Let\'s see some efficiency numbers. Chain drives are already extremely efficient with the bonus of being simple and plentiful.
This looks like a solution in search of a problem.

Considering it can be as reliable, durable and cheap as the traditional chain drive system, then it is welcome. One thing I\'m sure about; It\'s gonna be a pain in the a$$ fixing it on the go.

My thoughts exactly colinshark. I\'d love to see some transmission efficiency numbers. While the cam design is quite intriguing, it looks as though there will be some obstruction problems with the strings to overcome. Also, can you shift under power?
The design is quite beautiful but as you said, solution searching for a problem.

I have a concern about the roller. I would hate to see a kid get their toe or finger or just clothing caught in there. The principal is good and clever - but is it safe? That area should have a shroud to cover it. Don

Too bad they couldn\'t work out a system that accepted return pedal power such as when a cyclist is clipped into the pedals and can exert force on the upward stroke.
Also, they will have to move the cams in buy 5mm in order to avoid contact with lower leg and shoes.
I would have preferred a shaft drive with all moving parts enclosed within a high-strength single-sided swing-arm. Logically, all gear selections should be at the crank, possibly in the form of a selectable CVT or simple transmission. Also, try dynamic crank-length adjustment rather than cam-oriented efficiency boosters. This will give the riders\' muscles a brief rest as other fibers are called into play and pedal power can be maintained, for example in a downhill situation, from the calf muscles (and ankle) rather than just the quads and/or hamstrings.
BMW and Cannondale, among others, have proven that single-sided forks and swing-arms are very reliable. Do all your math at the crank and let the transmission of power and rear hub be simple and require zero maintenance.

I see some issues here : What happens when a string breaks? Will it be as easy to replace as a chain with a quick-disconnect link? How do you maintain a constant string tension?

What is the range of transmission? I don\'t see this providing a wider range of gearing than a derailleur chain drive or hub drive, even if the cam angle can be varied.

Lastly, the efficiency statement is false - serious cyclists wanting to get more out of their bikes use \'clipless\' pedals, SPDs or \'spuds\', of which there are myriad variations in clever designs like look, time, crank brothers, frog beyond the common shimano type where a special shoe fitted with a cleat engages with the pedal.

The principle of the spud pedal is that you can exert additional torque by pulling the pedal up with one foot while pushing down with the other, this can give you up to a third more torque when sprinting out of the saddle than just pushing down one foot at a time. This string system only seems to allow for torque to be produced by the downgoing crank, which is less efficient.

Otherwise looks very clever, in a heath robinson/rube goldberg sort of way but I don\'t see the point. This is an effort at reinventing the wheel...

How about using two independent strings so you can push both feet at the same time for double the power, this would probably work better on a recumbent bike with a back rest to push against.

It\'s a variation of the \"treadle\" drivetrain, probably dates back to the late 1830s. Examples with cloth or leather belts, instead of string, were manufactured in the US as recently as the 1920s, maybe later.
Well, it works. I have no idea if it has any inherent advantages over a chain drive, and changing drive ratios might be challenging (I can think of a couple strategies off the top of my head, but it would make the system unnecessarily complicated).

This works exactly like the worlds first gasoline powered motorcycle. Used two rods and a ratcheting system to pull the cogs of the rear wheel. This is also reminiscent of the bike the Giant Bikes made back in the 80s.

It\'s like a conventional bicycle mated with a Harris vertical bicycle and this is their offspring. There have been some other similar designs that used two levers pumped up and down. In other words there\'s a ton of prior art they had better include in any patent applications.
Since this design has no way to provide power by the feet pulling up on the pedals, there\'s no advantage over the Harris or other lever designs.
Instead of reinventing the wheel, they\'ve reinvented the double freewheel pull action drivetrain. ;)