Chain drive

Chain drive is a method of transferring mechanical power from one place to another. Chain drives are widely used in vehicles such as bicycles and motorbikes, to transmit power to the wheels. It is also used in many types of machines.

Typically, power is transmitted by a roller chain, called the drive chain. Either the drive chain, which passes through a chain gear, with the teeth of the gear meshing with the holes in the chain links. The gear is rotated, and this pulls the chain putting mechanical force into the system.

Industrial chains are made up of a number of rigid links attached together by pin joints to provide the flexibility needed to cover the drive and drive wheels.

These wheels have specially shaped teeth and fit into the corresponding recess in the chain link. Wheels with teeth are called chain wheels. The sprocket and chain are thus restrained from moving together without slipping and ensuring the correct speed ratio.

Chains are mainly used to transmit speed and power from one axle to another when the center distance between their axles is short such as bicycles, motorbikes, agricultural machinery, conveyors, rolling mills, road rollers, etc.

Chains can also be used for long center distances. The chain is used for speeds up to 25m/s and power up to 110 kW. In some cases, high power transmission is also possible.

The chains also used in conveyors are usually block chains and consist of solid or laminated blocks connected by side plates and pins. The blocks mesh with the teeth on the sprocket. Depending on the material being moved, buckets, hooks or other devices are connected to the blocks.

Terminology of Chain Drive

• Chain pitch: Is the distance between the hinge center of one link and the corresponding hinge center of an adjacent link. It is often denoted p.

- Sprocket pitch circle diameter: This is the diameter of the circle on which the chain's hinge center rests when the chain is wound with a ball. The hinge centers of the string and the circle drawn through these centers are called the pitch circle and its diameter is called the corner circle diameter.

The following are three types of drive chains:
• Chain and bridge.
• Conveyor chain.
• Transmission chain.

Rafter chain and structure

A hoist is a device for lifting or lowering loads using drums or forklift wheels with ropes or chains. It can be operated manually, electrically or pneumatically and can use chains, threads or ropes as the lifting means.

The best known form is the elevator, a conveyance that is raised and lowered by a lifting mechanism. Mostly, hoists are attached to their load by a lifting hook.

These chains are used for bridges and operate at a maximum speed of 0.25 m/s. Chain bridges usually have the following two types:

• Chain with oval links: This type of chain has oval shaped links. Each bonded joint is welded. The sprockets used for this type of chain have receptors to obtain linkage. These types of chains are only used at low speeds as chain hoists and anchors in marine operations.

• Chains with square links: The links of this type of chain are square in shape. Such chains are used in hoists, cranes, dredgers. The production cost of this type of chain is lower than that of chains with oval links, but in these types of chains, overloading can easily lead to kinks.

Conveyor chain

A type of chain specially developed for chain conveyor systems. It consists of a series of plain bearings held together by connecting plates. Each bearing consists of a pin and a bush on which the chain roller rotates.

These chains are used to continuously lift and convey materials at speeds up to 2 m/s. There are two types of conveyor chains:

• Detachable chain or hook type chain: This type of conveyor chain is used in conveyors where the length between the transmission units is short.

• Closed-joint chain: This type of chain consists of a barrel and link and is molded into a single block, then the chain is heat-treated to provide high durability.

Conveyor chains are usually made of ductile cast iron. These chains do not have smooth running properties. Conveyor chains operate at a slow speed of about 0.8 - 3m/s.

Chains Used in the Electrical Industry

Transmission chains are used to transmit mechanical energy when the distance between shaft centers is short. These lines have provisions for effective lubrication. Chains used in the electrical industry have the following three types.
1. Block chain or cast chain.
2. Cast roller chain.
3. Silent chain.

1) Block chain or cast chain

This type of chain was used in the initial stages of development in the field of power transmission. It causes rubbing noise between the teeth and linkage when the sprocket is near or away from the teeth. These types of chains are used to some extent at low speeds as conveyor chains.

2) Cast Roller Chain

Bushing roller chain consists of outer plate or pin link plate, inner plate or roller link plate, pin, bushing and roller. A pin passes through a bushing secured in the hole of the roller between the two sides of the chain.

The rollers rotate freely on the bushing to protect the sprocket teeth from wear. Pins, bushings and rollers are made of alloy steel.

Tubular roller chains are extremely sturdy and simple to manufacture. It serves well in harsh conditions. There is a slight noise with this chain due to the impact of the rollers on the sprocket teeth. This chain can be used in places where light lubrication is required.

When one of these chains becomes slightly elongated due to wear and stretching of the components, the elongated sprocket becomes larger than the pitch of the wheel. The rollers fit unevenly in the wheel wells. As a result, the total weight falls on one tooth or a few teeth. Stretching the parts increases the wear of the roller surfaces and sprocket teeth.

Roller chains are standardized and manufactured on a highly specialized basis. These chains are available in single-row or multi-row roller chains, such as simplex, duplex or a triple strand.

3) Silent chain

Noise reduction chain is also known as reverse tooth chain. It is designed to eliminate the negative effects of stretching and create noiseless walking. As the chain is stretched and the chain pitch is increased, the chain links will grip the sprocket teeth at a slightly increased radius.

This automatically corrects small changes in pitch. There is no relative slippage between the teeth of the reverse tooth chain and the sprocket. When properly lubricated, this chain will last and run very smoothly and quietly.

Advantages of chain drive

These are some of the advantages of chain drives over belt and gear drives
• They can be used for long and short distance fishing.
• Several shafts and driven from a single chain.
• They are compact and have small overall dimensions.
• Even during the fire hazard, it does not face any bad problems.
• Temperature and environmental conditions do not affect their performance.
• Initial tension is not required in the chain drive.
• They have very high efficiency (up to 96%).
• No slipping or creep during power transmission, ensuring perfect speed ratio.
• The chain drive is easy to install.
• Chain drive has low maintenance costs.
• They can withstand abrasive conditions.
• They can operate in wet conditions.

Disadvantages of chain drive

• Chain drive systems cannot be used when sliding is a requirement of the system.
• It requires precise alignment relative to belt drive.
• The output of chain drive is higher than that of belt drive.
• Chain drives require regular lubrication.
• load capacity is less than gear drive.
• Conventional chain drives vibrate due to the chord effect.
• They are not suitable for shafts that are not parallel.
• They cannot be used where precise movement is required.
• The chain drive needs to be installed correctly and carefully.
• They require adjustments for slack like tensioning devices.

Application of chain drive

Chain drives are used in many types of industrial applications, such as:
• Device widely used for power transmission in which the shafts are separated at a distance greater than that at which gears are practically used.
• Making trusses and moving heavy materials.
• Operate hydraulic forklifts.
• Increase or decrease the driver output speed by changing the gear ratio between the driver and the driven sprocket.
• Overhead hoist.
• Operate conveyor belts.
• Chain drives are used in several industries for several purposes such as transportation industry, agricultural machinery, material handling equipment, building construction.