It (…the hybrid cam…) has become popular for two reasons: first, it shoots really well and, second, it shoots really well. From my own personal perspective I think it aims better than anything else I’ve shot and to an aging shooter with a surgically repaired shoulder that’s a real advantage. Everyone is familiar with the twin-cam systems that have been available on compound bows since the 4-wheelers and 6-wheelers evolved to that stage. Both the top and bottom wheels are mirrored images of each other. In other words, they were symmetric to each other. Symmetric wheels will reel out equal amounts of string as the bow is drawn while both cables are reeled onto the cable track at the same rate.

An early generation of this wheel system was a non-symmetrical or “asymmetrical” system produced by Lloyd Napier. The top wheel string-track in the system has a slightly larger diameter than the string-track of the bottom wheel. In this system the top wheel would reel out more string than the bottom wheel. The cable tracks are equal in circumference. This system would allow the nocking point to reach a position that would be nearer to the arrow rest Level than a symmetrical design.

The biggest variation from the symmetrical two-wheel system is, of course, the single cam. In this system the bottom cam has three tracks which control the amount of string reeled out over the top idler pulley and how fast the cable is reeled onto the center cable track.

Rex Darlington of Darton Bows pioneered the CPS cam system back in 1996. The “asymmetrical cam” has a three-track cam on the bottom and a two-track cam on the top. The top cam “takes up” the secondary string or “control cable” and reels out the primary string at different rates. In other words, the two tracks are of different circumferences. The outer tracks of the bottom cam reel out string; the left-most track (right-handed system) reels out the primary string while the right-most track reels out the secondary string or “control cable”. The bottom cam center track reels in the one power cable and is the track most suited to the draw length module concept.

How much string reels out into the system from both ends determines where the nocking point ends up at full draw. Where it ends up affects the dynamic forces required to maintain the archer’s “aim” at full draw. Get those forces balanced properly and you can aim the bow well. Get them unbalanced and aiming is more of a challenge.

The path of the nocking point on its forward power stroke is also important. If it is oscillating up and down during its forward travel then the nock-end of the arrow is doing likewise and tight groups will be more difficult to obtain. If the nock travel path is straight or near straight and level then arrow groups should be easier to attain. This was Rex Darlington’s intent when he made his first designs and according to Norb Mullaney, “Rex is the best cam designer in the industry.”

Controlling the nock travel by using two differently shaped cams also enables you to build in a wider range of wheel timings. One wheel can be adjusted (by cable twisting) several degrees while holding the other static and little change in impact point occurs nor is there a change in grouping ability. This feature allows me to adjust the system to get a slightly different “feel” or “balance” at full draw and still have good groups.

I also like the idea of less torque on the cable guard. With only one top-end yoke cable and a three-track wheel on the bottom, less side-force is exerted on the cable guard. Only the top power-cable yoke hooks to the far-left side of the axle pulling force across the bow’s centerline to the far-right cable guard. This torque force is at its maximum at full draw and affects aiming but less so on the asymmetric cams. If you don’t believe this just try a shoot-through cable system on a twin cam bow and notice how easy it aims down the middle and how the handle reacts so stable on the release.

Much has been made of the nock-travel path over this past year and I have no intention of getting into that fray. I ask one question, what groups the best? The proof is always in the arrow groups in the target and that’s what I need to know. I want groups not theory.