jueves, febrero 26, 2015
Cranktip los pedales con palanca
Cranktip pedals first look
by Matt Wikstrom - February 25, 2015
Cranktip pedals were invented to improve pedalling efficiency. The design places the pedal platform well in front of, and below, that of a traditional design. As a result, Cranktip pedals offer more leverage on the downstroke and a shorter upstroke. In this review, Matt Wikstrom takes a closer look at the new design and tests its performance.
Cyclists have always placed their feet on top of the pedals, above the axles, which accentuates the length of the cranks at the top of the pedal stroke rather than the bottom. Since the leverage of a crank arm depends upon its length, there has always been a possibility that the efficiency of pedalling could be improved by re-positioning the pedal.
Lowering the pedal axis is not a new idea. The first dropped pedal, the Ramsey Swinging Pedal, was invented in 1898 and the North American company promised an immediate improvement in efficiency or a full refund. There have been other dropped pedal designs since then—Sansax, Hi-E, CycleBinding, Power Pedals, and most recent, Side Mount pedals—yet none of these designs have ever been widely adopted.
Will Anderson started working on this problem about eight years ago. As an inventor, he was interested in whether there was a way to improve the efficiency of pedalling. His initial designs included an extendable crank and a dropped pedal but the only way he could move forward was to come up with a unique design and a “rock-solid patent”.
The inspiration for the Cranktip pedal design came from a children’s gondola swing. Anderson wondered if the rocking action of a dual pivot design could be used to improve upon the performance of a dropped pedal.
It’s the combination of actions that distinguishes Cranktip pedals from previous designs. Anderson not only lowered the pedal axis, he also extended it to place it in front of the crank. Then he added a dual-pivot lever to the rear of the pedal so that it is able to rock on a separate plane. According to Anderson, this action prevents the foot from rolling over the pedal.
The result is that the circuit of the Cranktip pedal is significantly displaced when compared to a conventional pedal, adding extra leverage to the downstroke while shortening the effective crank length for the upstroke. The result is a “biomechanical advantage” that promises more torque, less fatigue and “an unmistakably smoother pedalling action”. Indeed, early field-testing with volunteers demonstrated immediate improvements while independent testing is underway at the AIS and Monash University.
Cranktip’s first product is a clipless racing pedal that retails for around $500 with a 30-day unconditional money-back guarantee. I recently spent some time riding the pedals to better understand how they work and what they had to offer.
THE CRANKTIP DESIGN
At first sight, Cranktip’s racing pedals defy understanding. There is a lot of extra hardware and the whole assembly looks more like some kind of industrial lever than a clipless racing pedal.
A conventional clipless pedal body is located at the front of the assembly, anchored to a substantial swingarm. At the other end of the swingarm, there is a dual pivot mechanism that forms a simple elbow with a long support arm that attaches to the rear of the pedal body. This is the joint that allows the pedal body to rock back and forth, with tabs to limit the amount of travel to a few millimetres.
The pedals attached to the cranks via a short axle in the swingarm. The difference between the position of this axle and the pedal body accounts for an offset lowers the pedal by 12mm and extends it by 16mm behind. Thus, the pedal body travels in front and below the eye of the crank on the downstroke, providing up to an extra 25mm of extension for the pedal compared to a conventional design.
One obvious disadvantage to offsetting the pedal is that there is a much greater risk of pedal strike. There is also a need to lower the saddle 16-25mm in order to accommodate the offset of the pedals. In addition, Cranktip pedals sit wider than conventional pedals, adding at least 10mm to the Q-factor of the cranks.
OUT OF THE BOX
Each Cranktip pedal weighs 397-399g, which makes for a significant increase in weight when compared to conventional pedals. Weight weenies will never be tempted however Cranktip argues that the increase in performance will compensate for the weight penalty.
The extra weight does inspire faith in the quality of the materials and the construction of the pedals. While the axle that attaches to the crank is very short, it is supported by a large diameter bearing, plus there is the rest of the swingarm to share the load. There is always a risk of play developing around pivot points, however the amount of travel is small and there appears to be plenty of support to resist lateral forces.
Cranktip pedals are easily installed with a 6mm Allen key. It’s important to remember to fit one of the supplied washers on each axle so the swingarm does not strike the cranks.
The pedals have adjustable spring tension for cleat entry and exit and are supplied with a pair of floating cleats, mounting hardware, and tools for installation. It is worth noting the pedals are only compatible with Cranktip cleats, with no option for fixed cleats.
Cranktip pedals have been approved for use in Australian and USA triathlons while the UCI is reportedly looking at the pedals. At present there are no regulations that forbid their use in road cycling events.
Cranktip pedals are available online and from a selection of retailers. Normally US$499, the company has dropped the price to US$400 (AU$500) on its website for an introductory period. As mentioned above, buyers are able to use the pedals for up to 30 days before returning them for a full refund if they fail to experience any benefits. For more information, visit Cranktip.
ON THE BIKE
As mentioned above, Cranktip advises lowering the saddle 16-25mm. After some experimentation, I settled on 16mm but found that I also needed to move the saddle forward a few extra millimetres. As a consequence, I was 10mm closer to the stem with less handlebar drop, making for a more upright position.
There was also a significant change in the position of my feet on the pedals. The ball of my foot (as defined by the head of the first metatarsel) is normally positioned directly above a conventional pedal axle; Cranktip pedals re-positioned it almost 30mm in front of that axis. It’s a profound difference and I was immediately aware of the reduced load on my toes along with a reduction in leverage on the pedal.
I’ve detailed all of these changes to illustrate an important point: switching to Cranktip pedals will have an impact on the positioning of all of the bike’s contact points, namely the saddle, pedals and handlebars. That the changes were 10mm or more is significant because they are large enough to influence the centre of gravity and balance on the bike as well as overall comfort. It is worth noting that Cranktip cautions that riders may need up to 2 weeks to adapt to their pedals.
OUT ON THE ROAD
I was underwhelmed by my first hour on Cranktip pedals, but slowly, I noticed some extra leverage on the downstroke. At the same time, there was less load on my calf muscles and it was easier to pedal through the top of each crank stroke. However, I felt as if the active phase of my pedal stroke was shorter (starting later) when compared to conventional pedals.
Cranktip pedals seemed most effective on short pinches and when riding into a headwind. I’m normally accustomed to rising out of the saddle to finish off pinches, using a little extra effort to keep the pedals ticking over rather than shifting to an easier gear. With Cranktip pedals, I was able to remain in the saddle without my cadence suffering or having to grunt to finish off the pinch. As for headwinds, the extra leverage seemed to make it a little easier to maintain my effort for longer.
Interestingly, all of the benefits of Cranktip pedals seemed to be lost every time I rose out of the saddle. In fact, I found myself missing the extra crank length at the top of the pedal stroke and I felt like I had less kick when attacking and sprinting.
There were a few occasions when the horizontal slide of the pedals was obvious—the sensation was a little like riding with a loose cleat—but it was only a transient sensation. In general, the pedals were sturdy under my feet, so I presume the issue was a matter of technique.
Swapping from Cranktip pedals to conventional pedals highlighted the difference in the quality of pedal stroke offered by the new design. Cranktip pedals offered a shorter upstroke that was easier to push through, my feet were more stable, and my calf muscles were not working as hard. However, my pedal stroke felt fuller on conventional pedals and my feet had more leverage on the pedals. In addition, I was more comfortable while riding conventional pedals, but this had more to do with my preferred handlebar position than the position of my feet.
During the course of my review, I suffered a couple of pedal strikes while riding Cranktip pedals, always as a consequence of forgetting that I didn’t have the same ground clearance. I expect the incidence of strikes will diminish with ongoing use but there could be situations, such as racing, when they could be riskier to use.
After a week of riding Cranktip pedals, I conducted some informal testing to see if they had any effect on my performance. We’re not aware of any scientific testing that has been done on products similar to Cranktip. This is a very difficult thing to test scientifically and not possible by simply using a powermeter or heartrate monitor because of the changes in joint angles, range of motion, positioning, muscle shortening, etc. There are too many things that are modified by using a system like Cranktip to fully understand its effects without proper scientific testing. To satisfy my own curiosity, I settled on comparing lap times for a local 9km undulating loop and a steady “perceived” effort.
There was a difference in my lap times on Cranktip pedals — I was around 30-40 seconds slower per lap—when compared to my regular Speedplay pedals. The reason for the difference is unclear: my pedal stroke seemed more effective while using my Speedplays, but I may have been slower on Cranktip pedals because I was sitting more upright and little less comfortably. I would have liked to experiment with my position some more, but with the stem slammed and the saddle at the limit of its fore adjustment, I needed a smaller frame. This is perhaps the worst-case scenario for any buyer, but it highlights the kind of re-adjustment that may be required to accommodate Cranktip pedals.
We have spoken to Dr. David Rouffet from the Institute of Sport Exercise and Active Living (ISEAL) at Victoria University who studies on the neuromuscular factors of human performance. In the coming months, his research team will run a scientific project aimed at evaluating how cycling performances can be affected by the use of Cranktip pedals. Dr. Rouffet explained that only a scientific approach will tell us if the modifications of the trajectory of the pedal and the associated changes in the mechanics of the pedalling movement caused by the use of a system like Cranktip can provide cyclists and triathletes with a benefit.
With an asking price of around $500, I expect most cyclists will want to see some hard data before they consider using Cranktip pedals. Independent testing is underway but until those results are made public, buyers will have to rely on anecdotal evidence and/or conduct their own testing to determine the effectiveness of Cranktip pedals. To this end, Cranktip’s 30-day unconditional money-back guarantee is a fair and conducive offer.
Cranktip advises that buyers should allow up to 2 weeks to adapt to the pedals. As I’ve noted above, the pedals demand a significant change in saddle height, which in turn, will influence the suitability of handlebar height and reach. Add to this re-positioning of the foot over the pedal axis and a broader stance, and the result is significant change to every contact point on the bike, more than enough to justify a period of adaptation. The difference in the quality of pedal stroke offered by Cranktip pedals only complicates this issue.
I was a little slower on Cranktip pedals compared to conventional pedals. I can only speculate on the reason(s) but my hunch is the explanation lies with the impact of Cranktip pedals on my position and biomechanics. The results aren’t enough dismiss Cranktip’s claims, but there may be more involved to using these pedals effectively than simply lowering the saddle.