The binary cam is a design for the

pulley A pulley is a wheel on an axle or shaft that is designed to support movement and change of direction of a taut cable or belt, or transfer of power between the shaft and cable or belt. In the case of a pulley supported by a frame or shell that ...

system of a

compound bow In modern archery, a compound bow is a bow that uses a levering system, usually of cables and pulleys, to bend the limbs. In general, compound bows are widely used in target practice and hunting. The pulley/cam system grants the user a mechan ...

. Craig Yehle, director of research and development at Bowtech Archery, received a patent for the design on December 11, 2007. Bowtech started equipping its bows with the new cam design in the 2005 model year.

Mechanics

The binary cam is described as a modified twin cam setup where each cam is slaved to the other via a loop of string connecting the two cams. This is contrasted with a typical twin cam setup where the ends of the

bowstring A bowstring joins the two ends of the bow stave and launches the arrow. Desirable properties include light weight, strength, resistance to abrasion, and resistance to water. Mass has most effect at the center of the string; of extra mass in th ...

are physically anchored onto each of the bow limbs. As a twin cam system relies on each cam rotating independently, based solely on the force of the string and the resistance of the bow limbs being absolutely symmetrical, there is room for a twin cam system to "lose tune" through wear and tear, string stretch, or just general age. The effect of a detuned twin cam bow is that the two cams rotate out of sync with each other, causing the bowstring to accelerate in two alternating directions upon release. This causes a number of adverse consequences, the most obvious being unsteady arrow flight. The binary cam overcomes this by 'slaving' each cam to the other; as one cam is unable to rotate without the direct equivalent action of the other, the two rotate in near perfect synchronization, with any possible differences in rotation automatically correcting themselves as the shot cycle is completed. In effect, a binary cam bow never needs cam-timing tuning, whereas a high end twin cam equivalent might need it done as often as every few months in order to maintain critical accuracy. Bowtech pays Rex Darlington of Darton Archery royalties for use of this cam design.

References

{{DEFAULTSORT:Binary Cam Bows (archery)