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Choosing The Correct Pulley Type: Drive Pulleys, Idler Pulleys, and Driven Pulleys

Belt drive pulley for power driving

Trying to determine what type of pulley you need to fix your engine? Maybe you need a specific part to repair a broken washer, fan, or snow blower. Pulleys are a critical component in many household machines and automobiles, but one type or size does not fit all. Choosing the correct pulley type to replace your worn or broken parts can be intimidating if you don’t know where to start. If you feel like your local mechanic is speaking a foreign language, then perhaps we can provide some context on different pulley parts and their purposes to help you find the pulley you need. We will look at drive pulleys, idler pulleys, and driven pulleys to learn more about their differences, similarities, and functions.

Drive Pulleys

What is a drive pulley? You may have guessed it by the name, but drive pulleys are in fact the driving force of a pulley system. The drive pulley connects to the power source, which could be the shaft of an electric motor, or even a hand crank. In turn, the drive pulley then applies a force onto the belt, which causes it to move. It’s important to know what size of drive pulley you need, since the size and shape of the drive pulley in comparison to the driven pulley can control the amount of torque and the speed of the belt. For instance, a larger diameter drive pulley will speed up the driven pulley but provide less torque.

Every drive pulley will be made of steel or some other hard material. There are a couple of defining features on every drive pulley, but they will vary from part to part. You will find a groove around the circumference of the pulley that seats the belt. There should also be some kind of attachment hub to connect the drive pulley to the power source. Drive pulleys may also have a keyway cutout in the center hole. This is another thing you can look for when trying to determine the type of pulley you need to replace.

Idler Pulleys

Where a drive pulley and driven pulley are essential parts found in every pulley system, most pulley systems don’t actually require an idler pulley. Often, larger, more complicated pulley systems will need an idler pulley. If the direction of a belt needs to change from one pulley system to another, that’s where an idler pulley comes in. Sometimes an idler pulley simply holds the timing belt in place, especially if the belt travels for long distances. In this case, the name can be deceiving, since you wouldn’t want your idler pulley to actually be idle! If an idler pulley stops spinning, that is when something can go wrong.

The size and shape of the idler pulley don’t impact the speed or output of the belt, since the pulley is spun by the belt. This might make it easier to find a replacement part, but you can always ask the experts to ensure you’re getting what you need.

Idler pulleys and drive pulleys can look fairly similar, so it may be hard to tell what part you need. A key difference to differentiate the two is to look for a bearing. A functioning idler pulley spins freely on its own. Try spinning the outside of the pulley. If it spins, there is a bearing present, and you know you’re looking at an idler pulley.

Driven Pulleys

Although it may be confused with drive pulleys, driven pulleys essentially provide the opposite purpose to a drive pulley. Where drive pulleys are characterized by their connection to a power source, the driven pulley doesn’t connect to a power source at all. The driven pulley is part of the pulley system, only connected to the drive pulley by a timing belt. The driven pulley complements the drive pulley, working together to move energy from one place to another.

You can often identify a driven pulley based on where it is located. Where a drive pulley can be found on a motor, the driven pulley would be on the other end of the belt, allowing the rotating machinery to operate.

How to Choose the Correct Pulley

Hopefully, we’ve clarified the differences between pulley types enough that you now know which one you need. But then what? There are still a few more things to consider before making a purchase. As mentioned above, the best place to start is to determine whether you need a drive or driven pulley. From there you’ll need to consider the sizes needed, especially if it’s paramount you keep your machinery operating at the same level as before when replacing a part. Think about any other considerations you might need, such as noise level, corrosion-resistant materials, or pulleys that are made for using ropes or chains instead of belts. Gather a list of specifications you need and work with a reliable manufacturer to get you what you need.

Get Manufactured to Order Parts from Illinois Pulley & Gear

Still stumped about finding the right part? Perhaps your business is out of stock on crucial older pulley parts. That’s where Illinois Pulley & Gear can help. Our custom pulley replacement parts fit the needs of any application.

With over 90 years of combined industry knowledge, we’re the experts at helping all kinds of industries find the right part they need, often faster than the original manufacturer. With the ability to custom manufacture at any time, there is nothing we can’t help you find. Now you won’t have to come back after initially picking up the wrong part, because we’ll leave you in good hands.

If you’re in the Chicagoland area and are lucky enough to catch a worn part before it breaks, we’ll personally come out and recreate the part, so you don’t experience any downtime! That’s what our team does best, providing excellent customer service and custom solutions to our customers every time. Contact us today to learn more about our full selection of custom pulley and gear parts we offer.

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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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