BELT AND CHAIN DRIVES
A belt drive system is a method of transferring rotary motion between two shafts. A belt drive includes one pulley on each shaft and one or more continuous belts over the two pulleys. The motion of the driving pulley is transferred via friction between the belt and the pulley.
A chain drive system is used to transfer mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles. It is also used in many other forms.
Types of Belt and Chain Drives
Types of Belt Drives
There are different types of belt drives. They include the following:
1) Flat belt: These belts transfer the effect of force by friction, an example is a belt over a pulley. These belts are made from leather, woven cotton, rubber and balata.
2) Vee-belt: It has a greater effect of force transfer than flat belt. It is made from hi-text woven textiles, polyurethane, etc.
3) Poly-vee belt: This belt is flat on the outside and vee-grooved along the inside. It uses one belt.
4) Timing (synchronous) belt: It has limited power capacity compared to chain and vee-belt.
It does not require lubrication. It is used in low power applications.
5) Vee link belts: Linked belts can be used in place of vee belts. It has an advantage over other belts because it can be adjusted and easily installed with removable pulleys. It is expensive and has limited load capacity.
Types of Chain Drives
Chain drives are most often made of metal. Chain drives consist of an endless series of chain links. It provides a positive form of power transmission. Examples of chain drives are:
1) Roller chain: It is a very efficient method of transmission compared to belts, with far less frictional loss. Different types of roller chains are: standard roller chain, heavy series roller chain, multiple strand roller chain, double-pitch roller chain, self-lubricated roller chain and precluded roller chain.
2) Detachable chain: It is designed for lowspeed and light load power transmission drives. This chain consists of identical links, which are easily detachable from one another.
3) Pintle chain: This is used as a drive chain for higher speed and heavier loads.
4) Silent (or inverted tooth) chain: It consists of a series of toothed link-plate assembled on pin connectors, permitting smooth joint articulation.
Silent chain assembly: The sprocket teeth of silent chains mesh with shaped links instead of rollers on the chain. The joints between links use rolling rather than sliding contact. The overall effect reduces noise.
5) Leaf (or lifting) chain: It is used in applications requiring a strong, flexible linkage for transmitting reciprocative motion or lift, rather than rotating power. Leaf chain is used on applications such as: over head hoists, hydraulic-lift trucks and counterweights that require tension linkages.
6) Laminated metal chain: It consists of thin strips of resilient metal that extend on each side of the link and conform to the ribbed sides of a sheaved face.
Applications of Belt and Chain Drives
Belt and chain drives are used in many types of industrial applications.
a) Applications of Belt Drive
Belt drives have applications in the following:
- Industrial motors.
- Wood industry.
- Industrial installation.
- Garden equipment.
- Cement mixers.
- Piston compressor.
- Tangential drive.
- Brushing machine.
- Ice cream machine.
- Gas engine forklift truck.
- Shaft fixing.
- Grinding machine.
b) Applications of Chain Drive
The chain drive is one of the oldest forms of power transmission. It has applications in the following:
- Bicycle chain.
- Grinding machine.
- Car engine.
- Overhead hoists.
- Hydraulic-lift trucks.
- Counter weights that require tension linkages.
- Automobile drives.
Advantages and Disadvantages of Belt and Chain Drives
Advantages of Belt Drives
The advantages of belt drives are:
- Belt drives have easy, flexible equipment design.
- Isolation from shock and vibration between the driver and driven system is allowed.
- Driven shaft speed can be conveniently changed by changing pulley sizes.
- Belt drives require no lubrication.
- Maintenance is relatively convenient.
- Belt drives are quiet, compared to chain drives, and direct spur gear drives.
- A wide range of speed is available.
- Belt drives are less expensive than chain drives.
- Single belt drives will accept more misalignment than chain drives.
- Flat belt drives are best for extremely high speed drives.
- Belt drives cushion shock loads and load fluctuations.
- Belt drives will slip under overload conditions preventing mechanical damage to shafts, keys and other machine parts.
Disadvantages of Belt Drives
The disadvantages of belt drives are:
- Belt drives are easily damaged by oil, grease, abrasive, some chemicals and heat.
- Belt drives cannot be used where exact timing or speed is required.
- Loose or worn belt drives can be a major cause of machinery vibration.
- Belt drives are less compact than chain drives.
- Belt drives cannot operate at high temperature.
- Belt drives do not operate well in wet conditions.
- Belt drives have narrow capacity compared to chains.
- Belt drives cannot be used in reversing drives.
Advantages of Chain Drives
Advantages of chain drives are:
- Chain drives, unlike belt drives, do not slip or creep.
- There is no power loss due to slippage in chain drives.
- Chain drives are more practical for slow speed drives.
- Chain drives are more compact than belt drives.
- Chain drives can operate effectively at high temperature.
- Chain drives are usually easier to install on power transmission drives than belt drives.
- Chain drives do not deteriorate due to oil, grease, sunlight or age.
- Chain drives withstand chemical and abrasive conditions.
- Chain drives can operate in wet conditions.
- Chain stretch due to normal wear is a slow process.
- Chain drives are effective when several shafts are to be driven from a single shaft.
- Chain drives require less take-up adjustment than belts.
- Chains can be used with varying shaft centre distances, whereas, gears usually cannot.
- Chains are simpler than gears and less costly.
- Chain drives can be used on reversing drives.
Disadvantages of Chain Drives
Disadvantages of chain drives are:
- Chain drives cannot be used where the drive must slip.
- Chain drives cannot accept much misalignment.
- Chain drives usually require frequent lubrications.
- Chain drives are noisy and can cause vibration within the machine.
- Chain drives do not have load capacities or service life characteristics equal to those of gear drives.