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Comment by oconnore | Hacker News Reader

Neat. I wonder if creating a vertical elliptical pedal path, or even a linear path would be an improvement. That way the cyclist would have more leverage on the down stroke, since at the bottom of a circular stroke you are forcing the pedal mostly rearwards, not downwards.

Also, to me it looks like the two rotating cylinders next to the rear wheel are ratchets, like a socket wrench.

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That's been done on regular gears, I'd imagine it would work much the same:

http://en.wikipedia.org/wiki/Biopace

It's my understanding that the pros don't use this. If you don't have enough torque, you're probably doing it wrong, and would soon be out of gas even with more mechanical advantage. Shift down, pedal faster.

This makes no sense. If you can generate the same power with less physical exertion, and no significant reduction in reliability or weight, why not take it?

I've seen comments about gear changing being slightly worse (which doesn't surprise me) and being overshadowed by things like moving from clips to SPD pedals.

Physical exertion equals power. You can't have the same power with less physical exertion. It's a trade-off between aerobic capacity and anaerobic capacity. You can pedal in a high gear, using more strength, or you can pedal faster in a lower gear, maintaining the same speed, but using more cardiovascular capacity. In both situations, if you are going the same speed, you are putting out the same amount of power.

Non-circular gears change the gear ratio as you pedal. It effectively shifts down in that part of the pedal stroke where you have the least strength. Since the bike doesn't slow down, your feet must speed up. Then, when your feet swing around to where you have more strength, it effectively shifts up.

My argument is, if you are pedaling at the limit of your strength, you are in too high a gear. Shift down and spin your feet faster. You'll use less strength, and more aerobic capacity, enabling you to maintain an equivalently high power output, but for longer. It's easier to run a marathon at a constant speed than to sprint 100 m at a time, taking walking breaks to maintain the same average speed.

Isn't your analogy in the last paragraph a good argument in favour of non-circular gears? Gears that allow you to output the same amount of power all the time.

Oval chainrings (like Biopace, Rotor Q-Rings, etc.) are used by some pro cyclists. The oft-touted advantage for the system is the elimination of the "dead spot" at the top of the pedal stroke, but it still seems to very much be a case of personal preference. Just like there are some pros that prefer to spin an easier gear up a climb, while some would rather mash it out in the big ring.

It all comes down to how good the motor (legs+lungs) is.

Thanks for the link.

It's funny how people are so resistant to innovation. "Biopace chainrings are often cited as the epitome of a solution looking for a problem among the biking press." While typing on a computer that likely contains a mechanical hard drive spinning at close to 10krpm, the author complains of a slight increase in mechanical complexity that will allow him/her to generate more power. The real question is whether or not the complexity is manageable, will it break down frequently? etc.

"People are so resistant to innovation" is one way to look at it. Another way to look at it is that sometimes innovation gets far enough ahead of expectations that it can't overcome challenges with user education and linkages to present technology.

I remember using Biopace and the part I remember the most was going up a steep hill and losing traction because of the change in torque. I was riding a bike the way I was accustomed to pedaling but the power output would surge because of the change in mechanical advantage. Maybe I could relearn how to pedal so I could take advantage of Biopace but I really just wanted to ride, not maximize every degree of the pedal arc.

If you want to really muse about missed innovations, look at recumbent bike designs. Every one uses upright bikes today.

Biopace-like designs returned to the PRO peleton a few years ago, though the shapes are a bit more radical.

I've usually found pedalling mostly downwards inefficient, because it pushes me off the seat. If I want to get power out of pedalling, I put particular care into pedalling back and forth - the top foot forwards, the bottom foot backwards. For this to work well, though, you need pedal straps or very toothy pedals.

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