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Wavetrans bicycle transmission provides seamless CVT-style shifting

Wavetrans bicycle transmission
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If you’ve ever driven a snowmobile or a car equipped with a CVT transmission, you’ll know how smooth the engines feel as they shuffle through their “gears”. With the creation of the Wavetrans bicycle transmission, that kind of smoothness could find its way onto your bicycle.

The Wavetrans is an electronically controlled drivetrain with a single front ring that expands or contracts to provide the equivalent of six different gears. The innovative concept claims to offer several benefits versus traditional derailleur setups. It provides a seamless feeling while you shift, can be shifted under load, operates quietly and smoothly, won’t double shift like derailleurs can, digitally displays what gear you’re in, and the inventor claims the chain will never fall off.

Currently only one prototype exists and actual production is a ways off, but it’s certainly an interesting idea. Video and more details below…

The Wavetrans’ single front chain ring is made of six separate sections that telescopically expand and contract to provide six different gears. The system is electronically controlled by a programmable logic controller (PLC) and a microprocessor. While the prototype is powered by nine AA batteries which provide about nine hours of juice, production models will likely house a few less.

Riders shift gears by using two buttons on the handlebar mounted control/display unit, one to shift up and one to shift down. The buttons will always be easy to press, whereas regular shifters can require some effort to overcome cable tension, friction or spring force.

The Wavetrans system cannot be used with a regular cassette and derailleur setup in the rear, so the cassette is replaced by a single cog with a sizeable looking chain tensioner. The standpoint of the inventor, Phoenix, Arizona’s Oliver Knittel, is that most riders don’t use every gear on their bike so six should provide an adequate range.

The range provided by the prototype model is equivalent to a 47t front ring matched to a 15-24t six speed cassette, but that can be adjusted up or down. With only six intervals the Wavetrans certainly won’t achieve the same spread as a traditional drivetrain, so riding in hillier terrain might be a bit challenging.

Wavetrans bicycle transmission, rider
Photos and video courtesy of Wavetrans

The concept puts forth several perceived benefits: It provides a seamless pedalling feel through gear changes, the capability to shift anytime, it runs quietly, includes a digital gear indicator, and apparently offers very reliable chain retention. However, there are of course several caveats. Firstly, internally geared hubs can also be shifted anytime and some offer more gear range. Also, other brands’ electronic derailleur systems display your current gear digitally, so that’s nothing new.

Also, the Wavetrans was designed for on-road riding only, and it’s not hard to see why. Durability for trail use is dubious, with a large six-piece front ring that can’t accommodate a bash guard. You don’t gain any additional clearance in the rear with the chain tensioner hanging down just like a derailleur, and perhaps most importantly the moving front ring segments are not recommended for use in muddy conditions (but should be able to handle rain and snow…we’re thinking it makes sense for commuter bikes). If you do damage or wear out the ring pieces, replacing them isn’t a complicated task.

The prototype transmission unit itself weighs 1200g, but the inventor notes that weight was not a priority in creating the first working iteration seen here. Keep in mind the Wavetrans does eliminate the weight of two derailleurs, a rear cassette and multiple front rings.

We assume a production version would look far nicer than this simple ‘proof of concept’ prototype, in fact the rather large display/control unit is already slated to shrink in size. While the price is yet undetermined, Knittel says it should be within reason.

Further options and innovations will likely come along if production moves forward. Knittel is already working on a seven speed version, and has suggested an option for smartphone control connectivity. Knittel has filed a patent for the design and is currently seeking a partner or buyer for the Wavetrans.

WaveTransmission.com

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Antipodean_eleven
8 years ago

Interesting stuff. Sitting here in my plush and expensive arm chair, I recline back and ponder why 6 gears? Thinking broadly about the way this works, it could be pushed further to be more like an ‘infinity’ gearing system… which would be very cool; just think, smooth gearing adjusted to just where you need it.

And before anyone say something about all these electronics (that’d usually be me btw), this actually seems more sturdy that those rather expensive and fragile electronic rear mechs dangling out in the breeze.

dailycardoodle
8 years ago

it can only jump in link intervals to keep meshing with the chain, that’s the restriction, so CVT isn’t possible

Ol Shel
Ol Shel
8 years ago

It’s good to see this year’s expanding chainring concept. Like the first blossoms of Spring, I look forward to them. The real issue is that road bikes don’t need a complicated solution to a very small problem. MTBs could benefit from better drivetrain, but segmented systems don;t work will in the small diameters that off-road bikes require. Plus you have this swiss clock getting hammered with dirt and rocks.

Maza
Maza
8 years ago

with cogs and a chain it can’t really be “infinite gearing” it would at minimum have to be in one tooth increments. unless you had a belt drive of some sort.

Emily
Emily
8 years ago

I half expected to see Mario and Luigi with the quality of that video.

mtbtec
mtbtec
8 years ago

Neat!

ed
ed
8 years ago

160% range? Go singlespeed instead

Finbarr Saunders
Finbarr Saunders
8 years ago

Did you really talk about wearing out ring pieces? Fnarr Fnarr

Colin
Colin
8 years ago

Are you serious? If a Di2 derailleur ever contacts pavement, you have no more warranty. Also if you hit hard enough to pop it into “safe” mode, it WILL fail, it’s just a matter of when. Also there is no way to revert firmware, so if you update and it doesn’t work right, you are boned.

Finbarr Saunders
Finbarr Saunders
8 years ago
Reply to  Colin

Evidently “Ringpiece” doesn’t mean the same in the US as it does over here in the UK!

Eric Hansen
Eric Hansen
8 years ago

There’s *nothing* fragile about Di2 derailers, but this looks like a really neat proof of concept.

therealgreenplease
8 years ago

The developer needs help with his promotional materials but it’s actually a pretty nifty concept.

evolvo13
evolvo13
8 years ago

Clever idea. That music in their video though? I was having EBM club flashbacks.

StephenM
StephenM
8 years ago

6 gears is not at all “cvt like”. In fact, it’s the opposite.

greg
greg
8 years ago

I saw a similar, non-electronic prototype at least 25 years ago at an “invention convention”.

anonymous
anonymous
8 years ago

This has been done before. I seen at least one system on BR before, and that wasn’t even the first. You only have to google “expanding chainring” to find multiple others.

Birdman
Birdman
8 years ago

Is six segments odd the same gear extending in and out. It IS very “CVT like” in my opinion.

Also, I think the reason they choose to do only 6 fix faux front chainrings is because of the size of the existing bike chain and sprocket pitch size. If they go to a fine pitch chain and sprocket arrangement then they could have more than 6 ratios. If they use belt drive then they could really achieve a true CVT style transmission.

Please keep the innovations coming, SUPER COOL!!!

Michael Knight
Michael Knight
8 years ago

Is power and control signal inductive, or are there brushes/springs transferring signal?

I think he rightly aims this at the “exercise bike” market, where people are sometimes confused by how shifting works, or stuck in a big gear due to “too much effort” to downshift out of the big ring.

The music and video production are straight from Knight Rider or Airwolf. ;). Loved it.

MotoPete
MotoPete
8 years ago

How about independently moving segments? Biopace into Hyperspace!

M. Johl
M. Johl
8 years ago

I’ve seen this in the early 90s. Wasn’t it Suntour before they had to give up due Shimanos dominance?

Craig
Craig
8 years ago

Regardless of how many gears it has, the range is severely limiting. I’m struggling to see how this offers any real advantages over an electronic Alfine hub (and the Alfine gear range is far better).

Droid
Droid
8 years ago

There was a bike a shop I worked in (late 1970s) that sold the “Volkscycle”, a 5 speed expanding segmented chainring bike. It had a twist grip; was cable operated, as I recall. It had a lumpy feeling while pedaling.

Jason
Jason
8 years ago

It’s an electronic version of the Deal Drive (from the 1980s!) If it’s all controlled electronically rather than by springs it may iron out a few of the flaws that the Deal Drive had

Ronny
Ronny
8 years ago

How is this Continuous Variable? Or is it supposed to be another CVt :).

Dave
Dave
8 years ago

Let’s see, very heavy, very limited gear range and fragile. Sounds like there is a lot of development work ahead before this thing is commercially viable.

I noticed the inventor had product name decals made for the demo bike so he’s at least that far along.

bart
bart
8 years ago

but can it only extend half of the teeth out to make an oval chain ring?

Andrew
Andrew
8 years ago

I wanted to do just this in university as my Mechanical Engineering Finaly-Year design project, but it got shot down by a prof that said the idea was impossible. …. beat me to it 😉

anonymous
anonymous
8 years ago

@Andrew
Well, it’s a pretty old concept. If your prof said it wasn’t a CVT though, he’d be right. If you assume each segment will have the same radius as all others, the system can only work when there is an integer of links (or half links depending on how you count) between each segment. For 6 sections, if you’re not willing to make the sprocket even less round, that means each discrete step is a whopping 6t difference.

pete
pete
8 years ago

I tested one 35 years ago, made of expanding plastic pieces. Though the CVT concept has been around for the front ring as well as the rear hub, as yet no one has ever gotten the chainring to work at a truly useable level.

Michael
Michael
8 years ago

My guess is that the reason for a fixed number of gears is that the expanding sections need to lock in a given place otherwise the pressure from the chain on the downstroke would be too much. They can expand on their way up without a chain pushing against them at all.

Very interesting.

Brooks
Brooks
8 years ago

Expanding chainring cranks actually go back almost to the beginnings of the safety bicycle in the late 1800s. There have also been a number of similar systems in the 70s and 80s, including the Hagen All-Speed, the Deal Drive, and the Excel Cambiogear. About the only difference between those and this one is electronic activation — and in that regard, it isn’t all that different from the Browning “automatic” transmission of the 80s which used hinged (not expanding) chainrings. Some might know that one as “The Beast” which was what SunTour called it when they licensed the design. All of these designs were abandoned after a year or two (except the Browning, which limped along in various guises for about a decade) because they were heavy, expensive, and overly complicated. There is a full description of expanding chainring cranks on The Retrogrouch Blog: http://bikeretrogrouch.blogspot.com/2016/01/new-is-old-again-expanding-chainring.html

anonymous
anonymous
8 years ago

@Michael
You can’t have an arbitrary distance spanning the gap between the end teeth of the sections. It has to be a discrete distance measured in half-inches, otherwise the tip of the teeth of the next section will end up hitting a pin instead of the valley catching the pin. If the design is so that each section always has an equidistant radius, and never ovoid, or triangloid or whatever, it means the only radii that the teeth will meet with the chain is in 6t intervals.

Lets say each section has 7 teeth. When it is closed all the way, and the sections are right next to each other, that makes 7*6=42 teeth. If you make the gap between each section one link, (half link won’t mate), that’s (7+1)*6=48, two links is (7+2)*6=54, 60, 66 and so forth. The transmission also only has a 160% range with 6 steps. This is a worse range than a walmart bike with a 1×7 tourney drivetrain.

rkantos
8 years ago

those things look sharp as sh*t! (like for your legs)

Cryogenii
Cryogenii
8 years ago

And now, the internet troll who has two engineering degrees and is a chartered member of an institution. Oh yeah and an aerospace R&D engineer.

Dumb as a box of spanners.

This will suffer horribly from a phenomena known as cogging. When the chain runs off the end of one segment it will make a straight line to the next segment instead of following the radius of each segment, causing a dip in perceived torque resistance. This will happen six times a revolution, giving a weird ba-dump ba-dump ba-dump feeling whilst spinning.

This is why we don’t cut chunks out of our chainrings to save weight.

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