Tuesday, January 22, 2008

Active Spokes

Did you ever see an invention and wonder, “Why didn’t I think of that?” I’ll tell you about my experience with that thought last summer after I was approached by a triathlete from New York who asked me to take a look at his new concept.

It wasn’t the first time someone had asked me to do this. But there had only been one previous invention I thought had any promise. That one was ten years ago and it became the PowerTap™ power meter. It has done pretty well. None of the others I’ve been shown made it to market. They didn’t have any real merit and it was obvious.

So when this triathlete asked me to sign a non-disclosure agreement before seeing his invention I was highly skeptical and was already trying to come up with excuses for why I couldn’t be involved in the project. But when I saw the concept it was like the V-8 commercial where the guy dummy slaps his forehead, only now it was, “I could’ve thought of that!” The concept is quite simple but it contradicts traditional thinking about bicycle wheels. That’s probably the reason no one else, including me, dreamed it up.

The traditional way of viewing race wheels is that they need to be light, especially near the rim, as heavy rims make acceleration more difficult. And since climbing a hill on a bike is essentially a series of alternating decelerations and accelerations with every pedal stroke, we certainly don’t want heavy rims when climbing a hill. Nor do we want heavy rims on a course with a lot of corners. I once did a 30k bike leg in a duathlon that had 36 turns. A heavy rim would have been a disaster for this race with all of the accelerations coming out of each corner.

But there are times when a heavy rim would be advantageous. Nobody ever talks about this, but it’s true. When coming down a hill, starting up the next hill at the bottom of a descent, or riding on a flat course a heavy rim has certain advantages. You’ve probably experienced what I’m describing here if you’ve ever ridden a bike at your gym or health club that has a heavy flywheel. You know how difficult it is to decelerate or stop the thing without using the brake. The wheel just wants to keep on going even without you adding any more energy to the system. If some how your rim could be heavier going down hills and on flat terrain when acceleration is not necessary and light when climbing or coming out of a turn you’d have an advantage. So you have a choice to use either a heavy-rimmed wheel or a light-rimmed wheel when racing. I’ve never known anyone to opt for a heavy race wheel.

We’re pretty much brainwashed by marketing and common practice to believe that a light wheel is the only way to go for all situations. No one goes out and looks for heavy-rimmed wheels when making a purchase. Even if you did decide you wanted to use a heavy rim in a certain race it would require you to buy a second pair of race wheels—if you could find a manufacturer who made an aerodynamic, heavy-rimmed wheel. Good luck.

These thoughts passed through the mind of the inventor I mentioned above during a tough interval training session he was in early last year. His name is Russ Kalil. He's an Ironman. During the session Russ wished he had a heavier rim for the downhills and flats and a lighter one for the uphills and corners. Then it dawned on him—why not make a wheel that changes from a light rim to a heavy rim during the race? So when he got home he went straight to his basement and began toying with the concept he had dreamed up during the workout—a wheel with small weights that move along the spokes back and forth between the hub and the rim. At slow speeds they would be next to the hub. At high speeds they would move to the rim. And when you slow down they’d move back to the hub again. His prototype was made with rubber bands and fishing weights. It worked, at least in his basement on a work bench. So he began to refine it. That’s about when he contacted me.

He wanted to conduct a study to see how it would work in the real world and needed an athlete to test it on. I immediately enlisted my son, Dirk Friel, to be the test subject. Russ also brought Joseph Voelkel, PhD, from the Rochester Institute of Technology, onboard to conduct the testing. So Dirk and Dr. Volekel spent the summer conducting field tests on the 5-mile, rolling course for the Boulder Time Trial Series. What they found was a two- to five-percent improvement in Dirk’s times at a given power with the moving weights compared with the same wheel without the weights. In fact, Dirk went on to have his fastest time ever in one of the races in the series using the invention, which is now called the Active Spoke™.

Now as a much more refined and elegant device Russ has figured out how to calibrate the weights so they move to the rim at a specified speed. So you can customize the wheel to your typical race speeds and the course you’ll be racing on. The device can be installed on your existing race wheels (see photos). Look for a manufacturer’s wheel with this technology built in to also be available soon.

This past weekend the website where you can find out more details and purchase an Active Spoke™ kit to customize your own wheels went online at http://active-spoke.com/. The concept is currently being examined by the ITU for use in multisport racing and appears, as of this writing, to have met their standards for use in sanctioned races. The UCI has yet to review it. It is being rolled out at the SICI convention in Denver the end of this month (www.serottacyclinginstitute.com).

The bottom line is that the concept works. You’ll race faster on certain courses using Active Spokes™. When you see the simple concept in action you’ll probably do the same dummy slap I did and wonder why you didn’t think of it.


At January 22, 2008 2:52 PM , Blogger Planet Berry Blog said...

Very cool site. Looking forward to returning soon.

At January 24, 2008 5:24 AM , Anonymous Karl McCracken said...

I now have a palm print on my forehead. How beautifully simple & elegant! I love the fact that you can buy different spring sets depending on your level - from 17mph to 23mph.

At January 24, 2008 11:16 PM , Anonymous Anonymous said...

a-ha, the one thing that was not mentioned was that there is no such thing as a free lunch. as soon as the weights begin to move to the rim, the wheel is in effect being braked, leaving you in the dust of another, otherwise identical rider. The additional weight would probably eke out a tiny advantage on a descent, but the poor aerodynamics might rob that advantage several times over. Then in the corners, when you're on the brakes, and the weights slide back to the hub, you now need to brake extra hard to slow down the conservation of angular momentum. then, get rewarded at the apex with acceleration more sluggish than a merely heavy rim. the only time this would actually be a distinct advantage is a very rapid transition between fast descent or flat, and a very steep hill. However, while zipping along the flat, the turbulent drag generated by these weights might hurt you more than the tendency for the now-light rim to speed up a bit would ever get you. It isn't as much energy as you believe, as the wheel is already slowing due to other forces. Another thing: wheels behave much differently on the ground than they do in the stand. A tire is motionless on the ground, and going twice the speed of the vehicle at the top. Inertia on rotating objects only applies on the road because the drag of the accelerating half of the wheel is balanced by the corresponding deceleration of the other half. Because the weights are kept in place by centripetal force acting against a spring of some form, when going fast, whenever the rim is on or near the ground, it's speed is essentially zero. so, the spring at this point would very effectively snap, or begin to snap the weight back up to the hub, only to have it be wrenched back to the outside of the rim at the other side. This might sound like a genius idea, but It seems to me you guys are trying to build a perpetual motion machine, or some moderation thereof. Being light, strong, and aero wins races. Light makes it easier to climb hills. Strong prevents efficiency losses. Aero reduces drag at speed. Same applies to rider as bike.

At January 25, 2008 6:03 AM , Blogger Eric Johnson said...

Does the 3-6 second per mile improvement touted on the website factor in the slightly worse aerodynamics>?

At January 25, 2008 6:15 AM , Blogger Joe Friel said...

eric--Yes, all of the testing was done in the real world--on the road.

At January 25, 2008 11:47 AM , Anonymous Russ Kalil said...

Hi – my name is Russ Kalil – I invented the Active-Spoke. While it is not my intention to promote our product, I think a response to the anonymous message will help.
No question, when the weights expand to the rim, there’s a performance penalty. Also, when going up hill, the additional ‘close to the hub – call it ~ static weight’ will also penalize a rider. But also worth mention: when the weights return, there’s an acceleration aspect and in so far as the static weight, we’re talking 9 to 11oz overall . In terms of performance, you’ve accurately traced out strategy! We modeled the theory using positive & negative slopes, varying gradients, distances and entry speeds. In essence, using our model, it came out as a wash. So, we conducted our lab trials with a 2by6 Factor DOE (to obtain resolution we needed as the effect, we expected was small). Results were promising – using , slope, gradient, slope distance and the change in load (i.e. the four possible scenarios – into hill, over hill, into d/hill hill, exit d/hill), Active-Spoke wheel was found to be significant and outperformed the Std wheel . I suspect from your valued commentary that possibly, the stand / non-road aspect may have influenced this. (we’re not challenging convention wisdom – we just focused on the outcomes of our experimentation). This outcome led to road trials, again, trying diligently to keep the external factors in control and minimized. This is a challenge as we all know. Again, the results suggested the Active-Spoke outperformed the standard wheel by 0.2-0.4mph over a 14mile zero net elevation course that included a 1km 8deg climb. In a completely subjective manner, I can say that the best Std time never came within 60sec of the best Active time – and the Active had rubber bands while the std wheel was a ‘aero clean’ equivalent. This sample was only 8 runs but provided the impetus for further testing. In subsequent testing, we continued to be challenged by environmental factors (mainly wind) even though the results were encouraging (3.6sec/mile). So, eventually we decided that a standard, classic Static Down-hill study would provide credible evidence of one aspect of what the impact of the weights would be…and it was significant – see our Roll-Down Abstract on our website.
We’ve never suggested that this would be valuable in a criterium or a road race – where accelerations at already high speeds are needed. We think this is ideal for triathlon and time trial applications with rolling course – we theoretically define ‘rolling’ as 4degrees or less and 500m uphill or less). Our field trials suggest, depending on the course , there are gains of up to 5sec/mile.
That’s how we got here. We certainly appreciate all the interest in our product and hope athletes will try it and see for themselves. For me, it’s been a trill to work with such a prestigious and supportive team.
Thank you.
Russ Kalil – Active-Spoke.com

At January 29, 2008 3:21 PM , Blogger Jorge Zuniga said...

Great idea Russ Kalil!
I read the abstract of the study in your website and I really encourage you to try to perform the study with a greater number of subjects (minimum 10 subjects of similar characteristics) and publish the paper in a sound scientific journal. I see a great potential in your product and I think that you may be able to show significant differences between DWW vs. SW for H1, H2 and H3.

Jorge Zuniga

At January 29, 2008 3:30 PM , Anonymous Jorge Zuniga said...

Great idea Russ Kalil!
I read the abstract of the study in your website and I really encourage you to try to perform the study with a greater number of subjects (minimum 10 subjects of similar characteristics) and publish the paper in a sound scientific journal. I see a great potential in your product and I think that you may be able to show significant differences between DWW vs. SW for H1, H2 and H3.
Jorge Zuniga


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