Pulsating loads, such as those generated by internal combustion engines and compressors, present special problems for V-belt drives. Intermittent forces tend to produce a whipping motion in the belts which, in the worst case, causes them to turn over in the pulley grooves. It is often said the worst possible drive from this standpoint is a compressor driven by a diesel engine.
Because high-power drives of this type use multiple belts, a solution to the problem is to join the belts by a top band, fusing them into a single broad belt immune to turnover. The basic belt element can be either classical or narrow. The joined configuration also avoids the need to order multiple belts as matched sets.
In a sense, joined V-belts are similar to the V-ribbed configuration. V-ribbed belts, however, require special sheaves, often not available from stock. Joined V-belts, in contrast, often are preferred because they fit on stock sheaves and can operate interchangeably with standard matched sets.
Anyone using joined V-belts should ensure they are not mounted on deep-groove sheaves, which sometimes are employed to minimize alignment problems or to avoid turnover in standard V-belts. Such sheaves have the potential for cutting the band of a joined belt. Extremely worn sheaves can produce a similar effect.
Another important feature of joined narrow belts is their ability to take advantage of high-strength tensile cords. Joined 5V and 8V belts are available with aramid-fiber reinforcement.