What Do You Mean by Type of Belt Drive?
As previously stated, belt drives can now handle a wide range of speeds and power transfer requirements. This has inspired more research and development, resulting in various types of belt drive designs. All engineers should be aware of the numerous varieties to make an informed decision when selecting a belt drive for their application. There are seven primary types of belt drives:
- Open-belt drive
- Closed or crossed belt drive.
- Fast and loose cone pulley
- Stepped cone pulley drive
- Jockey pulley drive
- Quarter turn belt drive
- Compound belt drive
This is the most basic sort of belt drive, in which two or more pulleys are connected by a belt. The driving pulley rotates when power is applied to the driving shaft. One or more driven pulleys are rotated while the belt moves with it.
Both pulleys rotate in the same direction in an open belt drive. To enhance the belt's angle of contact with the pulleys, a horizontal pulley arrangement places the tight side of the belt at the bottom and the slack side at the top.
Closed or Crossed Belt Drive
This type of belt drive is used when two pulleys must rotate in opposite directions or when power transfer requires a higher wrap angle. After passing over the top of the driven pulley, the belt meets the driving pulley from the bottom in a crossed belt drive (also known as a twisted or closed belt drive). As a result, the shape of the belt resembles the number 8. The belt rubs against itself between the two pulleys, and the rubbing causes the belt to wear away. This can be addressed by using the maximum distance between pulleys and running the machine at slow speeds.
Fast and Loose Pulley
This type of belt drive has two pulleys, one fast and the other loose, as the name implies. Both pulleys are attached to the driving shaft. The driven shaft is keyed to the fast pulley, which means it rotates at the same speed as the shaft. The loose pulley is attached to the shaft without a key, allowing it to revolve freely. This pulley is unable to transmit power. A gun-metal or cast-iron bushing with a collar on one end is used to keep the loose pulley in place. This eliminates axial movement. The loose pulley's diameter is smaller than the fast pulley's to give the belt some slack. This drive allows the driven shaft to start and stop instantly without modifying the driving shaft's speed.
Stepped Cone Pulley Drive
A driven pulley with different diameters is used in this sort of belt drive. The pulley is known as a stepped cone pulley because it resembles a stepped cone. This drive is used when the driven shaft needs to be rotated at different speeds. Shifting the belt to a lower or bigger diameter step on the pulley can raise or reduce the speed of the driven shaft. Lathes and drilling machines are common uses for these types of belt drives. A stepped cone pulley allows users to get varied output speeds from the same drive motor.
Jockey Pulley Drive
In this type of belt drive, the contact area between the belt surface and the pulley is reduced with smaller pulleys. The power transmission capacity is reduced if the pulley diameter is too small to make meaningful contact with the belt's surface. If the pulleys are required to be close to each other, the wrap angle around the smaller pulley must be lowered. This restricts its ability to transmit power.
A jockey wheel or an idler pulley can be used to solve the problems described above. A jockey wheel is a machine element that steers or guides another element in mechanical systems. The idler pulley is located on the belt's slack side. They increase the performance of the belt drive by reducing vibration by supporting the belt. For smaller pulleys, idler pulleys can increase the wrap angle, increasing the surface area between the driving belt and the pulley.
Quarter-Turn Belt drive
Most belt drives can only be used with parallel shafts. However, this isn't always the case. When rotating shafts are at right angles, quarter-turn belt drives can be used. After performing a quarter turn, a belt on a quarter turn belt drive (also known as a right angle belt drive) passes around two perpendicular shafts. The width of the pulley must be at least 40% wider than the cross-section of the belt to keep it in place. Guides or idler pulleys are sometimes used to improve belt tracking and reduce slippage.
Compound Belt Drive
Belt drives are commonly used to reduce shaft speed. For this reason, most belt drives transfer motion from a smaller pulley to a larger one. However, the speed ratio achieved by a single pair of pulleys may not always be sufficient. Compound belt drives can be used in these situations since they allow for larger speed ratios. In this type of belt drive, there exist numerous pulleys keyed to at least one of the shafts and more than two shafts. Through several shafts, the driving pulley distributes power from one shaft to another. This configuration enhances the speed ratio without requiring a larger driving pulley or taking up too much space.
Accelerate your GATE preparations with BYJU'S Exam Prep and get unlimited access to all structured live courses and mock tests:
All the Best