Chopping bike with Driven transmission

Danish bearing and bicycle parts company CeramicSpeed ​​unveiled a working concept bike with a high-speed drivetrain, no chain and no derailleurs at Eurobike 2018. The transmission is 13-speed with a lightweight aluminum-carbon fiber shaft that transfers rotation from the drive sprocket to the rear wheel "cassette". The developers claim that the transmission efficiency of the new transmission is 99 percent.

Today there are several options for high-speed bicycle transmissions, the most common of which is a chain drive with one or two derailleurs. In this version of the transmission, the transmission of rotation from the drive sprocket to the sprocket block of the rear wheel is carried out by means of a chain. The design of such a transmission is relatively easy to maintain, although it has not very high efficiency - when pedaling, part of the power is spent on overcoming friction between the chain and the sprockets, between the links, as well as on stretching the metal chain itself.

On average, chain drive efficiency is around 70 percent, but can decrease or increase significantly depending on the quality of the bike components and materials used. For example, the efficiency of expensive professional transmissions for road bike can be as high as 98 percent. At the same time, the efficiency indicator is not constant and decreases over time as the chain and stars become dirty, and lubricant is used up and lost.

The new transmission presented by CeramicSpeed ​​is called Driven. It is a type of shaft bicycle transmission and provides the ability to shift speeds. The leading and driven "stars" are made in the form of disks with hooks on one of the planes, evenly distributed around the circumference. The leader has one ring of protrusions, but it can have several. The driven "star" is equipped with 13 rings of the protrusions.

The driving and driven discs are connected by a shaft. In the front part, the shaft is equipped with a disc with bearings on the edge, which with their outer rings fit into the grooves between the hooks of the driving disc. The same disc is installed at the rear of the shaft. It can move along the axis of the shaft forward and backward. Thanks to this, it can engage with different rings on the driven disc, due to which the transmission ratio changes in the same way as in a conventional bicycle chain transmission. Driven has 21 radial bearings in total.

The developer assures that the transmission is designed to transfer more than one thousand watts of power. For comparison, during a normal race, the average power generated by a cyclist is about 250 watts. Drivetrain Driven Passes First stage tests. How it will work during rain and pollution, whether it will withstand load surges is still unknown. It is likely that transmission maintenance and repair will be quite difficult and expensive due to the need to flush or even change the radial bearings.

The presented bike with a new transmission is aerodynamic. By the design of the frame and the shape of the steering wheel, it can be assumed that it is intended for competitions with separate starts, that is, it is designed for semi-professional and professional level use. It can be assumed that the use of a bike with a Driven transmission will be prohibited in official races. The fact is that the hooks of the driven "star" can pose a serious danger to cyclists during an accident - during rotation it actually turns into a meat grinder.

In professional road cycling, the use of disc brakes has long been banned for safety reasons. Cyclists often use rafting to save energy at the expense of an opponent in front. With this technique, one rider walks closely behind the other, and if the distance is not kept, a collision is possible. It was believed that in such a collision at a speed (at road racing the average speed is usually 35-38 kilometers per hour) cyclists can severely cut themselves on the brake disc.

In January of this year, German engineer Andrea Mocellin bicycle wheel folding design. It is assumed that such a wheel will greatly facilitate the transportation of a bicycle, for example, in the trunk of a car. The rim of the 26-inch wheel, called the Revolve, consists of six sections connected by a metal frame. The wheel can be pulled on the center section and folded. Attaches to the Revolve bike using a standard eccentric.

Vasily Sychev

A gimbal-driven bike delivers torque specifically through the shaft, not the chain mechanism. The shaft drive was invented over a hundred years ago. The most complicated technology and the inadmissibility of changing the gear ratio did not allow the invention to obtain a good continuation. With the onset of the 21st century, technological methods began to develop, then the gear ratio of a particular chain drive was equated with the mechanics of internal bushing gearboxes. As a result, the market was somewhat replenished with serial bikes equipped with shaft drives.

How ideas evolved

The idea of ​​creating such drives without a chain appeared at the end of the 19th century. In addition to the shaft, there were completely variants of the chain, which did not receive further distribution. The first devices were developed in 1890 by the United States and Great Britain at the same time. England was skeptical of the shaft drive, hence it got into American company Pope Manufacturing Company, which bought the rights to develop a unique device in the states.

The shaft drives got their start from the League Cycle Company. After a short time, French developers released the first bicycle without a chain, which soon began to be mass-produced.

Technical support

The gears are shifted by a drive shaft connected to an internal hub reducer. Among modern manufacturers of bicycles with a driveline, the largest are Sturmey-Archer, along with Shimano and, directly, SRAM.

Thanks to the bevel gears, the rotation of the torque axis from the pedals is provided mainly by 90 degrees. The power of rotation is transmitted to the rear wheel through two pairs of bevel gears. The first pair is in close proximity to the carriage shaft, the second is next to the rear hub. The transmission is done in a Z-shape.

The bevel gears guarantee an optimal change in the angle of the felling axle, which results in less friction than worm gears.

A bicycle with a gimbal is somewhat easier and safer to operate. When driving over rough terrain, the risk of chain jerks is eliminated. Because it is cleaner, the cyclist's clothes and bike chain are not greasy. The closed drive has a fairly long service life and is resistant to breakage.

Seven Key Benefits of a Gimbal Bike

1. Safe for cyclists. It excludes clothing getting into the chain and jerking of the mechanism, since the gimbal bike does not have a sprocket and an oil chain.
2. High reliability due to the minimization of the number of moving parts.
3. Durability provided by the closed mechanism design.
4. Low preventive maintenance requirements.
5. Good aerodynamics.
6. Increased distance between the bike frame and the road. Good spacing is achieved due to the absence of a chainring.
7. The originality of the design.
8. High cost price.

Drawbacks of a shaft drive bike

1. The structure weighs not so little - 1-3 kg.
2. High cost price.
3. Difficult renovation. In the event of a breakdown, it is better to take the bike to a tire fitting.
4. Impossibility of compact implementation of a large number of gears, although their switching is considered to be smoother.
5. The ride is somewhat stiffer than a chain bike.

Conclusion

A shaft-driven bike is ideal for city riding, as there is no need for extra effort on a flat road. A large number of speeds when driving on asphalt is also not required. The purchase of a unique bike will one day allow you to use it for a very long time in the future.

Photos from open sources

The bicycle, despite the desire of some to write it off on "yesterday", does not want to leave the arena the most popular types transport, only acquiring more and more perfect qualities over time. Another novelty of this timeless bike is a constructive solution that eliminates the usual chain for a bicycle. This is exactly the unique property of the DrivEn concept, which CeramicSpeed ​​presented at Eurobike 2018. (site)

Instead of the usual metal chain, this bike has a shaft, but not the same as a car or motorcycle, but light and flexible, made of carbon fiber. On both sides of this shaft there are special ceramic bearings, as well as teeth bent at 90 degrees, due to which it, rotating itself by means of a pedal, rotates rear wheel bike.

Photos from open sources

Thanks to this design, the developers say, they were able to reduce friction (compared to a conventional chain, even the most advanced Shimano Dura Ace) by 49 percent. Friction is reduced due to the absence of eight points of contact from the chain transmission in this design (the place where the chain passes over the sprocket, cassette, derailleur).

Photos from open sources

The unique DrivEn bike has thirteen speeds and can demonstrate truly fantastic performance on a good track, while significantly saving the cyclist's strength. It is no coincidence that the new invention was immediately awarded the Eurobike Award, which was received by the developers of the University of Colorado.

And this, experts say, is just the beginning in the development of more and more perfect chainless bicycles.

Photos from open sources

By the way, we note that the other day we wrote that, moreover, of a rather modern design, it was noticed in India in the 2000-year-old Panchavarnaswami temple, which can serve as indirect evidence that the design of a two-wheeled vehicle is so harmonious that it is not afraid of any technological advances, it is simply not subject to time. And this was once again proved by the developers of the DrivEn chainless bike (watch the video and admire the simplicity and genius of this solution).

At Eurobike, the drivetrain for the bicycles of the future was shown. There is no chain in it, there is only one "sprocket" on the rear wheel, and most importantly, there is almost no friction and associated losses. The creators claim to have achieved an efficiency one and a half times higher than in the current solutions for cycling professionals.

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The company reinvented the bicycle CeramicSpeed : in its concept, the pedaling power is transmitted to the rear wheel by a rotating shaft rather than a traditional chain.

The company claims that this way of spinning the wheels is one and a half times more efficient than the advanced traditional solution for professionals - Shimano Dura Ace cassettes and level derailleurs. Co-creator of the system, Jason Smith, in an interview with Bikeradar explains this is a colossal reduction in points of friction. And also the careful selection of bearings and lubrication - in this the company was helped by the Friction Facts laboratory from Colorado.

“Every time the chain is pulled, there is friction. Each time it looses, friction arises. When you pedal at 95 rpm, there are 40,000 of these points per minute, ”says Smith.

According to him, a rotating shaft, through which energy is transmitted, is a very traditional concept. For example, in an automobile differential, the wheel speed is compensated by bevel gears. With this approach, there are only four points of friction. But all attempts to adapt the mechanism for use in bicycles have failed due to enormous friction. So the creators of the new transmission discarded bevel gears and began to invent a different way of "perpendicular" transmission of force.

The solution was a circle of bearings that spins one "sprocket" - not five or seven, as on today's bicycles, where the chain must be moved in order to vary the effort.

The novelty was shown in action at the Eurobike exhibition. According to Smith, frictional losses were reduced to just 2%. True, Bikeradar points out that the system is most efficient at medium power levels - up to 300 watts.

CeramicSpeed ​​recognizes that its solution has a long way to go from prototype to mass production. First, while the device is not able to change gears. To do this, it is necessary to supplement the rod with a mechanism that moves the "sun" from the bearings along the "sprocket". But this, according to the creators, is not difficult. More importantly, a special frame needs to be produced for the new system - which means that the bicycle revolution needs to attract the attention of major manufacturers. Third key moment- protection of precision bearings from road dust, dirt and moisture. In a demonstration prototype, where it was important to show how the system works, its insides are open to all winds.

If CeramicSpeed ​​manages to overcome these difficulties, it is possible that the time trial bikes on one of the following Tour de France cycle races will look something like this:

In the big high-tech + wrote about another trend in rethinking bicycles - compact electric motors that allow you to travel huge distances or easily overtake competitors.

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