Raw-Edge vs Wrapped V-Belts

In 1917, the first rubber V belt was born. From this time on, the v-belts became standardized through trade and manufacturing associations. During the same period, the types and models of V belts were expanded to accommodate a wider range of applications. Traditional or wedged, wrapped or toothed, and the many materials used throughout the process make up an impressive list.

The main point of this post is to compare raw edge v belts to wrapped v belts. Before we begin to analyze the pros and cons, it would be helpful to know a little more about how these belts work.

Wrapped (or smooth) v-belts

The wrapped belt can be considered a standard V-belt. The term cladding comes from the fabric that covers the inside of the belt, giving it a very uniform look and feel, as well as a fairly quiet running characteristic.

The purpose of wrap is twofold. The fabric provides wear resistance, making the belt more durable. The contact between the belt and the wheels is constant and can occur at very high speeds. This additional protection prevents contamination and wear of the belt and pulley, allowing the belt to run longer before it wears out to the point where it cannot properly transfer the required power.

Another benefit is that the belt slips, which is critical in applications that require it. While the triangle belt may seem counterintuitive in skidding in the wheel, it can prevent significant damage. The covered belt is more prone to slip than the original belt when a spike in torque or a sudden change in drive speed causes the belt drive to react. In most cases, the belt will break before it can transfer power back to the gearbox or motor, so the belt’s ability to slide is a safety factor.

Finally, the fabric coating has high oil resistance. The original belt may become clogged with contaminants and absorb moisture. This will cause the belt rubber to expand and cause fracture.

Raw-edge (or cogged) v-belts

The bottom of the Raw-edge belts has gears, giving up the fabric wrap on the outside of the belt, leaving the interior material exposed to the side. The belt has a higher coefficient of friction and now holds the pulleys better. This increased grip means that the raw-edged belt transmits more horsepower at higher speeds, in some cases as much as 30 percent more.

Increased power is a substantial benefit of this type of belt. There are other benefits worth mentioning. The raw-edged belts, due to the inclusion of gears, are better wound around the smaller wheels. These belts are also cooler when operating at higher speeds and generally have better temperature resistance.

V-belt similarities

The V-belt operates through the mechanical advantages of the wedge. Once the belt is installed and properly tensioned, its tension can move huge loads and achieve very high speeds. One type of belt, called a wedge-shaped V-belt (3V, 5V, 8V), has a greater wedge effect in the wheel grooves than a traditional V-belt. This means that the tension increases and the power increases.

The operation of all v-belts is similar. However, details such as tension levels and how much power they can transmit will vary. These numbers will vary depending on the application and the type and model of the individual belt. All traditional belts (A, B, C) will have the same contact Angle as the above wedge belt.

V-belt structures are also mostly universal. It has a rubber layer on top and bottom. Between these two layers, further surrounded by damping rubber, is the tension rope. The rubber compounds and rope materials used will vary by manufacturer and model. For example, polychloroprene layers and polyester ropes are common. Manufacturers use aramid fibers in more punitive or high-output applications (think Kevlar).

How the wrapped sideband and the original sideband start to differ is completely outside the band.

What’s the difference?

The main difference between V belts and wedge belts is the profile shape. As their names suggest, V belts feature a V-shaped profile with tapered sides, whilst wedge belts have a wedge-shaped profile.

Wedge belts take the lead when it comes to load carrying capacity, thanks to their ability to transmit more power than a V-belt of the same top width. This makes wedge belts more suited to industrial applications with higher load carrying requirements, or where drive space is limited.

V-belts are usually the belt of choice in applications where load requirements are light or where there is the drive space for multiple belts to be used. This is due to their low cost and high levels of efficiency.

Which is better? Smooth or cogged?

Generalizations or generalizations are problematic because there are always exceptions to the rule. After reading the last section about raw-edge belts, some of you may find their answer obvious. However, the cost of the raw-edge belts is higher than wrapped belt, so the fewer grooves in the wheel, the lower the cost for a transmission that runs only one belt. For the same reason, a single groove wheel also does not provide any reduction in weight, with no additional benefit to the overhanging load of the bearing.

Some of the inherent benefits of the raw-edge belt (increased power, smaller edge, quieter operation) still apply to a single grooved wheel, but with fewer additional benefits. We cannot overemphasize the importance of the ability of the sash to slide more easily inside the wheel.