Chain Drives and Types of Chains
Chain drives and types of chains:
The main disadvantage of the belt drives and the rope drives is that the velocity ratio does not remain constant, but varies on account of slip. Since chain drives are positive drives there is no slip, hence the velocity ratio will remain constant.
Chain drives are suitable for small centre distances and can be used generally up to 3 meters but in special cases even up to 8 meters. Chain drives transmit power up to 100kw and operating peripheral velocity up to 15m/s. The velocity ratio can be as high as 8:1.
Chain drives are employed for the wide range of power transmission applications, like in bicycles, motorcycles, rolling mills, agricultural machinery, machine tools, conveyors, coal cutters, etc.
A chain drive consists of a chain and two wheels, called Sprockets. The sprockets are toothed wheels over which an endless chain is fitted.
The different types of chains used in power transmission are,
- Roller chain
- Silent chain
- Leaf Chain
- Flat-top Chain
- Engineering Steel Chain
Regardless of the types of chains, their styles are classified as follows.
- Straight link chains, which have an alternate ‘outside’ and ‘inside’ links.
- Offset link chains, which have all links alike. These include integral link chains, such as bar-link, flat-top, and welded steel chains,
Roller chains are ones that are commonly used in bicycles, motorcycles, machine tools, etc. A silent chain is an inverted tooth chain which is extensively used for smooth and noiseless operations at low velocities.
Types of Chains
From an industry standpoint, the major types of chains are as follows
1. Roller Chain (Bush Roller Chain)
This type of chains is most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire- and tube-drawing machines, printing presses, cars, motorcycles, and bicycles.
Roller chain consists of a series of short cylindrical rollers held together by side links. It is driven by a toothed wheel called a sprocket. It is a simple, reliable, and efficient for power transmission.
These chains are generally smaller in diameter than the height of the link plates of the chain. the link plates serve as guides when the chain engages the sprockets,
Chains are also served as a guide to support material carried on it on tracks or ways, as is characteristic of conveyors and some bucket elevators. Roller chains are used for both drive and conveyor applications.
- The most commonly used chain for drives is the single-strand standard series roller chain. The power rating capacities of these chains cover a wide range of drive load requirements.
- Multiple-strand roller chains are used to provide increased power capacity without the need for increasing the chain pitch or its linear speed.
2. Silent Chain
The silent chain also called inverted tooth chain, consists of a series of toothed link plates assembled on joint components in a way that allows free flexing between each pitch.
Silent chains are made up of stacked rows of flat link plates with gear-type contours designed to engage sprocket teeth in a manner similar to the way a rack engages a gear as shown in the figure. The links are held together at each chain joint by one or more pins, which also allow the chain to flex.
Silent chains from different manufacturers usually cannot be connected together. Standard silent chains are used in a wide variety of industrial drives where a compact, high-speed, smooth, low-noise drive is required.
High-performance silent chains are available in a wide range of sizes with pitches and in widths and are used on very-high-speed drives where exceptional smoothness and quietness are required. These chains are commonly used in industrial equipment where ultimate smoothness is required.
3. Leaf Chain
Leaf chains are designed for lifting rather than power transmission. Tensions are very high, but speeds are slow. Normally the chains work intermittently. The main considerations in the design of the leaf chains are tensile loads, joint wear, and link plate and sheave wear.
Leaf chain doesn’t mesh with sprockets, because they are intended to run over sheaves, so there is no provision for them to engage a sprocket. Leaf chains must often lift very large loads, and hence they need high yield strength and do not get permanently stretched when they lift large loads. The most common use for leaf chain is probably on lift trucks.
4. Flat-top Chain
Flat-top chains are widely used on conveyors, most basically used on the special type of slat conveyor.
The Flat-top chain consists of.
- A series of steel top plates with hinge-like barrels curled on each side.
- Pins are inserted through the barrels to make a joint. These act as both beams and bearings.
- Pins are retained by press fits or heading in the barrels of one top plate and are free to articulate in the barrels of the next link.
- The connecting pin is usually either knurled or enlarged on one end to retain the pin in one barrel of the top plate.
- Thus a continuous length of the flat-top chain is formed.
- The flat-top chain is intended only for conveying.
5. Engineering Steel Chain
Engineering steel chains were first developed in the 1880s were designed for difficult conveying applications. Most engineering steel chains are used in conveyors, bucket elevators, and tension linkages. Only a few are used in drives. The main design considerations for these chains are tensile loads, several types of wear, lubrication, and environment.
Wear the most important parameters while designing an engineering steel chain. Joint wear, roller and bushing wear, and sidebar and track wear all are of great concern for conveyor chains.
The Chain Used In Bicycle
Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust or simply for stylish.
Chain drive was the main feature which modified the safety bicycle introduced in 1885, with its two equal-sized wheels, from the “high wheeler” type of bicycle. The popularity of the chain-driven safety is still a basic feature of bicycle design today.
A bicycle chain has a very high efficiency because it moves the point of pressure farther away from the axle, putting less stress on the bearings, thus reducing friction in the inner wheel. The higher chain tension was found to be more efficient.
Chain Drives In Automobile Vehicles
A chain-drive system transmits power from a differential to the rear axle in a vehicle.
Back in earlier days of the automobile chain drives are the very popular power transmission system. It gained prominence as an alternative to the Système Panhard with its rigid Hotchkiss, Driveshaft and universal joints.
Chain drives are simpler to design than driveshaft and universal joints.
Because of less unsprung weight at the rear wheels, it allows the suspension to react to bumps more effectively. By this means the vehicle would have a smoother ride.
Advantages and Disadvantages Of Chain Drives
- They are positive non-sail drives.
- Efficiency is very high (up to 99%).
- It can be employed for the shaft which is at small and as well as large centre distances up to 3m.
- They permit high-velocity ratio up to 8:1 in one step.
- They can transmit higher power than belt drives.
- Because the sprockets are lighter than the pulleys, they produce less stress on the shafts compared to the belt drives.
- Unlike the belt drives they can operate under adverse temperature and atmospheric conditions.
- They occupy less space and are more compact than belt drives.
- Maintenance is low.
- The driving and driven shaft should be accurately aligned so that their axes are exactly parallel.
- Requires more lubrication.
- High initial cost.
- Stretching of the chin makes it impossible operation having periodic reversals.
- Velocity fluctuations are more.
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- Transmission of Power: Belt Drives and Types of Belt Drives [completed]