The Powercrank Thread

[JayKosta]

Minimal energy is used in my back stroke because all that's involved is drawing back the pedal/lower leg around 5 o'c as knee is bending and unweighting around 7 o'c where upward acceleration of leg weight begins, from 9 o'c muscles are already being prepared for maximal forward force application at 11 without reducing down stroke power as is the case with the PC and circular styles. This is because total concentration is always focussed on the 180 deg. power strokes. Letting the momentum of the downward leg drive the rising pedal up and over TDC would be the sensible way to do it

--------
If there is
'drawing back' from 5 to 7, and
'acceleration' from 7 to 9, followed by
continued acceleration to prepare for maximum force at 11 -
then that technique should work perfectly well with PCs because the actual (or attempted) speed of the foot is not less than the speed of the pedal.

But if 'downward leg drive' is pushing the foot of the 'rising pedal up and over TDC' then PCs would verify that by uncoupling at that point.

If it is desired to eliminate having the pedal 'push against the foot', then PCs would be an excellent tool to develop that technique. But they wouldn't be of value if having the pedal 'push the foot around' in some sectors is desired or acceptable.

Jay Kosta
Endwell NY USA

 

[coapman]

How do the muscles used in lifting your knee to your chest differ from those used to kick a soccer ball? The combination of muscles used to achieve any particular directional force vary depending upon the orientation and direction. Plus, this is constantly changing around the pedaling circle as the orientation and direction constantly changes.

How does tangential effect of the force you are attempting to apply from knee to pedal during the upstroke compare with tangential effect of down stroke force?

 

[JayKosta]

With PCs, I think (having never used them) that one of the primary skills that is learned is how to keep the 'instantaneous tangental speed of the foot' the same as that of the pedal - which gives complete 'unweighting' but does not un-couple the PCs. This might be useful because it eliminates negative torque being applied to the BB spindle.

After the rider has developed the skill to not allow slowing of foot speed during any segment of the crank rotation, the techinque can be extended to apply some (even minimal) positive torque in the segments other than the primary power-stroke segment.

Jay Kosta
Endwell NY USA

 

[FrankDay]

How does tangential effect of the force you are attempting to apply from knee to pedal during the upstroke compare with tangential effect of down stroke force?

Considering only the applied pedal forces, it is smaller on the upstroke than the downstroke primarily due to the effects of gravity.

 

[FrankDay]

With PCs, I think (having never used them) that one of the primary skills that is learned is how to keep the 'instantaneous tangental speed of the foot' the same as that of the pedal - which gives complete 'unweighting' but does not un-couple the PCs. This might be useful because it eliminates negative torque being applied to the BB spindle.

That is correct. Simple unweighting to keep the cranks coupled is the first thing the new user learns.

After the rider has developed the skill to not allow slowing of foot speed during any segment of the crank rotation, the techinque can be extended to apply some (even minimal) positive torque in the segments other than the primary power-stroke segment.

Jay Kosta
Endwell NY USA

The additional changes that occur over time are not something that the user does consciously but they occur as the body better learns to unconsciously anticipate all of the direction changes involved. Of course, the direction changes are infinite and constant but even if simplified it goes beyond what anyone could possibly think is doable. For instance, at a cadence of 90, if we simplify the system to just 4 direction changes (up, forward, down, back) we are talking 360 direction changes a minute or 6 per second FOR EACH LEG AT THE SAME TIME. If we simplify the circle into 8 different directions we are talking 12 direction changes per second, or less than 0.1 seconds per change (and this is a simplified analysis)! This is shorter than the time it takes for a nerve impulse to get from the brain to the muscles. I think it is clear that if one wants to pedal in such a fashion one cannot think about it, it has to become unconscious. And, I think it becomes evident why people cannot perfect it in a couple of weeks, just like they can't perfect playing the piano in a couple of weeks. No wonder people want to think that "just pushing harder" is the only way to go. Doing anything more boggles the mind, if one has to think about it.

 

[coapman]

--------
If there is
'drawing back' from 5 to 7, and
'acceleration' from 7 to 9, followed by
continued acceleration to prepare for maximum force at 11 -
then that technique should work perfectly well with PCs because the actual (or attempted) speed of the foot is not less than the speed of the pedal.
But if 'downward leg drive' is pushing the foot of the 'rising pedal up and over TDC' then PCs would verify that by uncoupling at that point.
If it is desired to eliminate having the pedal 'push against the foot', then PCs would be an excellent tool to develop that technique. But they wouldn't be of value if having the pedal 'push the foot around' in some sectors is desired or acceptable.
Jay Kosta

Only unweighting takes place between 7-9 by raising the knee and letting the swinging leg be steered by the pedal, there is no acceleration. There is no acceleration between 9-11 because here all muscles are in neutral mode as all the necessary muscles are been primed for maximal force application at 11 which is something FD believes is impossible. Between 10-11 the crank has to be moved upward by the downward leg, using only minimal energy. This rules out the use of PC's. All the 180 deg. of my power is maximal power which comes from the hips through the knees in only one direction, using the ankles to convert 90 deg. of it into maximal torque. FD's PC power comes from the knees, using the swinging movement of the lower legs to make the most of what limited power he can produce around the circle. At moderate to high cadence you can't combine maximal power with minimal power without losing power in the most important sector of the pedalling circle.

 

[coapman]

Of course, the direction changes are infinite and constant but even if simplified it goes beyond what anyone could possibly think is doable. For instance, at a cadence of 90, if we simplify the system to just 4 direction changes (up, forward, down, back) we are talking 360 direction changes a minute or 6 per second FOR EACH LEG AT THE SAME TIME. If we simplify the circle into 8 different directions we are talking 12 direction changes per second, or less than 0.1 seconds per change (and this is a simplified analysis)! This is shorter than the time it takes for a nerve impulse to get from the brain to the muscles.

You are correct and that is why (when using the circular or PC style) the brain fast forwards through all sectors, including the important 2-4 sector where maximal torque is normally applied, resulting in less power application here.

 

[FrankDay]

You are correct and that is why (when using the circular or PC style) the brain fast forwards through all sectors, including the important 2-4 sector where maximal torque is normally applied, resulting in less power application here.

Everyone is stuck with the same circle so why doesn't it do that for everyone? Why only the PC style?

 

[FrankDay]

Only unweighting takes place between 7-9 by raising the knee and letting the swinging leg be steered by the pedal, there is no acceleration. There is no acceleration between 9-11 because here all muscles are in neutral mode as all the necessary muscles are been primed for maximal force application at 11 which is something FD believes is impossible. Between 10-11 the crank has to be moved upward by the downward leg, using only minimal energy. This rules out the use of PC's. All the 180 deg. of my power is maximal power which comes from the hips through the knees in only one direction, using the ankles to convert 90 deg. of it into maximal torque. FD's PC power comes from the knees, using the swinging movement of the lower legs to make the most of what limited power he can produce around the circle. At moderate to high cadence you can't combine maximal power with minimal power without losing power in the most important sector of the pedalling circle.

I am just wondering how you ensure/know that everything happens on the backside just the way you want it to when all of your concentration (as you have explained to us many times) is on the opposing leg's pushing action?

 

[coapman]

Everyone is stuck with the same circle so why doesn't it do that for everyone? Why only the PC style?

Because like my semi circular style, the masher's brain has only one force direction to take into consideration (with or without unweighting) during each leg's pedalling revolution.

 

[coapman]

I am just wondering how you ensure/know that everything happens on the backside just the way you want it to when all of your concentration (as you have explained to us many times) is on the opposing leg's pushing action?

Because that's how it developed as the technique was being perfected. When there is simultaneous switchover of maximal force application everything has to work like clockwork during the recovery stroke.

 

[FrankDay]

Because that's how it developed as the technique was being perfected. When there is simultaneous switchover of maximal force application everything has to work like clockwork during the recovery stroke.

If you say so.

 

[FrankDay]

The Burns paper (Effects of Short-Term Training With Uncoupled Cranks in Trained Cyclists), regularly referred to here as "proving" PowerCranks don't work, is now available at researchgate and it is now possible for reviews to be posted. I have reviewed the paper with my criticism. Both are available here. Hopefully, the authors will respond to my review. You can also add your own review or respond to my comments if you want to but, I believe, you have to be member of the community (not hard) and cannot do so annonymously.

 

[FrankDay]

I finally have the iCranks prototype and the TA software up and working together. Right now it only works indoors when hooked up to the computer. I have put together a short screen cast showing the potential. You can see there are some issues. Unless the PC's have done much more than I have ever believed it is clear the output is rotated 90º since I find it unlikely my torque is highest at BDC. This was done with me riding 125mm cranks so the power is, by my best estimate from rudimentary efforts to find a compensation factor, about 40% low. I was a little surprised to see how much work I was doing on the upstroke and how little my technique changed when going to one legged pedaling. here is the link.

 

[sciguy]

I finally have the iCranks prototype and the TA software up and working together. Right now it only works indoors when hooked up to the computer. I have put together a short screen cast showing the potential. You can see there are some issues. Unless the PC's have done much more than I have ever believed it is clear the output is rotated 90º since I find it unlikely my torque is highest at BDC. This was done with me riding 125mm cranks so the power is, by my best estimate from rudimentary efforts to find a compensation factor, about 40% low. I was a little surprised to see how much work I was doing on the upstroke and how little my technique changed when going to one legged pedaling. here is the link.

Frank,

Do you know if anyone other than you is working to validate the function of the Icranks? I understand why you're assuming that the software is showing your output 90 degrees out of phase but a glaring error like that making it through gives me little confidence that the developers got anything right along the way.

Who's in charge of developing the power compensation algorithm? It seems like years of development work still ahead here. If you really want people to have any faith in the data coming from these I'd suggest you do your out door work paralleled with a PowerTap wheel just as DCrainmaker does in his test work.

You won't find any of us just willing to take your word for any data generated by the Icranks without some decent level of corroboration with another power meter. If the total power output shown by an Icrank matches up closely with a known good Power Tap that would go a long ways toward me having some trust in the round the circle data as well.

Hugh

 

[FrankDay]

Frank,

Do you know if anyone other than you is working to validate the function of the Icranks? I understand why you're assuming that the software is showing your output 90 degrees out of phase but a glaring error like that making it through gives me little confidence that the developers got anything right along the way.

I guess I can see your concern because you have no history. However, what is going on is trying to transfer software that has been up and working on their Fitbike, the biobike, for several years to ANT+ and to work on a regular bike with the iCranks. Apparently the magnetic pickup on the Biobike is at TDC. Anyhow, the developers of the cranks and the software have been working closely with the AIS (Austalian Institute of Sport) and have had many pros and Olympians on the cranks and software. I might add that I believe I am the only person in the world with the software outside of the developers and it was Version 0.0.1 (beta) so I think we can forgive even a glaring error or two "making it through."

Who's in charge of developing the power compensation algorithm? It seems like years of development work still ahead here. If you really want people to have any faith in the data coming from these I'd suggest you do your out door work paralleled with a PowerTap wheel just as DCrainmaker does in his test work.

Like I said, the basic algorithm has been around a long time. There are not years of work still to be done. What is different is taking the data and showing the components around the circle. The total will be the same whether one is using this software of a Garmin head unit or anyother device. The main error they made is simply forgetting that the magnets are placed differently on a bike than on what they are used to using. Not a big deal IMHO. When I move to the Velotron I will put the magnets at TDC so any confusion is removed until they fix the problem.

I have to laugh as if you think that corroboration (riding with a bunch of meters at the same time) means anything. It is simple enough for me to corroborate the iCranks with the Velotron, probably the most accurate power meter available except the Velotron measures power at the wheel and the iCranks measure at the pedal. So, they will be different even if they are both perfectly accurate. So what? The most important aspect is reliability and reproducability. I know that my cranks are currently reading about 40% too low. Would that hurt my ability to use the device if I didn't know that? No, because I would ride to the power my meter tells me is right for me. It doesn't matter if that power is correct or not unless I am trying to do a study. Anyhow, they tell me the final device should be more accurate than the SRM so this shouldn't be an issue even if you would like it to be one. In other words, if my PM reads 180 watts but I am really at 230 watts would it be any different to my training or racing if I tried to maintain 180 watts on the first meter or 220 watts on the second meter? It is simply a number that denotes a relative effort.

You won't find any of us just willing to take your word for any data generated by the Icranks without some decent level of corroboration with another power meter. If the total power output shown by an Icrank matches up closely with a known good Power Tap that would go a long ways toward me having some trust in the round the circle data as well.

Hugh

I don't expect anyone to take my word for anything. It is why I try to give people data when available. Wouldn't it be nice if everyone did the same? At least now I will be able to give pedaling technique data to support my arguments when such data would be helpful.

 

[sciguy]

I guess I can see your concern because you have no history. However, what is going on is trying to transfer software that has been up and working on their Fitbike, the biobike, for several years to ANT+ and to work on a regular bike with the iCranks.

Correct me if I'm wrong but aren't the Fit bike and Biobike static trainers? The initial Stages power meter looked great when ridden on a trainer but functioned rather poorly once taken outside on to real roads. How much road mileage do you or the Icrank folks have on their design? Interesting things often happen when a new design enters the real world.

I have to laugh as if you think that corroboration (riding with a bunch of meters at the same time) means anything. It is simple enough for me to corroborate the iCranks with the Velotron, probably the most accurate power meter available except the Velotron measures power at the wheel and the iCranks measure at the pedal.

Your Velotron correlation is all well and good for an indoor trainer environment but I fail to see how it helps prove the unit will work as you expect outdoors. As I mentioned above the initial iteration of the Stages power meter did not.

I don't expect anyone to take my word for anything. It is why I try to give people data when available. Wouldn't it be nice if everyone did the same? At least now I will be able to give pedaling technique data to support my arguments when such data would be helpful.

I think you're completely missing the boat if you don't have a second power meter mated up in your outdoor system. If you did you'd be able to give us some additional data we would really like to see. I bet we can find you a good Powertap wheel to borrow if $$$$ is the problem.


Hugh

 

[CoachFergie]

I think you're completely missing the boat if you don't have a second power meter mated up in your outdoor system. I bet we can find you a good Powertap wheel to borrow if $$$$ is the problem.

Well lets face it Powercrankers have had that option for the last 15 years to test their beliefs and the claims of the Creator.

 

[FrankDay]

Correct me if I'm wrong but aren't the Fit bike and Biobike static trainers? The initial Stages power meter looked great when ridden on a trainer but functioned rather poorly once taken outside on to real roads. How much road mileage do you or the Icrank folks have on their design? Interesting things often happen when a new design enters the real world.

No clue what they have. I probably have 1000 miles or so on two units.

Your Velotron correlation is all well and good for an indoor trainer environment but I fail to see how it helps prove the unit will work as you expect outdoors. As I mentioned above the initial iteration of the Stages power meter did not.

My experience is that the calibration or reading doesn't seem to change just because one moves outdoors. Only time will tell I suppose.
[/QUOTE]
I think you're completely missing the boat if you don't have a second power meter mated up in your outdoor system. If you did you'd be able to give us some additional data we would really like to see. I bet we can find you a good Powertap wheel to borrow if $$$$ is the problem.
Hugh[/QUOTE]
I think others can do that just fine, if they want to. None of you would believe anything I did anyhow.

 

[sciguy]

My experience is that the calibration or reading doesn't seem to change just because one moves outdoors. Only time will tell I suppose.

Based on????????????????? A wild Xssed guess? Why not actually measure the similarity or difference with proven technology rather than sticking your head in the sand? I'd be thrilled to learn that the Icrank actually tracked a Power Tap closely and consistently in a variety of outdoor riding conditions and for a period of months. Just because it seems to track your Velotron indoors gives me zero faith that it perform as reliably outdoors. Quarq, Power2max, Powertap, Rotor and Stages power meters all experienced initial "teething problems" You seem unwilling to take a critical look at the Icrank despite how inexpensive it would be to do. Asking customers to pony up $3500 for something you refuse to perform appropriate testing on is just plain outrageous.

Hugh

 

[FrankDay]

Based on????????????????? A wild Xssed guess? Why not actually measure the similarity or difference with proven technology rather than sticking your head in the sand? I'd be thrilled to learn that the Icrank actually tracked a Power Tap closely and consistently in a variety of outdoor riding conditions and for a period of months. Just because it seems to track your Velotron indoors gives me zero faith that it perform as reliably outdoors. Quarq, Power2max, Powertap, Rotor and Stages power meters all experienced initial "teething problems" You seem unwilling to take a critical look at the Icrank despite how inexpensive it would be to do. Asking customers to pony up $3500 for something you refuse to perform appropriate testing on is just plain outrageous.

Hugh

Cool. I am sure someone when they do a review of the product will check this out. I personally don't really care much about how accurate the device is (I am not the least bit upset that my numbers are about 40% too low because I am riding 125 mm cranks and they are calibrated to 172.5 length) as long as it is consistent as I am more interested in looking at technique than power per se.

 

[CoachFergie]

Hugh, all you need is faith and a very well calibrated RPE!

Then just give Frank your money and the 40% gain is all yours.

 

[sciguy]

Cool. I am sure someone when they do a review of the product will check this out. I personally don't really care much about how accurate the device is (I am not the least bit upset that my numbers are about 40% too low because I am riding 125 mm cranks and they are calibrated to 172.5 length) as long as it is consistent as I am more interested in looking at technique than power per se.

Well that should be comforting to potential customers asked to pay $3500
"Yeah the guy promoting it doesn't care if it's accurate but so what."

Hugh

 

[sciguy]

No clue what they have. I probably have 1000 miles or so on two units.

I think others can do that just fine, if they want to. None of you would believe anything I did anyhow.

So in the mean time until reviews and early purchasers do the testing for you you'll continue to act like this guy

and not carry out what one can only be considered your due diligence. What an incredible lost opportunity! You've already let 200 + hours pass by when you could be collecting some excellent data regarding how the unit performs under real world conditions. The really rich part is that your justification for not doing the testing is that we might not believe you. How about doing the testing to see if the darn thing actually behaves as you hope in the field. It seems just doesn't cut. Until backed up by some objective data I'll consider the outdoor use of the unit untested.

Hugh

 

[FrankDay]

First, it isn't my product so it really isn't my job to do any testing other than what an individual might do, which I am trying to do. Second, isn't that the case with all early adopters, that not all the features or bugs in a product may be identified at the time of release.

You, of course, are welcome to delay purchase or avoid it all together when the product becomes available. All I am doing is saying I think the software offers a large advance over the current crop of available PM's (with the possible exception of Pioneer). To me the power of this power meter is in the software, not the strain gauges.