Crossbelt

Crossbelt, also known as a crossed belt drive, refers to a mechanical power transmission arrangement where the belt is twisted 180 degrees as it runs between two pulleys. This crossing causes the driven shaft to rotate in the opposite direction to the driving shaft.

In operation the belt path forms a crossed, figure-eight-like layout, increasing the belt’s contact with the pulley surfaces. The greater wrap and friction allow higher torque transmission at a given belt tension, but at the expense of efficiency and belt life. The arrangement also introduces lateral forces on the pulleys and bearings and is more sensitive to misalignment and tension distribution. The driving and driven pulleys rotate in opposite directions, a property that can be advantageous in certain layouts.

Applications and history: Crossbelt drives were common in early industrial machinery that used flat belts, particularly where a reverse rotation was required without additional gears. With the advent of V-belts, stronger belt materials, and timing belts, the use of crossed belts declined in favor of more efficient and reliable arrangements. They are now primarily encountered in legacy equipment or in situations where the additional complexity of gearing is undesirable and reverse rotation is needed.

Design considerations: Proper pulley diameters, belt specification, and tensioning are important to minimize slip and wear. Crossbelts impose greater lateral load on bearings and require careful alignment to avoid belt mis-tracking and increased wear compared with open-belt drives.

See also: open belt drive, belt drive, pulley.