What is a Timing Belt and How to Select Its Type?

What is a Timing Belt and How to Select Its Type? - Timing belt is one type of transmission belt that is already known the general public, especially in automotive, because timing belt is one of the automobile parts. Timing belt selected based on standard type, width and length. This post will explain how to choose the timing belt type in accordance with rotation speed and power are transmitted, how to determine the timing belt width corresponding to power capacity that is transmitted and how to determine the timing belt length corresponding to the distance between shaft and the diameter of timing pulley. But before selecting timing belt, we need to know in advance what is a timing belt.

What is a timing belt?

Timing belt is a belt transmission which has a tooth profile and paired with the timing pulley-shaped gear as well. Therefore, timing belt hook can perform transmission like gears and chains so it can be used for motion with a fixed ratio of rotation (without slippage).

Timing belt is made of neoprene rubber or polyurethane plastics as raw material with a core made of glass fiber or steel wires as well as teeth are carefully molded inner surface of belt. Timing belt has a maximum speed limit of approximately 35 m/s which is higher than v-belt and power transmitted can be reach 60 kW up to 100kW.

Generally, belt transmission has advantages such as low cost, simple construction and easy to get a speed ratio needed. Timing belt has another advantage is that it avoids the occurrence of slippage between belt and pulley.

How to choose the timing belt type

Selection of timing belt types based on small pulley rotation speed and power transmitted. If the higher speed of small pulleys and the greater power transmitted so the greater timing belt size is selected. Selection of timing belt size refers to the diagram supplied by the manufacturer of the timing belt. Each type of timing belt has a different diagram. For security timing belt, the power transmitted is motor power multiplied by some factor correction with the following formula:

Note:

Pd = Power transmitted (kW)

P = Motor electric power (kW)

fc = Load factor

f’c = Velocity ratio factor

Based on tooth shape, timing belt has several types like inch timing belt, metric timing belt and high torsion timing belt. For each type of tooth has a size variation determined based on the distance between the teeth timing belt (pitch). How to choose the timing belt size? Here we will explain how to choose the timing belt size for each type.

Inch type of timing belt (XL, L, H, XH)

Inch type of timing belt also called classical timing belt has a teeth trapezoidal shape with the distance between teeth (pitch) in inches units. Classical timing belts offer a maintenance free and economical alternative to conventional drives like chains and gears. This timing belt is capable of transmitting up to 100 kW and speeds of 10.000 rpm. This timing belt can be used in a wide range of applications from light duty office machinery to heavy duty industrial drives. 

To select a drive it is necessary to know the driver and driven shaft speeds, the demand power, proposed centre distance and duty cycle. This timing belt has a variation size with codes are XL, L, H and XH. We can be use the diagram below to select a timing belt size with regard to small pulley speed and power transmitted.

Metric type of timing belt (T2.5, T5, T10, AT5, AT10)

Metric type of timing belt has a teeth trapezoidal shape with the distance between teeth (pitch) in metric units. The metric timing belt series was created to meet industries need for polyurethane belts with a high quality ratio. They provide maximum power transmission combined with perfect tooth meshing. This timing belt is capable of transmitting up to 60 kW and speeds of 10.000 rpm.

To select a drive it is necessary to know the driver and driven shaft speeds, the demand power, proposed centre distance and duty cycle. This timing belt has a variation size with codes are T2.5, T5, T10, AT5 and AT10. We can be use the diagram below to select a timing belt size with regard to small pulley speed and power transmitted.

High torsion type of timing belt (3M, 5M, 8M, 14M)

High torsion timing belts or HTD timing belt offer optimized load distribution through the rounded tooth form, guaranteeing high power transmission in low speed and high torque applications. HTD timing belt is capable of transmitting up to 300 kW and speeds of 14.000 rpm. HTD timing belts can be used in a wide range of applications from minimum drives like electronic power tools to heavy duty machinery where durability and low maintenance is required. 

To select a drive it is necessary to know the driver and driven shaft speeds, the demand power, proposed centre distance and duty cycle. This timing belt has a variation size with codes are 3M, 5M, 8M and 14M. HTD timing belt made by certain manufacturers such as Japanese Misumi is usually to use the code of SM likes S3M, S5M, S8M, and S14M. We can be use the diagram below to select a timing belt size with regard to small pulley speed and power transmitted.

That is a description about What is a Timing Belt and How to Select Its Type?. If you find misconceptions in this post, please provide the correction in the comment box.