Copenhagen Wheel

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redsonic
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Copenhagen Wheel

Postby redsonic » Thu Oct 12, 2017 12:07 pm

Despite its awful red "look at me" design, this new electric hub looks interesting:

https://content.superpedestrian.com/the-copenhagen-wheel

uart
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Re: Copenhagen Wheel

Postby uart » Fri Oct 13, 2017 11:54 am

redsonic wrote:Despite its awful red "look at me" design, this new electric hub looks interesting:


This is an absolutely brilliant idea in my opinion. The complexity of wiring the external battery, controls and sensors is a major drawback to many current ebike designs. For example on some ebikes it's a minor drama just to remove the rear wheel, and every external wire or connection is a possible failure point reducing reliability. I only know two people with ebikes, and both of them have suffered intermittent problems where sometimes they refuse to turn on, and then you just have to go around unplugging and re-plugging things until they eventually work. :( (And both had these problem within about a month of purchase from new!).

Now purists will point to the unnecessary increase in rotating mass of having the battery turning there within the wheel, however the negative effects of rotating mass are often overstated (and indeed often misunderstood). A rotating mass does (disproportionately) increase inertia, but that is all. It has no additional effect on things such as hill climbing or rolling resistance. So for example, if the wheel contained a 3 kg battery at an effective radius of 30% of the wheel radius, then having it rotate increases the inertia of the bike by the equivalent of about an additional 900g, but has none of the other negative effects of a real in increase weight.

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redsonic
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Re: Copenhagen Wheel

Postby redsonic » Fri Oct 13, 2017 12:26 pm

Unfortunately, the hub weighs 7.6kg, so a considerable inertia there. For comparison, a quick google reveals a Rohloff hub weighs just under 2kg, NuVinci hub around 2.5kg, and regular electric bike hubs 4-8kg.

uart
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Re: Copenhagen Wheel

Postby uart » Fri Oct 13, 2017 1:01 pm

redsonic wrote:Unfortunately, the hub weighs 7.6kg, so a considerable inertia there. For comparison, a quick google reveals a Rohloff hub weighs just under 2kg, NuVinci hub around 2.5kg, and regular electric bike hubs 4-8kg.

Yes there is an electric motor in there so it has to weight more then a regular hub.

My point is that for any hub motor design the rotating mass of the motor is unavoidable, but rotating the battery is completely unnecessary. So that aspect is an unnecessary increase in inertia, but like I said, I think the benefits outweigh the negative of having perhaps an extra 900g of inertial (and only inertial, not actual) mass.

BTW. 7.6 kg is reasonably light for a complete ebike kit (battery, motor, controls and sensors). Very easy to build a 16kg ebike from a low cost entry level alloy bike, which would be about 8.5kg sans the rear wheel. Most of the ebikes I've seen are well over 20kg, often around 25 kg.

Edit: Just to avoid confusion. In the example I posted above the battery mass was 3kg. That 3kg gets added as both real mass and inertial mass no matter how the battery is mounted, whether it's rotating or not. If however the battery is rotating, it adds about 900g to inertial mass on top of that, but it adds only to inertial mass.

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Re: Copenhagen Wheel

Postby AUbicycles » Fri Oct 13, 2017 9:10 pm

The Copenhagen wheel has been around since 2013 so not really new, but they are quite distinct and keep on pushing it. For interest, they have a close competitor called the Flykly Electric Bike Wheel who launched on Kickstarter and I understand were in production first.

As an upgrade option, a hub motor is the only option however the trend is towards complete e-bikes which means it is integrated with battery, typically a mid-drive motor and electronics from the display / controller and lights.

Anyone considering should weigh up the price, weight, suitability for their riding, ease of installation, ease of use and not to mention aesthetics as I think it is a "you either love it or hate it" type product.


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redsonic
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Re: Copenhagen Wheel

Postby redsonic » Sat Oct 14, 2017 12:27 pm

Thanks for the FlyKly link. I am looking for something for my Mum's recumbent trike, and FlyKly make a 20inch wheel. Has anyone out there had any experience with the FlyKly?

uart
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Re: Copenhagen Wheel

Postby uart » Sat Oct 14, 2017 12:47 pm

Just thinking about this a bit more, scrub what I said previously about the rotating battery. I just realized that being located within the wheel doesn't necessarily mean the it has to rotate. Clearly there is a stationary part (stator) and a rotating part (rotor) within that motor, so yeah the battery need not rotate. Don't know why I didn't think of that before. :oops:

TBH I don't know whether the battery rotates or not in their design. Only that it need not necessarily do so. :)

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