The comments on the Kickstarter project have a few good explanations of both why the design is effectively identical to a straight crank, and why the plan to make carbon-fiber versions is dangerous.
Now leverage: if you tried to push down on the pedal (as shown in the
video) when it was exactly top dead center and stopped, it doesn't
matter if it is a normal crank or the Z-Torque, it will not want to
move. They are two rigidly attached points in space, so it doesn't
matter WHAT you use to connect them, 'physics' just treats them as
though connected by a straight bar.
Simple proof: If you move the
Z-torque back just 2 degrees before top dead center and apply a force
(you could try with a weight rather than a foot to make it
scientifically valid), you will see that it doesn't move FORWARD as
would happen if your crank worked as you argue (advancing the leverage
because of the bend), but still BACKWARDS the exact same as a normal
It looks different but it works THE SAME.
..and why it is dangerous:
2) You absolutely cannot take a design that is optimized for machining
"mold them out of carbon fiber". Woven composite strength is highly
anisotropic. If anything, your design shown in your picture is weaker,
not stronger, than the machined part, if molded out of carbon fiber
(and by that I assume you mean, "molded out of cast polymer with a
carbon fiber veneer on the front surface).
A true carbon fiber crank
would have the fiber direction laid out (often by hand) in such a way
that the fiber direction (or grain direction) aligns with the force
exerted on the piece. So all that ladder structure that you've molded
into the part,would actually make it a LOT weaker. It would also have
machined metal components laid into the part and bonded to the
composites for a metal-on-metal mating surface. See
http://www.zipp.com/support/identify/carbon_cranks.php for an example
of the construction technique - note the use of an aluminum spider
that the actual crank is bonded to.
5) Finally, and the most worrying point: You are dealing with an important piece of a bike's drive train. The failure mode on this is likely going to be the a cyclist cranking away and your crank giving way and breaking off. This is the makings of a serious, and possibly life altering accident.
Non-destructive testing and examination of composite materials is no joke. I can assure you that the folks from Shimano and RaceFace has years of experience building, validating and testing composite structures that they built. The failure modes of composite materials is also very different than traditional metal - there is very little to none inelastic deformation.
The mold and setup you show is good for producing cosmetic composite components (like my buddy's "Carbon fiber" gas and brake pedal). A mission critical drive train piece, not so much.
The complete comment is worth reading.