes have exact warmth dissipation properties.

Cone

Cone brakes encompass a cup and a cone this is covered with a warmth- and wear-resistant friction material. During actuation, the cone is pressed towards the mating cup surface. Cone brakes aren't normally used.

Several engagement techniques are to be had for hydraulic brakes, including:

• Noncontact—braking motion is accomplished thru a non-touch era consisting of a magnetic field, eddy currents, etc. Friction—Friction among touch surfaces transmits energy. This is the maximum not unusual place sort of brake.
• Toothed—toothed touch surfaces transmit energy without slipping or warmth generation. Teeth are engaged simplest whilst stopped or strolling at a sluggish speed (< 20 rpm).
• Wrap Spring—a coiled spring wraps downward onto the rotating element. The brake is disengaged whilst the spring is uncoiled through a manipulate tang at its end.
• Oil Shear—braking motion is engaged through the viscous motion of the shearing of transmission fluid.

Q13) What are uses of hydraulic brakes?

A13)

1. Though Hydraulic Brakes are maximum acquainted to us as they're utilized in our cars, they're found in many different transportation and rolling inventory industries together with aerospace, heavy transport, marine, and off-highway.
2. Hydraulic brakes also are discovered in commercial device like conveyors, system tools, motors, pumps, robotics, and automation.
3. Hydraulic brakes are considerably less difficult to modulate than mechanical brakes; you get extra pressure added to the pads, and, as a result, extra preventing energy for the equal input. Additionally, you'll enjoy quicker and extra steady pad withdrawal upon release.

Q14) What is power brake?

A14)

Power brakes are a machine of hydraulics used to sluggish down or prevent maximum motor automobiles. It makes use of a mixture of mechanical additives to multiply the pressure implemented to the brake pedal through the motive force into sufficient pressure to actuate the brakes and prevent a car which could weigh numerous tons.

The brake pedal is hooked up to the vacuum booster that is step one of the pressure multiplication.

The booster passes the pressure to the grasp cylinder, which applies a compressive pressure to a liquid (hydraulic or brake fluid) and forces it thru the brake traces to the brake calipers.

The liquid pushes the brake calipers, which withinside the case of disc brakes, push in opposition to the brake rotor inflicting friction that slows and subsequently stops the rotation of the automobiles wheels.

Q15) Explain ABS.

A15)

ABS or often referred as anti-skid braking systems is a safety system used on different airplanes and other moving vehicles like cars, trucks, buses etc. ABS first came into existence in 1920s developed by a French researcher to assist braking on aircraft. In 1970's the modified and reformed version of ABS was presented to the commercial market. Today it is used in every car and motorcycle for steering and traction control.

ABS prevents the automobile tyres/wheels from locking up and helps in maintain the steering control during braking by keeping tractive contact with the road surface. This automated system works on two techniques which was successfully used by skilled drivers before ABS widely used. ABS follow the principle of

1. Threshold braking 
2. Cadence braking.

Fig. ABS Technology

Q16) What are main components of Antilock braking system?

A16)

The four major components of a typical anti-lock braking system (Fig 14) are:

1. Sensors - monitors how fast the wheels are spinning
2. Valves -    permits, blocks and relieve pressure on the brakes
3. Pump -      filled with fluid for applying pressure to the brake drums when needed.
4. Controller - Consist of an ECU (electronic control unit) which is the heart. It takes data from sensors and decide if pumping of the brake is required or not.

ABS works by releasing and then 'pumping' the brakes to automobile wheels in hard braking conditions. As the sensors notice that the speed of any wheel (s) is dipping significantly in comparison to other wheels, the ECU instantly sends the indication to the valves of the desired wheel(s) to reduce the pumping (brake) pressure, and the valves get shut off. After sometime, the wheels start to quicken again, sensor sends the signal to ECU, which in turn sends an indication to increase the brake pressure and open the valve and ultimately brakes are applied. This cycle keeps on repeating till brake application becomes normal.  So fundamentally, this system works in three stages:

1. Brake pedal is pressed/released
2. Speed sensors detect skidding/ locking or decrease in speed
3. Pumping the brakes