Bicycles

CeramicSpeed's radical DrivEn bicycle drivetrain can now shift gears

The CeramicSpeed DrivEn drivetrain utilizes a split-pinion master/slave system to shift gears
The CeramicSpeed DrivEn drivetrain utilizes a split-pinion master/slave system to shift gears
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The CeramicSpeed DrivEn drivetrain utilizes a split-pinion master/slave system to shift gears
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The CeramicSpeed DrivEn drivetrain utilizes a split-pinion master/slave system to shift gears
The CeramicSpeed DrivEn drivetrain in motion
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The CeramicSpeed DrivEn drivetrain in motion

We covered a lot of bike-related innovations last year, but by far the most popular was CeramicSpeed's DrivEn pinion-style shaft-drive system. Now, its designers have taken it much closer to real-world usability, by giving it the ability to shift between gears.

To recap our previous coverage, the original version of the setup consisted of a cylindrical carbon fiber shaft that reached from a single chainring in front to a flat 13-speed cassette on the rear wheel. Mounted on either end of that shaft were sets of very-low-friction ceramic bearings (a total of 21) contained within front and rear cylindrical devices known as pinions – these engaged the teeth on the chainring and the cassette cogs. As the rider pedaled, the bearings transferred torque from the chainring through the shaft and into the rear wheel, turning it.

At the time, the system's Colorado-based inventors proclaimed that DrivEn was the world's most efficient bicycle drivetrain – when it came to converting pedaling energy into wheel motion, that is. And just last month, it was announced that wind tunnel testing conducted in partnership with Specialized revealed that it is also one of the most aerodynamic. Now, at this year's Eurobike show, the system's master/slave-type gear-shifting functionality is being unveiled.

A close-up view of the shifting mechanism
A close-up view of the shifting mechanism

At the heart of the new system is a laterally-split rear pinion.

In response to a wirelessly-transmitted signal from a handlebar-mounted shifter, the side/half of the pinion that is not currently engaging the cassette cog teeth gets moved forward or backward by an actuator inside the shaft. As the bearings on that (master) side of the pinion proceed to rotate 180 degrees and engage the teeth on a new cog, the linked (slave) side of the pinion also gets pulled over onto that cog, so that both sides of the pinion are now back in line with one another, but on a different cog.

The mechanism is illustrated in the following video.

Driven Explained

According to CeramicSpeed CTO Jason Smith, all of the shifting hardware (except for the bar-mounted shifter) is located on or in the shaft. He says that battery life should ultimately be similar to existing wireless electronic shifting systems, such as Shimano Di2 – in the system's current form, one charge has proven to be good for at least 1,800 shifts, with plenty of juice left over.

In terms of the number of gears, the present prototype has a 13-cog cassette, plus the front pinion could also be split, allowing it to be shifted between two chainrings. That said, Smith tells us that the design allows for an almost unlimited number of cogs or chainrings – within practical limits, that is. "You wouldn't want a rear cog as large as your rear wheel," he says.

The CeramicSpeed DrivEn drivetrain in motion
The CeramicSpeed DrivEn drivetrain in motion

The system is said to be suitable for both road and mountain bikes (even full-suspension models), and requires no lubrication. Initially, bikes equipped with it might be a bit pricier than most others, although once the system reaches full production, those prices should drop to the range of other electronically-shiftable bikes.

"We're now at the point where we've taken this as far as we can, we've got the shifting down, the ride-ability, we've addressed a lot of the challenges," says Smith. "We're starting to consider looking for somebody to team up with that has deeper pockets and is potentially in the drivetrain market or would want to be."

So, should anyone from a company such as Shimano, SRAM or Campagnolo be reading this … Jason and his team can be reached via the link below.

Source: CeramicSpeed

7 comments
Mik Fielding
Very interesting, but they have spoilt the concept a bit by having to use a battery and wireless link to change gear when a simple mechanical system activated in the same way conventional bike do. The extra complexity adds cost and reduces reliability and convenience. Suddenly finding you can't change gear because the battery needs charging would be annoying, as is the fact that a mechanical system can last for decades with little maintenance but batteries don't and wireless controllers may not either. Shame, it could be a truly great system otherwise ...
Bob Stuart
I too would prefer all mechanical operation, but this is only the second out of dozens of similar attempts I have seen that looks promising. Rolling-contact gears are clearly the best. I'm not so sure about the ball bearings, though; a single captive element could accommodate both directions of slip. I'd also look very carefully at the drive shaft, to see if it can match the rigidity of a chain and chainstay. That does not matter with motors, but with legs, it can be a big loss.
Expanded Viewpoint
Yes, PLEASE leave the electronics part out of the equation, pretty please! How is that going to hold up to the shock of bouncing up and down all of the time with no suspension to take the jolts first?? What is wrong with using a conventional cable to handle the shifting chore? What about water intrusion messing with the shifting? Just because someone thinks that electronic shifting is hip and cool, do the costs outweigh the benefits??
Kpar
Mik, I felt the same way, but I came to realize that a mechanical shifter could get far more complex, and make the whole thing ungainly and difficult to maintain. I would like to know more- very interesting indeed.
Johannes
An initially simple idea, with some technical drawbacks, now getting more complex with the addition of wireless electronic shifting. I panned this originally because I was sure that the rear gear-set wouldn't be stiff enough not to skip in the (s)lower gears, when the rider is often trying to put the maximum torque through the drivetrain. The CGI doesn't exactly allay that concern.
Naldo the magnificent
I agree about the mechanical shift, much more sensible. Although this system is VERY neat, I don't believe the claim about it being the most efficient means of transferring energy. In the motorcycle world, it has been known for decades (if not hundreds of years) that chain drive is more efficient than shaft, due to the fact that a simple rotating device has less friction involved than one which has to transfer energy through 2 right-angles. Very, very neat though.
Ralf Biernacki
A lot of commenters want to see this as a fully mechanical system, but this is simply not feasible here. With the split pinion, the shift has to be timed exactly right, when one of the pinion halves is out of mesh---not before and not after. And both halves of the pinion must move, sequentially, in a split second. To do this properly requires electronic control of timing---you cannot have a mechanical connection between the operator and the pinion, not unless you have a mechanism of byzantine complexity, essentially a mechanical logic processor. Such things did at some time exist, but are way too complex, too expensive, and too jam-prone for this application.