Chain drives are most commonly used to transmit power between two components that are at a greater distance, but they may also be used for short distances.
They are one of the five most frequently used mechanical power transmission methods alongside shaft couplings, gear drives, belt drives and lead screws.
Each method has several advantages and disadvantages over others, which means engineers must be careful before making the final selection.
In this article, we’ll take a look at chain drives and their various types. They are a crucial part of many machines and they can also be used in applications other than just transmitting power, but more on that later. Let’s start from the beginning.
What is a Chain Drive?
A chain drive is one way of transferring mechanical power from one place to another place. Chain drive is widely used in vehicles like bicycles and motorcycles, to transfer power to the wheels. It is also used in a wide variety of machines.
Most often, the power is conveyed by a roller chain, known as the drive chain or transmission chain, passing over a sprocket gear, with the teeth of the gear meshing with the holes in the links of the chain. The gear is turned, and this pulls the chain putting mechanical force into the system.
The chains are made up of a number of rigid links that are hinged together by pin joints to provide the flexibility needed to wrap driving and driven wheels.
These wheels have special profile teeth and fit the corresponding recess in the chain link. Toothed wheels are known as sprocket wheels or bus sprockets. Sprockets and chains are thus constrained to move together without sliding and ensure the correct velocity ratio.
Chains are mostly used to transfer speed and power from one shaft to another when the center distance between their shafts is short such as bicycles, motorcycles, agricultural machinery, conveyors, rolling mills, road rollers, etc.
The chain can also be used for long center distances of up to 8 metros. Chains are used for velocities up to 25 m/s and power up to 110 kW. In some cases, high-power transmission is also possible.
The chains also used in conveyor belts are commonly blockchains and consist of solid or laminated blocks connected by side plates and pins. The blocks engage with teeth on sprocket wheels. Depending on the material being moved, buckets, hooks, or other devices are connected to the blocks.
Terminology of Chain Drive
- Chain pitch: This is the distance between the hinge center of a link and the corresponding hinge center of an adjacent link. It is usually denoted by p.
- Pitch circle diameter of chain sprocket: This is the diameter of the circle on which the hinge centers of the chain lie when the chain is wrapped with a ball. The hinge centers of the chain and the circle drawn through these centers are called pitch circles and its diameter is known as pitch circle diameter.
Types of Chain Drive
Following are the three types of chain drive:
- Hoisting and hauling chain drive
- Conveyor chain drive
- A power transmitting chain drive
#1. Hoisting and Hauling Chain.
A hoist is a device for raising or lowering a load using a drum or a lifting wheel around which a rope or chain is wound. It can be operated manually, electrically, or pneumatically and can use chain, fiber, or wire ropes as a lifting medium.
The best-known form is an elevator, the carriage of which is raised and lowered by a lifting mechanism. Most hoists are attached to their loads with a lifting hook.
These chains are used for hoisting and hail and operate at a maximum velocity of 0.25 m/s. Hoisting and ruling chain are of the following two types:
- Chain with oval links: This type of chain link is oval-shaped. Each link joint is welded. The sprockets used for this type of chain have receptors to obtain the link. These types of chains are used only at low speeds such as in-chain hoists and anchors for marine operations.
- Chains with square links: The links of this type of chain are square-shaped. Such chains are used in hoists, cranes, dredges. The manufacturing cost of this type of chain is less than a chain with oval links, but in these chains, overloading is easily kinking.
#2. Conveyor chain.
A conveyor chain is a chain that has been specially developed for chain conveyor systems. It consists of a series of plain bearings that are held together by connecting plates. Each bearing consists of a pin and a bushing 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 or hook joint type chain: This type of conveyor chain is used in a conveyor where the length between power transmissions is short.
- Closed joint type chain: This type of chain consists of a barrel and link and is made into a single casting, then the chain is heat-treated to provide high strength.
Conveyor chains are usually made of malleable cast iron. These chains do not have smooth-running properties. The conveyor chain operates at a slow speed of about 0.8 to 3 m/s.
#3. Power Transmitting Chain.
power transmission chains are used for the transmission of mechanical power when the distance between the centers of shafts is short. These chains have provisions for efficient lubrication. The power transmitting chains are of the following three types.
- Block or bush chain
- Bush roller chain
- Silent Chain
1) Block or bush chain
This type of chain was used in the initial stage of development in power transmission. It causes noise when rubbing between the teeth and the link when the sprocket is near or exiting the teeth. These types of chains are used to some extent at small speeds as conveyor chains.
2) Bush Roller Chain
A bush roller chain consists of an outer plate or pin link plate, inner plate or roller link plate, pins, bushes, and rollers. A pin passes through the bushing which is secured in the hole of the roller between the two sides of the chain.
The rollers are free to rotate on the bush which protects the sprocket wheel teeth against wear. Pins, bushes, and rollers are made of alloy steel.
A bush roller chain is extremely strong and simple to manufacture. It serves well in severe conditions. There is a slight noise with this chain due to the impact of the rollers on the teeth of the sprocket wheel. This chain can be used where there is slight lubrication.
When one of these chains becomes slightly elongated due to wear and stretch of parts, the extended chain sprocket is greater than the pitch of the wheel teeth. The rollers fit unevenly in the cavities of the wheel. The result is that the total weight falls on one tooth or a few teeth. Stretching of parts increases the wear of roller surfaces and sprocket wheel teeth.
Roller chains are standardized and manufactured on a pitch basis. These chains are available in single-row or multi-row roller chains such as simplex, duplex, or triple strand.
3) Silent chain
A silent chain, also known as an inverted tooth chain. It is designed to eliminate the bad effects caused by stretching and to create noiseless walking. When the chain is stretched and the pitch of the chain increases, the links ride on the teeth of the sprocket wheel in a slightly increased radius.
This automatically corrects small changes in pitch. There is no relative sliding between the teeth of the inverted tooth chain and the sprocket wheel. When properly lubricated, this chain gives durable service and runs very smoothly and quietly.
Advantages of Chain Drive
This are some advantages of chain drives compared with belt drive and gears:
- They can be used for both long and short distances
- Several shafts and be driven from a single chain
- They are compact and have small overall dimensions
- Even in fire hazards it does not faces any bad problem.
- Temperature and environmental conditions do not affect their working
- Initial tension is not required in the chain drive.
- They have very high efficiency (up to 96%)
- No slip and creep during the power transmission, ensure the perfect velocity ratio.
- The chain drive is easy to install.
- Chain drives have a low maintenance cost
- They can withstand abrasive conditions
- They can operate in wet conditions
Disadvantages of Chain drive
- Chain Drive can not be used where slip is the system requirement
- It requires precise alignment compared to belt drives
- The production of chain drives is higher than belt drives.
- Chain drive require frequent lubrication
- load capacity less compared with gear drives
- Conventional chain drive suffers vibrations due to the chordal effect.
- They are not suitable for non-parallel shafts
- They can not be used where precise motion is required
- The chain drive needs accurate and careful mounting.
- They require adjustments for slack like tensioning device
Application of chain drive
Chain drives are used in many types of industrial applications, such as:
- Chain drive is a device widely used for the transmission of power where shafts are separated at distances more significant than that for which gears are practical.
- Rigging and moving heavy materials
- Hydraulic lift truck fork operation
- Increasing or decreasing a driver’s output speed by altering gear ratios between the driver and the sprocket being driven
- Overhead hoists
- Operating conveyer belts
- Chain drive used in several industries for several purposes like Transportation Industry, Agriculture Machinery, Material Handling Equipment, Building construction.