Is Shimano working on a hub-charged electronic shift system?

Shimano has just been granted a patent for a new rear derailleur hanger that suggests it is working on an electronic shift system that’s powered by a hub dynamo.

Why would we draw this conclusion? Well, US patent 2023/0166813 for a ‘Bracket apparatus and bracket assembly’ is detailed, giving us 55 pages of pictures and explanation. Although the focus is on the bracket – which is how Shimano describes the rear derailleur hanger – the interesting stuff concerns what surrounds it.

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Okay, so the hanger attaches to the bike frame and the derailleur attaches to the hanger – nothing unusual there – but then things get… strange.

As well as extending downwards from the dropout in the usual way, the derailleur hanger reaches forward, running next to the inner face of the chainstay. Interesting!

Why would it do that? Because at the end of this forward extension there’s a mount point for another component.

Obvious question: what would that component be? Shimano keeps its options open – patents usually cover as many possibilities as possible to stop anyone else muscling in on the territory – but says that the component would contain an electric device.

“The electric device includes at least one of a battery, a generator, a sensor, a communicator, an actuator, an informing unit, a display (eg a light emitting diode, a liquid crystal display), a user interface (eg an operating switch, an on-off switch), and a compactor for an electric cable. However, the electric device is not limited to the above examples.”

The derailleur hanger features cable grooves. The cables that slot into the grooves connect different components.

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Shimano suggests that examples of one of these components could be “an electric power source and a hub assembly including a power generator”. In other words, the derailleur hanger is specifically designed to take power generated by a hub dynamo to other components.

Shimano already offers hub dynamos and we know that it has been working on a new design because another recently published patent application (US 2023/0037945 A1) tells us so.

Shimano goes on to suggest that the hub dynamo could be connected to “an electric derailleur, an electric power source, and other electric components such as a control unit”.

Again, Shimano is covering a range of possibilities but it’s interesting that it sticks an electric derailleur at the top of the list.

Shimano continues, “Electricity is supplied from the electric power source to the motor and/or the controller of the electric derailleur via the first cable.”

Why would you want an electronic rear derailleur that’s powered by a hub dynamo?

Shimano's current Di2 electronic shift systems use derailleurs that are powered by a central battery housed inside the frame (rather than each derailleur having its own battery). Di2 batteries last ages on a single charge, Shimano claiming “approximately 1,000km [625 miles] of worry-free riding” for its 105 system, for example, but generating your own power would mean that you’ll never find yourself out of charge when riding in the back of beyond. That might be handy for multi-day bikepackers, although that’s a relatively small market, or for anyone else who struggles to keep on top of regular charging.

Shimano says the human power vehicle its design is aimed at could be a mountain bike, road bike, city bike, cargo bike, hand bike or recumbent bike. It could also be an electric bike… so pretty much anything, then.

One feature that makes us think that Shimano’s new rear derailleur hanger isn’t especially focused on road bikes is that one embodiment described in the patent includes a “chain stabiliser” with two prongs that are designed to point into the gaps between sprockets “to remove foreign material”. That sounds like something that would be more useful off-road.

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A final feature that’s worth a mention is that the pictures show a small button on the inside of the chainstay right next to the rear derailleur hanger. That button isn’t labelled in Shimano’s patent and its purpose isn’t explained so we’re not sure if this is something that frame manufacturers will be required to add.

Overall, this patent is a really odd one and we’re not 100% sure what to make of it at the moment. We’ll keep our eye on new publications over the next few weeks for more clues.