Bad ideas eventually drift out of contemporary thought and then get re-invented. In this case, the infamous P.M.P. "L" crank has reappeared as the "Z-Torque™" crank.
The "Z-Torque" crank retains all the core bad ideas of the P.M.P. crank.
From z-torque.com as of 2012/09:
Get more out of your bike with this unique and proven crank design. The Z-Torque Crank is an innovative crank assembly made for all types of bicycles. This patented and tested crank technology provides riders many advantages, inluding
- Smoother pedaling
- More power to climb hills
- Less perceived effort to pedal
- Faster acceleration
- Less affected by headwinds
- Ability to turn higher gearing
Z-Torque has been scientifically tested and proven to provide more available power than a typical pedal assembly. Get more out of your bike. Get Z-Torque.
As with P.M.P. cranks, these claims are not possible. Or, rather, they are possible only due to psychology, but not to biomechanics or mechanical design.
Indeed, as with the P.M.P. crank, the Z-Torque is clearly marked "175", showing at least somebody understands this is simply a heavy 175 mm crank.
From z-torque.com/About/TheInventor.aspx as of 2012/09:
Except for top dead center and bottom dead center, this crank had no dead spots.
True! Except for top dead center and bottom dead center, no crank has dead spots. And Z-Torque is just a crank.
Z-Torque also has much less ground clearance than a straight crank, much less even than a P.M.P. crank.
The patent U.S. Patent 5,899,119, metnions stiffness and one drawing includes a hinge with a spring. However, the actual claims of the patent do not mention stiffness. Thus, stiffness and/or resulting dimensional changes are not factors; it is an ordinary crank.
Two graphs "demonstrate" the Z-torque crank is different than an straight crank. However, a crank is just a crank, so this difference must be due to either details of how they measured, or errors in how they measured. There is not enough information provided to know which it is.
From z-torque.com/Video.aspx as of 2012/09:
Participants achieved similar maximal oxygen consumption, peak power outputs and gross efficiencies with the Z-Torque and normal crank configurations (Table 1). In addition, ratings of perceived exertion (RPE) at 150 and 200 W, heart rate (HR) at peak power output, 150, and 200 W, and cadence at 150 and 200 W were not significantly different. However, participants perceived their effort to be significantly lower at peak power output with the Z-Torque crank.
Yup, just a crank.
As of 2012/09, Z-Torque cranks are offered for sale here, with a basic set costing US$270 (cranks and spider) and no weight listed.
From http://www.z-torque.com/Order/Warranty.aspx as of 2012/09:
RETURN POLICY: We know you'll love your Z-Torque crank arms and components. In fact, we guarantee it! If you are not completely satisfied with your Z-Torque crank arms or components, return them shipping prepaid within thirty (30) days of receipt for a full refund (not including shipping and handling costs). To return a product for refund, go to www.z-torque.com and click on "contact us". We apologize that altered, modified, or physically damaged items cannot be accepted for return.
LIMITED WARRANTY: Z-Torque billet crank arms and aluminum spiders are warranted to be free from defects in materials and workmanship for a period of Twelve (12) months from the date of purchase. All other components are warranted for Ninety (90) days. To obtain warranty service the item must be returned shipping prepaid along with proof of purchase in the form of the original or a copy of the dated purchase receipt to:
717 EMIL DRIVE
FORT PIERCE, FL 34982
Coment Enterprises' entire liability for item(s) determined by us to be defective in materials or workmanship, and your sole remedy, shall be limited, at our discretion, to repair or replacement of the Z-Torque component(s) or refund of the purchase price, excluding shipping and handling costs. Product failure or damage caused by alteration, modification, normal and reasonable wear and tear, failure to perform normal and reasonable maintenance, neglect, misuse, abuse, crash, or impact is excluded. Alteration, modification, or misuse voids warranty. Cosmetic damage or defects are excluded and not covered by this warranty. THERE ARE NO OTHER WARRANTIES EXPRESS OR IMPLIED WHICH EXTEND BEYOND THE DESCRIPTION ON THE FACE HEREOF. WARRANTIES OF MERCHANTABILITY AND SUITABILITY FOR A PARTICULAR PURPOSE ARE EXCLUDED. Any and all promises or representations made by sellers or dealers beyond the express provisions of this warranty are void. This warranty gives you specific legal rights. You may have other rights which vary from state to state.
LIMITATIONS: Coment Enterprises' liability is limited to the amount of product purchase price and shall exclude incidental or consequential damages.