For techies who are very much into bicycle gears, this would be a blast: 150 milliseconds, a touch longer than the blink of an eye, are needed by the planetary gearbox in the rear wheel hub to change gears. This is what Mathias Plouvier, CEO of the Belgian start-up Classified Cycling, assures; he speaks of the “currently most efficient drive hub in the bicycle industry”. A claim that bicycle experts will not buy for the time being without independent testing. To date, it was considered typical for the design that gears were changed with a comparatively long delay.
The Powershift hub in question is intended to change that. The centrepiece of Classified's bicycle gears is an electronically controlled planetary gearbox in the rear wheel hub. The gearbox virtualises the front derailleur, making the latter and the second chainring superfluous. Although the front derailleur still provides the necessary fine-tuning of the gears with a wide range of transmission ratios it is delicate and repeatedly provokes shifting errors resulting in chains dropping and slipping when accelerating. History remembers, for example, an incident during the 2010 Tour de France when the chain of the Luxembourg cyclist Andy Schleck dropped and the Spanish cyclist Alberto Contador was able to take the yellow jersey as a result. “In races, the front derailleur was always an issue for the two to three front chainrings”, says Dirk Zedler, Managing Director of Zedler-Institut für Fahrradtechnik und -Sicherheit in Ludwigsburg.
Chain drops caused by a front derailleur are excluded by the Classified system. The encapsulated virtual front derailleur is low-maintenance and low-wear compared to the exposed mechanics of the front derailleur, according to the company headquarters in Turnhout, Belgium. What turns the system into hybrid gears: The planetary gearbox shares the work of gear shifting with a self-developed matching sprocket set on which a conventional rear derailleur moves the chain, thus combining hub and derailleur gears.
Chain defeats hub
A statement that Roland Huhn, expert of the German Cycle Association (ADFC) can hardly believe. The “queen of speedhubs”, the Rohloff 500/14, which has been undisputed for years and is referred to in specialist literature, has an efficiency of “better than 90 percent” and thus cannot compete with derailleur gears. In addition, the chain line “as a possible source of loss is shifted even more with a single chainring than with a double chainring”, if it is operated properly: using the larger sprockets with the small chainring and vice versa, i.e. without “cross-shifting”.
Expert Dirk Zedler is also sceptical: "I would treat ambitious statements with caution until the presentation of proof.” In all tests to date, gear hubs have been more inefficient than properly maintained derailleurs. That’s why all attempts to establish gear hubs in sport have failed so far. But Plouvier counters: Oblique chain lines are a thing of the past, as the remaining front chainring is positioned in such a way that both the largest and the smallest sprocket of the cassette can be easily reached. What is more according to Classified, people will use the hub more often in practice because it is so fast which makes “cross-shifting” less likely.
And as there is no small chainring anymore, there are no more losses of its efficiency: If the chain rotates on a small chainring, the chain tension is higher, which leads to more friction losses. This is excluded with the Classified system, says Plouvier. At the same time, the system weighs less than a standard dual system.
The developers of Classified Cycling have been working on the Powershift system for over seven years, have invested an “eight-figure sum” in the project and obtained several patents. The person in charge of the development was Roëll van Druten, the former chief engineer at Punch Powertrain, a Belgian automotive supplier specialising in CVT and dual clutch transmissions. Today, van Druten is Technical Director at Classified. The starting point for the development was that the core technologies of the drive train on bicycles have not changed in the past decades, says Plouvier: “Taking account of the duopoly Shimano and Sram and very strong competitors that produce very good products worldwide, the product had to be absolutely perfect.”
The impression during riding suggests that there could be some truth in Classified's claims. We were able to try out the system on a gravel bike from Ridley. Almost at the same moment as you actuate the lever at the shifter on the handlebar, the two-speed gear changes the transmission via a radio receiver on the right side of the axle. This works almost silently and brilliantly even under load. If you put a lot of pressure on the pedals when climbing, for example, the virtual small chainring changing from a 1:1 to a 0.7:1 ratio analogous to a chainring combination, is activated quickly and without grumbling.
Shifting the sprocket in the rear, however, feels unspectacularly good and as smooth as with high-quality derailleurs from Shimano or Sram. The fact that Classified had to develop its own cassette matching the hub does not seem to detract from the shifting precision and speed of the rear derailleurs from Shimano, Sram or Campagnolo that can be combined with the Classified system. A long-term test would have to show whether the overall system is particularly low-wear as promised. And Dirk Zedler adds that “how efficient Classified Cycling's hub gear is, I am not able to say, and I don't think anyone is able to say without solid testing".
Read the entire German article online
Author: Stefan Weißenborn