Every few years, someone tries to redesign the way a bicycle is pedaled. odd shaped gears and complex looking cranksets abound in the bicycle's history. Yet, as different and exotic as they all may look, each and every one of them is attempting to do the exact same thing; create a smooth, unchanging flow of power to the rear wheel.

The problem is this. A human being's legs aren't made to apply smooth, unchanging power in a circular motion. What they were designed to do is:

1. Raise the person, and themselves, against gravity, and
2. move the person forwards.

As a result, some of the muscles evolved to be stronger than others. As a result, when they are called upon to pedal a bike, they cannot move the feet at a constant speed around the pedal stroke the way the pedals do. The result is what cyclists call the "dead spot". For many years, cyclists have used a method called "spinning" to minimize this unevenness, and lessen the dead spot. And for years this has worked very well. That's not to say that the issue is dead, however, despite what many "retrogrouches" may believe.

The mechanical solutions to this uneven problem have varied from oddly shaped gears, to Rube Goldburg looking crank systems, even to the total elimination of gears, cranks and chains altogether. One such example of the later was a treadle type contraption, not unlike the early sewing machines. This design works by alternately pushing down on the two "pedal" like contrivances, which are attached, one on each side by rods, to a crankshaft that was conneted to the bicycle's wheel.

As the years went by, however, more and more tinkerers turned towards modifying the increasingly popular gear and chain system.

Ellipsis

One such "tinker" was a chainring in the shape of an ellipse. these designs varied from modest to extreme in their obliquity ("ellipse-ness", or out of roundness), but all were based on the same idea of "making hay while the sun shined". The way they did this was to place the major axis, that is, the largest diameter, or "high gear part", in the position that would cause it to be pulling on the chain when the cyclist's feet were pushing down on the pedals, and using the strongest leg muscles. When the rider's legs reached the dead spot, the minor axis would come into play, and the pedals would "zip" through the dead spot. The theory behind this was to reduce to a minimum the amount of time the weaker muscles would be used, thereby (hopefully) creating a more even flow of power to the pedals. It made sense at the time...

These chainrings never did catch on very well, however. For one thing, the rings did not create the smooth flow intended, and the "skip and push" pedalling motion was uncomfortable for many. And in some cases actually did more harm than good. Also, you could only mount one of these sprockets on your bike, unlike "round" rings, which could be combined in groups of two or three different sizes.

Cams and Cadence

Around about the mid to late '70's one of the tinkerers came up with a mechanical contraption which he called "Bio-Cam". This was not a specially shaped chainring. In fact, that was one of it's selling points; it used regular, "round" chainrings, thereby allowing multiple chainring combinations.

As with elliptical chainrings, it worked by changing pedal speeds as the cranks turned. There was a significant difference, however. Unlike elliptical chainrings, it achieved this by a cam operated device that caused the crank arms to speed up and slow down while the chainrings maintained a constant speed. The second difference was that it had round rings that could be used with a front derialler, and therefore multiple front gears.

So why didn't this idea catch on? Well, first, it was a complex mechanism, and therefore heavier than regular cranksets, and more vulnerable to failure. Also, shortly after it's introduction and far to soon for the bicycling public to overcome it's reluctance to new ideas, another, much less complex product came along that took the "get rid of the dead spot" idea to the next level. And it could be not only be used with multiple chainrings, but they fit on a regular crankset.

The eggs bring home the bacon.

This product was devised by the bicycle giant Shimano, and was called BioPace. It too worked by varying pedal speed through the crank cycle, but instead of a mechanical cam, it accomplished this in a similar way as an elliptical chainring, through it's shape. But unlike an elliptical sprocket, it not so extreme that it couldn't be used with a derailler, so again, multiple front gears were possible.

However, BioPace was not elliptical. In fact, it was completely backwards fron the elliptical school of thought. It was the first chainring designs to owe it's conception to computer aided design. What Shimano did was to carefully analyze the motion of a rider's feet throughout the pedal stroke at a slower, "non-spinning" cadence. They recorded their speed at each point. Then used this information to design a chain ring that would cause the pedals to mimic those speed changes as the crank rotated; speeding up on the up/down stroke, slowing on the fore/back, and by how much at each point Because this difference in the two motions changed under different circumstances, flat as compared to hills, for example, it was decided to make the smaller chain rings match the more exaggerated hill climbing motions, while the larger rings would be designed more circular for the easier pedaling in the flats.

At first, it looked like Shimano had solved the problem. Unlike former attempts this one actually caught on. However. Shimano was not very clear about explaining exactly how the new rings were supposed to be used, so when many experienced cyclists tried them with their smooth, "round" spinning motion, they found it didn't work. The result, of course was a lot of bad publicity, and some really stupid sayings, like: "BioPace inhibits spinning", Which, of course, is like saying "This oval gear is no good because I couldn't force my round cadence into it!"

The death of the dead spot?

Whether you believe BioPace, or any other method worked or not, their is no escaping the fact that none of them really did get rid of the dead spot. Even if you match pedal motion to leg motion perfectly, you will still never be able to apply the same force to the pedals at the dead spot as you can during the up/down stroke for the simple reason that the muscles you must use there are weaker. But there may be a light on the horizon. Recently a new design has been tinkered into exsistance. Rotor Systems of Spain has come up with a Bio-Cam like crankset they call "Rotor RCK" that they claim not only increases power output, but also reduces lactic acid production (the chemical that causes the familiar "burn" of overstressed muscles). Like Bio-cam, it modifies the motion of the crank arms in relation to the motion of the sprockets.

However, unlike Bio-cam, or BioPace, it doesn't slow down the pedals so you can push through the dead spot, rather, it insures that only one of your feet is in the dead spot at a time! It works like this: The crank arms are not locked into a straight line like other cranksets. Rather, they alternatly speed up and slow down in relation to each other. So as one goes through the dead spot, the other is always in the down stroke, the greater power supplied by that leg making up for the lack of power being produced by the other. Sounds like that would feel to funky to use, doesn't it? Well, I haven't tried it yet, but from what I've read and heard from cyclists who have used it, it takes about fifteen minutes, then you don't even notice the assymetrical motion.

The advantages of this design are it too can accomodate multiple chainrings, and theoretically, it should work regardless of how fast or slow the rider likes to pedal.

So, will this be the final word? Maybe, It's still too early to tell. Besides, they have a few hurdles to overcome first. One, because of the cam mechanism, it is still heavier than a standard crankset, and this may turn off many of the gram sensitive racing set. And what they don't like, rarely stays on the markert for long. Especially since it comes with a price tag that only a racer would be willing to pay. As of this writing, around $800. That's more than most cyclists payed for their entire bike! Even if it does catch on with the professionals, they will still have to find a way to get this price down to a level that all but the most dedicated (or obsessed!) rider would even think of laying down.

I think about 80-85% off would be about right, don't you?