Bicycles have evolved a lot from the bikes that our grandfather's had, but there are things that never change. They all had two wheels, pedals and a pair of cranks; always the same. Nevertheless, there are people always trying to turn a bit more the screw. Maybe, you have seen bike-alike things without wheels that ride on water or snow, and several other bicycle inventions.

When we pedal our legs generate an alternative movement that has to be turned into a circular one by a crankset. Crank systems have always had one problem: When cranks are vertical, no matter how much force you exert on them, the power will not be transmitted to the axle as a turning force ( torque in physical terms ).

Overcoming this limitation was one of the main goals with ecliptic chainrings, such as Shimano Biopace. It may have been a good idea but it was incompatible with indexed front shifting systems and never were accepted by most riders, so they were withdrawn in 1993.

One step beyond
Now, there is a company that has faced this problem from every point of view: the physical, the ergonomic, the physiological and the mechanical. This company is Rotor. Their first version was a quite complex system that needed a special frame, but since they finished the development of the new RCK (Rotor Concept Kit) everybody can enjoy the advantages of Rotor researches without buying a different bike.

What is exactly the RCK System? It is a set of two cranks, a bottom bracket and chainrings in which the axle, the right lever and the rings can move independently. The cranks are connected by two struts and it allows the cranks move more slowly downwards and faster upwards.

Rotor's Roots
This is not the typical romantic garage invention. The idea comes from the Aeronautic Engineering School from Madrid, where some students developed a prototype back in 1995. After the president approved the project, the University's Manufacturing Department Laboratory helped with the prototypes.

The designers decide to establish a society to finish the development and start the business. After the first working Rotor bicycles are internationally introduced, Dr. Conconi shows a great interest on the idea and asks for a sample to make a performance research. Conconi concludes the system is a real advantage.

Manolo Sáinz from the ONCE professional road team wanted to use the Rotor, but sponsors don't allow him to use it in races. The Spanish Paralympics Team tried the system successfully and Dr. Alfredo Cordova from Valladolid University proved that the system provides a clear physiological advantage.

Early versions of the Rotor were available in 1998. They were manufactured by the high end componentry Spanish company EDR. The early system needed a special frame because is was possible to put the mechanism inside a conventional bottom bracket frame box. Now this limitations has been overcome, for 2001 the new Rotor RCK is available, and this allows to enjoy the Rotor's advantages in every frame.

Once seen the benefits it's easier to afford the extra complexity, even the extra weight. Compared to Dura-Ace it will add another 240 grams to your ride. Field tests on a Angliru mountain pass with 23.5% slopes proved that the system improves performance during uphill climbs.

Biopacing again?
Obviously, pedaling on a Rotor equipped bike feels very different than on a conventional one. First of all it seems you are stronger than you really are. It's easier to move the big chainring and it's easier too to pedal with a very slow cadence. During the first two minutes there is a strange sensation of swinging. It is as if the frame is broken. But, after a period you find yourself pretty well adapted. The only remarkable thing is the tendency to use smaller rear cogs than with a conventional bike in any given road. On the downside it seemed more difficult to reach high pedaling cadences.

On mountain technical trails, it is more difficult to adapt due to the strange feeling of asyncronicity between both cranks. You feel it the most during the downhills when you try to move your feet in the right position for a corner by moving pedals backwards Because both pedals move independently sometimes when one pedal is in the right place, the other one seems not to be.

I found that when I tried to climb very steep trails it was easier because a smaller amount of strength that was needed to move the crank from its upper position. I found that it was possible to surpass trails I had never thought I could have.

This is very different from biopace because completely eliminates the lack of power that is exerted when the crank is in the vertical position and it is compatible with all front indexed shifting systems.

A new path
As can be seen, there are more advantages than disadvantages. The RCK system has recently been approved by UCI officials for competitive use. In my opinion the only problem that the Rotor has is that manufacturers and cyclists refuse to test it. But, if the industry's behavior is the same as it was with suspensions, maybe in a few years of all as will have a Rotor equipped bike.

What would happen if it was Shimano who had developed Rotor?

More info at www.rotorbike.com

By David Díaz Blanco