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Comment by deaps | Hacker News Reader

I think one of the biggest problems is as the rear cassette shifts toward a larger gear, flex could become an issue. The driveshaft will push out on those larger gears making the 'disc' flex toward the wheel. Those larger gears are where you'd be when climbing a hill - where you're typically putting out a good bit of power too.

It's a great idea, and I do love innovation. I've honestly never really had a problem with a chain though, myself.

I have about 6,000 miles on my cross bike (that gets used in some pretty dirty, dusty, sometimes-muddy conditions). And maybe 2400 on my newer road bike. I just clean the chain with wd-40 when it's dirty (sometimes water/soap first if really muddy), dry it well with a rag, then apply some liquid chain lubricant (sometimes after every ride, if it's needed).

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Their motivation is not to reduce maintenance but to increase efficiency.

"[...] the company had already pushed the envelope with lubrication, bearings and pulleys about as far as possible — creating a roughly 98% efficient driverain"

“The quest was, how can we get a 99% efficient drivetrain?”

I have more miles than you :-) (14,000) ((I have exclusively biked for over a decade))

But you know what might be an interesting design idea:

Make a shaft drive like this which is centrally aligned. But the bike has TWO rear wheels as closely spaced as possible and the shaft drives a single axle for the rear -- but has more gearing up front...

But make the two rear wheels with a camber such that they angle out slightly such that their centerlines are as clos as possible - allowing for turning to be essentially the same as a single-rear-wheel bike...

I'm curious as to how you would drive both rear wheels with a single central shaft? Both sides would rotate in opposite directions; I can't find a good example to illustrate what I am saying, unfortunately. I trust you understand what I mean.

Now - there might be a way around this, but it would probably introduce more complications and friction to the mix (one way would be to drop/raise the central shaft off-center of the driving wheels centerline, then have separate fore/aft gearing on the shaft to drive the wheels in the proper direction).

Shoot I think you may be correct. I hadnt thought of that aspect. Maybe it would require the central shaft to rotate a single gear in the forward direction which was attached to via smaller chain that rotates the axle between the two wheels...?

Yeah... basically what you said in the second paragraph of your comment....

This would be a fun design challenge. Anyone Solid on Solid Works want to give it a go???

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OH . I thin I have it, but I dont know how efficient it would be:

A Worm Gear:

https://i.imgur.com/BgJODdP.jpg

Here's a solidworks tutorial making a differential gear which is how many/most vehicles solve this problem.

https://youtu.be/qqFTMhubEtc

A differential gear solves both the direction problem and the distance between the wheels when turning problem.

If they enclosed the gearbox, they could add a roller bearing on the reverse side of the sprocket to provide counterpressure to prevent flexing. Enclosing it would prevent grit from getting in as well.

I think they mean the gear (cassette) on the wheel - not the one up at the pedals; there wouldn't be a way to "enclose" that end.

Instead, though - flex might be able to be eliminated by making the "hub" larger, so that the disc (according to the article and renderings, it's a flat and not conical system) has something "solid" on the backside (this isn't shown in the renders from what I could see).

I'm not sure what such a change would do to the performance or handling of the bike, due to the shorter lengths of the spokes to the rim, and the larger mass of the hub, and who knows what else. I haven't been on a bicycle in well over a decade, and even then it was just a cheap Huffy I bought at Walmart for Burning Man use...

So one could say that this technology, even if it were real, would not be targeted at me as a consumer or bike user...

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