Performance of Timing Belt Profiles
Determining the exact differences between power transmission (PT) systems can be a daunting task without some guiding clarification about the fundamentals. Within this quick guide, the fundamentals of the relative performances of the PT drives, flat belts, V-belts, and timing belts– will be examined in order to provide the system designer with a more complete knowledge toolbox that can be applied to the design of even the most complex automation applications.
Chain Drive
One common, inexpensive transmission system that warrants consideration for simple applications is the chain drive system. This type of drive functions especially well in applications that require a long and potentially adaptable travel length due to the fact that it is relatively easy to simply add more chain links into to the system. Chain drives, however, are generally more vulnerable to wear failures than belt systems due to the metal-on-metal contact of the mating components; because of this, lubrication of some sort is required to optimize performance and they generally require shorter maintenance intervals when compared with belt drive systems.
Chain system used to transmit power to the rear wheel of a motorcycle
Friction Belts (Flat and V profiles)
In contrast, belt and pulley systems usually do not require any lubrication and as such are able to undergo longer maintenance period intervals. These drive systems rely primarily on friction to transmit motion, and the two most common belt PT systems are the flat belt and V-belt drives. In contrast, V-belt profile systems, are literally V shaped and mate in a V grooved pulley or sprocket, and these systems are able to operate systems more efficiently than a flat drive.
While flat belts profile drive systems are usually the slightly more cost effective belt option when compared to V-belt drives, both types are still friction systems and therefore require the high belt tensions in order to properly operate. These types of friction systems are also prone to slip under higher loads and speeds and should not be used for such applications where such slipping is not desired. Additionally, since both profiles are friction systems, they are not very mechanically efficient, generate large amounts of heat, and simply aren’t able to transmit as much power as a comparable synchronous belt drive system.
Flat belt drive in the machine shop at the Hagley Musuem
For these reasons, while the V and Flat belt systems are serviceable for a wide variety of applications, their uses are more limited under high performance design requirements such precision demands, a desire for synchronization, and a small, structurally optimized drive system.
Synchronous Belt Profiles
The best profile choice for these performance applications is a synchronous belt drive system. These belts feature a trapezoidal or circular toothed profile that meshes with a corresponding profile on the pulley or sprocket. These types of drives maintain system synchronicity far more effectively when compared to flat or V belt profile drives through the use of this toothed profile and mating pulleys or sprockets systems.
Because of the mechanical advantages in the drive system, along with the fact that the belt tooth profiles are comprised of complex geometric shapes that can be difficult to fabricate, timing belts profile systems are also typically the most costly option.
Synchronous drive system
Conclusion
Although the brief survey contained here only scratches the surface of the various types of PT systems performance strengths, it still serves as a solid starting point for even further inquiry into these topics. The most important point to remember when designing a power transmission system specification is that every application is unique, and there may not be a “one size fits all” belt system that can be employed every time. Some applications function very well with a basic chain drive, while others may require a highly specialized timing belt tooth profile.
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