Types of Belt Drives: Material, Applications, Advantages & Disadvantages : The rotation motion is the best and simplest way to transmit mechanical power with minimal losses. Transmission systems or drives are systems that allow rotational motion to be transferred from one mechanical element to another.
The rotation motion is the best and simplest way to transmit mechanical power with minimal losses. Transmission systems or drives are systems that allow rotational motion to be transferred from one mechanical element to another.
These systems are either driven by a prime mover or transmit rotational motion to the various parts of a machine. Shafts are commonly used to transmit rotational motion.
- The one who drives is referred to as the driving system, and
- The other, which is driven, is referred to as a driven system.
What is a Belt Drives ?
Belt drives are a type of frictional drive that transmits power from one shaft to another via pulleys that rotate at the same or different speeds.
The illustration depicts a belt drive. It consists of two pulleys with an endless belt passing over them. Because of the frictional grip between the belt and the pulley surface, mechanical power or rotary motion is transmitted from the driving pulley to the driven pulley.
The section of the belt with the less tension is known as the slack side, while the section with the most tension is known as the tight side. The difference in tension between the slack and tight sides of the belt is the effective pulling power that causes the driven pulley to rotate.
The tensions in the tight and slack sides of the belt are determined by the angle of contact; therefore, the belt drives must be configured so that the slack side is above and the tight side is below the pulleys.
The angled contact of the belt on the driven side is increased by this arrangement. In a belt-drive system, there is always the possibility of some slipping between the belt and the pulleys, causing the driven pulley to rotate at a slower speed and, as a result, reducing power transmission. As a result, belt drives are classified as a Negative type of power transmission system.
The amount of power transmitted depends on the following factors:
- The speed of the belt.
- The amount of tension applied to the pulleys by the belt.
- Contact arc formed by the belt and the small pulley.
- The circumstances in which belts are used.
Types of belt drives
There are seven different types of belt drives available, which are as follows:
- Open belt drives
- Crossed belt or closed drive
- Fast and loose cone pulleys
- Stepped cone pulleys
- Jockey pulley drive
- Quarter turn belt drives
- Compound belt drive
1. Open belt drive
Open belt drive refers to a configuration in which the endless (joint) belt moves from the top of one winch to the top of another pulley without crossing it. The induced shaft will rotate in the same direction as the driver shaft in this case.
The open belt drive employs shafts that are parallel and rotate in the same direction. The driver then pulls the belt from one side and delivers it to the other.
As a result, the tension in the lower side belt will be greater than that in the upper side belt. The lower side belt is referred to as the tight side belt, whereas the upper side belt is referred to as the slack side belt.
When the shafts are too far apart, the bottom of the belt should be tight and the top should be slack. As a result, when the upper side becomes the dull side, it relaxes due to its own weight, increasing the arc of contact.
2. Closed Or Crossed Belt Drive
In cross belt drive, the belt travels from the top of one pulley to the bottom of another, crossing itself. Every rotation, the entire belt remains in the same plane. In this case, the belt bends in two different planes with each rotation. In this case, both the driver and the driven shafts rotate in the same direction.
Cross or twisted belt drives are used with rotating shafts that rotate in both parallel and opposite directions. The driver in this case pulls the belt from one side and delivers it to the other.
As a result, the tension on the bottom side of the belt will be greater than on the top side of the belt. Due to high tension, the belt is known as the tight side, while due to low tension, the belt is known as the slack side.
When two parallel shafts must rotate in opposite directions, this type of belt drive uses a belt. The belt rubs against itself and wears off at the crossroads. To avoid excessive wear, the shafts should be kept as far apart as possible and operated at very low speeds.
A little consideration will reveal that where the belts cross, they rub against each other, resulting in excessive wear and tear. To avoid this, the shaft should be placed at a maximum distance of 20 B, where B is the width of the belt and the belt speed should be less than 15 m/s.
3. Fast And Loose Cone Pulley
When the driven or machine shaft must be started or stopped without interfering with the driving shaft, this type of belt drive is used. A fast pulley is one that is keyed to the machine shaft and runs at the same speed as the machine shaft.
A loose pulley runs freely over the machine shaft and cannot transmit any power. When the driven shaft required to be stopped, the belt is pushed onto the loose pulley by a sliding bar with belt forks.
4. Stepped cone pulleys drive
A step or cone pulley drive is used to vary the speed of the driven shaft while keeping the main or driving shaft constant. This is accomplished by moving the belt from one section of the steps to the next.
A step cone pulley is an integral casting that consists of three or more different sizes of pulleys adjacent to each other, as illustrated in fig. On the drive shaft, a set of driven cone pulleys is mounted upside down. A pair of pulleys will be wrapped in an endless belt.
The speed of the driven shaft can be changed by shifting the belt from one pair of pulleys to another. The diameter of the pulleys that drive and operate the belt is such that the same belt will operate when transferred over pairs of different pulleys.
Belt drives of this type are used when the speed of the driven shaft must be changed frequently, as in the case of machine tools such as lathes and drilling machines.
5. Jockey pulleys drive
A jockey pulley drive types of belt drive which is used to increase the angle of contact in an open belt drive. It is mounted near the smaller of the two pulleys and is placed on the slack side of the belt. It increases the angle of contact, resulting in increased power transmission capacity of the drive.
In an open belt drive arrangement, if the center distance is small, or if the driven pulley is too small, the arc of the belt’s contact with the driven pulley will be very small, reducing the tension in the belt, or if the belt requires Stress cannot be achieved by other methods, a sluggish pulley, called a jockey pulley, is placed on the slack side of the belt, as shown in fig.
Belt drive for the Jockey Pulley
This increases the arc of contact and thus stress, resulting in increased power transmission.
6. Quarter turn belt drive
Right-angle belt drives are another name for quarter turn belt drives. It is used with shafts that are at right angles and rotate in the same direction. To keep the belt from slipping out of the pulley, the width of the pulley’s face must be greater than or equal to 1.4 b, where b is the width of the belt. If a pulley cannot be arranged or reversible speed is desired, a quarter-turn belt drive can be used.
7. Compound belt drive
A compound belt drive is used when power is transferred from one shaft to another via multiple shafts.
Factors To Consider Before Using Different Types of Belt Drives :
- To ensure uniform tension in the belt section, the shaft must be properly lined.
- The pulleys should not be too close together in order to maximize the arc of contact on the small pulley.
- The pulley must not be positioned far enough away from the belt shaft to cause heavyweight on the belt shaft, increasing the friction load on the bearings.
- A long belt rotates from side to side, causing the belt to exit the pulley and form crooked spots.
- The tight side of the belt should be at the bottom, so that any sag on the loose side expands the arc of contact on the pulley.
- To achieve good results with flat belts, the maximum distance between the shafts should not exceed 10 m and the minimum distance should not be less than 3.5 times the diameter of the larger pulleys.
Classification of belt drive
Belt drives are typically classified into three categories:
- Large drive
- Medium drive
- Heavy drive
Light drives are used in agricultural machines and small machine tools to transmit small forces at belt speeds of up to 10 meters per second.
Medium drive: They are used to transmit medium forces at belt speeds greater than 10 m/s but not exceeding 22 m/s, such as machine tools.
Heavy drives are used in compressors and generators to transmit large forces at belt speeds greater than 22 m/s.
Types of belt
Four different types of belt are following : –
- Flat belt
- V belt
- Teethed belt
Flat belts are also used to transfer power from one shaft to another. The flat belt transmits power by utilizing the friction output between the belt and the pulley. The pulleys on a flat belt all rotate in the same direction.
They are typically classified as small woven endless belts or high strength flat belts. Because of the semi-elastic material used in construction, woven endless belts are especially useful where minimal vibration on the driven pulley is required.
High-strength flat belts are frequently useful because they eliminate the need for high belt tension to hold the pulleys, reducing the load on the shaft bearings.
A viscous resistant abrasive compound is used to make high strength flat belts.
V-belts are commonly used in factories and workshops where a large amount of power must be transmitted from one pulley to another, or when two pulleys are very close to each other.
The V belt solved the slippage and alignment issues. It is now the original belt for power transmission. They provide the best combination of traction, movement speed, bearing load, and service life. They are usually infinite, with a broadly trapezoidal normal cross-section.
The round belt is a belt with a circular cross-section that is designed to run in a pulley with a 60-degree V-groove. Round grooves are only appropriate for idler pulleys that guide the belt or when using O-ring type belts.
V-grooves increase friction by transmitting torque through palpation. Round belts, on the other hand, are only for use in low torque situations and can be purchased in various lengths or cut to length, and can be connected using a staple, a metal connector, gluing, or welding. To great effect, early sewing machines used a leather belt, either attached to a metal staple or glued.
Timing belts are a type of positive transfer belt that can track relative movement. These belts have teeth that fit into a corresponding toothed pulley. When properly stressed, they have no slippage, move at a constant speed, and are frequently used to transfer direct motion for the purposes of sequencing or timing.
They are frequently used in place of chains or gears, which reduces noise and eliminates the need for a lubrication bath. These belts are frequently found in automobile camshafts, short timing systems, and stepper motors. Timing belts require the least tension of any belt and are among the most efficient.
Slip and creep in belt
Slip in belt
Consider an open belt drive that rotates in a clockwise direction, with the belt rotating over the pulleys due to a strong frictional grip between the belt and the pulleys.
When the frictional grip becomes insufficient, there is a possibility of forward motion of the driver without the pulley, which is referred to as slip in a belt.
As a result, slip can be defined as the relative motion of the pulley and the belt in it. This reduces the velocity ratio, which is usually expressed in percentages and denoted by S.
Creep in belt
Consider an open belt drive that rotates in a clockwise direction. The tight side is the portion of the belt that leaves the driven and enters the driver, and the slack side is the portion of the belt that leaves the driver and enters the.
During rotation, the belt on the tight side expands and the belt on the slack side contracts.
Because of the uneven expansion and contraction of the belt over the pulleys, there will be a relative movement (motion) of the belt over the pulleys, which is known as creep in a belt.
Selection of belt drive
The following are some of the most important factors to consider when choosing a belt drive:
- The speed of the driving and driven shafts,
- ratio of speed reduction,
- The amount of power that will be transmitted,
- The distance between the shafts’ centers,
- positive driving conditions,
- Shaft configuration,
- There’s a location available, and
- Service teems
Applications of belt drive
Belt-drives are used in a variety of applications, including:
- To transfer power, a belt drive is used.
- Drive to the rotor on the rotor spinning machine.
- Conveyor makes use of a belt drive.
- Drive to drafting rollers and other rolling elements on a single delivery drawing machine.
- Drives the opening rollers, friction drums, and take-off rollers on a friction spinning machine.
- The main drive on the draw-texturing machine.
- The mill industry makes use of belt drives.
- Drive to the creel-rollers of a high-speed drawing machine.
Advantages and disadvantages of belt drive
Following are the advantages of belt drive:-
- It is inexpensive and simple to use.
- The new belt-drive efficiency can reach 95-98 percent.
- Belt drive requires little maintenance.
- A parallel shaft is not required for belt drives.
- They have overload and jam protection.
- The difference in speeds can be obtained by using a step or tapered pulley.
- When there is a long distance of power transmission between shafts, belt drives are the most cost-effective option.
- Noise and vibration are reduced, and load fluctuations are absorbed, extending the life of the machinery.
- By releasing belt tension, you can activate clutch action.
Disadvantages of belt drive
Following are the Disadvantages of belt drive :-
- Belt drive is not suitable for short distances.
- High levels of slip and creep cause a loss of performance.
- A constant velocity ratio cannot be achieved between the drive and driven pulleys.
- It generates a lot of noise.
- It has a low mechanical efficiency.
Materials used for belt drive
Materials used for construction of belt drive are following :-
- Leather belts
- Cotton belts or Fabric belts
- Rubber belts
- Balata belts
- Plastics belts
Conveyor belts are made of five different materials: thermoplastics, metal, rubber, fabric, and leather. Polyester, polyvinyl chloride, silicone, and polyethylene are examples of plastics.
The metals are stainless steel and carbon steel, and the fabric is canvas or cotton. A rubber composite is the most commonly used material because it is flexible, resistant, smooth, and seamless.
1. Leather belt
Leather is the most important material for a flat belt. The best leather belts are made from 1.2-1.5-meter-long strips cut from either side of the backbone of top-grade step hides.
The flesh side of the leather hair is smooth and hard, but the flesh side is strong. The fibers on the hair side are perpendicular to the surface, whereas the fibers on the flesh side are interconnected and parallel to it.
2. Cotton or fabric belt
The majority of fabric belts are made by stitching together three or more layers of canvas or cotton duck. These belts are also woven into a desired width and thickness strip.
They are applied similarly to linseed oil with a filler to make the belt waterproof and prevent fiber damage. Cotton bands are inexpensive and work well in humid climates and environments. Cotton belts are mostly used in farm machinery, belt conveyors, and other similar applications because they require little maintenance.
3. Rubber belt
Rubber belts are made of fabric layers that are held together by a rubber structure and have a thin layer of rubber on the face. These belts are extremely flexible, but they are quickly destroyed when exposed to heat, oil, or grease.
One major advantage of these belts is that they can be made indefinitely. These belts have been found to be suitable for use in sawmills and paper mills where they are exposed to moisture.
4. Balat belt
These belts are similar to rubber belts, but instead of rubber, balata glue is used. These belts are acid- and water-resistant, and they are not affected by animal oils or alkalis.
The belt should not be kept at temperatures above 40 ° C because the sanding begins to soften and become sticky at this temperature. Balata belts outperform rubber belts in terms of strength by 25%.
5. Plastic belt
Plastics used for belt include polyester, polyvinyl chloride, silicon, and polyethylene
Check Out Other Important Topics
|IC Engine||Important PDFs||Boilers||Synergy Maritime Exam||Naval Arch||MEO Class 4|
|Interview Questions||Difference Between||Types of Pumps||Auxiliary Machines||Types of Valves||Home|