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Common belt failures

Mechanical drive 🔗

Date of publication : 27/08/2023

Reading time : 4 Minutes


Mastering Common Belt Failures : Discover our complete article analyzing problems and proposing solutions for your transmissions.

The belt, in the context of power tools, plays a crucial role in ensuring the efficient transmission of motion and power between different parts of a machine. This allows for a variety of tasks, from cutting to sanding to drilling. Its operation is based on a simple but ingenious principle: it connects two pulleys, one driving (which supplies the energy) and the other receiving (which receives the energy). In this article, we will explore common belt failures in detail.

The operation of the belt

To ensure the proper functioning of the belt, it is important to maintain the correct tension from the start of its use. This initial tension ensures optimum adhesion between the drive belt and the pulleys, which contributes to the efficient transmission of motion through the machine. It is often necessary to add a mid-range system or an additional tensioner to adjust the initial tension of the belt and compensate for its elongation over time.

When the machine is running, the belt slips on the surface of the pulley, which may cause a slight fluctuation in the transmission ratio of the movement. This situation is common for most types of belts, with the exception of timing belts which work with a precision coupling mechanism.

The characteristics of the belt

Compared to other transmission modes, such as chains or gears, the belt offers obvious advantages that greatly improve the use of power tools:

  • It's flexible so you can place the motor and receivers wherever you want
  • It is quiet even at high speeds
  • Effectively dampens transmission jerks, shocks and vibrations
  • It is economical because the belt replaces gears, countershafts, bearings and rigid gears

Types of belts at ITAFRAN


Belt functionstrapezoidal most commonly used:

  • Predominance in use due to their low cost
  • Cost-effective solution for power transmission
  • Price and performance optimization
  • Excellent ratio between price and transmitted power
  • Suitable for optimal speeds, ranging from medium to highs
  • Wide range of use for different powers
  • Generally quiet, however raw edge belts can generate noise
  • Used very frequently and are the most common choice for power transmission

Advantages of V-belts:

  • Effective hold of the strap in its groove
  • Higher power transfer for the same applied voltage
  • Ability to operate at speeds up to 33 m/s
  • More compact size compared to flat belts

Toothed belts 

Main functions of timing belts:

  • Transmission of power from a motor shaft to a driven shaft
  • Precise meshing with pulley or gear teeth to transfer torque and rotational speed efficiently
  • Precise synchronization between motor and driven shafts for perfect coordination in various systems such as combustion engines, machine tools and automation
  • Reduction of noise and vibrations thanks to the smooth meshing of the teeth of the toothed belt
  • Lightweight and simple compared to other transmission methods

Advantages of timing belts:

  • No need for lubrication
  • High yield
  • Shock absorbing capacity due to elasticity
  • Fewer maintenance requirements
  • Affordable cost

Courroies POLY-V

Functions of specific belts in very large series:

  • Very quiet operation
  • Small footprint with minimal spacing between elements

Advantages of specific belts in very large series:

  • Long life expectancy
  • Superior durability compared to V-belts
  • Excellent soundproofing during use
  • Possibility of obtaining high reduction ratios
  • Primarily used in mass-produced applications such as appliances, automotive, conveyors and power tools
  • Some variants are elastic and install easily


When should belts be serviced?

When it comes to power tools, belts wear out quickly. It is very important to regularly check:

  • Loss of elasticity : If the belt is installed incorrectly on the pulley, it may lose its elasticity and slip
  • Lack of tension : a badly tensioned belt can produce a hissing sound, which means less grip
  • Natural wear : Age and heavy use cause belt wear, which can lead to breakage and engine damage.

 Belt maintenance should be done regularly, with a quick visual and sound inspection once a month and a thorough inspection of the unit with a complete driveline shutdown once or twice a year.

What types of belt failure are there?

Belt cracks 

The presence of small cracks in the belt may be due to rubber curing caused by overvoltage, excessive sliding of the belt on the rollers, unsuitable temperatures or ageing. Replacing the belt, checking the condition of the housing and monitoring the heat of other components can be preventive measures.

Clean break 

If the belt undergoes a clean tear, possible causes include the presence of a foreign body between the belt and the pulley, excessive tension, defective materials, the use of inappropriate tools, or solid or liquid pollution. In such cases, changing the belt, checking the drive system and inspecting the pulley for wear are important steps.

Tension fault 

When the back of the belt shows pronounced wear, excessive tension or slippage due to inadequate tension may be the cause. To remedy this, we recommend replacing the belt, checking the entire belt routing, ensuring the tensioner is correctly tensioned, and following the installation instructions.

Sidewall wear 

Premature wear of one side of the belt, with a risk of fraying and significant noise, may be due to misalignment of the pulleys and/or tensioners, contact with a foreign body, or an offset when fitting the pulley. To solve this problem, we recommend replacing the belt, realigning the pulleys, checking all system components, and strictly following the manufacturer's installation instructions.

Tooth pull-out 

Belt tooth pull-out can result from heat-accelerated ageing, foreign bodies in the grooves, partial or complete blockage of engine components, or direct tooth pull-out. Recommended actions include replacing the belt, checking and restoring the drive system, and inspecting the engine guards to avoid future problems.

Irregular breakage

Transverse belt tears with back damage can be caused by gravel penetration in the absence of protection, belt over-tensioning, a blocked external component, or the presence of solid or liquid pollution. To solve this problem, we recommend replacing the belt and checking the drive system, while observing the installation instructions.

Particle pull-out 

Material is pulled off the belt and accumulates in the ribs. This can be the result of abnormal particle sticking, pulley misalignment, pulley wear, excessive tension or high operating temperature. To avoid this, it is advisable to follow the installation recommendations, check motor cooling and pulley condition, and ensure that the belt remains clean and free of greasy liquids.


Cutting - Welding

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