Is there a bicycle out there that transfers power to the rear wheel while you shift?

You know how when you change gears on a bike, there's a split second where the chain is loose if you were mashing the pedal the chain would just slap hard onto the next gear? Well yeah, I'm wondering if there's a gear system out there that grips on to the gears at all times or changes so smoothly so that power transfer would be continuous, without the brief delay.

The delay isn't important to me at all. I just thought it'd be cool if there was a gear system that shifted flawlessly. Thanks guys! all great answers.

Many moons ago in my early youth, I had a very old bike, with rod and roller brakes and a three speed Sturmey Archer hub gear! If I recall, I used to be able to change gear flawlesly on that!

Bearing this in mind, I wonder if the same is true of the 14 Speed Rohloff Hubs??? Never having ridden one, I don't know, maybe you could check this out, or try one!

I often change gear whilst accelerating hard with my Ultegra set, they delay is minimal, which brings me to ask why the small delay is so important to you?

EDIT:
Take a look at this, it's rather weighty though, . . . But If you have an inventive side ?? ?
http://en.wikipedia.org/wiki/Variomatic

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someone came up with the idea of a split main sprocket,i don't know if into 3 or 4,parts, and they were joined with springs, the idea was as you increased pressure on the peddles the sprocket would reduce in size and so change the ratio of front to back gears,the idea sounded good but not enough to sell

just buy an expensive drive train because i dont get that split second on my road bike with full dura-ace and i really dont understand what you are asking

I'll join the crowd and say it's a mute point. The delay is simply too minor to worry about for me. The chain and derailleur concept is not very refined in a design sense but it's high efficiency has kept it alive and well these many years.

The basic concept in Mr Gs URL, has been around a while. A similar take off of this concept is what drives many clutch systems on small motor products. I first noted this many
years ago when I learned to work on mini bikes. While the concept works, the efficient transfer of power is less then ideal hence we still have derailleur systems.

I don't think derailleurs are never to be replaced, but efficiency is paramount, not ridding ourselves of a fractional second delay. I will say MTB riding would benefit most as anyone who's got stuck on a steep hill in the wrong gear would attest to. But, then again, that's what skill is for.

I thought of using two opposing cones connected by a belt. The gear ratio would change by moving the belt up and down both cones simultaneously. The gear ratio would be continuously variable and power would be applied all the time.

Just a dream...

I have seen an all wheel drive bike as well as the cone theory(similar to that of Nissan shifting). Seemed to work ok.. But the price is normally high with added weight. Trek also has the automatic shift, (little clunky though). I personally think the next evolution in shifting will be laser remote, NO; cable, wires or adjustments. The chain still has hold the test of time...

don't worry about it at all

you would ony save about 0.1 of a second buying a special hub for 拢50 so don't bother- its a total waste of money