What are Mechanical Components?
Mechanical components are the foundation of machines and work producing devices. Though technology has progressed, and old parts have been replaced by more up to date and modern methods, at the heart of every piece of equipment is some form of mechanical component that performs reliably and economically. In essence, the purpose of mechanical components is to take input force and change it through the combination of various machine elements such as gears, bearings, rotaries, and other components.
In efficiently operating equipment, mechanical components reduce friction and carry loads for linear or rotary motion. They are designed to change input to output speed ratios. Each one is designed to perform a specific function to increase the efficiency and provide exacting precise control.
As with many aspects of engineering, mechanical components are the small, insignificant part of equipment that we tend to ignore but perform a vital function. From the family car to the most complex industrial devices, these small pieces ensure smooth and inexpensive operation.
How Mechanical Components Are Made
There are a wide variety of mechanical components. Each is manufactured to precise specifications and include springs, bearings, actuators, clamps, snap rings, etc. Though most are very common, for most applications, they are designed to fit into their place in a piece of equipment.
The process begins with the development of a CAD design. From this initial rendering, each of the components is defined including measurements, function, and placement. When deciding on a component, it is important that it meets the standards of the overall design. They are available in multiple shapes and sizes and may have to be engineered from a standard form to specialized application.
The size of a bearing or spring can mean the difference between a properly functioning machine to one that needs constant repair. Trained professional engineers are able to account for the differences of equipment and create parts that guarantee a smooth running device. In the design phase, the amount of torque and stress of the mechanical component is calculated to determine the materials for its production. This essential computation is based on the ratio of force to output. The computer age has enhanced this process by allowing designers to test the stress on a part in a computer simulation, which leads to the determination of the materials and fabrication of each of the critical components.
Mechanical components are made from several different types of materials from high grade steel to various forms of plastic. The material used depends on the final function of the equipment, the importance of the part, and specified requirements. In most cases, components that are capable of enduring high torque and stress are required. In some cases, they are readily available in a specified final form, such as springs of specific dimensions. In other cases, it may be necessary for them to be fabricated. What is critical is that production of special components be replaceable, repairable, and economical.
The types of materials used to manufacture mechanical components depends on several factors such as use, type of component, needed resistance, and possible torque. In the case of ball bearings, they have to be made from chrome steel or stainless steel to ensure that they can withstand wear and stress. Actuators can be produced using a variety of materials from high density plastic and aluminum to thermo bimetals coated with a chemical or having an electroplated surface.
In the case of springs, they are usually made from some form of steel alloy. The most common types are high carbon, oil temper low carbon, chrome silicon, chrome vanadium, and stainless steel. Though they are the most common, other materials are available such as copper, bronze, or titanium. Other varieties are made from specialized materials designed specifically for their function.
Snap rings, much like bearings, are made from some form of steel. Some varieties include a form of copper, but several types can have different finishes for corrosion protection. The material used depends on how the snap ring will be used and the amount of wear it must endure.
The majority of threaded inserts are made from brass for its long thread life and secure fastening base. Though brass is the most common type, there is a collection of threaded inserts made from aluminum or some form of steel. Since they are used to reinforce plastic, threaded inserts have to be very dependable and have lasting materials.
The type of material for a mechanical component is specified by how it will be used in the overall design of where it will be installed. Some form of metal is the preferred choice since it guarantees that the component will last. There isn‘t a set rule regarding mechanical components and must be examined on a case by case basis.
Actuators and Positioning Systems
An actuator is a device that supplies force that can be utilized to move other devices. There are electrical actuators that depend on electrical current to produce force and are easy to interface with electrical control systems.
Benefits of electric actuators:
- Easier to diagnose in case of electrical or mechanical faults
- Ease of control
Selecting an electric actuator depends on performance metrics, which include energy efficiency, angular acceleration, angular speed, and overall acceleration. Though these are some of the main concerns, it is important to consider durability, operating conditions, and the mass to be moved.
The technical specifications for an actuator have to be scientifically defined and analyzed. Before installing one, it is advisable to factor in temperature ranges, weight of the actuator, disposal volume, the type of power AC or DC, the actuator‘s dynamic, the controlling range, and whether the type of movement is linear or rotational.
The difference between magnets and electromagnets is that electromagnets use electric current to generate a magnetic field, which determines the magnets function.
They can be set to concentrate the effects of the magnetic field and to direct it. It is the reason they are used to produce an electromagnetic force and generate a controlled magnetic field in a predetermined space
Electromagnets are used in electric motors, generators, relays, and scientific instruments. Their ability to attract metals makes them a perfect tool for lifting industries where the magnetic can be used to pick up heavy metal objects. Aside from their use as an industrial tool, they are important for fire doors, circuit breakers, and in magnetic recorders such as tape and video recorders where magnetized metallic particles save information.
A screw jack operates by turning a leadscrew to lift heavy weights. It increases the magnitude of a force enabling it to lift a few kilograms to 100‘s of tons as well as create movement in several directions. They are most valuable where huge loads need to be controlled and positioned with accuracy such as moderately heavy weights like vehicles, raise and lower the horizontal stabilizers of aircraft, and adjustable supports for heavy loads like the foundation of a house.
Screw jacks are self-locking and remain motionless when the force on the screw is removed. Even when holding a huge load, it will not move backwards. They can be operated electrically, hydraulically, or pneumatically depending on the amount of accuracy required.
A screw jack may use a machine cut lead screw or a rolled or ground ball screw to transfer rotational energy to linear energy, which is created by the worm screw acting on the lead screw by the worm wheel. It is the work of the worm wheel acting directly on the lead screw that creates the energy or work.
An actuator converts an energy source such as electric current, pressure of pneumatic or hydraulic fluid into movement. A linear actuator changes the energy into a straight line responding to orders from a control system.
Linear actuators are found on industrial machinery, computer peripherals, printers, and disk drives. The simplest example is a DVD tray opener. They use lead screws to change energy into a linear motion with the lead screw allowing for a wide range of options and directionalities.
There are several types of linear actuators such as mechanical, hydraulic, pneumatic, piezoelectric, and electromechanical. With the assistance of hydraulics or pneumatics, they can create greater output potential since those types of devices use pressurized gas or liquid to create linear motion.
When considering a linear actuator, it is important to understand that actuators are designed to endure high speed or high force, or a combination of the two. When making the choice of an actuator, it is important to examine travel, speed, force, accuracy, and lifespan.
Telescopic Linear Actuators are useful where space is limited since they can extend many times greater than an actuator at rest. Linear actuators are best known for their simple design and high speed with the additional benefit of few moving parts making them easy and cost effective to maintain. They also have identical and predictable extending and retracting capabilities.
Hydraulic cylinders are also known as linear hydraulic motors and are found in all types of engineering vehicles and industrial machinery. Their power comes from a pressurized fluid inside the cylinder. The fluid for most hydraulic cylinders is an incompressible oil that does not lose its viscosity under pressure. Applied pressure is transferred through the fluid and is concentrated and multiplied to create force. For example, hydraulic cylinders on large earth excavators control the machine‘s linkages enabling them to move and lift with increased capacity in any position.
Hydraulic cylinders are barrels containing a piston and piston rods sealed at either end. One end is the base and the other is where the piston rod comes out of the cylinder with sliding rings and seals to ensure the fluid remains pressurized. A hydraulic pump assists in controlling the flow of fluid to the cylinder allowing the piston to move smoothly.
The two most used types of hydraulic cylinders are ‘Tie Rod‘ Style and ‘Welded Body‘ Style. Tie Rod Cylinders can be taken apart for repair and maintenance while welded body cylinders have welded end caps and are designed to custom requirements for different sizes, which are normally shorter overall and include special features. Welded hydraulic cylinders are found in construction equipment like bulldozers, earth movers and heavy mechanical machinery.
Bearings and Linear Guides
Needle roller bearings are mechanical parts designed to work under very small cylindrical rollers that are used to minimize friction from rotating surfaces. They work under the principle of a roller style rolling element that minimizes friction on a rotating surface. They have smaller diameter cylindrical rolling elements where the length is greater compared to the diameter. Though they have a small cross-sectional height, they have a load-bearing capacity and rigidity that is relative to their volume.
Modern needle bearings have three parts - the shaft, needle rollers, and outer casing.
The design is unique where a small cross-section area provides a large load carrying capacity. Needle bearings can exert low inertia forces that provide mechanical advantages and are the main reason they are applied as engine components in transmissions, rocker arm pivots, pumps, and compressors. Due to the inertia forces, needle bearings are found in oscillation motions as an addition to compact and lightweight machine designs.
Linear bearings or linear-motion bearings provide linear motion in one dimension. They can be divided into two categories:
- Motorized – driven by a mechanism
- Non-motorized - powered by inertia or hand using a sliding function
They use recirculating ball pathways to enable motion and can handle heavy loads in any environmental conditions. Linear bearings have the advantage of reducing friction while providing precision movement control.
Rolling-element bearings have a sleeve outer ring with a series of balls-rows enclosed in a cage. They combine smooth motion, low friction, high rigidity, and a long life as well as being economical since they are easy to maintain and replace. This form of bearing is restricted to use with hardened and stainless steel shafting since they are slightly rigid and subject to contamination. Sealant and lubrication are required.
Plain bearings, unlike rolling bearings, slide without using ball bearings. They can be used like rolling-element bearings as well as with hard-anodized and plain aluminum and some forms of soft steel. One of their significant features is their less rigidity and ability to handle contamination without any sealant. An added benefit is their capability of handling a wider range of temperatures without any lubrication.
Ball bearings use balls to maintain the separation between bearing tracks and aim to reduce the friction while improving the links between elements by replacing sliding with rotational movement. They are composed of two races containing a ball with one race being stationary while the other is in a rotating hub. Each ball is lubricated and maintained in a cage. Movement of the races moves the ball inside them.
There are a wide variety of uses for ball bearings as well as multiple materials used to manufacture them. Most of them are made from steel or ceramics for resistance to high compression. Lubrication is necessary to protect them from jamming. They are designed for a specific use.
Angular contact ball bearings have asymmetric tracks. The greater the contact angle, the higher the axial load supported. These are found in high speed applications because of the centrifugal force generated by the balls. Although angular contact bearings can accept thrust loads in only one direction, they can be manufactured at different contact angles between 0 and 45 degrees to transfer the load acting on the bearing.
Axial bearings, or thrust bearings, can withstand force in the same direction as the shaft. In some applications, ceramic bearings, a type of radial bearing, are used to withstand high rotational speeds. The rolling elements are ceramic, which is significantly lighter than steel and reduces the centrifugal force at high speeds.
Deep groove ball bearings are the most common type of ball bearing and are used in electric motors, household appliances, car motors, office machinery, automation control, and common tools. They have deep grooves with race dimensions close to the dimensions of the balls. They come in several sizes and materials. High-temperature types can withstand temperatures up to 350°C (660°F) and are suitable for machines in the metals industry or industrial ovens.
Ball bears are made in different sizes for different loads according to their application from miniature ones for light loads and small assemblies to large deep grooved ones for heavy loads with deep grooves.
The Gearbox is the part of the machine that converts speed and torque or the speed-torque ratio, torque being power. An example would be that of the manual gearbox in a car, where the speed and power delivered to the drive shaft is managed by the changing of gears. A gearbox transfers energy from one device to another. The driver is responsible for smoothly transitioning the vehicle's speed.
A gear box provides gear reduction, which is a key to increasing torque while reducing speed so the vehicle can be controlled at lower speeds. Modern gears and their special tooth profile called an involute, it is possible to maintain a constant speed ratio between two gears.
In industry, spur gears are used in couples or grouped together to create large gear reductions. Spiral bevel gears are used where the drive input is at 90° to the final drive direction, like the drive shaft of a car. Some gear boxes have specific applications like the multi-turn gearbox used in nuclear power plants applicable in situations requiring high torque. The nature of that type of environment demands exceptional reliability during operation.
Important criteria regarding the selection of a gearbox:
- Input Speed
- Output Speed
- Output torque
- Duration of operation
- Operating Temperature conditions
- Starting frequency
- Gear Ratio - input speed divided by output speed
Like other types of rotating equipment, gearboxes depend on lubrication to reduce friction and provide cooling for problem free operation. Manufacturers provide recommendations for the type of lubricant as well as lubricant intervals. Actual gearbox lubrication requirements depend on environmental conditions, proper maintenance, and overloading.
Permanent Magnet Motor
Simple electric motors use electricity and a magnetic field to turn the motor. A DC Motor requires magnets of opposing polarities in an electric coil. As the magnets attract and repel one another, the motor turns. Simple motors need at least one electromagnet with permanent magnets. Electromagnets require an electric current to make them magnetic. Permanent magnets are made of materials that are naturally magnetic and have a permanent magnetic field such as neodymium magnets.
Permanent magnets in DC Motors have enabled the design of custom motors. Traditionally, they have been smaller and more compact since it has been difficult to find materials able to maintain a permanent magnetic field. Recently, with the discovery of neodymium magnets, very compact, high power, permanent magnet motors are available.
Permanent magnet motors have become a fixture in many parts of our lives from CD and DVD players to ATM machines and toys. However, the most powerful permanent magnet is not as powerful as an electromagnet. An efficiently functioning motor requires both.
Permanent magnet motor manufacturers are chosen based on:
- Flexibility of design
- Speed, strength & robustness
- Precision movement and quality
- Torque output
- Thermal efficiency
- Vibration Efficiency
The next revision of motors will cover enclosed motors with extended lower power. Manufacturers and OEMs need to be involved to ensure the end result is useful and realistic. For industry to benefit from the next generation of motors, new products need to be easy to understand and operate for end users.
Gear Wheels are a fundamental of gears, a rotating device enabling the control of speed, direction, or torque. Gear movement creates rotation.
Gear wheels are circular discs with ‘teeth‘ or ‘cogs‘ that mesh into other gear wheels to create a desired effect. Working together, they combine to create mechanical power advantage or gear ratio where power can be increased or decreased. Gear ratio can be described as when one gear wheel makes two revolutions in the same time that another gear wheel makes one. In this case, the gear can double the amount of mechanical power. Gears have the ability to quadruple the amount of mechanical power.
Gear wheels date back to the time of the Ancient Greeks. Rudimentary geared devices were invented for astronomical calculations. Following their initial use, gears have developed into a powerful force enabling the amount of mechanical power to be increased almost infinitely.
Automobiles are an example of a common use of gear wheels. The transmission is the name of the process of sending power from a source to a drive mechanism using gears. For example, the drive shaft and steering wheel are driven by a gearbox.
The difference between external gears and internal gears is the placement of the teeth. A spur gear is a simple form of gear while worm gears look like a screw and helical ones act in a spiral. There are several forms of gears as well as combinations of them that can be set in different orientations to perform simple to complex drive tasks.
Gears are used in many mechanical devices. Their central function is to provide gear reduction in motorized equipment. A small motor spinning very fast can provide enough power for a device but not enough torque. An electric screwdriver has a large gear reduction because
It needs torque to turn screws. The motor for it is designed to produce a small amount of torque at a high speed. With gear reduction, the output speed can be reduced as the torque is increased.
Belts link two or more shafts using a mechanical flexible material to provide motion and to efficiently transmit power. They can be crossed or aligned to drive pulleys. In this system, V-Belts, Vee belts or wedge ropes are the best way to resolve slippage and alignment problems as well as being considered a basic part of power transmission. V belts are a combination of traction, speed of movement, bearings‘ load, and have high life expectancy.
The name comes from the trapezoidal cross-section shape that ideally fits in the grooves of a pulley. The wedge shape of V-belts increases traction improving torque. The greater the load, the better the wedging action.
To increase power, two or more V belts can be placed side by side to form a "multiple V-belt" configuration. V-belts are made from rubber or synthetic rubber stocks and have the flexibility to bend around sheaves in drive systems. Fabric materials of different kinds cover the stock material to give a layer of protection and reinforcement.
V-belts look like relatively benign and simple pieces of equipment, a glorified rubber band. As with other forms of belts, V-belts have undergone tremendous technological development since their invention in 1917. New synthetic compounds, cover materials, construction methods, tensile cord advancements, and cross-section profiles have led to a wide array of V-belts designed for specific applications to deliver different levels of performance. Though they may appear simple on the surface, as with other parts of a machine, they have a technical side to be considered.
A coupling couples two rotating pieces of equipment while allowing some degree of misalignment and end-movement. Rigid couplings join two shafts in a motor or a mechanical system and can connect separated systems such as a motor and generator or the connection inside a single system. They are used to reduce shock at the meeting point of the shafts.
Due to their precise alignment and maintenance of two shafts, rigid couplings maximize performance increasing the life expectancy of a machine. They are the most efficient way to get a precise alignment and a secure holding.
Rigid Coupling Designs:
Sleeve style couplings are affordable and easy to use and are composed of a pipe whose bore is the size of the shafts. Torque is transmitted with the help of a keyway. The coupling is locked in position by two threaded holes.
Clamped rigid couplings, or compression rigid couplings, differ from the sleeve style by the sleeve being split on one side. Shafts are connected and keyed to the sleeves and screwed together.
Rigid coupling's primary function is to transfer power from one end of a shaft to another.
Common uses include:
- Change vibration characteristics
- Connect driving and driven parts
- Protection against overloads
- Connect shafts of separately manufactured devices
- Enable disconnection for repairs or alterations
- Allow for misalignment of shafts
- Produce mechanical flexibility
- Reduce shock loads between shafts
- Slip when overloads happen
Though the definition of couplings is very simple, they are easy to install and maintain, which can lead to reduced loss of time and lower production costs.
Hydraulics is the name of a system that uses fluid under pressure in a confined space such as a shaft or cylinder to transfer power from one place to another. They convert the created pressure into torque and rotation or mechanical force. Hydraulic motors can be run in a forward or reverse mode inverting the direction of the transformation of energy. A part of a hydraulic motor is the hydraulic pump, which is available in different speed applications. While a hydraulic motor converts fluid into energy, a hydraulic pump converts mechanical energy.
Hydraulic motors were developed over 300 years ago and are noted for their ability to create power. They can handle larger loads than traditional electric motors that have the risk of damage or burn out doing heavy loads. Hydraulic motors are often found at construction sites, in industrial settings, on industrial machinery, in unloading and loading bays, on aircraft and cars. Industrial settings requiring pressurized conditions such as injection molding will use hydraulic motors.
For machinery, which requires different levels of torque for different speeds, applications or conditions, gears can be added. The force of a hydraulic motor can best be described as the difference between the power required to move a tank over a tarmac versus over mud. With the addition of gears, the tank, including the hydraulic motor, needs the ability to brake to remain secure, manageable, and safe regardless of the surface.
Various types of Hydraulic Motors exist to meet different requirements of speed and torque.
How to choose a hydraulic motor :
- Density of Power output
- Economic design or
- Space saving
Hydraulic motors can produce more power than other motors of the same size. They take on larger loads and are most commonly used in aircraft, construction vehicles, and automobiles. An essential function of a hydraulic motor is to lift heavy loads. Constructed as small components in a complex mechanism or one very large hydraulic motor performing a single task, they have become an essential part of manufacturing.
Standard Mechanical Components
The names C-Clips, circlip, or Jesus Clips, given to snap rings, describes the appearance of these handy tools. Shaped like an open-ended circle or C-shape, made of a semi-flexible material, they can be fitted into internal grooves or slotted over a shaft into external grooves. They are mechanical components used on circular objects such as trees, axes or bore processes. One of their functions is to perform axial stops and recovery of slack to reduce noise from machines. The name "Jesus clip" is from the clip's spring action when it is removed or installed, which leads to the remark "Oh Jesus, where did it go?" since the clips take off rapidly when adjusted.
There are two categories of snap rings – external and interior circles. Externals are slipped on the axis direction and have a narrow opening. Interior is axially set up and has an opening that is reduced during assembly. The difference between the two refers to whether they fit into a bore or over a shaft. One of their major uses is to secure pinned connections.
To install and remove snap rings, circlip pliers are used, but needle nose pliers can be performed just as well. The pliers grab the ends of the open circle and move them towards each other making the snap ring smaller so that it will pop out of its groove.
Snap rings can be integrated into many applications. Filter bags can have built-in snap rings to fit them easily into a filtration system. A simple example of a snap ring application might be on a bicycle wheel where the ring keeps the sprocket in position on the shaft.
A threaded insert, also known as a threaded bushing, is a fastener used by drilling a hole, or by using a ‘pre-tapped hole‘, to connect and mend panels. Once in place, a nut, screw, or bolt is added to permanently lock the insert.
Threaded inserts can be used to:
- Fix a stripped threaded hole
- Repair a damaged or a worn-out thread
- Dispose a thread on a very thin material
- Create a threaded hole in a soft material
- Simplify the modifications between unified threads and metric ones.
There are many varieties of threaded inserts, the choice depends on how they will be used. Plastic ones are used in plastic materials and applied with thermal insertion or ultrasonic welding machines. Furniture that is shipped to be assembled, such as shelves or cabinets, are shipped with threaded inserts. Sheet metal, sandwich panels, or honeycomb composite materials use threaded inserts to spread shear, tension, and torque loads.
As threaded inserts are available in various sizes and can be made of various materials, they are very versatile, easy to set up and dependable.
Types of Threaded Inserts
Also known as screw thread insert is larger than the desired hole and can easily anchor themselves in a tapped hole.
Captive nuts are used in thin materials. They have a knurled small ridges base that can easily be set up for the use of an arbor press.
External threaded inserts have threads on both sides. Placed in a tapped hole they can be attached to a variety of materials including nylon and Loctite.
Sizes of threaded inserts are standardized but different brands can provide different sizes. As with all forms of mechanical devices, it is important to determine whether a threaded insert will be resistant to deterioration from vibration, corrosion, or high temperature.
Brass inserts are a good choice for wood and particle boards. Where there are electronic or technical devices that may be vulnerable to ambient electrical charges, threaded inserts are non-conductive but provide a lasting hold as well as being able to be easily adjusted and replaced.
Stainless steel inserts are perfect for molding and metal works, for repair jobs and manufacturing. They are often used where cleanliness and disinfection is important in industries such as food and beverage production. An added benefit of stainless steel inserts is their resistance to corrosion and rust.
Blind threaded inserts are designed for efficiency, durability, and versatility. They provide strength with reusable threads for sheet materials where only one side is accessible.
Versatile and easily installed threaded inserts can be a valuable tool that has multiple applications in a variety of materials that include plastic, wood, and various metals. A carefully chosen threaded insert can provide a secure connection for years.
Shocks are designed to control the effects of bumps, impacts, or jolts. In vehicles, they prevent wear and tear on internal components when driving on uneven ground. The kinetic energy generated by a bumpy surface needs to be redirected away from passengers and the mechanics of the vehicle. In most cases, fluid in the shocks converts the disruptive energy into harmless heat. Other terms used to describe shocks is dashpots, which is a dampener resisting motion using some form of viscous fluid. Also, damper is used, which means to have a dulling or deadening influence.
Aircraft landing gear use a complex hydraulic system to improve safety during takeoff and landing adding to passenger comfort. The design of these special components includes the installation of industrial-strength springs to ensure a smooth ride.
In private vehicles, shock absorbers are crucial to the suspension system and safety of the occupants. Highly sophisticated racing vehicles have finely tuned shock absorption systems to improve the speed of the vehicle.
For many years, areas prone to earthquakes could not build tall buildings. Recently, a shock absorbing system has been developed that can withstand the violence of earthquakes and keep the structure standing. This has allowed areas such as San Francisco, CA, and Los Angeles, CA, to build skyscrapers.
The decision to purchase a shock absorber depends a great deal on how it will be used. Since family cars operate mainly on smooth surfaces, they require shocks for everyday use. Off road vehicles and high performance models need to have shocks that are fine tuned for their specific application and may need to be specially designed. At the center of the buying decision is safety, which is the main purpose for having a shock absorbing system.
Air springs are part of a vehicle‘s suspension system. Air springs are powered by an electric or engine-driven pump or compressor that moves air into flexible bellows made from reinforced rubber. Unlike hydropneumatic systems, air springs use pressurized air, which inflates a bellows and raises the chassis of a vehicle. The air pump absorbs the kinetic energy generated when a vehicle hits a bump. Unwanted energy is absorbed and deflected before it reaches the passengers and prevents damage to the vehicle‘s systems. The operator of the vehicle has greater control of the operating height of the vehicle, a useful feature for vehicle performance.
Racing vehicles using air springs can run on lower ground. Buses need air springs since their height varies depending on their passenger load and allows the bus to be lowered to accommodate disabled and elderly passengers.
High performance vehicles require air springs to adjust to surface conditions. As with many types of components, the first thing to consider when purchasing air springs is how they will be used. Commercial vehicles require heavy duty equipment to endure their stressful use. Off road and sport vehicles need air springs to adjust to a variety of terrains.
Air springs are another part that can substantially add to the protection and safe operation of any vehicle. They offer an extra level of control for vehicle operation and the ability to adjust to adverse conditions.
Friction clutches transfer power from one moving shaft component to another. They are used to control the transmission of power and contain material much like that on disc brake pads. In modern cars, the deterioration of friction clutch material is minimal since the clutch disc and flywheel are locked together in sync and no wear occurs.
In a car, the friction between the engine‘s flywheel and the clutch plate creates the power to rotate the car‘s wheels. Engaging and disengaging the clutch controls momentum and speed.
Friction Clutches can be Dry without lubrication or Wet with lubrication. Lubrication keeps the clutch cool and clean but may result in a slight loss of energy. Push or Pull Clutches are the most commonly used since the diaphragm spring needs to be ‘pushed‘ to enable the clutch to disengage.
In applications where additional torque is required, and especially in fast engines for racing and F1 cars, additional plates are added to the clutch without increasing the clutch diameter to give greater control and precision to gear changes without a loss in speed. Multiple plate clutches are used in automobiles and machinery where high torque is required.
Advantages of friction clutches
- Smooth engagement with little shock
- Can be engaged while the engine is running
- Ease of operation
- Can send partial power or energy
- Another form of safety device
- Can be applied and reapplied multiple times
How to decide on what is a good friction clutch
- The friction of the contact surface needs to be high enough to hold the load
- It should not need any form of exterior force
- High performing clutch must be lightweight
- Limited amount of heat from the contacting surfaces
- Minimum amount of wear
- Easily accessible for repair and replacement
Modern clutches use resin with a copper wire facing or ceramic material. Ceramic is used for racing or heavy-duty usage. Semi-metallic materials of steel, iron and copper are harder, heat resistant, and durable. They can handle heavy loads but not high speeds.
Ceramic clutches include glass, rubber, carbon, or Kevlar. They are best for larger vehicles with very intense usage. Trucks and race cars depend on ceramic clutches to withstand the stress and strain of their operation.
Organic clutches with high copper content increase heat transfer and are most reliable.
This form of clutch is used for vehicles under standard driving conditions since they provide long life and smooth engagement. Organic refers to the type of materials to make the clutch discs, which is a metallic fiber combined with organic materials. They are suitable for a wide range of driving conditions and perform well in city traffic.
Safety clutches known as slip clutches disengage when higher than normal resistance is present. This special feature is important for the safety of the operator and machinery. A good example is the motor of a lawnmower. The clutch and power disengage if the mower hits a hard object.
The centrifugal clutch uses generation of centrifugal force and is considered the smoothest form of clutch since it engages the load of the engine gradually allowing the engine to reach its optimal torque range before carrying a load. They can be found on small motorbikes, scooters, mopeds, and go-karts. A small engines‘ drive shaft engages only after it reaches adequate RPM‘s and disengages when there isn‘t any pressure on the accelerator. Chainsaws have to reach a sufficient level of power before cutting down a tree. The centrifugal clutch determines the proper level and engages when it is reached. When the power level drops, the clutch disengages and serves as a necessary safety feature.