The Admiral is the third generation of center-pivot limb bows produced by BowTech. It shows the progression of design simplification that results from engineers studying a product and determining that it can be made with fewer parts or using a different approach.
Having the limb pivot at or near the center of its span creates a few design problems that differ from those of more conventional compound bows. More conventional bows hold a generally thicker limb butt within a limb pocket, and encourage the limb to bend as a cantilever beam. Center-pivoted limbs are usually a bit thicker at the center and taper in thickness toward both ends. Alternatively they can be of uniform thickness but wider in the center and narrower in planform toward the ends. In all cases, they are confi gured to provide reasonably uniform stress distribution along the length of the limb balanced about the center support.
However, this type of limb-bending does create a distinct problem that must be dealt with. As it bends and recovers, the arc of the limb increases and decreases. The chord of the curve of the limb shortens when it is being loaded and lengthens when it is being unloaded. Depending on just how the limb is connected to the handle of the bow, either the point of attachment or the pivot point must provide for some linear movement (along the length of the limb) to allow for the change in the length of the chord. In the Quadraflex, the first commercial version of a center-pivoted limb bow, Joe Caldwell fixed the limb pivot and used a flexible cable to control the positioning and loading of the limb. Since the position of the cable was not restrained, this allowed for the linear motion necessary to accommodate the lengthening and shortening of the chord of the arc as the limb bent.
On the Guardian (2007), the first of BowTech’s center-pivot limb bows, they elected to “rotatably” attach the split limb to a fitting that accepted the limb adjustment bolt that, in turn, was threaded into a rigid extension of the handle. The limb was mounted in a clamp that was pivoted on the end of a short arm that was, in turn, pivoted on a part of the handle. The double pivot permitted the limb to rotate slightly and move fore and aft as it flexed when loaded and unloaded. The General (2008), the second BowTech center-pivot limb bow, followed the same design pattern as the Guardian, utilizing a double pivoted arm and clamp to mount the split limb. *Read the rest of the report by downloading the PDF