Comment by antonvs
1 day ago
Basically, the Copenhagen Wheel moved all the complexity of setting up a hub motor drive system - motor, battery, controller, sensors, computer - into the hub shell itself.
Which made it seem neat and clean, but meant it had serious reliability issues, couldn't handle wet conditions[], wasn't really repairable, and was expensive compared to more reliable alternatives with better battery life, etc.
[] The manufacturer apparently stated that "[...bad bearings] can occur when the Wheel is repeatedly exposed to wet conditions. Due to the nature of the problem, this cannot be repaired": https://forums.electricbikereview.com/threads/known-issues-p...
Psst, you can escape an asterisk [*] with a backslash.
Hub gears work quite well though don't they? In particular respect of being sealed and protected from the weather. Unclear why there's an opposite effect for this wheel.
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.
1 reply →