2008 but still applicable:
A DETAILED LOOK AT CAM STYLES
Prior to the mid-1990s, there was only one cam style on the market: dual cams. Around 1995, Mathews Archery introduced the single-cam and shortly thereafter Darton Archery introduced the first hybrid cam. Today there are four basic cam styles on the market: two-cam, single-cam, hybrid cam and a combination of the two-cam and hybrid called the modified hybrid cam or binary cam. I’ll tell you a little about each style and some of their tradeoffs.
Two-cam systems: Two-cam bows became a problem when their designs started to become aggressive. When that happened, the cams became very sensitive to synchronization problems. In other words, if one harness was made a tiny bit longer than the other or stretched slightly more after assembly, the cams didn’t turn over at the same time and this resulted in poor arrow flight – a tail-high or tail-low arrow flight that was impossible to eliminate by moving the rest and nocking point.
If you checked your timing every couple of days and kept a bow press handy, you could keep these high-performance two-cam bows working fine, but you had to really watch them closely. One hot day in the back seat of the car and the synthetics making up the string and harnesses cooked. The wax between the fibers melted out and everything stretched.
I remember arriving at a Colorado elk camp after driving 22 hours in my old Cherokee. Both of my bows were in a black hard case in the back of the Jeep and the sun beat on them for many hours. When I pulled the bows out in camp, I was shocked. The cam timing was a mile off on both bows. Fortunately, I had a bow press with me, but that was the reality of the day. Those fast, high letoff two-cam bows were a handful to keep shooting well.
How the bow feels when you draw it, and the kind of back wall it possesses are both functions of the cam design.
By the way, modern synthetics are sufficiently improved and stretch-proof that some bow manufacturers are once again making aggressive two-cam bows and this time around they work much better.
Most archers didn’t want to be bothered with a bow that could go out of synchronization at any time, but they still wanted to shoot a fast arrow. That is why the single-cam style entered the market and became so popular – it solved this problem.
Single-cam system: The top limb of a single-cam bow carries an idler wheel and the bottom limb carries the cam. The idler wheel provides no mechanical advantage; it is simply there to unroll the string as you draw the bow. The bottom cam does two things, it takes up the control cable as you draw the string (this is what flexes the limb tips toward each other) while at the same time letting out the other end of the string at the correct rate to keep the nock traveling straight back and straight forward.
The single-cam is not sensitive to changes in power cable length. If the power cable stretches a little, the bow remains in tune because there is only one cam.
Hybrid cam systems: You can think of hybrid cams as a mix of single-cam and two-cam technology. They do about the same thing as a single-cam bow. In other words, 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 of the two-cam bow. Therefore, hybrid cams are more reliable than two-cam bows because they are much less sensitive to timing issues.
Hybrid cams are supposed to make it easier to attain a perfectly level nock travel back and forward. This is important for good arrow flight. Not all bows produce perfect nock travel. That means that some bows are easier to tune than others are and some can’t be tuned at all. I’ll dig into the important subject of nock travel in the next chapter.
It is debatable whether the hybrid has any tuning advantages over a well-made single-cam. This system is certainly better than poorly made single-cams that I have shot. I have endured some amazingly bad arrow flight from single-cam bows whose cams were not properly designed for all draw lengths. I think if these poorly made single-cams had been effectively policed off the market by some licensing agreement, the hybrid never would have gained traction Instead, people began blaming all single-cams for the problems of only a few.
Regardless of why it became popular, the hybrid is now a big part of the bow landscape. Most bow companies have some form of hybrid cam.
Modified hybrid cam systems: Modified hybrids are the newest style on the market. Some companies call them binary cams. The top and bottom cams are mirror images of each other. Rather than the harness attaching to the opposite limb tip, it attaches to the opposite cam. In this way, the cams are slaved together just as they are with a standard hybrid cam, but the harness tracks and string payout tracks are identical on top and bottom making it very easy to produce level nock travel.
The biggest difference between the hybrid and the modified hybrid cam is the fact that there is no set slave and master. It changes depending on the lengths of the harnesses. All that matters is the fact that the cams are linked together so they can’t change rotation independently and go out of time.
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