Comment by antonvs
8 hours ago
Thanks - I'd have to have noticed that I used an unescaped asterisk first... too late now.
Did you mean hub gears or hub motors?
The Copenhagen had an ungeared hub motor. Comparing it to other hub motors, theirs was only IPX4-rated, which is basically splash-proof, not waterproof. Decent hub motors are IPX5 or 6.
On top of that, when your hub motor leaks and bearings seize up, fixing it is typically simple and cheap. Pop in a new bearing and new seals and you're done. Most bike shops can do it. With the Copenhagen Wheel, the manufacturer's advice was to throw it away.
The waterproofing rating seems to have been a design decision they made to simplify the design, keep costs down, etc. Since it all had to be custom, they couldn't benefit from the decades of experience, millions of units manufactured, and standardization that hub motor companies like Bafang or Bosch rely on.
See the page about it by the company that actually designed the wheel: https://www.mistywest.com/posts/project/copenhagen-wheel/ :
> "MistyWest had to work around the constraints posed by fitting a heat sensitive component next to a heat generation component in a closed system that allows for very little heat dissipation. The engineering team’s understanding of thermal physics enabled a stable battery system to be designed and adopted for the smart wheel. The inventors of the wheel were the first to ever fit a motor and a power source into a fitted bicycle wheel."
It was a challenging level of complexity. Even if they'd had more funding and stuck with the product, it's hard to see how they would have made it efficiently repairable.
It seems to me that the fundamental issue is that almost every other design is preferable from an engineering perspective. The only attraction of the Copenhagen Wheel was that it made for a quick and easy drop-in upgrade. But at the $1500 price it sold for, you can now buy a whole, much better ebike.
(As for hub gears, they're sealed and filled with oil, grease, or traction fluid, which helps keep water out.)
Spokes could make a fantastic heatsink, plenty of airflow. Or make the battery annular-ish (even just divide it into three batteries arranged in a triangle) and keep it away from the hub, they have the whole wheel to play with, jeez. This is a shame, it could have been a cheap conversion kit that doesn't break.
It did have an annular battery layout, with 7 battery pods around the outer edges each containing three batteries. That may have been preferable for weight distribution reasons, if nothing else, but it was probably mainly determined by use of space.
You can see it in this image: https://vcoregon.com/cdn/shop/products/e-bike_technology_db0...
There's a picture of the assembled internals here: https://www.sefiles.net/merchant/130/images/zoom/tech-copenh...
Both images give some idea of the complexity. In bicycle engineering, there's a lot of value in simplicity. Fewer failure points, more easily detectable failure modes, and gradual failures are all features of classic bike design. Systems like this one throw that all out the window, and are much less likely to succeed as a result.
Re spokes as a heatsink, the problem is that the major source of heat is the hub motor, which is stationary, while the spokes rotate. Transferring heat between them would be difficult.
> it could have been a cheap conversion kit that doesn't break.
I seriously doubt that, especially the "cheap" part. There's one of those classic "pick two of three" triangles at work here: in this case complexity, reliability, and cost. To have that complexity be reliable is going to be expensive.
Btw, several other companies tried this. The FlyKly Smart Wheel (defunct), the Electron Wheel, the Evelo Omni Wheel, and the Zehus BIKE+ hub. None of them achieved "cheap conversion kit" status. Some of them, like the Zehus, were only available preinstalled by manufacturers, so their value proposition was making the manufacturer's life easier.