Nepedia
Back to Discover
Advanced Reader
💻

Compound bow

technology Maturity 11-13 Next article →

A compound bow is a highly efficient piece of archery equipment. It uses a levering system to bend its limbs. This system usually consists of cables and pulleys. These pulleys are often called cams.

Compound Bow full
Compound Bow full

Modern compound bows are used for hunting and target practice. They are much more energy-efficient than traditional longbows or recurve bows. This efficiency happens because less energy is lost during limb movement. The advanced construction also makes the bow more accurate. It is less sensitive to changes in humidity or temperature.

The mechanism of a compound bow relies on the rotation of cams. These cams are part of a category called bow eccentrics. As an archer draws the string, the cams begin to turn. This movement imparts force to compress the bow's limbs. Initially, the archer experiences a mechanical disadvantage. This means the pull feels very heavy at the start of the draw. However, as the string approaches maximum extension, the cam reaches a new position. This provides a mechanical advantage known as "let-off."

2013 FITA Archery World Cup - Women's individual compound - 3rd place - 04
2013 FITA Archery World Cup - Women's individual compound - 3rd place - 04

Let-off is the difference between the peak draw weight and the holding weight. Modern bows often have a let-off between 65% and 80%. Some recent designs even achieve a let-off exceeding 90%. This lower holding weight allows the archer to aim more carefully.

There are several different types of cam systems used in these bows. These are classified by how they manage energy and let-off. The four most common types are Single Cam, Hybrid Cam, Dual Cam, and Binary Cam. There are also less common designs like the Quad Cam or the Hinged system. Some designs use a single cam at the bottom and a round idler wheel at the top. This specific setup uses one long string instead of separate cables. The shape of the cam also determines the acceleration of the arrow. A "soft cam" accelerates the arrow gently. A "harder" cam is used by advanced archers to gain more speed.

The history of the compound bow is distinct from older archery tools. In the 1920s, some writers used the word "compound" to describe composite bows. However, the modern mechanical compound bow did not exist then. Holless Wilbur Allen developed the first modern version in 1966. He worked in North Kansas City, Missouri. A United States patent was later granted for his invention in 1969. This invention changed the way energy is stored and released in archery.

Construction of the bow involves several specialized parts and materials. The central mount is called the riser. The riser holds the limbs, sights, stabilizers, and quivers. It must be very rigid to maintain accuracy. Many risers are made from 7075 aluminum alloy, magnesium alloy, or carbon fiber. The limbs are typically made of fiberglass-based composite materials. These limbs store the kinetic energy needed to launch the arrow.

2013 FITA Archery World Cup - Women's individual compound - Semifinals - 18
2013 FITA Archery World Cup - Women's individual compound - Semifinals - 18

The strings and cables are usually made of high-modulus polyethylene. This material has great tensile strength and very little stretch. This ensures the bow transfers energy to the arrow as efficiently as possible.

Archers use specific tools to improve their performance and accuracy. Many use a mechanical release aid to hold the string. This device attaches near the nocking point. The archer can then release the string with a trigger or a slight increase in tension. Using fingers to release the string can cause the string to twist or torque. This twisting can derail the string from the cams. A mechanical release minimizes arrow oscillation. This leads to a much more consistent shot. Additionally, many bows use rubber-covered blocks as draw-stops. These create a "wall" that helps the archer find a consistent anchor point.

Arrows must also be carefully selected to match the bow's power. Most modern arrows are made of carbon fiber or aluminum alloy. Wooden arrows are rarely used because they are too fragile. Because compound bows are so powerful, they require stiffer arrows. The stiffness of an arrow is known as its spine. The International Bowhunting Organization recommends using arrows with a specific minimum weight. Using arrows that are too light can damage the bow. This is similar to the damage caused by "dry firing" a bow. Using the correct arrow weight also protects the manufacturer's warranty.

707 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (3)
File:Compound Bow full.jpg
Compound Bow full.jpg
File:2013 FITA Archery World Cup - Women's individual compound - 3rd place - 04.jpg
2013 FITA Archery World Cup - Women's...
File:2013 FITA Archery World Cup - Women's individual compound - Semifinals - 18.jpg
2013 FITA Archery World Cup - Women's...
More to explore

🔬 Go deeper

More advanced topics to explore

🪜 Step back

Simpler topics to build understanding

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.