{"id":12821,"date":"2022-02-08T16:36:41","date_gmt":"2022-02-08T14:36:41","guid":{"rendered":"https:\/\/fractory.com\/?p=12821"},"modified":"2024-12-16T11:41:38","modified_gmt":"2024-12-16T09:41:38","slug":"belt-drives","status":"publish","type":"post","link":"https:\/\/fractory.com\/belt-drives\/","title":{"rendered":"Belt Drives & Types of Belts"},"content":{"rendered":"
A belt drive is one of the most popular types of power transmission methods<\/a> besides gears, chain drives, shaft couplings<\/a> and lead screws. The use of these highly efficient mechanical drives is increasing with every passing year.<\/p>\n Due to the many advances in belt technology, they are now able to meet high-power demands while being extremely safe, efficient and durable. In this article, we shall take a detailed look at the different types of modern belt drives and belt types.<\/p>\n A belt drive is a frictional drive that transmits power between two or more shafts using pulleys and an elastic belt.<\/strong> In most cases, it is powered by friction but it may also be a positive drive. It can operate at wide ranges of speed and power requirements. It is also highly efficient.<\/p>\n When it comes to cost, a belt drive is considerably cheaper than gear and chain drives<\/a>. It costs less to install as well as maintain. Belt drive sheaves or pulleys undergo little wear compared to chain drive sprockets over extended periods of use.<\/p>\n Contrary to most chain and gear drives, a belt drive can handle some degree of misalignment. Correct alignment, however, increases service life. Excessive misalignment is responsible for issues such as improper belt tracking, uneven pulley wear, noisy operation and belt edge wear. The intensity of these issues is directly proportional to the belt’s width.<\/p>\n Belt tracking refers to the belt’s ability to be centrally located on the pulley and not shift to either side when in operation. Crowned pulleys can alleviate belt tracking issues.<\/p>\n It is also worth noting that a belt drive usually reduces shaft speed. For this reason, the driving pulley is usually smaller than the driven pulley. This provides a greater wrap angle on the driven pulley which is beneficial in friction-based drives. Designers may also use an idler pulley to increase the wrap angle and to maintain the recommended belt tension.<\/p>\n The belt is subjected to tension when the driving pulley pulls it. This belt tension, in addition to the static belt tension, is responsible for the transfer of mechanical force. High belt tension prevents heat buildup, slippage and alignment problems as there is little to no relative motion between the belt and the pulleys.<\/p>\n On the other side, the driving pulley pushes the belt away towards the driven pulley. This causes slacking of the belt. Thus, a belt drive sets up fluctuating loads in the belt. If these loads are not considered in the design process<\/a>, premature belt failure can occur. Fatigue is responsible for more belt failures than any other issue.<\/p>\n It is easy to identify the slack side from the side under tension. Whichever side of the belt approaches the driving pulley is under tension. The other side is the slack side.<\/p>\n As discussed above, belt drives today are capable of handling a wide range of speeds and power transmission needs. This has prompted further R&D, providing us with an array of different belt drive designs. All engineers should be familiar with the different types to facilitate an informed choice when selecting a belt drive for their application.<\/p>\n We can classify belt drives into seven main types, these are:<\/p>\n This is the simplest type of belt drive where two or more pulleys are connected with a belt wrapped around them. When power is supplied to the driving shaft, it rotates the driving pulley. The belt moves with it and rotates one or more driven pulleys.<\/p>\n In an open belt drive, both pulleys rotate in the same direction. With a horizontal pulley arrangement, the tight side of the belt is at the bottom and the slack side is at the top to increase the belt’s angle of contact with the pulleys.<\/p>\n This type of drive is used when two pulleys need to rotate in opposite directions or require a greater wrap angle for power transfer. In a crossed belt drive (aka twisted or closed belt drive), after passing over the top of the driven pulley, the belt contacts the driving pulley from the bottom. Thus, the belt’s shape resembles the number 8.<\/p>\n Between the two pulleys, the belt comes in contact with itself and the rubbing causes the belt to wear off. This can be mitigated by placing pulleys at the maximum allowed distance and running the system at slow speeds.<\/p>\n The crossed belt drive can transfer greater power for the same pulley dimensions and centre distance as the contact angle is higher. However, a longer belt is required as is evident by its crossed positioning.<\/p>\n This type of belt drive uses a driven pulley with multiple diameters. As the pulley resembles a stepped cone, it is known as a stepped cone pulley drive.<\/p>\n This drive is used when the driven shaft needs to be rotated at different speeds. Speed of the driven shaft can be increased or decreased by shifting the belt to a smaller or larger diameter step on the pulley respectively.<\/p>\n Common applications for this type of drive are lathes and drilling machines. A stepped cone pulley enables to use the same drive motor to obtain different output speeds.<\/p>\n As the name suggests, this drive consists of two pulleys – one fast and the other loose. Both of these pulleys are mounted on the driven shaft.<\/p>\n The fast pulley is keyed to the driven shaft so it rotates at the same speed as the shaft. The loose pulley is mounted without a key so it rotates freely relative to the shaft. This pulley is incapable of power transmission.<\/p>\n To hold the loose pulley in its place, a gun-metal or cast-iron bushing with a collar on one end is used. This prevents any axial movement. The diameter of the loose pulley is smaller than the fast pulley’s to allow the belt some slack.<\/p>\n This drive permits the immediate start and stop of the driven shaft without changing the speed of the driving shaft. When power needs to be transferred, the belt is shifted from the loose pulley to the fast pulley and when it needs to be stopped, the belt shifts back to the loose pulley.<\/p>\nWhat Is a Belt Drive?<\/h2>\n
Belt Tension and Slack<\/h2>\n
Types of Belt Drives<\/h2>\n
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Open belt drive<\/h3>\n
Cross belt drive<\/h3>\n
Stepped cone pulley<\/h3>\n
Fast and loose cone pulley<\/h3>\n