String Bike
 

I did a quick forum search and didn't see anything, so thought I'd post this here. Interesting concept. It'd be fun to try.

http://www.stringbike.com/

Anyone had the opportunity to see or ride one?

Thats interesting. I'll admit a bike driven by string or rope make me a bit uneasy. The design is pretty interesting though. I would love to try one out.

It's intriguing, no doubt, but that seems like a lot of extra moving parts. I'd still love to try riding it, though!

Looks like a solution searching for a problem.

Agreed

I think I would prefer belt drive....

This was my first thought as well.

If we always just stuck with what works now, there would be a lot of modern innovations lacking. Encourage innovation... you never know what amazing things you'll end up with. :)

Does it only work on the down stroke? The short video clip doesn't make it clear enough for me. If this drivetrain can't use the upstroke then I wouldn't be interested.

Hydraulic rim brake? I guess stringdrive technology isn't disc compatible.

It seems like the bike is auto-shifting by itself! I really wonder how this works because the website wasn't very clear. There might be something to this and I hope it's alot better than the Landrider. It's going to be expensive!

Seems like a whole lot of stuff to get your pant leg caught in too... I wonder how they could ever make a guard for it?

Seems like it uses a simpler gear shifting mechanism with the possibility of some sort of continuous variable gearing.

im down

Answer: This was a new design introduced at Interbike Vegas this year. It's not string but wires. There was a detailed video with its creator from Interbike, but the link was moved and I can't locate it currently.

So long as the two crankarms are connected by an axle, you should have upstroke right?

This is actually and old design with a face lift, I actually came across it in a book today. I wish I new what the original design was called.

Supposedly one benefit is that it doesn't need a chain guard (string guard?) because you don't get your pant leg caught and there is no grease. Of course, one can't know if this is really true or not until you try...

Right - the String Bike thing is just a marketing name for the drivetrain. The website compares it to high-strength wire-rope used in sailing. No idea if that's accurate.

Yes, AIUI it "auto-shifts". Not sure exactly how either, but I'm not super mechanically inclined. And yeah, it'll definitely be expensive until/if it catches on.

Much of the rear wheel and hub, along with the basic drive idea, is from the lever cycle which dates back to as early as 1905 or so in France on the Terrot Levocyclette. The difference in the rear is the original design used chains on either side along with two freewheels, one on either side of the rear wheel. The idea was revived in the 1980s by the Alenax Lever Cycle. By moving the chains or cables on the oscillating leg operated levers a very wide range of drive ratios can be achieved.

http://www.sheldonbrown.com/brandt/a...s/alenax1.html

The new idea with the string cycle is the cams and added front mechanism used to convert the rotary motion of the crankset to the oscillating motion needed by the cable drive. As noted, in earlier designs the cables were replaced by chains and sprockets.

I am not sure how the cable is rewound at the rear for the next pull but if it uses springs or other tensioning devices then I would expect the overall efficiency to be poor as you are operating against spring pull as well as trying to move the bike while riding. Added complication and weight along with reduced efficiency while trying to solve a nonexistent problem IMO.

If some theoretical physicists are right, I already have a string bike.

It does not auto shift ... there is a pivot point ( the black round wheel on the "rachet" side of each arm/lever ) that is adjustable via grip shift type, shifter on the handlebar.

There is more than one, built ... : o) Some only have plain v-brakes, some with front disc ...

I'm a really sceptic - but this actually looks quite good.

It doesn't use wire, it uses the same woven cord as used for rigging and halyards on sailing yachts. Very easily obtainable.

I expect the rope/cord will wear out a lot faster than the inventor assumes. Once grit gets into the cord, it will quickly cut away the fibres.

Inventors love to make efficiency claims but they're easy to manipulate and exaggerate. I don't see any advantage to this thing, one disadvantage is getting the rear wheel off - similar problem as a belt drive but now you've got both sides; I'm sure they've got a way to do it but I didn't see it on the page.

Seems to me the old lever-drive bikes were invented with the assumption that stair stepping was a better biomechanical motion than crank rotating and that they never caught on because the assumption was wrong. Now this thing looks like it corrects the bad assumption by providing a rotating crank but keeps the kludge introduced to accommodate the bad assumption in the first place.

They have a bunch of short videos in YouTube about the details, here's the one showing rear wheel removal:


--J