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Comment by beloch | Hacker News Reader

Here's why I like this design.

5 kg is light for a battery/motor module, but it still adds about 50% to the weight of a decent bike. The added thickness also means it's probably not practical to put a multi-gear cassette on it. End result, this will cripple most bikes once the battery runs out. More weight and poor gear ratios = hell for the cyclist. However, most smart-bikes are crippled anyways once they run out of juice.

The great thing is that you can use the same bike for commuting that you use for your sweatier, long-haul weekend trips. All you have to do is swap the original dumb-wheel back in. If you buy a dumb-bike and a smart-wheel you almost get two bikes for the price of one.

Tip for the makers: Stress the ease of hot-swapping that wheel in even more than you are now. This is a major selling point.

P.S. I don't see a quick-release clamp on this sucker in your pictures or video. This is a no-brainier and absolutely needs to be on there.

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> P.S. I don't see a quick-release clamp on this sucker in your pictures or video. This is a no-brainier and absolutely needs to be on there.

I'd only put a quick release on it if I was sure that everyone who used it was going to lock up their back wheel (I'd encourage the Sheldon Brown lock strategy [1]). Most people lock the frame and maybe the front. This back wheel would make up the majority of the cost of your average bicycle in the rear wheel alone, making it easier to steal isn't the best idea. Maybe ship it with a nice hex wrench to make taking it off easier, but a quick release on that would be a bad idea if you're marketing it to cycling novices.

I know if I got it, it'd be pitlocks all the way. My commuter is barely worth $500, this would double what it's worth in a single easily-removed part.

[1] http://sheldonbrown.com/lock-strategy.html

The weight of the bike doesn't matter. A 20 pound bike plus a 200 pound rider is about the same as a 30 pound bike plus a 200 pound rider. You're the heavy part, not the bike. (People complain about citibikes being too heavy, but I rarely get passed even on a citibike, so my guess is the problem's the rider, not the bike.)

Also, I don't think a quick release will work for this. The motor needs to push against the bike in order to move the wheel relative to the bike. A quick release will slip.

Not necessarily. QR systems such as Maxle are sturdy enough for competitive downhill use.

Also 10 pounds is a huge difference not just in the effort needed to propel the bike forward but also in terms of maneuverability, especially as it is rotating weight. And in city usage you often have to carry the bike down stairs etc. where again 5 kg and a messed up center of gravity is a big deal.

I bike about 5000 miles a year in the city and have never needed to carry my bike down stairs while riding. Once you get it home, you might need to lug it up to your apartment, but it's well within the realm of possibilities for a healthy adult to carry a 40 pound bike up a few flights of stairs. (Then again, it's also rather easy to pedal the bike around without a motor. But I digress.)

Most European cities will make you carry your bike from time to time or make huge detours. But, like you, I'm not the target customer for this so maybe people in general are more careful with route planning.

Also, I don't think a quick release will work for this. The motor needs to push against the bike in order to move the wheel relative to the bike. A quick release will slip.

Look more closely at your bicycle. The axle doesn't turn in the dropout. Rather, the hub shell turns around the axle. That's why the bearings are mounted in the shell rather than in the dropouts.

Actually I think their pill-shaped peg that slides into the dropout but won't turn within it is kind of brilliant. A very simple solution, and there is no reason it couldn't accommodate a quick release skewer.

I agree that bicycle weight is a fairly minor consideration for commuting in moderately hilly areas; I've ridden a longtail that's close to 50 lbs. for years. Maybe I don't notice the weight because I am a fat bastard.

I know how wheels work. Look closely with a bike that is internally-geared or that has a drum brake. The hub is secured to the frame or has an antirotation washer installed to prevent the hub from rotating.:

http://sheldonbrown.com/sturmey-archer_tech.html

Remember Newton's law of motion here: for every action, there is an equal but opposite reaction. As the motor drives the wheel forward, the resistance from the street will try to spin the motor backwards, causing the hub to spin in the dropouts. That's why a quick release alone isn't adequate for internally-geared hubs, drum brakes, or motors.

You assume that they need anti-rotation washers, but it's clear from the video that they have a better solution: the pill-shaped peg I mentioned already. See here for the device installed with a QR skewer for a test ride:

http://www.blogcdn.com/www.engadget.com/media/2013/10/flykly...

You are not alone in having bicycled and taken physics!

>>More weight and poor gear ratios = hell for the cyclist.

>>Stress the ease of hot-swapping that wheel in even more than you are now. This is a major selling point.

These points are really crucial. A true pedal assist is something that can assist you while it can, and then not make it difficult for you to pedal when it can't.

Besides, I feel this market has immense potential you could do amazing things with a good control system on that smart wheel. And probably some day even an ECU.

Riding my local streets, I always need to have my rims trued. Were I to buy one of these, I'd want the beefy model, or some assurance that I could find someone who could true it.

It looks like the rim is normal: they say you can specify which rim you want. Therefore I'd say the spokes are attached to the rim by normal nipples. Therefore the wheel can be trued just like any other, unless one's truing stand has some weird limitations.

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