Multi-Plate Clutch: Construction, Working, Application and Advantages

The four common types of multi-plate clutch systems are:

Centrifugal Multi Plate Clutch

These clutches work by using centrifugal force. When the engine speeds up, this force pushes the clutch shoes outward, making the clutch engage. This type of clutch is popular in small engines like lawnmowers, go-karts, and motorcycles.

Wet Multi Plate Clutch

This type of clutch is dipped in oil, which cools and lubricates the clutch plates. The oil lowers wear and tear, making the clutch last longer. Wet multi-plate clutches are often used in motorcycles and high-performance cars.

Dry Multi Plate Clutch

Unlike wet clutches, dry multi-plate clutches work without being in oil. They use friction between the plates to engage and disengage. Dry clutches are simpler to design and maintain but wear out faster than wet ones. They're often seen in vehicles like cars and trucks.

Hydraulic Multi-Plate Clutch

As the name implies, this clutch uses hydraulic pressure to engage and disengage the clutch plates. When you squeeze the clutch pedal, hydraulic fluid is transferred to the clutch actuator, which applies pressure to the clutch plates and allows them to engage. Hydraulic multi-plate clutches are commonly found in modern vehicles.

Some of the common multi-plate clutch parts include:

Clutch Plate

In a multi-plate friction clutch, the manufacturer stacks the clutch plates together and alternately fits them with the flywheel and the pressure plate. This system enables torque transfer from the engine to the transmission system through frictional contact between the clutch plates and the flywheel.

Each clutch plate has a friction material coating, which improves its grip and allows for smooth engagement and disengagement of the clutch. When you apply the clutch pedal, the pressure plate parts away from the clutch plates, reducing the frictional force and disengaging the clutch from the engine. This hinders the power flow from the engine to the transmission and allows for gear changes or a complete stop without stalling the engine.

Pressure Plate

The pressure plate is a metal disc. It works in conjunction with multiple clutch plates stacked together. This design increases the surface area for friction and allows the system to handle more power without increasing the clutch's overall size.

The pressure plate is fitted on a splined shaft. This permits it to move back and forth. The movement is controlled by the clutch pedal, which, when you press, causes the pressure plate to exert or release pressure on the clutch plates.

This component is engineered to handle significant wear and tear, as it is constantly subjected to friction and heat during clutch operation.

Clutch Cover

The clutch cover is bolted to the engine’s flywheel. This strategic positioning allows it to exert pressure on the clutch plates through a series of springs or diaphragm mechanisms. When the clutch pedal is engaged, the cover moves and applies force to the clutch plates, pressing them against the flywheel. This action creates the necessary friction to transmit power from the engine to the transmission.

The clutch cover must be robust enough to handle the high stresses and heat generated during clutch engagement and disengagement. It is usually made of heavy-duty materials like steel or cast iron to withstand these conditions. The cover’s design includes ventilation features to dissipate heat and prevent overheating, which can lead to clutch failure.

Springs or Hydraulic System

Springs are coil springs around the clutch's pressure plate. When you press the clutch pedal, these springs compress to reduce the pressure on the clutch plates and disengage the clutch. This action interrupts the power flow from the engine to the transmission, enabling you to change gears. Upon releasing the pedal, the springs expand, pressing the plates together and re-establishing the connection between the engine and the transmission.

Alternatively, in the hydraulic system, hydraulic fluid is pressurised by a master cylinder. When you engage the pedal, the hydraulic pressure decreases to allow the clutch plates to separate. When you release the pedal, the pressure increases to push the plates together for engagement.

Both springs and hydraulic systems are designed to handle the high torque and power demands of modern vehicles.

Flywheel

The flywheel is a bulky, rotating disc that is placed on the engine's crankshaft. Its function is to store rotational energy. It provides a smooth surface against which the clutch plates can engage and disengage.

When the engine runs, the flywheel maintains a consistent angular velocity. This helps in smoothing out the pulsations from the engine's power strokes.

Clutch Hub

The clutch hub is the central connection point for the clutch assembly's multiple friction and steel plates. It engages with the transmission's splined shaft to transfer the rotational force from the engine to the wheels.

Clutch Housing

The clutch housing provides structural support to the multi-plate clutch parts and ensures their alignment and proper functioning. They are made of sturdy materials like aluminium or steel to withstand operational stresses and thermal expansion.

Clutch housing removes contaminants by enclosing the clutch plates, pressure plate, and other related components.

Throw Out Bearing

When you press the clutch pedal, the multi-plate clutch system's throw-out bearing helps disconnect the engine’s flywheel from the clutch disc. This disconnection is crucial because it stops the engine’s power from going to the transmission, making it possible to change gears smoothly.

Pilot Bearings

Pilot bearings can be found within the flywheel or at the end of the crankshaft. This placement helps to support the tip of the transmission input shaft, which is crucial during the transition between different engine speeds and gear shifts.

The pilot bearing helps to keep the input shaft stable and prevents it from shaking. If the shaft moves too much, it can quickly wear out the clutch parts and cause problems with the car’s power being sent to the wheels.

Fulcrum Pin

The fulcrum pin is the pivot point for a lever connected to the clutch pedal. When you press the clutch pedal, the lever pivots on the fulcrum pin to initiate a series of movements that ultimately lead to the clutch's disengagement. This action allows the pressure plate to move away from the clutch plates to interrupt the power transmission from the engine to the transmission shaft, enabling gear changes.

The key benefits of the multi-plate clutch are:

Higher Torque Capacity

A multi-plate clutch can transmit higher torque than a single-plate clutch. The increased surface area of multiple clutch plates boosts the frictional force necessary for power transmission.

This clutch system is ideal for high-performance cars, heavy machinery, and motorcycles.

It ensures that high-performance engines' torque effectively gets transferred to the transmission shaft without slippage. This helps during rapid acceleration or when hauling heavy loads.

Smaller and Lighter

This clutch system is not only smaller but also lighter. It allows them to fit in a vehicle where space is premium. This reduction in size and weight contributes to overall vehicle efficiency by improving fuel economy and performance.

Moreover, the lighter clutch improves the vehicle’s handling. It reduces the rotational inertia, allowing for easy acceleration and a more responsive driving experience.

Improved Heat Dissipation

Friction occurs between the plates when the clutch engages and disengages, generating heat. In a single-plate clutch, this heat can build up quickly and lead to overheating, which reduces the clutch’s efficiency and lifespan.

However, in a multi-plate clutch, the multiple plates are soaked in cooling fluid, which helps to carry away the heat more effectively. This cooling fluid flows between the plates, absorbing the heat generated during the clutch operation and transferring it away from the friction surfaces.

Handles RPM

RPM stands for Revolutions Per Minute. It is a unit of measurement that indicates how many times an engine’s crankshaft completes a full rotation within a minute. In vehicles, it reflects how fast the engine operates at any given moment.

When an engine operates at high RPM, the risk of clutch slippage increases due to high forces exerted on the clutch components. Slippage is detrimental as it can lead to power loss and excessive wear. The multiple-disc clutch combats this by distributing the load across multiple plates, thereby enhancing grip and reducing the likelihood of slippage.

Reduced Jerks

The multi-plate clutch’s ability to engage smoothly minimises jerky movements during gear shifts. Whether accelerating or slowing down, the transition between gears becomes seamless. This benefit is particularly valuable in both everyday driving and high-performance applications.

The multi-plate clutch is not without the following drawbacks:

Increased Complexity

These clutches are more complex than single-plate because of their multiple friction discs and steel plates. This complexity can make maintenance and repair tasks more challenging and time-consuming.

Higher Cost

Multi-plate clutches' additional components and complexity often result in higher manufacturing costs. In the event of replacement, this clutch can impact your vehicle maintenance budget.

Potential for Overheating

In some cases, multi-plate clutches can be prone to overheating, especially under heavy loads or aggressive driving conditions. Overheating can cause the clutch components to warp or glaze. This will reduce their effectiveness and potentially lead to clutch slippage or failure.

Reduced Fuel Efficiency

The additional friction and weight of multi-plate clutches can have a slight influence on fuel efficiency. While the difference may be negligible in everyday driving conditions, it can become more noticeable in high-performance vehicles or during prolonged periods of stop-and-go traffic.

Clutch Judder

Multi-plate clutches may be more prone to clutch judder which is characterised by a vibration or shudder sensation during clutch engagement. This phenomenon can occur due to uneven wear on the clutch plates or improper clutch adjustment.

Multi-plate clutches remain essential in vehicles because they offer efficient power transmission and enhance driving performance. While multi-plate clutches offer advantages like higher torque capacity and improved heat dissipation, they also have drawbacks. These include increased complexity, higher cost, potential for overheating, reduced fuel efficiency, and the possibility of clutch judder.

To ensure you remain financially stress-free when other components start degrading due to issues in the multi-plate clutch, get a car insurance policy with zero depreciation car insurance. This insurance for four-wheelers from Tata AIG covers repair and replacement costs for damaged components caused by road accidents, natural calamities, man-made riots, and fires.

If you already have this policy, you must proceed with car insurance renewal within the due date to ensure you receive a premium discount for not claiming the policy tenure.

How does a Multi-Plate Clutch work?

The clutch consists of several components, including a flywheel, pressure plates, friction plates, and steel plates. When engaged, the pressure plate applies force to the friction plates, allowing power transmission between the engine and the gearbox.

Why is the thrust spring important in a multi-plate clutch?

The thrust spring maintains firm contact between the friction plates and steel plates, allowing smooth rotation.

How does the Pressure Plate function in a Multi-Plate Clutch?

The pressure plate applies force to the friction plates, ensuring they rotate together as a single unit.

What is the role of the Clutch Drum in a Multi-Plate Clutch?

The clutch drum is connected to the engine shaft and has slots for externally threaded friction plates to slide into.

What advantages does a Multi-Plate Clutch offer?

The key advantages include high torque capacity, smaller size compared to single-plate clutches, efficient power transmission, and being suitable for heavy vehicles and racing cars.