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Anatomy of a Compound Bow

A key factor in being able to select the right bow for the type of shooting or bow hunting you’ll be doing is having a proper understanding of what all the bow’s various pieces are and how they work.  In the following article we will break down the many components that work in harmony to make modern compound bows the smoothest, fastest and most efficient arrow shooting machines ever developed.

Riser

Mathews Geo Gridlock Riser

Most modern compound bow risers are made from aluminum, although some are now made of light weight carbon fiber.

The bow’s riser is the “middle” portion of the bow which contains the grip and is attached to the bow’s limbs.  Most compound bow risers are made from aluminum and are either forged or machined.  The generally feature a multitude of cut-outs that serve to reduce the bow’s overall weight while still maintaining their strength.  In recent years several bow manufacturers have developed compound bows with carbon fiber risers which are said to be stronger than aluminum risers while being extremely light weight and warm to the touch.

Many bow accessories are attached directly to the riser including sights, arrow rests, quivers, wrist slings, stabilizers and more.  All mounting holes on a bow riser are universal size and placement, which ensures you can use virtually any accessory on any bow.  The riser is truly the foundation of what is known as the modern compound bow.

Bow Limbs

Mathews Creed XS limb options

Compound bows are offered with either solid 1piece limbs or what is known as “split limbs” which are simply two thin limbs that connect the bow riser to the axle which holds the cam.

A bow’s limbs are connected to the riser and to the bow’s cam system.  The limbs flex when the bow is drawn in order to help store energy which is then passed to the arrow upon release.  Most modern bow limbs are constructed of fiberglass or other composite materials with some being one solid piece and others consisting of several layers of various materials laminated together.

Some bow manufacturers use a single, solid limb design while others utilize split limbs.  While solid limbs tend to be more prone to failure (cracking, splintering or breaking) some critics of split limbs say they are prone to warping or wearing differently thus affecting arrow flight and accuracy.

Most of today’s hunting bows feature “parallel” limb designs rather than the traditional d-shaped bows of years gone by.   The advantage of the parallel limb design is that each limb bends in an opposite direction and helps to offset noise and vibration during and after the shot.

Cam System

Single cam vs. Dual Cam

The primary types of cam systems offered on today’s compound bows are either a single cam or a dual cam. Both have their pros and cons.

There are two major types of cam systems found on compound bows; dual cams and single cams.  A dual cam bow utilizes two eccentric cams which are identical to one another on either end of the bow.  In most modern dual cam systems these cams are directly connected to one another via two cables.  Connecting, or slaving, the cams to one another ensures they are less likely to go out of time and thus be more reliable and consistent.  This particular dual cam system is referred to as a “binary” cam.  While there are a variety of small differences between the manufacturers the basics of the dual cam system remain the same no matter who puts their name on it.

Single cam systems use a single, large cam on the bottom limb and an idler wheel on the top.  The single cam feeds the string off the track as the bow is draw, while a single power cable that runs from the single cam to the top limb compresses the limbs to store energy.  Many people believe to their simple nature and lack of timing issues that single cam bows are easier to tune and shoot than dual cam systems.  Although like most things in archery this is simply a personal preference.

Bow String & Cables

Bow string

Depending on how often you shoot your bow most technicians suggest replacing your string and cables at least once every 2-3 years if not sooner.

While it probably doesn’t need saying, the bow’s string what an archer uses to pull back the bow and what ultimately propels the arrow forward upon release.  Most dual cam systems utilize a single string and 2 cables, while a single cam system uses one very long string and a single cable.  Modern bow strings are made from high tech materials such as Dyneema, which is used in everything from commercial fishing nets to bullet proof vests.

Most bow technicians recommend replacing your bow’s strings and cables every 2-3 years in order to maintain the best performance from your bow.

String Silencer

Bow string silencer

Unlike the old balls of yarn or rubber “spider legs” our fathers used, today’s bow string silencers are small and typically made from advanced vibration dampening materials. They also come in a variety of shapes and colors.

String suppressors are small rubber items that can be mounted either in between the strands of a bow string, or around it.  They are designed to help dissipate noise and vibration caused by the bow string upon release.

String Suppressor

Bow string suppressor

Most bows come with a string suppressor installed from the factory. However if yours does not there are a variety of aftermarket suppressors available that work wonders.

First made popular in the mid 2000’s the string suppressor mounts directly behind the bow’s stabilizer and is most commonly consisting of either a metal or carbon fiber rod with a rubber bumper on the end.  The bumper serves to stop forward string travel after the shot which helps reduce noise and vibration.  Additionally, a string suppressor can help prevent unnecessary slapping of the bow string on the archer’s forearm.  Most technicians recommend a gap of 1/16″ to 1/8″ between the rubber stopper and the bow string.  Additionally, it is recommended to always have your bow string served where the bumper will make contact.  This helps prevent unnecessary wear on your string.

Arrow Shelf

The place on a bow’s riser directly above the grip where the arrow rest is mounted is referred to as the arrow shelf.  While modern compounds use an arrow rest to hold the arrow before and during the shot, in traditional archery the arrow is most commonly shot directly off the shelf, which is where the name comes from.

Cable Guard

Mathews Reverse Assist Roller Guard

Advanced cable guard systems use a series of rollers to help reduce friction and result in a smoother drawing bow.

In order to keep the cables out of the path of the arrow, and the archer’s arm, a cable guard is used.  This guard pulls the cables off to the side in order to provide clearance for the arrow.  Most cable guards are either made from machined aluminum or a carbon fiber rod, and may use either a Teflon sleeve or metal rollers to all the cables to move when the bow is drawn and fired.

Limb Pocket & Limb Bolt

Bow limb pocket

The limb pocket is what attaches the bow’s limbs to the riser. They may be constructed from aluminum or molded from high strength plastic or other materials.

The primary job of the limb pocket is to hold the bow limb securely in place.  Limb pockets are often made from machined aluminum, although sometimes they are made of durable ABS plastic or other materials.  The bow limb will rest inside the limb pocket, which is then bolted to the bow riser.

The limb bolt is what connects the limb pocket to the riser.   Most limb bolts use a standard allen key to adjust them.  Tightening the limb bolt will increase the draw weight of the bow, while loosening it will lower the draw weight.  When adjusting limb bolts it is important to adjust them both the same amount.  Failure to do so can cause your bow to go out of tune.

Grip

Wood bow grip

Most bow grips are made from either wood, plastic or rubber.

The bow’s grip is where you hold the bow while shooting.  Grips can be made from wood, plastic, rubber or even metal.  Each bow’s grip will feel different so it is important to try and find one that feels right in your hand.  There are also a variety of custom grips on the market that offer flexibility in both size, hand position and color.

Wrist Sling

Nitro Wrist Sling in Yellow

Wrist slings are popular bow accessories that are easy to install and very affordable.

Many archers like to use a wrist sling when shooting their bow.  This sling mounts between the bow’s riser and stabilizer, and serves to hold your bow in place should you lose your grip during the shooting process.  Wrist slings typically don’t come with your bow from the factory and are aftermarket additions.  They are available in a variety of sizes, colors and materials to suit the individual archer’s needs.

Axle to Axle Length

Axle to Axle Length

While axle-to-axle length isn’t a physical part of a bow, it is something commonly referenced when talking about bows.  Commonly referred to as “ATA” length, this is the distance between the axles that run through the cams and limbs while the bow is at rest.

Brace Height

Measured as the distance between the throat of the bow grip (the deepest part) and the string, brace height is often used as an indicator of speed and forgiveness.  Bow’s with short brace heights (under 6 ½ inches) are generally considered less forgiving, as they can be more sensitive to flaws in the archer’s form.  Bows with longer brace heights, those great than 6 ½ inches, are referred to as more forgiving and easier to shoot.

Brace height of a compound bow

Brace height is the distance from the string to the back of the grip when the bow is in its undrawn position. The shorter this distance, the more energy the bow will store for any given draw length. However, there is a tradeoff. A short brace height typically makes the bow slightly less forgiving. Many hunters choose a bow with a brace height around 7 inches.

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