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V-Belts
An Investigation Into V-Belt Drives
Summary
A V-belt drive is a rubber and fabric belt (with a v cross section) stretched around two pulleys that transmit rotational energy from one pulley to the other. Compared to gear speed reducers and variable frequency drives, V-belt drives are an economical solution for speeding up or slowing down output RPM. In this article, the reader gains abetter understanding of V-belt construction, types, operation, sizing, and maintenance.

RB02006 Rob Bretz 10 pages June 2004 (revised) SKF Reliability Systems @ptitudeXchange 5271 Viewridge Court San Diego, CA 92123 United States tel. +1 858 496 3554 fax +1 858 496 3555 email: info@aptitudexchange.com Internet: www.aptitudexchange.com

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V-Belts

Introduction
V-belt drives transmit rotational energy between two shafts through a fabric reinforced rubber belt, in relatively high speed and low torque applications. Compared to gear speed reducers and variable frequency drives, V-belt drives are an economical solution for speeding up or slowing down output RPM.

combined with burgeoningelectric motor use, began replacing main shaft driveline systems.

History
The V-belt drive is an invention of the twentieth century. The predecessor to the Vbelt drive consisted of two flat-faced pulleys and a flat leather belt, and was traditionally found in single driveline applications (a large shaft that ran through the entire factory). Numerous leather belts were slipped on and off the main linedrive to the individual equipment driven pulley.

Figure 2. Cogged V-Belt in a Fan Application.

Construction
V-belts drives work by wedging the belt into the sheave (pulley) groove. Tension is applied to the belt by increasing the center distance between the two pulleys. This forces the belt firmly into the sheave groove, which generates a large coefficient of friction. The frictionaccommodates transfer of rotational energy. V-belts are built on a mandrel with a diameter that is specifically relative to the V-belt length. Layer by layer the V-belt components: covers, rubber, tensile members, and reinforcement, are rolled onto the mandrel. Heat and pressure are applied to the layers for a specified period of time to vulcanize it all together. The V-belts are then cut to the correctwidth.

Figure 1. A Traditional Mill Interior, With Leather Belting Attached to the Line Shafting (Hanging From the Ceiling), and Probably a Water Wheel or Turbine.

Many belt manufacturers claim credit for the invention, but it is difficult to determine exactly when the V-belt was developed. It is safe to say that V-belts were created for the automobile, due to their quiet and low maintenancecharacteristics. Yet the displacement of leather belting didn’t begin until after the First World War (1914-1918), when rubber V-belts,

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V-Belts Classical V-Belt (A, B, C) The “classical” V-belt is cut edge (raw edge) construction. Ranging from ½” to 7/8” (12.7mm to 22.23mm) in width, the classical belt is designed for medium dutyapplications.

Figure 3. Raw-Edge V-belt Cross-Section.

While there are many different styles of Vbelts, the construction remains basically the same. Wrapped Belts A wrapped cover V-belt undergoes the same manufacturing process as the traditional cut edge V-belt, except a rubber-encapsulated cloth is wrapped around the finished belt. Again, heat and pressure are applied to vulcanize the cover tothe belt.

Figure 5. Cross Section (Classical V-Belts).

(Conversion A=12.7mm x 9.53mm, B=16.67mm x 11.11mm, C=22.23mm x 14.29mm) Light Duty (3L, 4L, 5L) The “light duty” V-belt is cut edge (raw edge) construction. Ranging from 3/8” to 5/8” (9.53mm to 15.88mm) in width, the light duty belt is designed for light duty applications.

Figure 4. Wrapped Belt.

Figure 6. Cross Section (Light...