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Has anyone ever designed or manufactured and automatic transmission (automatic shifter?) for cycling?

I imagine such a device would automatically change the gearing to allow the rider to maintain constant cadence or constant torque on the cranks.

I used to daydream about the existence such a system many years ago when riding my first (battered, secondhand) racer as it was such an ordeal to change gears.

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Wondering about that, and about what you said you wondered, I think the act of shifting is the problem, but the right to choose the exact gear you want, and the time of shifting, that is invaluable (imagine the bike "arbitrarily shifting" when you don't expect or don't want). Regarding that, shifting systems have become more and more ergonomic, and there are some good attempts to build CVT transmission for bikes, for example the NuVinci hub. – heltonbiker Jul 17 '12 at 23:09
Automatic gearboxes tend to be heavier and have more friction (i.e. you would have to peddle harder to get the same result), which is why they're never used in cars when performance is important. Since peddling a bicycle is bloody hard work as it is, I don't think automatic transmissions are a good idea. The in-hub gears in my bicycle are pretty damn close to automatic however. – Abhi Beckert Jul 18 '12 at 7:29
It is not manufactured AFAIK. However it's certainly possible, my friend already invented it. However I would not use it, not because it would be harder to use or something like that. But rather because having control over the gear you're in is VERY valuable compared to a system that automatically chooses it for you. In case you're interested. It doesn't use electronics or anything special like that. It just adapts depending on the amount of pressure there's on the pedals (or so I understand it). – Eduan Mar 21 at 1:54

5 Answers

up vote 8 down vote accepted

http://www.landriderbikes.com They were very heavily advertised several years ago but currently they seem to show up more on craigslist than on TV.

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Lol. I had to laugh at the video on the site. But I do indeed see how they could be useful for older people who do not want to deal with shifting gears. – Keegan McCarthy Jul 17 '12 at 22:51
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I knew someone that has one of these, they have hard time with it since you have to keep pedaling to keep the right gear. – Carson Reinke Jul 18 '12 at 17:11
Would you consider adding a summary about the hub system you're referring to and how it works? – amcnabb Mar 29 at 18:17
up vote 6 down vote

Trek had a bicycle a few years ago named "Lime" which had 3 speed automatic gearing. I don't think it sold well. It used a gearing system called "Coasting" that was created by Shimano and actually controlled by a computer chip from signals from the front hub.

"A dynamo is fitted on the front hub that gauges the revolutions of the wheel. It sends this information to a computer chip housed near the pedals on most of the bikes.

From there, the chip, which controls the planetary gears located on the back hub, determines whether to shift up or down. All the chip needs to make its determination is for a rider to pedal four or five times, according to Shannon Bryant, Coasting project coordinator for Shimano."

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up vote 4 down vote

I have ridden one - it used weights thrown out by centrifugal force and springs to move the derailleur in and out. Horrible is all I can say. Maybe it was me not being used to it, but things like not being in the gear you left it in, and less than smooth changes - which you have not idea when they are going to happen, especially under power. The only redeeming feature was it was a borrowed bike I could give back at the end of the weekend holiday.

That said, for cruising around a by someone who otherwise would not ride, and only on flat, even ground), its would do the job.

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sounds terrible, I guess on 'flat, even ground' there is no need to change gears, so the problems go away? :-) – Ken Jul 19 '12 at 17:14
I assume that there are a variety of designs that provide automatic gearing--do you remember which particular type you tried? – amcnabb Mar 29 at 18:16
@amcnabb - sorry no, it was a long time ago when I was ignorant of basic bicycle components and construction. – mattnz Apr 1 at 6:20
up vote 2 down vote

There have been attempts over the years, but never particularly successful. One I recall used a 5-speed rear hub that was shifted by weights on the spokes, similar to a centrifugal governor.

I expect that, with the new electric shifters, there will be some new attempts at it in the next year or two. With a computer it should be possible to be reasonably "smart", especially if mated to some sort of torque meter.

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up vote 0 down vote

There's the Nuvinci Harmony

http://www.fallbrooktech.com/cycling/harmony

It uses the Nuvinci N360 CVP hub, which is a continuously variable transmission, meaning there are no shift points. The Harmony controller changes the ratio based on cadence, or it can be adjusted manually.

http://en.wikipedia.org/wiki/NuVinci_Continuously_Variable_Transmission

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Would you consider expanding your answer to give a brief summary of how this hub works? – amcnabb Mar 29 at 18:06

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