Belt Drives are a type of frictional drives used to transmit power from one shaft to another by means of pulleys which rotate at the same speed or at the different speed.
CONTENTS :
❑History
❑ Introduction
❑ Applications
❑ Materials used for Belts
❑ Selection of Belt Drive
❑ Types of Belt Drive
❑ Velocity Ratio of Belt Drive
❑ Power transmitted by Belt Drive
❑ Advantages & Disadvantages
2. Contents
History
Introduction
Applications
Materials used for Belts
Selection of Belt Drive
Types of Belt Drive
Velocity Ratio of Belt Drive
Power transmitted by Belt Drive
Advantages & Disadvantages
3. History
Ancient Roots:
15 BC: Silk quilling
machine in China
(earliest record)
1st-15th Centuries:
Water-powered
bellows, spinning
wheels (China)
Industrial
Revolution:
18th Century: Flat
leather belts power
factories
20th Century and
Beyond:
V-belts invented
(increased grip,
power)
1917: Endless
rubber V-belt
revolutionizes
technology
Modern Era:
Diverse belt types
for various
applications
5. Introduction
Belt Drives are a type of frictional
drives used to transmit power from
one shaft to another by means of
pulleys which rotate at the same
speed or at the different speed.
The power is transmitted due to
the friction between the belt
and pulley.
It is used for long distance
power transmission.
6.
7. Applications of Belt Drives
Automotive
Industry
Industrial
Machinery
Agriculture
Machinery
Home
Appliances
Exercise
Equipment
Printing
Industry
Textile
Industry
HVAC
Systems
9. Selection of Belt Drive
POWER TO BE
TRANSMITTED
SPEED OF THE
DRIVING AND
DRIVEN SHAFTS
SPACE AVAILABLE CENTRE DISTANCE
BETWEEN THE
SHAFTS
SHAFTS LAYOUT SERVICE
CONDITIONS
SPEED REDUCTION
RATIO
11. Types of Belt Drives
1. Light drives
used to transmit small powers at belt speeds up to about 10 m/s,
as in small machine tools.
2. Medium drives
These are used to transmit medium power at belt speeds over 10 m/s to 22 m/s
as in agricultural machines, conveyer systems, water pumps.
3. Heavy drives
These are used to transmit large powers at belt speeds above 22 m/s
as in compressors, generator & heavy machinery.
13. Flat Belts
Used to transmit moderate amount
of power from one pulley to another
When the two pulleys are not more
than 8 metres apart.
used in industrial machinery, such
as conveyor systems, printing
presses, and textile machines
14. V - Belt
Used to transmit moderate amount
of power from one pulley to another
when the two pulleys are very near
to each other
used in automotive engines, power
tools, and industrial machinery
15. Circular Belt or Rope
Used to transmit a great amount of
power from one pulley to another
when the two pulleys are more than
8 meters apart.
16. Types of Flat Belt Drives
I. Open belt drive
II. Crossed or twist belt drive
III. Quarter turn belt drive
IV. Belt drive with idler pulleys
V. Compound belt drive
VI. Stepped or cone pulley drive
VII. Fast and loose pulley drive
17. 1. Open Belt Drive
used with shafts arranged parallel
and rotating in the same direction
18. 2. Crossed or Twist Belt Drive
used with shafts arranged parallel
and rotating in the opposite
directions
19. 3. Quarter Turn Belt Drive
also known as right angle belt drive
used with shafts arranged at right
angles
and rotating in one definite direction
20. Quarter Turn Belt Drive with Guide Pulley
In case the pulleys cannot be
arranged or when the
reversible motion is desired, then a
quarter turn belt drive with guide
pulley may be used.
21. 4. Belt Drive with Idler Pulleys
used with shafts arranged parallel
and when an open belt drive cannot
be used due to small angle of
contact on the smaller pulley.
This type of drive is provided to
obtain high velocity ratio and when
the required belt tension cannot be
obtained by other means.
22. Belt Drive with many Idler Pulleys
When it is desired to transmit
motion from one shaft to several
shafts, all arranged in parallel, a belt
drive with many idler pulleys is used
23. 5. Compound Belt Drive
used when power is transmitted
from one shaft to another through a
number of pulleys
24. 6. Stepped or Cone Pulley Drive
used for changing the speed of the
driven shaft while the main or
driving shaft runs at constant speed.
This is done by shifting the belt from
one part of the steps to the other.
25. 7. Fast and Loose Pulley Drive
used when the driven or machine
shaft is to be started or stopped
whenever desired without interfering
with the driving shaft.
26. Slip of Belt
• Slip occurs when the belt slips on
the pulley due to insufficient tension
or excessive load.
• Slip can cause a loss of power
transmission and can lead to
premature wear of the belt.
27. Creep of Belt
• Creep refers to the gradual
elongation of the belt as it passes
over the pulleys.
• This is caused by the elastic
properties of the belt material.
28. Velocity Ratio of Belt Drive
It is the ratio between the velocities of the driver and the driven.
When the thickness of the belt (t) is considered,
29. Velocity Ratio of Compound Belt Drive
the power is transmitted from one shaft to another, through a number of pulleys.
For 4 pulleys,
For 6 pulleys,
30. Power transmitted by Belt Drive
Power transmitted by a belt,
T1 = Tensions in the tight slack side of the belt (in Newtons)
T2 = Tensions in the slack side of the belt (in Newtons)
v = Velocity of the belt (in m/s)
Belt drives have been used for over 200 years.
The earliest mention of a mechanical belt drive is in a 15 BC Chinese text that describes a quilling machine that uses a pulley machine to wind silk fibers onto bobbins.
The Babylonians and Assyrians also used chains for water drawing machines, which were the first belts. These chains were flat and operated on flat pulleys.
In 1917, the vulcanized rubber V-belt was developed, which uses cotton or hemp rope with V-groove pulleys to reduce belt tension.
A mechanical transmission system refers to a system of components that transmit power or motion from one part of a machine to another. It is commonly used in various types of machinery, vehicles, and mechanical systems. The main purpose of a mechanical transmission system is to transfer power or torque from a power source, such as an engine or motor, to the desired output mechanism. It allows for the control and manipulation of speed, torque, and direction of rotation.Some common examples of mechanical transmission systems include:
Gear systems: These systems use gears of different sizes and configurations to transmit power and control speed. They can be found in vehicles, industrial machinery, and appliances.
2. Belt and pulley systems: These systems use belts and pulleys to transmit power and motion. They are commonly found in engines, conveyor systems, and agricultural equipment.
3. Chain drives: These systems use chains and sprockets to transmit power and motion. They are often used in bicycles, motorcycles, and industrial machinery.
4. Shaft and coupling systems: These systems use shafts and couplings to transmit power and motion between rotating components. They can be found in pumps, fans, and various mechanical systems.Overall, the mechanical transmission system plays a crucial role in enabling the efficient and controlled transfer of power and motion within machinery and mechanical systems.
the size of the pulleys determines the mechanical advantage of the system.
The driver pulley is the pulley that is typically connected to a motor or other power source, while the driven pulley is the pulley that is typically connected to the driven device.
The larger the driver pulley is, the more torque it can provide, and the higher the speed of the driven pulley will be.
Conversely, the larger the driven pulley is, the lower the speed of the driven device for a given speed of the driver pulley.
The size of the pulley that is larger will depend on the specific application requirements.
If a larger torque is required, then the driver pulley may be larger, while if a higher speed is required, then the driven pulley may be larger.
Tension : Apply a force to (something) which tends to stretch it.
Torque is a measure of the force that can cause an object to rotate about an axis
“When it comes to power transmission, sometimes the simplest solutions are the best. That’s the beauty of belt drives.”
Belt drives: quiet, efficient, and low-maintenance, the workhorses of power transmission.
The tight side of the belt is the side that is under tension and is responsible for transmitting the driving force from the driver pulley to the driven pulley. It is usually the side of the belt that is in contact with the larger pulley.
On the other hand, the slack side of the belt is the side that is not under tension and is responsible for carrying the return portion of the belt. It typically wraps around the smaller pulley and has a looser tension compared to the tight side.
The tension difference between the tight side and the slack side is essential for maintaining proper belt grip on the pulleys and ensuring efficient power transmission. It helps prevent slipping or excessive stretching of the belt during operation.
Having improper tension on the tight and slack sides of a belt drive system can lead to several consequences, including:
Slippage
Excessive wear
Reduced power transmission
Belt misalignment
Noisy operation
This is because, when the upper side becomes the slack side, it will sag due to its own weight and thus increase the arc of contact.
1. Automotive Industry: Belt drives are extensively used in vehicles for various applications such as driving the alternator, water pump, power steering pump, and air conditioning compressor.
2. Industrial Machinery: Belt drives play a crucial role in industrial machinery for transmitting power between different components, such as motors, pumps, compressors, and conveyor systems.
3. Agricultural Equipment: Belt drives are used in agricultural machinery like tractors, combine harvesters, and irrigation systems for tasks such as driving the PTO (power take-off) shaft, harvesting equipment, and conveyors.
Home appliances: Belt drives are used in home appliances such as washing machines, dryers, and vacuum cleaners to drive various components such as the drum, blower, and brush roll.
4. HVAC (Heating, Ventilation, and Air Conditioning) Systems: Belt drives are utilized in HVAC systems for driving fans, blowers, and compressors, allowing efficient air circulation and temperature control.
5. Printing Industry: Belt drives are commonly found in printing presses to transfer power and drive various mechanisms involved in printing, including paper feeding, ink distribution, and plate cylinders.
6. Fitness Equipment: Many fitness machines, such as treadmills and stationary bikes, employ belt drives to transfer power from the motor to the running belt or flywheel, providing a smooth and continuous motion.
7. Material Handling: Belt drives are extensively used in conveyor belt systems for transporting goods and materials in industries like logistics, warehouses, airports, and manufacturing plants.
8. Textile Industry: Belt drives are employed in textile machinery for tasks like driving spinning frames, looms, and other components involved in the textile production process.
9. Power Tools: Many power tools, including drills, sanders, and saws, utilize belt drives to transfer power from the motor to the cutting or sanding mechanism.
10. Exercise Equipment: Belt drives are used in exercise equipment such as rowing machines, elliptical trainers, and weight machines to provide resistance and a smooth exercise experience.
1. Light Drives:
- Small household appliances: Light drives are used in small appliances like electric fans, blenders, and mixers.
- Office equipment: Light drives are used in printers, scanners, and small paper shredders.
- Light-duty machinery: Light drives can be found in small woodworking tools, hobbyist machines, and small-scale manufacturing equipment.
2. Medium Drives:
- Automotive applications: Medium drives are commonly used in vehicles for power transmission, such as in engine accessories like water pumps, alternators, and power steering systems.
- Industrial machinery: Medium drives are used in equipment like compressors, pumps, and medium-sized manufacturing machinery.
- Conveyor systems: Medium drives are used in moderate-load conveyor systems found in warehouses, airports, and distribution centers.
3. Heavy Drives:
- Heavy-duty machinery: Heavy drives are used in large-scale industrial machinery, such as mining equipment, construction machinery, and heavy manufacturing machinery.
- Large-scale power transmission: Heavy drives are used in power generation systems, including turbines, generators, and large-scale compressors.
- Marine applications: Heavy drives are used in marine propulsion systems for large ships and vessels.
- Off-road vehicles: Heavy drives are used in heavy-duty trucks, agricultural machinery, and construction vehicles.
Light drives
Transmit small powers at belt speeds up to 10 m/s. Light drives have many applications, including:
TV backlighting
Smartphone backlighting
LED displays
Automotive lighting
Dimming of lights
Medium drives
Transmit medium power. Medium voltage drives are used in many applications, including:
Mining
Oil and gas
Raw materials
Chemical and petrochemical
Cement industries
Regulating and controlling rotating equipment such as fans, conveyors, machine spindles, and pumps
Timing belt is an integral component of an internal combustion engine responsible for synchronizing the rotation of the camshaft and the crankshaft. It enables the proper opening and closing of the valves of the engine during both the intake and exhaust strokes of each cylinder.
1. Flat belts: Flat belts are commonly used in industrial machinery, such as conveyor systems, printing presses, and textile machines. They are also used in agricultural equipment, such as grain elevators and threshers. Flat belts are preferred when the drive pulleys are far apart because they can transmit power over long distances.
Flat belts
Commonly used in belt conveyors, food industries, and sawmills. Flat belt drives are suitable for long distance power transmission.
At high belt speeds, a flat belt can deliver significant power.
Operation with minimal noise
High efficiency (up to 98%)
Because of the narrow bending cross-section, there is less bending loss.
High flexibility
No need for groove
long service life due to their ability to handle dust and filth.
It can be reinforced for increased strength.
2. V-belts: V-belts are commonly used in automotive engines, power tools, and industrial machinery. They are preferred over flat belts when high torque transmission is required. The V-shaped design of the belt allows for better grip and prevents slippage, which makes them ideal for high-power applications.
V-belts are also used with grooved pulleys,
Trapezoidal in crossection
V-belts
Commonly used in electric pumps, compressors, and machine tools.
Available in a broad range of sizes, strengths, and materials,
high power transmission capacity.
Low cost
Installation is simple and inexpensive.
The arrangement is compact.
Due to the wedging effect with pulleys, flat belts have a lower efficiency than flat belts.
. Circular belts: Circular belts are commonly used in exercise equipment, such as treadmills and elliptical machines. They are also used in sewing machines and other small appliances. Circular belts are preferred for their flexibility, durability, and ability to transmit power over small pulleys.
Available in different sizes, colors, and textures
There is no fraying.
Economical
Strong and long-lasting
Cleaning is simple.
Fit different pulley shapes
Non-marking
Can be strengthened for added durability
Abrasion resistance and UV resistance can be enhanced as necessary.
Slip refers to the relative motion between the belt and the pulleys.
This can occur when there is insufficient friction between the belt and the pulleys, or when the belt tension is too low. When slip occurs, the driven pulley will rotate at a slower speed than the driving pulley.
To prevent slip, the belt tension must be properly adjusted, and the load should be within the design limits of the belt and pulley
Creep occurs when the belt stretches over time, causing it to become longer than the distance between the pulleys. This can cause the belt to ride up on the pulley, which can cause uneven wear and a loss of power transmission. To prevent creep, the belt should be properly tensioned at installation and periodically re-tensioned as needed. Some belt materials, such as polyester, have lower creep rates than others and may be preferred for applications where creep is a concern.
In summary, slip and creep can both lead to reduced power transmission efficiency and premature wear of the belt. Proper belt tensioning and load management are key to preventing these issues.
Creep refers to the gradual elongation of the belt as it passes over the pulleys. This is caused by the elastic properties of the belt material. As the belt stretches, it loses contact with the pulleys for a brief moment, which can cause a slight reduction in the speed of the driven pulley.
As the belt stretches, it loses contact with the pulleys for a brief moment, which can cause a slight reduction in the speed of the driven pulley.
where,
d1 = Diameter of the driver
d2 = Diameter of the follower
N1 = Speed of the driver in r.p.m.
N2 = Speed of the follower in r.p.m
t = Thickness of the belt
d1 = Diameter of the pulley 1,
N1 = Speed of the pulley 1 in r.p.m.,
d2, d3, d4, and N2, N3, N4= Corresponding values for pulleys 2, 3 and 4.
Fig shows the driving pulley (or driver) A and the driven pulley (or follower) B the driving pulley pulls the belt from one side and delivers the same to the other side.
So the tension on the former side (i.e. tight side) will be greater than the latter side (i.e. slack side)
The effective turning (driving) force at the circumference of the follower is the difference between the two tensions (i.e. T1 – T2).
A little consideration will show that the torque exerted on the driving pulley is (T1 – T2) r1.
Similarly, the torque exerted on the driven pulley i.e. follower is (T1 – T2) r2.
Cost-effective: Belt drives can be up to 95-98% efficient. They are less expensive than chain drives for low horsepower and low ratio applications.
Simple to use: Belt drives are simple to use and don't require parallel shafts.
Low maintenance: Belt drives require less maintenance and can last for years.
Quiet: Belt drives run quieter than metal chains.
Wide speed range: Belts can handle a wide range of speeds, from high horsepower drives to slow speed and high speed drives.
No lubrication: Belts don't require lubrication.
Breakdown: If the belt breaks, you're stranded and will need a tow and a new belt.
No side flexibility: Belt drives have no side flexibility and cannot be split up.
More expensive than chains: Belt drives are more expensive than chains.
Less common: Belt drive bikes are less common.
High slippage: Flat belt drives can have high slippage and creep, which can result in loss of power.
Low mechanical efficiency: Flat belt drives can have low mechanical efficiency.
More space: Belt drives require more space and can only operate up to a certain speed.
Wear out: Belt drives are prone to wear and tear.
