Pulley: Types, Uses, Examples, and How it’s work?

What is a Pulley?

A pulley is a simple machine that consists of a rope and a grooved wheel. The rope fits into the groove in the wheel, and pulling on the rope turns the wheel. Pulleys are generally used to lift objects, especially heavy objects. The object lifted by a pulley is called the load.

A pulley is a wheel that carries a flexible rope, cord, cable, chain, or belt on its rim. Pulleys are used singly or in combination to transmit energy and motion. Pulleys with grooved rims are called sheaves.

In belt drives, the pulleys are attached to their axles on the shafts, and the power is transmitted between the shafts through an endless belt that runs over the pulleys.

One or more independently rotating pulleys can be used to provide a mechanical advantage, particularly for lifting weights. Shafts where pulleys can attach them to frames or blocks, and pulleys, blocks, and a combination of rope or other flexible material are called blocks and tackles.

Nowadays, plastic pulleys are also available in the market to carry small loads. This can be freely rotated about an axis running through its center. It can change the direction of a force, which makes it much easier for people to lift something. This feature allows you to pull down on one end to lift the 10 kg / s and one-meter-high object.

The earliest evidence of pulleys comes from the twelfth dynasty (1991–1802 BC) and ancient Egypt in Mesopotamia in the second millennium BC. In Roman Egypt, the hero of Alexandria identified the winch, one of the six simple machines used to lift weights. Pulleys are assembled to form a block and to handle it to provide a mechanical advantage for applying large forces.

Pulleys

To transmit power from one rotating shaft to another, the pulleys are also assembled as part of belt and chain drives. Plutarch’s Lives recalls a scene where Archimedes proved the effectiveness of the compound pulleys and block-and-tackle system by using one to pull a fully laden ship as if it were through the water Was gliding.

What are the uses of pulley?

The original primary use for pulleys was to make it easier to lift heavy items. A pulley is a simple machine made with a wheel and a rope, cord, or chain.

Pulleys can be found everywhere to help make tasks easier. In addition to lifting things, pulleys can be used singly or with many pulleys working together to transport people or things. They can also be used to provide power from one shaft to another.

Examples of a Pulleys include:

  1. Elevators use multiple pulleys in order to function.
  2. A cargo lift system that allows for items to be hoisted to higher floors is a pulley system.
  3. Wells uses the pulley system to hoist the bucket out of the well.
  4. Many types of Sports and Exercise equipment use pulleys in order to function.
  5. Construction pulleys are used in order to lift and place heavy materials.
  6. A simple technique of pulley is used in the case of blinds, and they help in pulling the curtains up and down. Similarly, in a theater system, pulleys are used to lift the curtains up.
  7. A simple pulley system holding a flower basket, that can be lowered to water the flowers.
  8. Crane used to lift heavy things, machines, collect debris, etc.
  9. Blinds on windows use a pulley system to move the blinds up and down. You pull the string on the blinds and the pulley system causes the blinds to open or close.
  10. Flagpoles use pulleys in order to hoist the flag up or to bring it down.
  11. Clotheslines can use pulley systems in order to make it easier to pull clothes toward the user.
  12. Pulleys can be used to place birdfeeders high in trees or on poles, and then to pull them down when they need to be refilled or removed.
  13. Roofers may use pulleys in order to hoist all of the shingles up onto the roof instead of attempting to carry them.
  14. Engines utilize a pulley system in order to work.
  15. Fans with chains are utilizing a pulley system in order to be turned on and off.
  16. A bulldozer is an example of the use of a pulley system.
  17. Pulleys are utilized regularly in oil derricks.
  18. Pulleys can be used to extend ladders.
  19. A sailing boat requires the help of pulleys to move the sails around as desired.
  20. Pulleys provide locomotion to workers to move up and down to wash buildings from the outside.
  21. Garage doors raise and lower utilizing a pulley system.
  22. Rock climbers use pulleys to climb steep rock surfaces easily.
  23. Timing belts in cars are examples of pulleys.
  24. Escalators utilize pulley systems to function.

These are all examples of pulleys. A cable system makes it easier to lift or move objects. Pulleys are required to move and lift very heavy or large objects. The simple principle behind pulleys makes them one of the most effective tools out there.

How does a Pulley Work?

The more wheels you have, and the more times you loop the rope around them, the more you can lift.

How do Pulley Work

One wheel

If you have a single wheel and rope, a pulley will help you reverse the direction of your lifting force. As in the picture below, pull the rope down to lift the weight. If you want to lift something weighing 100 kg, you need to pull down with a force of 100 kg, which is 1000 N (Newtons). If you want to lift the weight 1 meter in the air, you will need to pull the loose end of the rope at the other end a total of 1 meter.

Two wheels

Now, if you add more wheels and wrap the rope around them, you can reduce the effort of lifting the weight. Suppose you have two wheels and a rope wrapped around it as shown in the following illustration. The 100 kg mass (1000 Newtons weight) is now effectively carried by two sections of the same rope (the two strands on the left) instead of just one (ignoring the loose end of the rope you are pulling with), and that means that She can lift it by pulling it with a force of just 500 Newtons – half as much! Therefore, we say that a pulley with two wheels and the rope so wrapped gives a mechanical advantage (ME) of two.

Mechanical advantage is a measure of how much a simple machine multiplies a force. The greater the mechanical advantage, the less force you will need, but the greater the distance you will need to apply that force. The weight increases by 1 m, but now we need to pull the loose end of the rope twice as far (2m). Where from? To add 1m to the weight, you need to let the two sections of rope that carry it increase 1m each.

To do this, you need to pull the loose end of the rope 2m. Note that we can also find the mechanical advantage by dividing the distance we need to pull the rope by the distance the weight moves.

Four wheels

Okay, what if you are using four wheels held together by a long rope looped around them, like in the picture below? You can see that the 100 kg mass (1000 Newtons weight) is now hanging from four sections of rope (the one on the left, ignoring the loose end of the rope you are pulling on).

This means that each section of rope carries a quarter of the total weight of 1000 Newtons or 250 Newtons. To lift the weight into the air, all you have to do is pull with a quarter of the force – also 250 Newtons.

To add 1m to the weight, you need to shorten each section of the rope by 1m so that you have to pull the loose end of the rope 4m. We say a pulley with four wheels and the rope wrapped in this way gives a mechanical advantage of four, which is twice as good as a pulley with two ropes and wheels.

Material use for pulleys

Pulleys can be made from a variety of materials, including cast iron, cast steel or pressed steel, wood, and paper. The cast material should have good friction and wear characteristics. The pulley made from pressed steel is lighter than cast pulleys, but in many cases, they have less friction and can produce excessive wear.

What are the Types of Pulley?

There are three main types of pulleys:

  • Fixed pulley
  • Movable pulley
  • Compound Pulley
  • Cone Pulley
  • Block and Tackle pulley

1. Fixed Pulley

A fixed pulley’s wheel and axle stay in one place. A fixed pulley changes the direction of the force on a rope or belt that moves along its circumference. A good example of a fixed pulley is a flag pole: When you pull down on the rope, the direction of force is redirected by the pulley, and you raise the flag.

A fixed pulley is a pulley with the drum attached to a single location. While the force required to lift or move an object is no different than lifting it by hand, the fixed pulley allows you to change the direction of the force required.

For example, if you’re attached to a bucket that pulling water from a well, you can pull sideways with a firm pull to lift the bucket more comfortably than if you were pulling a bucket of water up hand in hand vertically. The water bucket still feels like the same weight, but it’s more convenient to lift.

Types of Pulley
Types of pulleys

2. Movable pulley

A movable pulley has an axle in a movable block. A single movable pulley is supported by two parts of the same rope and has a mechanical advantage of two.

A movable pulley is one in which the drum moves as you are moving the load. There is no change in the direction of the force that you need to apply, but the load will “feel” lighter than it is. If you were hauling a heavy hay bale up into the loft of a barn, for example, a movable pulley would make the load feel much lighter, although the direction you are pulling would be the same.

3. Compound Pulley

In a compound pulley system, there is both a moveable pulley as well as a fixed pulley. This means that not only does the load “feel” lighter, but you can also change the direction of the force.

Although this type of configuration makes it possible to move heavy loads very easily, the tradeoff is that considerably more motion is required to do the work.

4. Cone pulley

The cone pulleys is another specialized pulley system that incorporates the basic mechanics of a pulley system while allowing for mechanical adjustments. A cone pulleys are essentially multiple pulleys of decreasing vertical circumference on top of each other, forming a cone shape.

This cone shape allows the pulley operator to transfer the speed of the pulleys’ movements, requiring less work with a smaller circumference, but also producing less work. Multi-gear bicycles essentially operate on the same system; Cyclists can easily shift between smaller gears that propel the bike at a slower speed, and more gears require more effort but move the bike more distances per revolution.

5. Block and Tackle pulley

A block and tackle are a specific form of compound pulleys that can dramatically reduce the amount of work required to move a heavy object. A block-and-tackle pulleys system consists of several fixed and movable pulses arranged parallel to each other; a Fixed pulley is aligned with fixed and movable pulleys with movables.

Each compound pair is associated with the next pair, and each set reduces the total work required. This pulley system is attributed to the popular ancient inventor and mathematician, Archimedes.

What is Flat belt pulley?

Flat belt pulleys are used in transmission systems that are operated by flat belts, typically high speeds in textiles, low power applications, paper making, and office machinery such as computer printers. The flat belts are also used for conveyors. Compared to equivalent horsepower plaid belts, flat belts are 25% or more thinner, which allows the flat belt pulleys to be smaller than the V-belt pulleys.

Flat belts are also less expensive than belts used in a serpent belt pulleys. A safety factor is that in high torque situations, the belt may slip, causing damage to equipment other than the belt. Flat belts require flat pulleys and flat pulleys idlers. They do not necessarily require a flattened flat belt pulley. A flat pulley idler can also be used for the backside of a traditional V-belt. Flat belt drives apply motive power to the police belt.

Types of Flat belt Pulleys

Following are the various types of pulleys for flat belts:

  • Cast-iron Pulleys,
  • Steel Pulleys,
  • Wooden Pulleys,
  • Paper Pulleys, and
  • Fast and loose Pulleys.

1. Cast Iron Pulleys

Pulleys are usually made of cast iron. The rim is placed on the web from the central boss or by arms or spokes. The arms may be straight or curved and the cross-section is usually elliptical. Cast iron pulleys are usually made with round rims.

When a cast pulley contracts into the mold, the arms are in a state of tension and are very liable to break. Curved arms yield rather than break. Weapons are near the hub. This slight convexity is known as a crown. The crown centers the belt on a pulley rim while in motion. The crown can be 9 mm to 300 mm in the width of the face.

cast iron pulley
Cast iron pulleys

Cast iron pulleys can be of solid or split type. When it is necessary to mount a pulley on a shaft that is already carrying pulleys etc. or its ends are swollen, the split-pulleys are easy to use. There is a clearance between the faces and the two parts are easily tightened on the shaft by a bolt. A sunk key is used for heavy drives

2. Steel pulley

Steel pulleys are made from steel sheets and have great strength and durability. These pulleys are lighter in weight (about 40 to 60% less) compared to iron pulleys of the same capacity and are designed to run at higher speeds. They present a coefficient of friction with a leather belt that is at least equal to that obtained by a cast-iron pulley.

Steel Pulleys
Steel Pulleys

Steel pulp is usually made in two parts that are tied together. The clamping action of the hub keeps its shaft pulley; Thus, no key is required except in the most serious service. Steel pulleys are generally equipped with interchangeable bushes with shafts of different sizes to allow their use.

3. Wooden pulley

Wood pulleys are lighter and have a higher coefficient of friction than cast iron or steel pulleys. These pulleys have 2/3 of the weight of a similarly sized cast iron pulley. They are usually made of selected maples that are placed in sections and glued together under heavy pressure. They are kept from absorbing moisture by protective coatings of shells or varnishes so that war does not occur.

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Wooden Pulleys

These pulleys are either solid or split with an iron hub with screws or have adjustable bushes that prevent the frictional resistance between them and the shaft from being installed. These pulleys are used for motor drives in which the contact arc between the pulley face and the belt is restricted.

4. Paper Pulley

Paper pulleys are made from compressed paper fibers and are formed with metal in the center. These pulleys are commonly used for belt transmission from electric motors when the distance from the center to the center shaft is small.

paper pulleys
Paper pulleys

5. Fast and loose pulley

Fast and loose pulleys, used on the shaft, enables the machine to be turned on or off. A fast pulley is mounted on the machine shaft, while a loose pulley operates independently. The belt operates on a fast pulley to transmit power by the machine and is transferred to a loose pulley when the machine is not required to transmit power. In this way, stopping one machine does not interfere with other machines that run by the same line shaft.

The loose pulley is provided with a cast iron or gun-metal bushing with a collar at one end to prevent axial movement. The rim of the fast pulley is made larger than the loose pulley so that the belt runs slower on the loose pulley. The loose pulley usually has a longer hub to reduce wear and friction and requires proper lubrication.

Advantages and Disadvantages of Pulley Drive

Advantages of pulley

The main advantage of the pulley is that it can actually reduce the force required to lift heavy objects and redistribute the direction of the force required to lift heavy objects. Together, these two benefits make pulleys an essential tool for heavy lifting.

  • It provides a mechanical advantage while lifting heavy loads. The profitability of the equipment is known as the load ratio in the effort.
  • The pulley when applied to an engine, can also be called a belt. It can be easily transported and in contact with metals other than grease or oil.
  • The pulley can also be referred to as a belt when attached to an engine. It can be easily transported and come into contact with metals other than grease or oil.
  • A moving pulley is a load pulley. Increases Distance Range muted. Long-distance moving ropes serve as support.
  • It helps in any direction Pulley systems for applying a force and rely on the relationship between load and effort.
  • Silent in operation
  • It is easier and less expensive to make than simple gear
  • No lubrication required

Disadvantages of pulley

  • It uses friction when transferring speed hence there is a possibility of slip. However, this problem can be solved by using the timing belt and timing pulley discussed above.
  • It is not a suitable solution for very high-power transfer at high rpm.
  • Lifting distance increases while taking mechanical advantage.
  • Long-term fatigue and creep break the rope.
  • Not reliable compared to gears.

Top Asked Questions

What is a pulley?

A pulley is a wheel that carries a flexible rope, cord, cable, chain, or belt on its rim. Pulleys are used singly or in combination to transmit energy and motion. Pulleys with grooved rims are called sheaves.

What are the uses of pulley?

Uses of pulley:
1. A cargo lift system that allows for items to be hoisted to higher floors is a pulley system.
2. Wells use the pulley system to hoist the bucket out of the well.
3. Many types of exercise equipment use pulleys in order to function.

What is an Examples of a Pulleys?

Examples of pulleys include:
1. Elevators use multiple pulleys in order to function.
2. A cargo lift system that allows for items to be hoisted to higher floors is a pulley system.
3. Wells uses the pulley system to hoist the bucket out of the well.

What are the types of pulleys?

There are three main types of pulleys:
1. Fixed pulley
2. Movable pulley
3. Compound Pulley
4. Cone Pulley
5. Block and Tackle pulley

How does a Pulley Work?

A pulley is a simple machine that consists of a rope and a grooved wheel. The rope fits into the groove in the wheel, and pulling on the rope turns the wheel. Pulleys are generally used to lift objects, especially heavy objects. The object lifted by a pulley is called the load.

What is the definition of a pulley?

Pulley is a simple machine or a wheel on a fixed axle or shaft, with a groove along the edges to guide a rope. Pulleys are used to reduce the time and energy taken to lift heavy objects. It is supported by a frame that does not transfer force to the shaft but is used to guide the cable or rope.

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