Compound bow

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Compound bow
Compound Bow full.jpg
Type Bow and Arrow
Archer Erika Jones shooting a compound bow. The bow has the axle attaching the limb to cam is mounted at the edge of the cam as opposed to the center. 2013 FITA Archery World Cup - Women's individual compound - Semifinals - 18.jpg
Archer Erika Jones shooting a compound bow. The bow has the axle attaching the limb to cam is mounted at the edge of the cam as opposed to the center.

In modern archery, a compound bow is a bow that uses a levering system, usually of cables and pulleys, to bend the limbs. [1] 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. Compound bows are widely used in target practice and hunting.

Contents

The pulley/cam system grants the user a mechanical advantage, and so the limbs of a compound bow are much stiffer than those of a recurve bow or longbow. This rigidity makes the compound bow more energy-efficient than traditional bows, as less energy is dissipated in limb movement. The higher-rigidity, more advanced construction also improves accuracy by reducing the bow's sensitivity to changes in temperature and humidity. In literature of the early 20th century, before the invention of compound bows, composite bows were described as "compound." [2]

Construction

A bow's central mount for other components (limbs, sights, stabilizers and quivers) is called the riser. Risers are designed to be as rigid as possible. The central riser of a compound bow is usually made of aluminum, magnesium alloy, or carbon fiber and many are made of 7075 aluminum alloy.

Limbs are made of fiberglass-based composite materials and are due to high tensile and compressive forces. The limbs store the kinetic energy of the bow – no energy is stored in the pulleys and cables. Draw weights of adult compound bows range is between 40 and 80 pounds (18 and 36 kg), which can create arrow speeds of 250 to 370 feet per second (76 to 113 m/s).

In the most common configuration, there is a cam or wheel at the end of each limb. The shape of the cam may vary somewhat between different bow designs. There are several different concepts of using the cams to store energy in the limbs, and these all fall under a category called bow eccentrics. The four most common types of bow eccentrics are Single Cam, Hybrid Cam, Dual Cam and Binary Cam. [3] However, there are also other less common designs, like the Quad Cam and Hinged. Cams are often described using their "let-off" rating. As a cam is rotated, the force required to hold the bow in position reaches a peak and then decreases as the bow approaches maximum extension (a position known as "the wall"). The percent-difference between the maximum force encountered during the draw and the force required to hold the bow in full extension is the "let-off". This value is commonly between 65% and 80% of the peak weight for recently designed compound bows, although some older compound bows provided a let-off of only 50% and some recent designs achieve let-offs in excess of 90%. [4]

As the string is drawn the cam turns and imparts force to compress the limb. Initially, the archer has the 'short' side of the cam, with the leverage being a mechanical disadvantage. High energy input is therefore required. When near full draw is reached, the cam has turned to its full extent, the archer has gained mechanical advantage, and the least amount of force needs to be applied to the string to keep the limbs bent. This is known as "let off". The lower holding weight enables the archer to maintain the bow fully drawn and take more time to aim. This let-off enables the archer to accurately shoot a compound bow with a much higher peak draw weight than other bows (see below).

However, there are some youth-oriented compound bows with low draw weights that have no let-off and have a maximum draw length deliberately set farther than the majority of young shooters would reach. This effectively makes the bow function very similar to a recurve, with the draw length determined by the shooter's preferred anchor point. This removes the necessity to adjust the bow draw length or use a different bow for different shooters (or to change bows as the shooter gets older). An example of this type of bow is the Genesis, which is standard equipment in the U.S. National Archery in the Schools Program.

Compound bow strings and cables are normally made of high-modulus polyethylene and are designed to have great tensile strength and minimal stretchability, so that the bow transfers its energy to the arrow as efficiently and durably as possible. In earlier models of compound bows, the cables were often made of plastic-coated steel.

Comparison to other bow types

Technical advantages

Albina Loginova at women's individual compound 3rd place, 2013 FITA Archery World Cup, Paris, France. 2013 FITA Archery World Cup - Women's individual compound - 3rd place - 04.jpg
Albina Loginova at women's individual compound 3rd place, 2013 FITA Archery World Cup, Paris, France.

Technical disadvantages

Circumstantial advantages

Circumstantial disadvantages

Specifications

AMO (Archery Manufacturers and merchants Organization, the former name of the body now known as the Archery Trade Association) standard draw length is the distance from the string at full draw to the lowest point on the grip plus 1.75 inches (4.4 cm). [7] Because the draw force may increase more or less rapidly, and again drop off more or less rapidly when approaching peak draw, bows of the same peak draw force can store different amounts of energy. Norbert Mullaney has defined the ratio of stored energy to peak draw force (S.E./P.D.F.). This is usually around one foot-pound per pound-force (3 joules per kilogram-force ) but can reach 1.4 ft⋅lb/lbf (4.2 J/kgf).

The efficiency of bows also varies. Normally between 70 and 85% of the stored energy is transferred to the arrow. This stored energy is referred to as potential energy. When transferred to the arrow it is referred to as kinetic energy. The product of S.E./P.D.F. and efficiency can be called the power factor.[ citation needed ] There are two measurement standards of this quantity – ATA and IBO speed. ATA is defined as the initial velocity of a 350-grain (23-gram) arrow when shot from a bow with a peak draw weight of 70 ± 0.2 lbf (311.38 ± 0.89 N) and draw length of 30 ± 0.25 in (76.20 ± 0.64 cm). IBO speed is defined as the initial velocity of an arrow with a weight of 5 grains (0.32 g) per pound of draw weight. While many manufacturers measure IBO speeds using a draw weight of 70 lbf (310 N) and draw length of 30 in (76 cm), the IBO standard allows a draw weight of as high as 80 ± 2 lbf (355.9 ± 8.9 N), and does not specify a draw length. [8] The average IBO speed for the majority of compound bows on the market hovers around 310–320 feet per second. [9]

Brace height is the distance from the pivot point of the grip to the string at rest. Typically a shorter brace height will result in an increased power stroke, but comes at the price of a bow that's less forgiving to shooter error and having harsher string slap.

Arrows

Arrows used with compound bows do not differ significantly from those used with recurve bows, being typically either aluminum alloy, carbon fiber, or a composite of the two materials. Wooden arrows are not commonly used on compound bows because of their fragility. Most arrows in use today are of the carbon fiber variety. An important distinction arrow-wise between recurve bows and compound bows is that of arrow spine. Compound bows and target recurve bows with fully center-shot cutaway risers tend to be very forgiving in regard to spine selection. Modern compound bows are typically equipped with substantially stiffer arrows than an equivalent draw-length and draw-weight recurve bow would be. Another advantage of the center-shot riser is that the arrow need not bend around the riser (nearly as much or at all) during the shot. Fine-tuning may be accomplished by adjustment of the arrow rest, or nock point on the string, rather than by changing arrow-length and tip weight.

Manufacturers produce arrow shafts with different weights, different spines (stiffness), and different lengths in the same model of shaft to accommodate different draw weights and lengths, matched to archers' different styles, preferences and physical attributes.

Arrow stiffness (spine) is an important parameter in finding arrows that will shoot accurately from any particular bow (see Archer's paradox), the spine varying with both the construction and length of the arrow.

Another important consideration is that the IBO (International Bowhunting Organization) recommends at least 5 grains per pound (0.71 grams per kilogram) of draw weight as a safety buffer. This means a bow that draws 60 pounds (27 kg) would need at least a 300-grain (19-gram) finished-with-tip arrow. Shooting arrows lighter than this guideline risks damage to the bow similar to that caused by dry-firing, which can in turn cause injury to the archer or anyone standing nearby. Shooting arrows that are too light also voids most manufacturer warranties. [10]

See also

Construction techniques

Related Research Articles

<span class="mw-page-title-main">Archery</span> Using a bow to shoot arrows

Archery is the sport, practice, or skill of using a bow to shoot arrows. The word comes from the Latin arcus, meaning bow. Historically, archery has been used for hunting and combat. In modern times, it is mainly a competitive sport and recreational activity. A person who practices archery is typically called an archer, bowman, or toxophilite.

<span class="mw-page-title-main">Crossbow</span> Bow-like ranged weapon

A crossbow is a ranged weapon using an elastic launching device consisting of a bow-like assembly called a prod, mounted horizontally on a main frame called a tiller, which is hand-held in a similar fashion to the stock of a long gun. Crossbows shoot arrow-like projectiles called bolts or quarrels. A person who shoots crossbow is called a crossbowman or an arbalist.

<span class="mw-page-title-main">English longbow</span> Type of ranged weapon

The English longbow was a powerful medieval type of bow, about 6 ft (1.8 m) long. While it is debated whether it originated in England or in Wales from the Welsh bow, by the 14th century the longbow was being used by both the English and the Welsh as a weapon of war and for hunting. English longbows were effective against the French during the Hundred Years' War, particularly in the battles of Sluys (1340), Crécy (1346), Poitiers (1356), and Agincourt (1415). They were less successful later on, as longbowmen had their lines broken at the Battle of Verneuil (1424), although the English won a decisive victory there; they were completely routed at the Battle of Patay (1429) when they were charged by the French mounted men-at-arms before they had prepared the terrain and finished defensive arrangements. The Battle of Pontvallain (1370) had also previously shown longbowmen were not particularly effective when not given the time to set up defensive positions.

<span class="mw-page-title-main">Arrow</span> Shafted projectile that is shot with a bow

An arrow is a fin-stabilized projectile launched by a bow. A typical arrow usually consists of a long, stiff, straight shaft with a weighty arrowhead attached to the front end, multiple fin-like stabilizers called fletchings mounted near the rear, and a slot at the rear end called a nock for engaging the bowstring. A container or bag carrying additional arrows for convenient reloading is called a quiver.

<span class="mw-page-title-main">Bow and arrow</span> Pre-gunpowder ranged weapon system

The bow and arrow is a ranged weapon system consisting of an elastic launching device (bow) and long-shafted projectiles (arrows). Humans used bows and arrows for hunting and aggression long before recorded history, and the practice was common to many prehistoric cultures. They were important weapons of war from ancient history until the early modern period, where they were rendered increasingly obsolete by the development of the more powerful and accurate firearms. Today, bows and arrows are mostly used for hunting and sports.

<span class="mw-page-title-main">Bow shape</span> Important aspect of archery

In archery, the shape of the bow is usually taken to be the view from the side. It is the product of the complex relationship of material stresses, designed by a bowyer. This shape, viewing the limbs, is designed to take into account the construction materials, the performance required, and the intended use of the bow.

<span class="mw-page-title-main">Composite bow</span> Bow made from horn, wood, and sinew laminated together

A composite bow is a traditional bow made from horn, wood, and sinew laminated together, a form of laminated bow. The horn is on the belly, facing the archer, and sinew on the outer side of a wooden core. When the bow is drawn, the sinew and horn store more energy than wood for the same length of bow. The strength can be made similar to that of all-wood "self" bows, with similar draw-length and therefore a similar amount of energy delivered to the arrow from a much shorter bow. However, making a composite bow requires more varieties of material than a self bow, its construction takes much more time, and the finished bow is more sensitive to moisture.

<span class="mw-page-title-main">Finger tab</span>

In archery, a finger tab or archer tab is a small leather or synthetic patch that protects an archer's fingers from the bowstring. It is strapped or otherwise attached to an archer's hand. In summertime, tabs are far more comfortable than gloves and can more conveniently use thicker material. They are also less expensive and easier to fit, and are the normal finger-protection used with recurve bows.

A flatbow is a bow with non-recurved, flat, relatively wide limbs that are approximately rectangular in cross-section. Because the limbs are relatively wide, flatbows will usually narrow and become deeper at the handle, with a rounded, non-bending handle for easier grip. This design differs from that of a longbow, which has rounded limbs that are circular or D-shaped in cross-section, and is usually widest at the handle. A flatbow can be just as long as a longbow, but can also be very short. Typical lengths would be 68–70 inches (172.5–178 cm) for a flatbow, 70–72 inches (178–183 cm) for an English longbow, and 72–76 inches (183–193 cm) for a warbow-weight English longbow; but these styles may easily overlap each other. Traditional flatbows are usually wooden self bows, though laminated and composite flatbows have been made in ancient and modern times. Modern flatbows commonly use fiberglass.

<span class="mw-page-title-main">Longbow</span> Type of ranged weapon resembling a tall bow and arrow

A longbow is a type of tall bow that makes a fairly long draw possible. A longbow is not significantly recurved. Its limbs are relatively narrow and are circular or D-shaped in cross section. Flatbows can be just as long, but in cross-section, a flatbow has limbs that are approximately rectangular.

<span class="mw-page-title-main">Turkish archery</span> Tradition of archery which became highly developed in the Ottoman Empire

Turkish archery is a tradition of archery which became highly developed in the Ottoman Empire, although its origins date back to the Eurasian Steppe in the second millennium BC.

<span class="mw-page-title-main">Archer's paradox</span> Phenomenon in archery

The archer's paradox is the phenomenon of an arrow traveling in the direction it is pointed at full draw, when it seems that the arrow would have to pass through the starting position it was in before being drawn, where it was pointed to the side of the target.

<span class="mw-page-title-main">Self bow</span>

A self bow or simple bow is a bow made from a single piece of wood. Extra material such as horn nocks on the ends, or built-up handles, would normally be accepted as part of a self bow. Some modern authorities would also accept a bow spliced together in the handle from two pieces of wood.

A bow draw in archery is the method or technique of pulling back the bowstring to store energy for the bow to shoot an arrow. The most common method in modern target archery is the Mediterranean draw, which has long been the usual method in European archery. Other methods include the pinch draw and the Mongolian or "thumb" draw. In traditional archery practice outside Western Europe the variations of the thumb draw are by far the most dominant draw types, with the Mediterranean draw restricted to the Olympic style of target archery.

This is a list of archery terms, including both the equipment and the practice. A brief description for each word or phrase is also included.

<span class="mw-page-title-main">Recurve bow</span> Type of bow shape in archery

In archery, a recurve bow is one of the main shapes a bow can take, with limbs that curve away from the archer when unstrung. A recurve bow stores more energy and delivers energy more efficiently than the equivalent straight-limbed bow, giving a greater amount of energy and speed to the arrow. A recurve will permit a shorter bow than the simple straight limb bow for given arrow energy, and this form was often preferred by archers in environments where long weapons could be cumbersome, such as in brush and forest terrain, or while on horseback.

Modern competitive archery involves shooting arrows at a target for accuracy and precision from a set distance or distances. This is the most popular form of competitive archery worldwide and is called target archery. A form particularly popular in Europe, North America, and South America is field archery, shot at targets generally set at various distances in a wooded setting. There are also several other lesser-known and historical forms, as well as archery novelty games.

<span class="mw-page-title-main">Release aid</span>

In archery, a release aid, mechanical release, or release is a device that helps to fire arrows more precisely, by using a trigger to release the bowstring, rather than the archer's fingers. It is used to make the release of the bowstring quicker and reducing the amount of torque put onto the bowstring from the archer's fingers.

Hoyt Archery is an American manufacturer of recurve and compound bows located in Salt Lake City, Utah. Most notable for their competition recurve bows, which are featured prominently in the Olympics; every gold medalist in individual archery at the 2012 Summer Olympics shot a Hoyt recurve. Hoyt is owned by Jas. D. Easton, Inc.

<span class="mw-page-title-main">Takedown bow</span> Bow assembled out of a riser and two limbs

A takedown bow is a bow assembled out of a riser and two limbs to make a working bow when strung.

References

  1. Paterson, W. F. "Encyclopaedia of Archery". St. Martin's Press, 1984, p. 18.
  2. Tutankhamun: Anatomy of an Excavation. (The notes were made in the 1920s and describe composite bows as "compound"; the modern compound bow did not exist at this time.) http://www.griffith.ox.ac.uk/gri/carter/135z.html
  3. "Compound Bow Cam Technology Explained - Hunter's Friend Archery". www.huntersfriend.com. Retrieved 2016-04-22.
  4. "Compound Bow Brace Height and Cam Specs - Hunter's Friend Archery". www.huntersfriend.com. Retrieved 2016-04-22.
  5. "Video Tutorial: 2016 PSE Draw Length Adjustment". betteroutdoors.net. Archived from the original on 7 April 2018. Retrieved 7 April 2018.
  6. "Rules World Archery - see Chapter 11". betteroutdoors.net. Retrieved 8 April 2018.
  7. "AMO Standards" (PDF). Archived from the original (PDF) on 2015-04-02. Retrieved 2015-03-08.
  8. "What is IBO speed?". Archery Country Blog. October 18, 2019. Retrieved November 17, 2023.
  9. Kenny, Tim (2023-08-27). "How Far Can a Compound Bow Shoot? - Bow to Hunt". Bow To Hunt. Retrieved 2023-08-28.
  10. "AMO Standards" (PDF). Texas Archery. Archived from the original (PDF) on 2015-09-06.
General references