Is this the beginning of end for the rear derailleur??

by Robb Sutton
9 comments

Back in the day, Truvativ (SRAM) came out with a crankset with internal gearing that was the beginning of the end for the front derailleur called the HammerSchmidt. Ultimately, technology of rear cassettes and rear derailleurs spelled the eventual death of the FD but drivetrains were simplified and front derailleurs were quietly retired into the “remember when” parts bucket box. I hope they are comfortable with rim brakes, threaded stems and 26″ wheels.

Shimano Internal Gearing Patent Filed

shimano gearbox patent

Shimano recently filed for a patent on an internal gearing system that would spell the death of the rear derailleur with internal gearing in the frame at the crank. If you take a good look at the pictures in the filing, it really looks like the e-bike trend has really paved the way for this technology. Unlike with the HammerSchmidt which had all of the internal shifting baked into the crankset, the Shimano filing puts it on the chainline like you see with e-bike motors in the form of a gearbox.

Jack Luke broke the story on BikeRadar.com:

“The gearbox is driven by a typical crankset that initially moves a chainring located within the gearbox. This, in turn, drives the first “transmission member” – a vague term used throughout the patent to describe a cassette of sorts – via a chain.

The cassettes illustrated are very typical looking 7-speed ones, with Hyperglide-like ramps and shaping. A secondary chain then connects to the second “transmission member” located towards the top of the gearbox. The patent suggests that the first cassette would be configured to be moved by “a positioning mechanism such as a 
ball screw”. In other words, the cassette would have the ability to move horizontally along the spindle it is mounted to. The second cassette would remain stationary. 

A chain guide that “could take a form similar to 
a bicycle rear derailleur” would guide the chain between these two cassettes, while also allowing for any change in chain length when shifting between gear combinations. 

The ability to move the first cassette along this horizontal axis means that the drivetrain could maintain a perfectly straight chainline at all times.”

The patent filed by Shimano also lays out the possible gear options of the setup.

It will be interesting to see how this plays out over time but we are finally seeing actual technological advancements in biking again instead of just “new” standards. Derailleurs are arguably the most annoying part of cycling so I would not be sad to see them go in favor of a better option.

9 comments

9 comments

dave singh November 10, 2019 - 9:51 am

I have a feeling this will be a somewhat proprietary frame interface, you’ll still have to deal with roller eccentricity and worn shift ramps and gates ( still uses a chain). It will be awkwardly heavy as total drive-train weight is concentrated in one spot( albeit a good one, down and low by the BB). Not sure about BB clearance but i’m sure it’ll be nip and tuck just like the electric mid-drive counterparts. Also pricing is going to be silly high as Shimano doesn’t offer much margin to retailers as of late. I would expect to see this in the same price point a a decent mid-drive electric. If I was Shimano I’d be looking into compounded planetary hubs instead of an “internal” derailleur system..like two nexus inter 8’s or Alfine 11’s, where one driveshell output feeds the second hub’s input..one chain line and damn near CVT levels of ratio availability.

Reply
Michael November 8, 2019 - 10:58 am

Maintenance?

Weight?

K.I.S.S.

My Front Derailleurs function just fine.

Reply
Robb Sutton November 8, 2019 - 11:07 am

I would actually argue that removing FD’s made bike setups even simpler. One less thing to worry about.

Reply
Mark Ifi November 8, 2019 - 10:51 am

further insight on high this might work?

Reply
Robb Sutton November 8, 2019 - 11:10 am

It would appear by the drawings that the chainline would actually run above the cranks. The cranks and that chainline would have their own cassettes that interact with each other for gear ratios. That is just trying to translate the drawings…

Reply
Mark Ifi November 8, 2019 - 1:05 pm

Do the two cassettes slide left and right with a short chain connecting them, without a derailleur, keeping the chain in the centre and keeping constant chain length on the sprockets, like an car constantly variable transmission would work with a belt? So if I shift, would the second cassette move one direction, while the first cassette move the other direction at the same time? we need to animate this.

Does this fit into the standard e-bike frame? (I know nothing about e-bikes)

Reply
Mark Ifi November 8, 2019 - 2:10 pm

sorry, my previous one was a stupid question. here’s a good explanation for those looking:
https://www.bikeradar.com/news/shimano-gearbox/

Reply
Eric Ditwiler November 8, 2019 - 10:28 am

The Nuvinci set up is much simpler.

Reply
Robb Sutton November 8, 2019 - 11:15 am

Variable planetary setup. Much like CVT in many aspects.

Reply

Leave a Comment

Related Posts