October 28, 2010
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With Mathews jumping into the two-cam market with a very interesting new design, the boundaries between brands are more blurred than ever. There sure are a lot of cam designs out there, and it's getting harder and harder to keep track of what they do -- and don't do.
We now have to decide among modular and non-modular single-cam, conventional two-cam, hybrid two-cam and binary two-cam. It's a lot to digest.
I decided to dig into this subject and, hopefully, clear up some of the confusion.
The New Mathews Two-Cam
Mathews calls its new two-cam technology AVS, which stands for Advanced Vectoring System. It is another great idea from Matt McPherson and company. Sometimes I get confused by all the hybrids, but this system is relatively easy to understand.
First, I need to point out a few characteristics of a conventional two-cam system before contrasting those with the Mathews AVS.
With a conventional two-cam system, the harness from one cam attaches directly to the axle at the other end of the bow. As long as the cams turn at exactly the same time, these systems work great. It is easy to control nock travel with a two-cam bow, and they are good at storing energy.
The big downside to conventional two-cam bows has always been that slippery eel called cam timing. If the cams aren't positioned identically, one cam will reach full draw before the other. Upon release, the nock point on the string will move up or down (depending on which cam gets to full draw first) as the string moves forward, causing poor arrow flight.
In the past, it was very hard to keep a radical, two-cam bow timed well enough to consistently produce proper nock travel. It wasn't so hard with soft cams and wheels, but seemingly no one (myself included) wants to shoot a slow bow anymore. The result was a need for high maintenance, and no one wanted that either. So, the two-cam bow faded away and the single-cam bow took over.
However, today's synthetic materials and harness production methods have improved dramatically since the mid-to-late '90s. Modern harnesses barely stretch at all, and once you break them in, they may never move again. So, you can now get away with a more aggressive two-cam system with limited maintenance. However, they still aren't as easy to maintain as single-, hybrid- and binary-cam systems.
Mathews' new AVS is a two-cam system with an interesting twist. Rather than each harness attaching directly to the axle on the other limb, it attaches to a small wheel mounted on the axle. Each harness has a looped end, and that loop goes around the wheel, which floats on bearings. As you draw, the wheel rotates, and its center actually moves from the front of the axle to the rear of the axle during the draw cycle. This benefits the shooter by increasing stored energy at the beginning of the draw and increasing letoff at the back end.
The results are impressive, with Mathews' McPherson Series Monster producing an IBO speed up to 350 fps with a six-inch brace height. The Monster XLR8 is even faster, pushing 360 fps with a five-inch brace height.
"For those who want the ultimate speed machine, these€¦are really the ticket," McPherson said. "They are the highest efficiency of any two cams we have ever tested, and the fastest of anything we have tested to date."
Hybrid and binary cams make it easier to produce wide drawlength adjustments with modules than do single-cam designs.
Photos and videos of the new AVS cams in action are available at Mathews' website (www.mathewsinc.com).
The single-cam system has the lowest maintenance requirement of any cam design. Because there is only one cam, there's no way the bow can go out of time. Sure, if the power cable or string stretches extensively, the cam could rotate into a position where it is not as efficient and doesn't produce perfect nock travel, but today's synthetics are so good that's highly unlikely. The only downside I have found with single-cam bows occurs when you try to push the draw length with a modular system.
Modular single-cam systems seem to work fine with small draw length adjustments, but when you try to push it more than an inch, nock travel suffers. For example, I have a 32-inch draw. I have never used a modular, single-cam bow that produced good arrow flight at my draw length. Most modular single-cams are optimized at 29 inches (the most common draw length). If you are near this length, you will be fine. Otherwise, I would shy away from modular single-cams. You're going to be better off with a non-modular single-cam optimized specifically for your draw length.
You can think of hybrid cams as a mix of single-cam and two-cam technology. Because the top cam is attached directly to the bottom cam (the top cam is called the slave and the bottom cam is called the master), these systems are less sensitive to power cable stretch. When the power cable stretches, both cams move instead of just one (as is the case with the two-cam bow). Therefore, hybrids are more reliable than two-cam bows because they are much less prone to timing problems.
Modular hybrid cams make it easier to attain perfectly level nock travel at all draw lengths than with modular single-cam bows. As I've discussed in previous columns, nock travel is a very important issue, because a bow with poor nock travel is nearly impossible to tune.
In simple terms, the binary-cam system is a pair of cams with the same profile -- mirror images of each other. The harness from one cam attaches to the other cam rather than the axle on the other side. Because the cams are connected, there is no set master or slave in this relationship that depends on which harness is the longest. If one harness stretches, both cams will pivot slightly to take up the slack, rather than just one cam taking up the slack (and going out of time) in a standard two-cam system.
Which One Is Best?
So, which cam system is best for you? Well, it's easier to say which is worst. At this time, I see no good reason to shoot a conventional, two-cam bow. It offers no advantages over the other cam styles. The only stre
ngth of the conventional, two-cam design is the ability to quickly and easily manipulate vertical nock travel by twisting up one of the harnesses. You can do exactly the same thing with the Mathews AVS, but the AVS is more efficient at storing energy. You can also do the same thing with the binary cam, but the binary cam is much less likely to produce arrow flight problems later.
With my long draw length, I am not a big fan of modular single-cam bows, but the non-modular ones work great for me.
Binary, single, hybrid and AVS: they are all good, seriously. When properly made, all will produce good arrow flight with minimal maintenance. When purchasing a new bow, I wouldn't spend a lot of time deciding on the cam. Instead, I'd base my selection on how the grip feels in my hand, how loud the bow is and whether I feel comfortable at full draw. Those design aspects will have more to do with your success next season than which cam the bow carries.