Advantages:
• Improves handling by reducing roll, sway, and dive
• Reduces aeration offering a greater range of control over a wider variety of road conditions as compared to non-gas units
• Reduced fade – shocks can lose damping capability as they heat up during use. Gas-charged shocks could cut this loss of performance, called fade
B. Twin Tube – PSD Design
Ride engineers had to compromise between soft valving and firm valving. With soft valving, the fluid flows more easily. The result is a smoother ride, but with poor handling and a lot of roll/sway. When valving is firm, fluid flows less easily. Handling is improved, but the ride can become harsh.
With the advent of gas charging, ride engineers were able to open up the orifice controls of these valves and improve the balance between comfort and control capabilities available in traditional velocity sensitive dampers.
A leap beyond fluid velocity control is an advanced technology that takes into account the position of the valve within the pressure tube. This is called Position Sensitive Damping (PSD).
The key to this innovation is precision tapered grooves in the pressure tube. Every application is individually tuned, tailoring the length, depth, and taper of these grooves to ensure optimal ride comfort and added control. This in essence creates two zones within the pressure tube.
The first zone, the comfort zone, is where normal driving takes place.
The second zone, the control zone, is utilized during demanding driving situations.
Advantages:
• Allows ride engineers to move beyond simple velocity sensitive valving and use the position of the piston to fine-tune the ride characteristic.
• Adjusts more rapidly to changing road and weight conditions than standard shock absorbers
• Two shocks into one – comfort and control
C. Twin Tube -ASD Design (Reflex )
A new twist on the comfort/ control compromise is an innovative technology which provides greater control for handling while improving ride comfort called Acceleration Sensitive Damping (ASD).
This technology moves beyond traditional velocity-sensitive damping to focus and address impact. This focus on impact is achieved by utilizing a new compression valve design. This compression valve is a mechanical closed-loop system, which opens a bypass to fluid flow around the compression valve.
Advantages:
• Control is enhanced without sacrificing driver comfort
• Valve automatically adjusts to changes in the road condition
• Reduces ride harshness
2. Mono-tube design (Standard Types)
These are high-pressure gas shocks with only one tube, the pressure tube. Inside the pressure tube, there are two pistons: a dividing piston and a working piston. The working piston and rod are very similar to the twin-tube shock design. The difference in actual application is that a mono-tube shock absorber can be mounted upside down or right side up and will work either way. In addition to its mounting flexibility, mono-tube shocks are a significant component, along with the spring, in supporting vehicle weight. Another difference you may notice is that the mono-tube shock absorber does not have a base valve. Instead, all of the control during compression and extension takes place at the piston.
During operation, the dividing piston moves up and down as the piston rod moves in and out of the shock absorber, keeping the pressure tube full all times.
Advantages:
• Can be mounted upside down, reducing the unsprung weight
• May run cooler since the working tube is exposed to the air
• Original equipment many import and performance domestic passenger cars, SUV and light truck applications
• Improves handling by reducing roll, sway, and dive
• Reduces aeration offering a greater range of control over a wider variety of road conditions as compared to non-gas units
• Reduced fade – shocks can lose damping capability as they heat up during use. Gas-charged shocks could cut this loss of performance, called fade
B. Twin Tube – PSD Design
Ride engineers had to compromise between soft valving and firm valving. With soft valving, the fluid flows more easily. The result is a smoother ride, but with poor handling and a lot of roll/sway. When valving is firm, fluid flows less easily. Handling is improved, but the ride can become harsh.
With the advent of gas charging, ride engineers were able to open up the orifice controls of these valves and improve the balance between comfort and control capabilities available in traditional velocity sensitive dampers.
A leap beyond fluid velocity control is an advanced technology that takes into account the position of the valve within the pressure tube. This is called Position Sensitive Damping (PSD).
The key to this innovation is precision tapered grooves in the pressure tube. Every application is individually tuned, tailoring the length, depth, and taper of these grooves to ensure optimal ride comfort and added control. This in essence creates two zones within the pressure tube.
The first zone, the comfort zone, is where normal driving takes place.
The second zone, the control zone, is utilized during demanding driving situations.
Advantages:
• Allows ride engineers to move beyond simple velocity sensitive valving and use the position of the piston to fine-tune the ride characteristic.
• Adjusts more rapidly to changing road and weight conditions than standard shock absorbers
• Two shocks into one – comfort and control
C. Twin Tube -ASD Design (Reflex )
A new twist on the comfort/ control compromise is an innovative technology which provides greater control for handling while improving ride comfort called Acceleration Sensitive Damping (ASD).
This technology moves beyond traditional velocity-sensitive damping to focus and address impact. This focus on impact is achieved by utilizing a new compression valve design. This compression valve is a mechanical closed-loop system, which opens a bypass to fluid flow around the compression valve.
Advantages:
• Control is enhanced without sacrificing driver comfort
• Valve automatically adjusts to changes in the road condition
• Reduces ride harshness
2. Mono-tube design (Standard Types)
These are high-pressure gas shocks with only one tube, the pressure tube. Inside the pressure tube, there are two pistons: a dividing piston and a working piston. The working piston and rod are very similar to the twin-tube shock design. The difference in actual application is that a mono-tube shock absorber can be mounted upside down or right side up and will work either way. In addition to its mounting flexibility, mono-tube shocks are a significant component, along with the spring, in supporting vehicle weight. Another difference you may notice is that the mono-tube shock absorber does not have a base valve. Instead, all of the control during compression and extension takes place at the piston.
During operation, the dividing piston moves up and down as the piston rod moves in and out of the shock absorber, keeping the pressure tube full all times.
Advantages:
• Can be mounted upside down, reducing the unsprung weight
• May run cooler since the working tube is exposed to the air
• Original equipment many import and performance domestic passenger cars, SUV and light truck applications
VALVE TRAIN: COMPONENTS, TYPES AND THEIR FUNCTION
The main function of the valve train, as indicated by its name, is to control the opening and closing of the valves and, for older models, the fuel output of the injectors. Most of the heavy-duty diesel engines we work with are 4 valve engines, meaning there are four valves in each cylinder: 2 intakes and 2 exhaust. The valve train uses different components based on the type, push on or lift up from the valves, allowing air into and out from the cylinder. In the middle of all the valves is the injector, which will be pushed down on to inject fuel into the cylinder. All of the timing for this process is incredibly precise. Newer engines use electrical signals to cue the injector, rather than the mechanical valve train, which makes that process even more precise.
Most new engines have overhead cam assemblies. Other designs locate the camshaft lower in the engine and use push rods to move valve assemblies. The camshaft is rotated by a timing belt, timing chain or direct gear.
VALVE TRAIN COMPONENTS
The valve train can have many components. The following are the most common components in the valve train. Depending on the type of engine, there may be varying quantities of the parts listed below or the engine may not contain all of the parts listed.
1. Camshaft
The camshaft is a long shaft that goes through the head or the block of the engine, depending on what type of engine it is. There are lobes along the length of the shaft positioned differently. The profile of the lobes has an egg-shape to them. The dimensions of these lobes are what determines the amount of lift. The more lift, the longer the valves stay open, which allows more air into the cylinder.
2. Camshaft Followers
A cam follower is a type of bearing that follows along the lobes of a camshaft as it rotates, providing a low-resistance surface for the lobe to push up against. A follower is also called a lifter, and sometimes a tappet. There are several types of cam followers, whose configurations generally depend on how they mount to their mating part. They will be used when the cam is in the block, rather than being overhead.
3. Push Rods
Pushrods are one of those parts that are not always used in a diesel engine. They will also only be used when the cam is in the block and not overhead. A push rod is a rod that pushes up on the rocker arm. It will move depending on the movement of the camshaft follower. Another job of the pushrod is to conduct oil up to the cylinder head.
4. Rocker Arms
A rocker arm is a pivoting lever that pushes on the valve stem. Rocker arms will sometimes be called rocker levers, or just rockers. Depending on the type of valve train, the rotating camshaft lobes will either push directly on the rocker arm, or on the pushrods, which will conduct the motion up to the rocker arm. In an overhead cam engine, the cam follower is built into the rocker arm in the form of a roller.
5. Rocker Shafts
Rocker shafts are simply the shafts that the rockers are on. It’s this shaft that is the pivot point for the rocker arms. The shaft also conducts oil to the various rocker arms.
6. Valve Bridges
Valve bridges are also sometimes called valve yokes. Bridges allow a single rocker to actuate multiple valves. It has a stem or bridge that sits on both valve stems, so that when the rocker is pressed down, the valve stems get pressed down as well.
7. Valves
A valve is composed of two major sections, the valve head, and the valve stem. The head of the valve is what allows air into and out of the cylinder. The stem is what gets pressed on by the rest of the valve train. At the end of the stem are grooves that keepers will fit into to hold the valve in place. Some engines have only two valves per cylinder, and some have four. The more common number in the heavy-duty diesel market is four. These are split evenly between the intake and exhaust valves.
The main function of the valve train, as indicated by its name, is to control the opening and closing of the valves and, for older models, the fuel output of the injectors. Most of the heavy-duty diesel engines we work with are 4 valve engines, meaning there are four valves in each cylinder: 2 intakes and 2 exhaust. The valve train uses different components based on the type, push on or lift up from the valves, allowing air into and out from the cylinder. In the middle of all the valves is the injector, which will be pushed down on to inject fuel into the cylinder. All of the timing for this process is incredibly precise. Newer engines use electrical signals to cue the injector, rather than the mechanical valve train, which makes that process even more precise.
Most new engines have overhead cam assemblies. Other designs locate the camshaft lower in the engine and use push rods to move valve assemblies. The camshaft is rotated by a timing belt, timing chain or direct gear.
VALVE TRAIN COMPONENTS
The valve train can have many components. The following are the most common components in the valve train. Depending on the type of engine, there may be varying quantities of the parts listed below or the engine may not contain all of the parts listed.
1. Camshaft
The camshaft is a long shaft that goes through the head or the block of the engine, depending on what type of engine it is. There are lobes along the length of the shaft positioned differently. The profile of the lobes has an egg-shape to them. The dimensions of these lobes are what determines the amount of lift. The more lift, the longer the valves stay open, which allows more air into the cylinder.
2. Camshaft Followers
A cam follower is a type of bearing that follows along the lobes of a camshaft as it rotates, providing a low-resistance surface for the lobe to push up against. A follower is also called a lifter, and sometimes a tappet. There are several types of cam followers, whose configurations generally depend on how they mount to their mating part. They will be used when the cam is in the block, rather than being overhead.
3. Push Rods
Pushrods are one of those parts that are not always used in a diesel engine. They will also only be used when the cam is in the block and not overhead. A push rod is a rod that pushes up on the rocker arm. It will move depending on the movement of the camshaft follower. Another job of the pushrod is to conduct oil up to the cylinder head.
4. Rocker Arms
A rocker arm is a pivoting lever that pushes on the valve stem. Rocker arms will sometimes be called rocker levers, or just rockers. Depending on the type of valve train, the rotating camshaft lobes will either push directly on the rocker arm, or on the pushrods, which will conduct the motion up to the rocker arm. In an overhead cam engine, the cam follower is built into the rocker arm in the form of a roller.
5. Rocker Shafts
Rocker shafts are simply the shafts that the rockers are on. It’s this shaft that is the pivot point for the rocker arms. The shaft also conducts oil to the various rocker arms.
6. Valve Bridges
Valve bridges are also sometimes called valve yokes. Bridges allow a single rocker to actuate multiple valves. It has a stem or bridge that sits on both valve stems, so that when the rocker is pressed down, the valve stems get pressed down as well.
7. Valves
A valve is composed of two major sections, the valve head, and the valve stem. The head of the valve is what allows air into and out of the cylinder. The stem is what gets pressed on by the rest of the valve train. At the end of the stem are grooves that keepers will fit into to hold the valve in place. Some engines have only two valves per cylinder, and some have four. The more common number in the heavy-duty diesel market is four. These are split evenly between the intake and exhaust valves.
8. Valve Springs
The camshaft creates an upward force that acts on the rocker arm, which in turn pushes the valve down. But as the cam rotates around, it does not pull the pushrod or rocker arm back with it. That’s why there is a valve spring to create force in the opposite direction and close the valve. The spring will hold the valve closed until the lobe of the camshaft comes around with a greater force and pushes it down.
9. Timing Belt:
A timing belt instead of a timing chain may be used to turn the camshafts. The inner side of the belt is designed with square (cogged) teeth which prevent the belt from slipping.
10. Belt Tensioner
The belt tensioner is a spring-loaded wheel which keeps the timing belt in tension and aligned with the cam sprocket. The smooth side of the timing belt rides over the tensioner. The tensioner applies a force on the backside of the belt. This keeps the belt in tension. Whenever the belt needs to be removed, the tensioner can be pulled away, freeing the belt.
TYPES OF VALVE TRAINS
1. OHV or Push-rod valve train
In case of OHV or push-rod systems, there are long rods which have to be pushed by the camshaft lobes to move the valve rockers, which in turn open the valves – thus the name ‘push-rod’. The long rods and the mechanical nature of the pushrod system make it heavy and it’s not compatible with engines which run at higher revolutions per minute. Now while OHV is an older design, it has its advantages in terms of simplicity of design, compact packaging and a simpler lubrication system requirement as compared to an OHC system.
The disadvantages, of a pushrod system, however, are many.
• To start with, the engines with an OHV system cannot run very high RPMs and such valve trains are suitable mostly for low engine speed applications such as heavy cruisers.
• Owing to the heavy components, the noise and friction on such systems are much more than an OHC system.
• Also, any issues with the camshaft require the entire engine to be opened up, as the camshaft sits inside the engine block, which increases the maintenance effort and cost in case of a breakdown.
• Finally, OHV engines lend their design well primarily to two-valves per cylinder layout. It’s not that there aren’t any three or four valves per cylinder engines with OHV, but that setup becomes way more complex, and OHC systems offer much more flexibility with multiple valves per cylinders.
2. OHC Valve trains
To overcome the shortcomings of the pushrod valve trains, OHC valve train was developed. As the name suggests, it’s a valve train configuration where the camshaft for the engine is placed over the head of the engine, above the pistons and valves. This design allows for very direct contact between the camshaft lobes and the valves or a lifter, thus reducing mass, reducing components and allowing better engine performance as well as more flexibility with the overall engine design.
A. Single Overhead Cam/SOHC
For this variety of valve trains, there is a single camshaft for each row of engine heads. So a single cylinder OHC engine will have one camshaft. However, if it’s an engine with multiple rows, say a V6, then it will have two camshafts – one for each row of heads, or each bank. For SOHC engines, the camshaft is connected directly to the crankshaft via a timing belt or chain to ensure that the opening and closing of the valves is perfectly in sync with the various strokes of the engine for each cylinder.
Now, with SOHC, there is an option to either open or close the valves directly with a shim between the cam lobe and the valve stem, or via a rocker arm. Valves have springs which return them back to their closed position once the pressure from the camshaft lobe is off. SOHC engines are also suited better for 2 or 3 valves per cylinder configuration. Not that a SOHC valve train cannot run on a 4 valve per cylinder layout, but the whole set-up then becomes too complex for the design of rocker arms and lobes and it’s generally considered better to employ a DOHC valve train is such scenarios.
The camshaft creates an upward force that acts on the rocker arm, which in turn pushes the valve down. But as the cam rotates around, it does not pull the pushrod or rocker arm back with it. That’s why there is a valve spring to create force in the opposite direction and close the valve. The spring will hold the valve closed until the lobe of the camshaft comes around with a greater force and pushes it down.
9. Timing Belt:
A timing belt instead of a timing chain may be used to turn the camshafts. The inner side of the belt is designed with square (cogged) teeth which prevent the belt from slipping.
10. Belt Tensioner
The belt tensioner is a spring-loaded wheel which keeps the timing belt in tension and aligned with the cam sprocket. The smooth side of the timing belt rides over the tensioner. The tensioner applies a force on the backside of the belt. This keeps the belt in tension. Whenever the belt needs to be removed, the tensioner can be pulled away, freeing the belt.
TYPES OF VALVE TRAINS
1. OHV or Push-rod valve train
In case of OHV or push-rod systems, there are long rods which have to be pushed by the camshaft lobes to move the valve rockers, which in turn open the valves – thus the name ‘push-rod’. The long rods and the mechanical nature of the pushrod system make it heavy and it’s not compatible with engines which run at higher revolutions per minute. Now while OHV is an older design, it has its advantages in terms of simplicity of design, compact packaging and a simpler lubrication system requirement as compared to an OHC system.
The disadvantages, of a pushrod system, however, are many.
• To start with, the engines with an OHV system cannot run very high RPMs and such valve trains are suitable mostly for low engine speed applications such as heavy cruisers.
• Owing to the heavy components, the noise and friction on such systems are much more than an OHC system.
• Also, any issues with the camshaft require the entire engine to be opened up, as the camshaft sits inside the engine block, which increases the maintenance effort and cost in case of a breakdown.
• Finally, OHV engines lend their design well primarily to two-valves per cylinder layout. It’s not that there aren’t any three or four valves per cylinder engines with OHV, but that setup becomes way more complex, and OHC systems offer much more flexibility with multiple valves per cylinders.
2. OHC Valve trains
To overcome the shortcomings of the pushrod valve trains, OHC valve train was developed. As the name suggests, it’s a valve train configuration where the camshaft for the engine is placed over the head of the engine, above the pistons and valves. This design allows for very direct contact between the camshaft lobes and the valves or a lifter, thus reducing mass, reducing components and allowing better engine performance as well as more flexibility with the overall engine design.
A. Single Overhead Cam/SOHC
For this variety of valve trains, there is a single camshaft for each row of engine heads. So a single cylinder OHC engine will have one camshaft. However, if it’s an engine with multiple rows, say a V6, then it will have two camshafts – one for each row of heads, or each bank. For SOHC engines, the camshaft is connected directly to the crankshaft via a timing belt or chain to ensure that the opening and closing of the valves is perfectly in sync with the various strokes of the engine for each cylinder.
Now, with SOHC, there is an option to either open or close the valves directly with a shim between the cam lobe and the valve stem, or via a rocker arm. Valves have springs which return them back to their closed position once the pressure from the camshaft lobe is off. SOHC engines are also suited better for 2 or 3 valves per cylinder configuration. Not that a SOHC valve train cannot run on a 4 valve per cylinder layout, but the whole set-up then becomes too complex for the design of rocker arms and lobes and it’s generally considered better to employ a DOHC valve train is such scenarios.
B. Double Overhead Cam/DOHC
DOHC or dual overhead camshaft design includes two camshafts for every row of cylinder heads. Talking about the example we took for SOHC, a DOHC setup for a single-cylinder engine will have two camshafts. However, if it’s a V6, it will have 4 camshafts, two for each row of engine heads, or banks. The primary advantage of such a setup is that it allows manufacturers to have a well-engineered answer to handling a 4-valves per cylinder. Generally, one of the camshafts handles the intake valves, while the second one handles the exhaust valves. The 4-valve per cylinder setup allows for better breathing for the engine, and better performance in most cases, making DOHC a choice for engines that need to rev higher. A DOHC setup also allows for putting the spark plug bang in the middle of the cylinder head, which facilitates better combustion, and enhances performance, and fuel efficiency of the engine. With SOHC, such a setup is not possible for 4-valves per head, as it has to sit in the middle of the cylinder head so as to operate both intake and exhaust valves. As mentioned before, though, SOHC engines too can handle four valves per cylinder, and while the construction of such valve trains is complex, it’s desirable in some cases. DOHC brings along the extra weight of the additional cam, though by allowing the positioning of the spark plug in the middle of the cylinder head it also enhances optimum combustion of fuel. In a nutshell, DOHC is more suited for high-performance engines which need to rev higher and perform in the higher rev range. SOHC systems have somewhat better lower end torque though.
Finally, a DOHC system, with its more fine-grained control over valves is more suitable to implement variable valve timing for engines. Such systems utilize variable camshaft profiles for different engine speeds to enhance performance across the entire rev band. The control over the speed and position of valves opening and closing is better in case of DOHC, and in today's electronics driven world, great benefits can be extracted using that fact. DOHC valve train is more expensive than SOHV though and coupled with its suitability for 4 valves per cylinder, it makes it feasible to employ that setup only on automobiles above a certain price point. For applications where everyday usability, low and mid-range torque, simplicity of design, easy construction and cost are important factors, SOHC system works well.
DOHC or dual overhead camshaft design includes two camshafts for every row of cylinder heads. Talking about the example we took for SOHC, a DOHC setup for a single-cylinder engine will have two camshafts. However, if it’s a V6, it will have 4 camshafts, two for each row of engine heads, or banks. The primary advantage of such a setup is that it allows manufacturers to have a well-engineered answer to handling a 4-valves per cylinder. Generally, one of the camshafts handles the intake valves, while the second one handles the exhaust valves. The 4-valve per cylinder setup allows for better breathing for the engine, and better performance in most cases, making DOHC a choice for engines that need to rev higher. A DOHC setup also allows for putting the spark plug bang in the middle of the cylinder head, which facilitates better combustion, and enhances performance, and fuel efficiency of the engine. With SOHC, such a setup is not possible for 4-valves per head, as it has to sit in the middle of the cylinder head so as to operate both intake and exhaust valves. As mentioned before, though, SOHC engines too can handle four valves per cylinder, and while the construction of such valve trains is complex, it’s desirable in some cases. DOHC brings along the extra weight of the additional cam, though by allowing the positioning of the spark plug in the middle of the cylinder head it also enhances optimum combustion of fuel. In a nutshell, DOHC is more suited for high-performance engines which need to rev higher and perform in the higher rev range. SOHC systems have somewhat better lower end torque though.
Finally, a DOHC system, with its more fine-grained control over valves is more suitable to implement variable valve timing for engines. Such systems utilize variable camshaft profiles for different engine speeds to enhance performance across the entire rev band. The control over the speed and position of valves opening and closing is better in case of DOHC, and in today's electronics driven world, great benefits can be extracted using that fact. DOHC valve train is more expensive than SOHV though and coupled with its suitability for 4 valves per cylinder, it makes it feasible to employ that setup only on automobiles above a certain price point. For applications where everyday usability, low and mid-range torque, simplicity of design, easy construction and cost are important factors, SOHC system works well.
DISC BRAKES: CONSTRUCTION, WORKING PRINCIPLE, TYPES, AND ROTOR MATERIALS
Brake rotors of disc brakes rotate with the wheels, and brake pads, which are fitted to the brake calipers, clamp-on these rotors to stop or decelerate the wheels. The brake pads pushing against the rotors generate friction, which transforms kinetic energy into thermal energy.
This thermal energy generates heat, but since the main components are exposed to the atmosphere, this heat can be diffused efficiently. This heat-dissipating property reduces brake fade, which is the phenomenon where braking performance is influenced by the heat. Another advantage of disc brake is its resistance to water fade, which occurs when the water on the brakes significantly reduces braking force. When the vehicle is in motion, the rotor spins at high speeds and this rotational motion discharges the water from the rotors themselves, resulting in stable braking force.
CONSTRUCTION
The brake rotor (disc) which rotates with the wheel, is clamped by brake pads (friction material) fitted to the caliper from both sides with pressure from the piston(s) (pressure mechanism) and decelerates the disc rotation, thereby slowing down and stopping the vehicle.
1. Rotor:
Circular disc bolted to the wheel hub that spins with the wheel. Rotors are most commonly made of cast iron or steel; however, some very high-end cars use a carbon-ceramic rotor. Rotors can be slotted or drilled for better heat dissipation.
2. Brake pads:
The component that pushes into the rotor, creating the friction that slows and stops a car. They feature a metal portion called a shoe and a lining that is attached to the shoe. The lining is what actually comes in contact with the rotor and wears away with use. Linings are made of different materials and fall into three categories: organic, semi-metallic and ceramic. The lining material chosen will impact the length of brake life, the amount of noise heard when the brakes are applied, and how quickly the brakes bring a car to a halt.
3. Piston:
Cylinder connected to the brake system hydraulics. The piston is what moves the brake pads into the rotor when the driver presses the brake pedal. Some brake systems have a single piston that moves both pads, while others have two pistons that push the brake pads from each side of the rotor. Others still have four, six, or even eight pistons for higher braking power, at the expense of added cost and complexity.
4. Caliper:
Housing that fits over the rotor and holds the brake pads and pistons, as well as contains ducting for brake fluid. There are two types of brake calipers: floating (or sliding) and fixed. Floating calipers “float” over the rotor, and only have pistons on a single side. When the driver presses the brakes, the pistons press the brake pads on one side into the rotor, which causes the caliper to slide over so that the pads on the non-piston side of the caliper also contact the rotor. Fixed calipers are bolted in place, and instead, have pistons on both sides of the rotor that move when the driver applies the brakes. Fixed calipers apply brake pressure more evenly and clamp more firmly on the rotor, however floating calipers are found on most cars and are perfectly adequate for everyday driving.
5. Sensors:
Some vehicles have brakes that contain sensors embedded in the brake pads which work to tell the driver when the pads are worn out. Other brake sensors play a part in the vehicle’s ABS system.
Disc brakes are generally used in passenger cars, but due to their stable performance at higher speeds and resistance to brake fade, they are gradually spreading into the commercial vehicle segment, where drum brakes were traditionally chosen for their longer service life. There are two types of disc brakes.
The "opposed piston type disc brake" has pistons on both sides of the disc rotor, while the "floating type disc brake" has a piston on only one side. Floating caliper type disc brakes are also called sliding pin type disc brakes.
Brake rotors of disc brakes rotate with the wheels, and brake pads, which are fitted to the brake calipers, clamp-on these rotors to stop or decelerate the wheels. The brake pads pushing against the rotors generate friction, which transforms kinetic energy into thermal energy.
This thermal energy generates heat, but since the main components are exposed to the atmosphere, this heat can be diffused efficiently. This heat-dissipating property reduces brake fade, which is the phenomenon where braking performance is influenced by the heat. Another advantage of disc brake is its resistance to water fade, which occurs when the water on the brakes significantly reduces braking force. When the vehicle is in motion, the rotor spins at high speeds and this rotational motion discharges the water from the rotors themselves, resulting in stable braking force.
CONSTRUCTION
The brake rotor (disc) which rotates with the wheel, is clamped by brake pads (friction material) fitted to the caliper from both sides with pressure from the piston(s) (pressure mechanism) and decelerates the disc rotation, thereby slowing down and stopping the vehicle.
1. Rotor:
Circular disc bolted to the wheel hub that spins with the wheel. Rotors are most commonly made of cast iron or steel; however, some very high-end cars use a carbon-ceramic rotor. Rotors can be slotted or drilled for better heat dissipation.
2. Brake pads:
The component that pushes into the rotor, creating the friction that slows and stops a car. They feature a metal portion called a shoe and a lining that is attached to the shoe. The lining is what actually comes in contact with the rotor and wears away with use. Linings are made of different materials and fall into three categories: organic, semi-metallic and ceramic. The lining material chosen will impact the length of brake life, the amount of noise heard when the brakes are applied, and how quickly the brakes bring a car to a halt.
3. Piston:
Cylinder connected to the brake system hydraulics. The piston is what moves the brake pads into the rotor when the driver presses the brake pedal. Some brake systems have a single piston that moves both pads, while others have two pistons that push the brake pads from each side of the rotor. Others still have four, six, or even eight pistons for higher braking power, at the expense of added cost and complexity.
4. Caliper:
Housing that fits over the rotor and holds the brake pads and pistons, as well as contains ducting for brake fluid. There are two types of brake calipers: floating (or sliding) and fixed. Floating calipers “float” over the rotor, and only have pistons on a single side. When the driver presses the brakes, the pistons press the brake pads on one side into the rotor, which causes the caliper to slide over so that the pads on the non-piston side of the caliper also contact the rotor. Fixed calipers are bolted in place, and instead, have pistons on both sides of the rotor that move when the driver applies the brakes. Fixed calipers apply brake pressure more evenly and clamp more firmly on the rotor, however floating calipers are found on most cars and are perfectly adequate for everyday driving.
5. Sensors:
Some vehicles have brakes that contain sensors embedded in the brake pads which work to tell the driver when the pads are worn out. Other brake sensors play a part in the vehicle’s ABS system.
Disc brakes are generally used in passenger cars, but due to their stable performance at higher speeds and resistance to brake fade, they are gradually spreading into the commercial vehicle segment, where drum brakes were traditionally chosen for their longer service life. There are two types of disc brakes.
The "opposed piston type disc brake" has pistons on both sides of the disc rotor, while the "floating type disc brake" has a piston on only one side. Floating caliper type disc brakes are also called sliding pin type disc brakes.
WORKING PRINCIPLEOF DISC BRAKE
When the driver steps on the brake pedal, the power is amplified by the brake booster (servo system) and changed into a hydraulic pressure (oil-pressure) by the master cylinder. The pressure reaches the brakes on the wheels via tubing filled with brake oil (brake fluid). The delivered pressure pushes the pistons on the brakes of the four wheels. The pistons in turn press the brake pads, which are friction material, against the brake rotors which rotate with the wheels. The pads clamp on the rotors from both sides and decelerate the wheels, thereby slowing down and stopping the vehicle.
• When the brake pedal is pressed, the high-pressure fluid from the master cylinder pushes the piston outward.
• The piston pushes the brake pad against the rotating disc.
• As the inner brake pad touches the rotor, the fluid pressure exerts further force and the caliper moves inward and pulls the outward brake pad towards the rotating disc and it touches the disc.
• Now both the brake pads are pushing the rotating disc, a large amount of friction is generated in between the pads and rotating disc and slows down the vehicle and finally, let it stop.
• When a brake pad is released, the piston moves inward, the brake pad away from the rotating disc. And the vehicle again starts to move.
When the driver steps on the brake pedal, the power is amplified by the brake booster (servo system) and changed into a hydraulic pressure (oil-pressure) by the master cylinder. The pressure reaches the brakes on the wheels via tubing filled with brake oil (brake fluid). The delivered pressure pushes the pistons on the brakes of the four wheels. The pistons in turn press the brake pads, which are friction material, against the brake rotors which rotate with the wheels. The pads clamp on the rotors from both sides and decelerate the wheels, thereby slowing down and stopping the vehicle.
• When the brake pedal is pressed, the high-pressure fluid from the master cylinder pushes the piston outward.
• The piston pushes the brake pad against the rotating disc.
• As the inner brake pad touches the rotor, the fluid pressure exerts further force and the caliper moves inward and pulls the outward brake pad towards the rotating disc and it touches the disc.
• Now both the brake pads are pushing the rotating disc, a large amount of friction is generated in between the pads and rotating disc and slows down the vehicle and finally, let it stop.
• When a brake pad is released, the piston moves inward, the brake pad away from the rotating disc. And the vehicle again starts to move.
TYPES OF DISC BRAKES
There are two types of disc brakes. One is called the "opposed piston type disc brake" which has pistons on both sides of the disc rotor, and the other is the "floating type disc brake" which has a piston on only one side. The floating type disc brakes are also called the sliding pin type disc brakes.
1. Opposed Piston Type Disc Brakes
The opposed piston type is a disc brake which has pistons on both sides of the disc rotors.
The opposed piston type disc brake features stable braking force as well as a high level of controllability.
The swept areas of the brake pads are enlarged to increase braking force, and here opposed piston types are favored. This is because of its advantage where the number of pistons can be increased to realize even distribution of pressure on the rotors from both sides. Depending on the size of the brake pads, there are several types, including the 4-pot type which has two pistons on each side for a total of four, and the 6-pot type which has three pistons on each side for a total of six.
2. Floating Type Disc Brakes
Floating type is a disc brake which has a piston on only one side and is also called the sliding type disc brake.
On the floating type disc brakes, the piston pushes the inner brake pad against the rotor when the brakes are engaged. This generates a reaction force that moves the caliper itself along with the slide pin, pushing the outer pad against the rotor to clamp it from both sides.
Many passenger car disc brakes are of the floating caliper type since this type has a relatively simple and lightweight construction, which allows for lower manufacturing costs.
Floating type disc brakes for commercial vehicles
Disc brakes are used mainly for passenger cars, but due to their consistent performance at higher speeds and resistance to brake fade, they are gradually spreading into the commercial vehicle segment, where drum brakes were traditionally chosen for their resistance against wear.
TYPES OF ROTOR
1. Smooth Rotors
Smooth rotors are identified by their flat, smooth surface. For most cars and trucks on the road, smooth rotors are original equipment (OE) because of their versatility for many driving conditions. The main benefit of smooth rotors is that they tend to wear evenly, helping your brake pads last longer. If you want to keep the smooth rotor but still go for the upgrade, look for premium metal that absorbs more heat.
2. Drilled or Dimpled Rotors
Drilled rotors are identified by the pattern of holes that have been drilled all the way through the rotor disc. Dimpled rotors are similar, though instead of holes there are dimples that have been drilled to the rotor’s minimum thickness level, retaining more structural integrity than a fully drilled rotor. These rotor types help the brake pads to better grip the rotor, giving it more initial bite and increasing stopping power.
*Note that drilled or dimpled rotors are typically found in combination with slotted rotors.
3. Slotted Rotors
Slotted rotors are recognized by carved lines found on the rotor. These carved slots help to cool the rotor during high-performance use. They also help to remove dirt and other debris from the disc and brake pad, helping to maintain consistent contact for more efficient braking. Slotted rotors are perfect for vehicles that see frequent, heavy towing.
4. Drilled/Dimpled and Slotted Rotors
Rotors that are both drilled (or dimpled) and slotted, while effective, are best for trucks that want the added aesthetic, such as those with wheels that have a more open design. Not only will they look great through an open-wheel, but the drilled holes assist with an initial bite while the slots are designed to remove dust and debris from between the rotor and brake pad.
There are two types of disc brakes. One is called the "opposed piston type disc brake" which has pistons on both sides of the disc rotor, and the other is the "floating type disc brake" which has a piston on only one side. The floating type disc brakes are also called the sliding pin type disc brakes.
1. Opposed Piston Type Disc Brakes
The opposed piston type is a disc brake which has pistons on both sides of the disc rotors.
The opposed piston type disc brake features stable braking force as well as a high level of controllability.
The swept areas of the brake pads are enlarged to increase braking force, and here opposed piston types are favored. This is because of its advantage where the number of pistons can be increased to realize even distribution of pressure on the rotors from both sides. Depending on the size of the brake pads, there are several types, including the 4-pot type which has two pistons on each side for a total of four, and the 6-pot type which has three pistons on each side for a total of six.
2. Floating Type Disc Brakes
Floating type is a disc brake which has a piston on only one side and is also called the sliding type disc brake.
On the floating type disc brakes, the piston pushes the inner brake pad against the rotor when the brakes are engaged. This generates a reaction force that moves the caliper itself along with the slide pin, pushing the outer pad against the rotor to clamp it from both sides.
Many passenger car disc brakes are of the floating caliper type since this type has a relatively simple and lightweight construction, which allows for lower manufacturing costs.
Floating type disc brakes for commercial vehicles
Disc brakes are used mainly for passenger cars, but due to their consistent performance at higher speeds and resistance to brake fade, they are gradually spreading into the commercial vehicle segment, where drum brakes were traditionally chosen for their resistance against wear.
TYPES OF ROTOR
1. Smooth Rotors
Smooth rotors are identified by their flat, smooth surface. For most cars and trucks on the road, smooth rotors are original equipment (OE) because of their versatility for many driving conditions. The main benefit of smooth rotors is that they tend to wear evenly, helping your brake pads last longer. If you want to keep the smooth rotor but still go for the upgrade, look for premium metal that absorbs more heat.
2. Drilled or Dimpled Rotors
Drilled rotors are identified by the pattern of holes that have been drilled all the way through the rotor disc. Dimpled rotors are similar, though instead of holes there are dimples that have been drilled to the rotor’s minimum thickness level, retaining more structural integrity than a fully drilled rotor. These rotor types help the brake pads to better grip the rotor, giving it more initial bite and increasing stopping power.
*Note that drilled or dimpled rotors are typically found in combination with slotted rotors.
3. Slotted Rotors
Slotted rotors are recognized by carved lines found on the rotor. These carved slots help to cool the rotor during high-performance use. They also help to remove dirt and other debris from the disc and brake pad, helping to maintain consistent contact for more efficient braking. Slotted rotors are perfect for vehicles that see frequent, heavy towing.
4. Drilled/Dimpled and Slotted Rotors
Rotors that are both drilled (or dimpled) and slotted, while effective, are best for trucks that want the added aesthetic, such as those with wheels that have a more open design. Not only will they look great through an open-wheel, but the drilled holes assist with an initial bite while the slots are designed to remove dust and debris from between the rotor and brake pad.
DISC BRAKE ROTOR MATERIALS
Brake rotors can be made of six different materials, each with its own advantages. Let’s take a look at each.
1. Cast Iron
This is the very definition of old school when it comes to a brake rotor. It’s one or two pieces and gets the job done. In fact, it’s the most common material for brake rotors. The right design (usually two-piece) can even work well in a performance vehicle. However, it’s also the heaviest option, which affects the overall weight of your car and its handling, since that weight is right up there with your front wheels.
2. Steel
Steel has been the racer’s choice for years because a steel brake rotor is thinner, weighs less and handles heat better. The downside: Steel rotors aren’t as durable as some others, and warped rotors can cause noise and a pulsating pedal when you brake.
3. Layered Steel
Layering sheets of steel together and laminating them makes them resistant to the warping you might find in a straight steel brake rotor. It’s a favorite of racers who don’t want frequent brake rotor replacement and repair, but manufacturers are currently only targeting professional racers and production is limited, so it’s not terribly common in passenger vehicle applications.
4. Aluminum
Aluminum brake rotors dissipate heat quickly, but they also melt at a lower temperature than other options. Aluminum is a favorite for motorcycles, which weigh less and are easier on the rotors when braking than a heavy car, truck or SUV.
5. High Carbon
These are iron, but with a lot of carbon mixed in. They can take a lot of heat and dissipate it quickly. The metallic content helps the rotor avoid cracking under high stress, and brake noise and vibration are reduced as well. The only downside is the price, which is significantly higher than straight iron or aluminum.
6. Ceramic
What’s your favorite super-car? Ferrari? Porsche? Lamborghini? Odds are it’s packing ceramic brake rotors. They offer the highest heat capacity (85 percent higher than cast iron) and superior dissipation, and they maintain a more consistent force and pressure as the temperature of the rotors rises. Ceramic is the highest-performance brake rotor available today.
ADVANTAGES AND DISADVANTAGES
Advantages
1. It is lighter than drum brakes.
2. It has better cooling ( because the braking surface is directly exposed to the air)
3. It offers better resistance to fade.
4. It provides uniform pressure distribution
5. Replacement of brake pads is easy.
6. By design, they are self-adjusting brakes.
Disadvantages
1. It is costlier than drum brakes.
2. Higher pedal pressure is required for stopping the vehicle. This brake system is installed with vacuum booster.
3. No servo action is present.
4. It is difficult to attach a suitable parking attachment.
Brake rotors can be made of six different materials, each with its own advantages. Let’s take a look at each.
1. Cast Iron
This is the very definition of old school when it comes to a brake rotor. It’s one or two pieces and gets the job done. In fact, it’s the most common material for brake rotors. The right design (usually two-piece) can even work well in a performance vehicle. However, it’s also the heaviest option, which affects the overall weight of your car and its handling, since that weight is right up there with your front wheels.
2. Steel
Steel has been the racer’s choice for years because a steel brake rotor is thinner, weighs less and handles heat better. The downside: Steel rotors aren’t as durable as some others, and warped rotors can cause noise and a pulsating pedal when you brake.
3. Layered Steel
Layering sheets of steel together and laminating them makes them resistant to the warping you might find in a straight steel brake rotor. It’s a favorite of racers who don’t want frequent brake rotor replacement and repair, but manufacturers are currently only targeting professional racers and production is limited, so it’s not terribly common in passenger vehicle applications.
4. Aluminum
Aluminum brake rotors dissipate heat quickly, but they also melt at a lower temperature than other options. Aluminum is a favorite for motorcycles, which weigh less and are easier on the rotors when braking than a heavy car, truck or SUV.
5. High Carbon
These are iron, but with a lot of carbon mixed in. They can take a lot of heat and dissipate it quickly. The metallic content helps the rotor avoid cracking under high stress, and brake noise and vibration are reduced as well. The only downside is the price, which is significantly higher than straight iron or aluminum.
6. Ceramic
What’s your favorite super-car? Ferrari? Porsche? Lamborghini? Odds are it’s packing ceramic brake rotors. They offer the highest heat capacity (85 percent higher than cast iron) and superior dissipation, and they maintain a more consistent force and pressure as the temperature of the rotors rises. Ceramic is the highest-performance brake rotor available today.
ADVANTAGES AND DISADVANTAGES
Advantages
1. It is lighter than drum brakes.
2. It has better cooling ( because the braking surface is directly exposed to the air)
3. It offers better resistance to fade.
4. It provides uniform pressure distribution
5. Replacement of brake pads is easy.
6. By design, they are self-adjusting brakes.
Disadvantages
1. It is costlier than drum brakes.
2. Higher pedal pressure is required for stopping the vehicle. This brake system is installed with vacuum booster.
3. No servo action is present.
4. It is difficult to attach a suitable parking attachment.
Forwarded from MECHANICAL AND AUTOMOTIVE ENGINEERING
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