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 The Reinvention Of Archery ©
By Frank H. Scott
The North American Archery Group, LLC & The Fred Bear Museum
At the outset of this series I will state that I am not a trained engineer, nor do I claim to be one. Basically, I am a salesman and am the Director of the Fred Bear Museum. Being involved with the museum, I am naturally interested in ancient archery equipment and its usage as compared to modern equipment.
 The observations made here should be considered layman's interpretation as opposed to a trained engineer's observations. In expressing my thoughts, I mean no disrespect to our generation of trained and hard working engineers and or research and development people. In many cases they have taken old ideas, refined and improved them to the present day state-of-the-art products.
In making comparison between the old and the new, a good case in point is the similarities between modern eccentric wheels, the compound bow, and the ancient Oriental composite bow.
 Contrary to popular belief, the compound bow is not a relatively recent invention. The compound was invented in 1928, by a gentleman by the name of Mr. Claude Lapp. However, it would seem that Mr. Lapp did not pursue the idea as far as a marketable product is concerned. It was left up to Mr. Hollis Allen of Missouri to pick up on the compound idea, adding innovations and patents of his own, thus making the compound bow a viable sporting goods product. The popularity of the compound bow is evident by its almost complete take over of the bow market, and it's all based on the simple principal of leverage.
Please note figures A1, B1, and C1 of the highly stressed Oriental bow. Bows such as these were generally constructed with buffalo horn on the belly or face, a wood core, and sinew on the back. These bows were very efficient and because of this configuration of the limbs the action of these limbs when drawn can be equated, to a minor degree, to the action of the eccentric wheel of the compound bow.
 You will notice in figures A1, B1, and C1 that there is a bump or shoulder at the point where the string meets the limb. In fact the string actually rests on top of this shoulder. Out from this shoulder is a stiff section called a Siyah. One purpose of this Siyah is to add length to the bow when the string is drawn. The second purpose of this Siyah, being stiff, is to act as a lever thus working the materials in the limbs harder, and therefore storing more energy in the limbs, resulting in a faster shooting bow.
At the point when the string is lifted off the shoulder, in the process of drawing the string, there is a rapid build-up of weight for the first few inches of draw. This action is equated to the action of the compound eccentric wheel during the first few inches of draw when the wheel is pulled "up hill", so to speak, such as in figures A2 and B2. It is somewhere during this part of the draw that the compound reaches its maximum or peak weight and then as the wheel reaches the point of C2 the bow is starting to reduce in weight. In figure D, the bow has reached its maximum let off of weight. When the string is released, the eccentric wheel reverses itself and the energy stored in the limbs is delivered to the arrow, by way of the string. As the string moves forward, it increases in speed all the way through its travel. As this speed increases more energy is delivered to the arrow.
You will notice in figure C1 that the limbs of the Oriental bow are virtually parallel with each other. The result of this design is a smoother drawing bow with a gentle and gradual build-up of weight, until the bow reaches full draw. This is a opposed to the last few inches of draw of a straight limb bow or the accepted recurve bow of today, where there is a rapid build-up of weight in the last 4 or 5 inches of draw. This is not to say the weight of this Oriental bow reduces in weight as the limb is drawn. It's just that the weight build-up is more gradual.
The difference in speed between the compound bow and the recurve bow can best be explained if you will keep the following facts in mind.
 The energy that goes into any bow comes from the shooter's muscles. The limbs of the bow store this energy until the string is released. In the case of the recurve bow, being modern or ancient, the limbs of the bow move 5 to 8 inches (depending on the design) as the bow is drawn. This means the bow uses 20 to 30 percent of the stored energy just to move itself. That also means it only has 70 to 80 percent of the stored energy to move the arrow. In the case of the compound, the ends of the limbs move only about 1 to 2 inches, (again, depending on the wheel and bow design) and it only loses 2 to 5 percent of the stored energy in moving itself, leaving 95 to 98 percent to apply to the arrow. There is some energy loss in the friction of the wheels, cable slides, etc., but not much.
In the case of the recurve or straight limb bow, when the string is about half way through its travel, the speed of the string is moving as fast as it will ever go.
 In the case of the compound, the string gathers speed all the way through the eccentric wheel's rotation.
The Oriental composite bow moderately gains speed as the string returns from full draw because of the action of the limbs, wrapping the string around the large symmetrical recurves and then there is a brief burst of speed as the Siyah, or stiff, sections of the recurve rotates past the shoulder of the recurve. It is this final action of the Siyah that can be directly related to the final action of the eccentric wheel of the compound.
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