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How Timing Belts Are Made

As an integral part of combustion engines, we rely on timing belts every single day. Whether used in our cars to get us from point A to point B, our lawn mowers, our washing machines, or anything else which uses an engine to operate, timing belts make life as we know it possible. Yet, there’s so much more to know and appreciate about these important pieces of equipment. Here, we will outline everything you need to know about how timing belts are made, what the best materials are, and how you can manipulate your timing belts for better engine performance. Let’s get started.

First, What Do Timing Belts Do?

In a combustion engine application, a timing belt’s main function is to synchronize the movement of the camshaft and crankshaft. As these two parts rotate, the timing belt works to ensure consistent, yet different speeds are maintained for each, relative to one another. A properly functioning timing belt is crucial to optimal engine performance, and without it, your engine will stop working completely.

What Are Common Timing Belt Construction Materials?

Rubber

As the most common timing belt construction material, rubber timing belts are widely used across industries and applications. In fact, most internal combustion engines still found in the majority of cars use timing belts made from some type of rubber or rubber compound.

While rubber is extremely common, it does have some drawbacks. Rubber timing belts are notorious for stretching and breaking relatively quickly when subjected to the high temperatures and quantities of motor oil found in vehicle engine blocks.

However, technology has advanced, and many types of temperature-resistant rubber compounds are now used to increase the lifespan of your timing belts, as well as their resistance to distortion. Improved rubber compounds and reinforcing fibers also provide greater strength and traction, guarding against sheared teeth, or other damage to the belt.

Polyurethane 

With naturally greater elasticity, as well as resistance to high temperatures and the harmful effects of oil, polyurethane has quickly become a popular option for timing belt construction. Polyurethane belts also offer long-lasting and extremely energy-efficient solutions for a wide range of applications. 

Typically capable of delivering high tensile strength, polyurethane belts also provide higher loading capacities, which is crucial for optimal torque production. Many in the industry also prefer these types of belts as they are relatively easy to clean and maintain. For many types of power transmissions and roller conveyor systems, polyurethane remains the best choice.

Fabric

When you require high-performance and acceleration forces, a fabric timing belt may be a great choice.

The wide array and combinations of materials used mean fabric timing belts offer fantastic tensile strength, low friction coefficients, and excellent resistance to temperatures, both high and low. When high torque or acceleration requirements need to be met, there are a wide range of fabric timing belt options that will be highly beneficial.

Timing Belt Construction & Design

Material

To this day, high-performing, durable rubber materials are still the substance of choice for timing belt manufacturing.

However, as mentioned above, rubber compounds are susceptible to degradation through constant exposure to excessive heat and contact with motor oil. This can result in lowered tension, impacting the precise times of the engine valves necessary for optimal performance.

To account for these issues, today’s timing belts are also constructed with sturdier materials, such as polyurethane, neoprene, or welded urethane, injected into molds.

Teeth

Timing belts rely on strong teeth to keep the crank and cam shafts synchronized, and those teeth come in a wide range of metric pitches. Pitch is a measurement of the distance between the centers of two adjacent teeth on the timing belt. A picture demonstrating how to measure pitch on a timing belt pulley is shown below.

Check out our technical data tables to get a better understanding of what pitches are and how they impact other timing belt pulley factors, such as diameter, and number of teeth.

When it comes to the design of the teeth, older belts typically make use of trapezoidal-shaped teeth. However, newer manufacturing techniques allow for curved teeth to combat the issues with noise and lifespan common for many trapezoidal toothed belts.

One final timing belt construction note: shortening the width of the timing belt reduces the weight and friction, helping to increase performance.

Timing Belt Tooth Profiles

Depending on the desired application and environment, timing belt teeth can be arranged in several different ways. As mentioned above, the first is trapezoidal, while more modern belts use curvilinear tooth profiles.

Trapezoidal Belts

Trapezoidal teeth are extremely effective at transmitting forces. However, at higher levels of torque or speed, teeth of this harsher, more blunt shape tend to wear down fast.

Despite their faults, trapezoidal teeth remain common, and are typically the primary choice for precision conveying and linear positioning belts.

Curvilinear Belts

With a smoother and more rounded tooth shape, curvilinear teeth reduce the risk of tension loss, and alleviate the high concentration of force trapezoidal teeth experience. While that may sound like a great improvement, curvilinear belts are not without drawbacks of their own.

Teeth of this profile are likely to suffer from a greater amount of play between the teeth of the belt and the grooves of the pulleys. Referred to as “backlash”, this difficulty usually results in less accurate positioning of the belt, and potentially decreased performance.

Modified Curvilinear Belts

Modified curvilinear belts seek to combine the strengths of both trapezoidal and curvilinear tooth profiles. With a shallower tooth depth and steeper sides, these belts are able to effectively transmit forces of higher speed and torque without sacrificing on durability. Accordingly, modified curvilinear belts are often a primary choice for demanding industrial applications.

Custom Timing Belt Pulley Stock From Illinois Pulley & Gear 

While timing belts are incredibly useful, they remain useless without the proper pulleys. Illinois Pulley & Gear produces made-to-order timing belt pulleys to exacting specifications. We are ready to help you find the products you need or to design your own custom equipment. We are ready to listen, understand your specialized requirements, and provide innovative solutions, every step of the way.

We invite you to browse our timing pulley stock to get started. However, if you would rather communicate directly with our team about your specifications and needs, you can contact us at any time via our online contact form. One of our product specialists will reach out promptly with further guidance, more information, or additional questions that will assist us in better serving you.

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    Eric BroseProject Manager, Technico Precision Manufacturing, Inc.
  • Illinois Pulley and Gear has been amazing to work with. They produce high-quality, custom parts, and they know their business.
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