Monday, January 11, 2016

New is Old Again: Expanding Chainring Cranks

You know what's wrong with front derailleurs? They're light, simple, and they work. Yes, it's true that if they're badly out of adjustment, you can drop the chain when shifting. But on the whole, they haven't changed much since the 1960s because they haven't really needed to.

People are always trying to find a better way, though, aren't they?

I saw a video for a new gear-changing innovation called Wavetrans Bicycle Transmission. "A new kind of bicycle transmission which uses a revolutionary logic," the website claims.

What is it, exactly? Wavetrans is essentially a crank with an expanding chainwheel. It has about 6 chainring "segments" which can expand or contract at the push of a button. Its inventor is trying to get backers for their concept, but you can see a working prototype on their website:

The company claims many "advatages" (sic) "compared to old gear shifter systems (Derailleur for example)." It can be shifted uphill, under load, the chain never comes off, and (my favorite) "no crunchy noises." Unless you're a dedicated granola-muncher. Then there's still lots of crunching.

Here you see the crank in its lowest gear. The prototype uses a pretty huge '80s-looking computer to control the unit and to shift gears. The FAQ page asks if users would be able to shift gears using their smartphone. "Yes, I'm sure there will be an option for that." Yes, I'm sure too.
Here, the chainring segments are expanded to the highest gear. 
You know what else is cool about Wavetrans? It's "something . . . that you have never seen before."

. . . Unless you actually know something about bicycle history, that is. In which case you know that these things go back almost to the beginning of the safety bicycle.

According to several sources, including Frank Berto's history The Dancing Chain, and Tony Hadland's Bicycle Design: An Illustrated History, there have been a number of expanding chain wheel systems, some dating back to the Victorian age -- most of them just variations on the same idea.

Here are a few:

1896 - Linley & Biggs Protean Gear. It used two half-chainwheels that could then be expanded by up to 4 teeth, though it took on an oval shape as it expanded.

1903 - Paradox expanding chainwheel. "Incorporated a complex mechanism to achieve a circular expandable chainwheel." (Hadland) It expanded in one-tooth increments up through 7 teeth.

1903 - Mitchell Any-Speed. "Rotated the chainwheel off-center. The eccentricity changed the effective diameter, giving infinitely variable gears." (Berto)

Searching on my own through some "expandable chainwheel" patents, I also found some of these diagrams:

One patent is for W.A. Leggo Jr. in 1894, and the other is for J.M. Cleland in 1898. I don't know if these ever made it onto the market.

None of the systems listed above lasted for more than a year or two. Development of such systems on the whole disappeared for a few decades as derailleurs and even internal hub gear systems proved to be simpler and reliable. But then, in the 1970s for some reason, they came back as more inventors once again looked to expanding chainwheels as the answer to a question nobody was asking.

Here are some of the more modern systems:

1974 - Hagen All-Speed Expanding Chainwheel. This had 6 smaller sprockets that moved outward as an inner spiral-plate turned. The gear range was 2.85 to 1, or 285%.
This Hagen All-Speed crank was up for sale on eBay last year. Top photo shows it in "low gear" position, and the bottom photo is "high gear." And it was infinitely variable in-between. At least one of the ads described it as having "a jillion speeds."

1983 - The Deal Drive had 16 speeds and a 2-to-1 range. It used 6 spring-loaded expanding segments. Pedal forces compressed the springs, retracting the chainwheel segments, thereby lowering the gear. An adjustment lever on the crank arm let users adjust the spring loading tension. Frank Berto described it as "well built and reliable. However it was heavy, expensive, and it had a limited gear range." Expired after 2 years.

A prototype of the Deal Drive. What must this thing have weighed? And how could anybody think that this was somehow preferable to a derailleur? (photo from Commutercycling)

1983 - Excel Cambiogear. Oddly enough, Excel was a division of Beatrice Foods, which tried to break into the bicycle business in the early 80s. The Cambiogear had 16 speeds, and a 3-to-1 range. Made of graphite-reinforced-plastic. It lasted 1 year.

The Excel Cambiogear, front, and backside. Made of graphite-reinforced plastic, it had small chainring "segments" that expanded or contracted on these spiral-like grooves, not terribly different from the Hagen All-Speed.
Here you can see one of the chainring segments.

The photos above are screenshots from an explanatory video of the Excel Cambiogear I found on YouTube. You can watch it here:

Clearly, this idea has been tried (and abandoned) numerous times in over a century. And the Wavetrans isn't even the only expanding chainwheel crank startup today. Another startup - the VECTr Variably Expanding Chain Tranmission - apparently applied for a patent last fall on their own version of this old idea.

Here's a prototype of the VECTr, which uses a heavily modified Deore crank. It looks like the little toothed chainring segments have 5 distinct positions, giving the user 5 gear selections ranging from 24 to 44 tooth equivalent.
So, about the only thing I can see that sets the Wavetrans apart from all these other systems is that it's electronically operated. Push-button electronic shifting chainrings, without a derailleur. Well, that's something we've never seen before.

Oh, wait. . .
Scan from a 1987 issue of Cyclist. The Browning Automatic Transmission used hinged (not expanding) chainrings, and an electronic control box to change gears. Early tests by a lot of the bike magazines of the time declared it an unqualified success. It was later put into full mass production by SunTour (called "The Beast") and suffered from reliability problems. Many were recalled. Then SunTour went out of business. Browning tried to keep the design going for a few years on their own, but never found a market for a shifting system that cost about twice as much as a Shimano derailleur-based drivetrain.

Something tells me that people today are no more likely to adopt a transmission that's heavier, more expensive, and more complicated than a derailleur system than they were 20, 30 or even 100 years ago. I just don't see the Wavetrans (or the VECTr, or any other similar ideas that might be brewing out there today) having any more success than their Victorian-era counterparts, or any of the revivals from the '70s and '80s.


  1. It's heavier, more complicated, more expensive, uglier, already tried and failed, and less reliable -- plus, it has portentous music! It must be good!

  2. "There is nothing new under the sun..." (Ecclesiastes)

  3. that's a great review of just this one idea that keeps attracting the home inventor! God bless them, the inventors want to create something that will change the world, and I can't blame them. It does seem like someone should be looking over their shoulder and saying "you might want to check the history on this sort of idea...".

    This would be a great theme for other ideas that were too bad to kill. Off the top of my head, the only thing that comes to mind are oval chainrings and curved crank arms. ..and pedals with an axle centerline that is above the sole of the shoe (Hi-E made one, as did Shimano, and I recall seeing one or two in Speedplay's on-line museum).
    Maybe add the idea of a gear cluster that stays with the frame when you remove the rear wheel, such as the Maillard Helicomatic?

  4. I am the inventor of VECTr, so thank you for the exposure. I've been aware of the history of expanding chainrings. You seem to think that they must all necessarily be "heavier, more expensive and more expensive than a derailleur system. . ." VECTr currently weighs 500 g and should cost $150-200. I detail this in comparison with other in-line transmissions on my "A Journey by Bike" blog at .

    1. Joseph - Thanks for writing. Wishing you the best of luck!

  5. My cousin bought a Harkey adult trike, with a Hagen all-speed, no chain tensioner on it, so having to build on, could not find much info on it, just some old newspaper adds.

  6. I think if you could run a single sprocket at the bike and get the ratio of front increments correct this would be a great step forward for aerodynamic groupsets.
    Do away with all the derailleurs and cabling and have one wireless electronic shifter for the front ring and that would be a seriously tidy setup!!


    What's your take on this one?

  8. This is some great research! I like when people think outside the box, and I believe there are reasons to want to improve on the current derailleur system. Personally, I wouldn't mind a system that could be shifted smoothly under load for those times when I misjudge a hill. I doubt the expanding chainring is the answer, as it comes with the inherent problems you mentioned. For mountain biking, I see disadvantages in the size (more likely to strike on rocks) and limited range as compared to a 1x12 gear set with 500% range. I still appreciate that people have gone down these avenues. The further an idea is developed, the more assuredly we can either eliminate it as a viable option, or embrace it as a success. These inventors are unsung heroes, whose work has not only shown us what not to do, but also what to strive for, which helps us all collectively to get one step closer to our goal of perfection.