Compound bow

Lore & Background

The compound bow was first developed in 1966 by Holless Wilbur Allen in North Kansas City, Missouri, and a US patent was granted in 1969. In literature of the early 20th century, before its invention, composite bows were described as 'compound'. The bow's central mount, called the riser, is typically made of aluminum, magnesium alloy, or carbon fiber, often 7075 aluminum alloy. Limbs are made of fiberglass-based composite materials or occasionally wood, and store the bow's kinetic energy—no energy is stored in the pulleys and cables.

The cam or wheel at the end of each limb varies in shape; common types include Single Cam, Hybrid Cam, Dual Cam, and Binary Cam, with less common designs like Quad Cam and Hinged. As the string is drawn, the cam turns, initially providing a mechanical disadvantage requiring high energy input, then near full draw the archer gains mechanical advantage and experiences 'let-off', a reduced holding force. This let-off, commonly between 65% and 80% of peak weight, allows the archer to hold the bow fully drawn longer for aiming. Some youth-oriented compound bows have no let-off and function similarly to recurves, with draw length determined by the shooter's anchor point.

When drawn, the limbs are pulled toward each other by cables, unlike longbows or recurves where limbs flex toward the string. This allows a horizontal or 'parallel' limb configuration that minimizes recoil and vibration. The pulley system often includes rubber-covered draw-stops that provide a solid 'wall' for consistent draw length. Compound archers frequently use a mechanical release aid to hold and release the string, reducing arrow oscillation and the risk of torquing the bowstring. The bow's moving parts require additional maintenance, and dry firing is more likely to cause damage. Draw length and let-off adjustments often require a bow press.

Reader's Guide

The compound bow represents a significant technological shift in archery, introducing mechanical advantage through its pulley and cam system. This design allows archers to shoot with much higher peak draw weights than traditional bows while maintaining a lower holding weight at full draw, enabling more time for precise aiming. The stiffer limbs and advanced construction materials—such as aluminum and carbon fiber risers and fiberglass composite limbs—make the compound bow more energy-efficient and less affected by environmental conditions like temperature and humidity, improving accuracy.

Its development in 1966 by Holless Wilbur Allen and subsequent patent in 1969 established a new category of archery equipment. The compound bow's let-off feature, typically between 65% and 80%, distinguishes it from recurves and longbows, though some youth models omit this to mimic traditional draw characteristics. The use of mechanical release aids is common to ensure consistent releases and prevent string derailment. However, the compound bow's complexity introduces more potential points of failure and requires specialized tools like a bow press for adjustments. Its heavier weight and sensitivity to torquing at full draw demand careful technique. Despite these considerations, the compound bow is widely adopted in target practice and hunting, offering arrow speeds of 250 to 370 ft/s from draw weights of 40 to 80 lb.

Did You Know?

• The let-off of a compound bow is commonly between 65% and 80% of the peak draw weight.
• Compound bows typically achieve arrow speeds of 250 to 370 ft/s.