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Tech-oblong chainrings, timed cranks = more power?
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I'm looking for some tech advice from the upper echlons of the forum. My question-is it possible to produce more power and compensate for a leg length discrepancy by going to custom ovalized chainrings and timing the crank arms by moving them forward or back from the 180 degrees opposed position?

I've got a 47 mm leg length difference due to an old auto accident. Of course this gives me an uneven pedal stroke, for which I compensated with a shim under the short leg cleat and moving the cleat forward. This has given me pretty good results, and I've been competitive in tt, but I'm always looking for an improvement. High Sierra Cycles in Ca. has a system with an infinitely adjustable crankarm/chainring configeration. He makes a chainring setup to correspond to my lld, and we experiment with timing of the cranks for the best result. He also came up with a drop pedal to reduce the size of the shim that I was using under the cleat. I mean, there is definitely a lot of thought that has gone into producing this system. Once the correct settings are found, he makes a special chainring/crankarm setup to replace the clunky adjustable one. He said that he could virtually guarantee a 50 watt or a 2mph increase in speed. I spoke with a couple of guys who had worked with him, and received glowing reports, so I signed on with him a year ago, at no small expense. I've put on over 8000 miles on the system, with major and minor changes to try to get results, but my spinscan numbers don't seem to vary much, nor do my test times. Last year's tt were about the same as w/o the system , but I also had a disc and skinsuit which should have accounted for an improvement.

My testing procedure consists of 8 miles at 80% on the computrainer, then 5 minutes at 90% with the last minute all out. I then graph the end of the tt and compare wattage, spinscan, etc.

I'm seeing virtually no results. I spoke with John Cobb before trying this, to get his thoughts. He said that if the system could do what was promised, "there would be a line to High Sierra's door stretching around the world". I tried it anyway because he was the only one around that specialized in my problem, but I think now that I probably should just have went to see John for a fit session and saved a lot of money.

I want the thoughts of others who are, hopefully, much smarter than I.



thanks
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Re: Tech-oblong chainrings, timed cranks = more power? [DougT] [ In reply to ]
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You would be better off with two different crank arm lengths. Shims only correct the leg length problem at the bottom of the stroke but aggravate the problem at the top. If you ever decided on getting a pair of PowerCranks you would be an excellent candidate for the adjustable crank length so you can determine the optimum crank length difference for you.

All of these other things may or may not have an effect on power but if they do then it would be applicable to everyone and I predict their effects would be very small.

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Frank,
An original Ironman and the Inventor of PowerCranks
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Re: Tech-oblong chainrings, timed cranks = more power? [Frank Day] [ In reply to ]
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Yes, I understand the problem with the shims correcting the problem at bdc but actually lengthening the crank at tdc, resulting in a more acute angle between the upper leg and body. He compensated for this with the drop pedal on the longer leg side, and a shorter crankarm on the shorter side so that the shim is only about 1/4". Your point is exactly what I've been wondering since not experiencing any improvements, in that the oblong chainring and timed crank should be used to fine tune just about everyone if it will work for my problem, just to a lesser degree. I welcome your thoughts and those of others such as yourself who have worked with these issues. I actually inquired about the system before purchasing it last Jan. and the post received no feedback. Thanks
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Re: Tech-oblong chainrings, timed cranks = more power? [DougT] [ In reply to ]
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Another problem that you probably have that this "fix" will do nothing for (I expect) is you are probably not 50/50 and your weak leg is probably your short leg. Have you ever been on CT Spin scan? Are your legs equal?

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Frank,
An original Ironman and the Inventor of PowerCranks
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Re: Tech-oblong chainrings, timed cranks = more power? [Frank Day] [ In reply to ]
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Actually, I was always pretty equal in my % of power output even with the shim, but I figured that my stronger leg was "helping" the weaker leg some. My tests usually run anywhere from 48/52% with the lower figure being the shorter leg to 50/50. Right now I have my older bike w/o the set up on the CT and I did a test and graph today. Tomorrow I'll put my newer bike with the set up on the trainer and compare the results of the graph. It seems to me that if the system is working my power and spinscan #'s should be much better on the new bike as opposed to the older bike just using a shim and regular chainrings. He says that I've built strength using the system that will skew the results of the old bike test because I'm stronger, but I still don't feel that I've improved anywhere near the point that I was going for(50watts).
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Re: Tech-oblong chainrings, timed cranks = more power? [DougT] [ In reply to ]
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It is not true that your spin scan numbers should change much if you get more powerful. SpinScan is a measure of smoothness and not roundness or efficiency, as it ignores the backstroke.

Many people get on PC's and see big improvements in power with only modest or little improvement in SpinScan. Improvements in Spinscan come with improvements at the top and bottom of the stroke.

--------------
Frank,
An original Ironman and the Inventor of PowerCranks
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Re: Tech-oblong chainrings, timed cranks = more power? [Frank Day] [ In reply to ]
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High Sierra says that the chainrings and timing of the crankarms will compensate for the unequal leg length, making me smoother(higher SC numbers) and more powerful. Eliminating the huge shim by going to different length crankarms and the drop pedal should also make me smoother, but I'm not seeing the improvement in my SC numbers. This is what is driving me crazy, in that I've went through huge changes with the equipment and definitely done the training and the miles, yet results are not forthcoming. I'll do the test on my TT7 with his system tomorrow and compare the results with today's, and will have more data. Once again,thanks for your input Frank.
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Re: Tech-oblong chainrings, timed cranks = more power? [DougT] [ In reply to ]
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Doug, just want to say I'm rooting for you to find something that really works well for you.

The dropped pedal thing seems like a mistake to my non-engineering-trained-background way of thinking. It seems to me that this dropped pedal would decrease the power of that leg, because it allows a rotation of the ball of the foot forward and backward at any time during the stroke. We riders have a very hard time producing a round stroke as we shove forward, scrape backwards, step over the top, etc....and a dropped pedal, swivelling forward and back as we try and pedal "roundly", would be wasting some of this power generated by a muscular contraction that was not applied perfectly "roundly".

I think you should try an approach that maximizes the power generated by each respective leg...unequal though they may be. Equality isn't the goal here, it's maximal efficiency of each leg regardless of what the other leg is doing. Spin Scan numbers don't have to be smooth as long as the mean power generated is as high as possible. I'm not saying it isn't a good goal to smooth the SS numbers out, but that shouldn't be the determining factor in how you are ultimately positioned.

Power, man, Power. Don't do anything that detracts from one leg for the satisfaction of a Spin Scan number.



Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)
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Re: Tech-oblong chainrings, timed cranks = more power? [yaquicarbo] [ In reply to ]
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I understand your point about the drop pedal, but High Sierra's position is that it's the best way to compensate for the lld. A shim on the shorter leg side makes the crank shorter at bdc(good) but longer at tdc(bad). This is used on the longer side to effectively make the longer leg's crank longer at bdc yet not make it shorter at tdc to even me out without going to a crank that is actually 47mm shorter than the other. He says that another disadvantage of using the large shim is that you lose power due to rocking torque on the short side due to the foot being so far away from the pedal spindle, which I think is what you're saying that I'm experiencing anyway, just that it's on the other leg now. I don't know either, because I just have to believe what people say until proven otherwise. I know that PNF used drop pedals on both sides at least one year-I don't know why or why she quit using them, but the concept apparantly has been around awhile.

I did another SC on my Trek that just uses the shim and regular cranks and chainrings today, and will put the TT7 on tomorrow and test two days to see the results. Today's end test was 20 watts higher than yesterday's on the same equipment, which is just why I wanted to test twice on the same equipment before trying the High Sierra equipped bike. It seems that the body can vary so much from day to day that it's really hard to compare results of a short test.

I'm hoping that people like Andrew Coogin(sp?) and John Cobb still monitor this site and will weigh in as to whether they think chainrings and crank timing can be used to produce more power in my case. I know that they used to monitor this site, but I haven't been on for about a year so don't know who's on any more.

It was good to hear from you and Frank Day. Thanks
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Re: Tech-oblong chainrings, timed cranks = more power? [DougT] [ In reply to ]
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Doug wrote: another disadvantage of using the large shim is that you lose power due to rocking torque on the short side due to the foot being so far away from the pedal spindle, which I think is what you're saying that I'm experiencing anyway, just that it's on the other leg now.

That is one of the things I was trying to say.

I don't have a clue as to why simply using cranks of different lengths wouldn't be the simplest, most effective way of addressing the problem. As far as that goes, even without a leg length discrepancy, if someone had a hip (knee or ankle) problem that limited their flexibility both up and down, a dissimilar crankarm length ought to be the ticket.

As far as PNF, or anyone else using a drop pedal, I can only imagine that it allowed them to get their heel to drop more quickly at the beginning of the downstroke...thereby enabling them to engage their gluteal muscles more/sooner. I can't imagine it helps much/at all, or people would be all over that pedal style for increased speed. I've never seen anyone ride that pedal style. Ever.



Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)
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Re: Tech-oblong chainrings, timed cranks = more power? [yaquicarbo] [ In reply to ]
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I tested two days on the Trek w/o the system, and was putting out 313 and 335 watts at the end of the test on the 2 days, with SC #'s of 69 and 71. Tonight I put the TT7 on which has the system and put out 328 watts with a SC# of 59. It just looks to me that I'm going nowhere and spending a lot of time and $ to do it. Going to test again tomorrow or the next night so I can average the tests. I'd like to see what some others think of the whole thing, but this subject is getting buried pretty far back. That's what I get for posting on the weekend.
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Re: Tech-oblong chainrings, timed cranks = more power? [DougT] [ In reply to ]
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Just keep posting...maybe someone will see it and have a really definitive suggestion.



Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)
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Re: Tech-oblong chainrings, timed cranks = more power? [yaquicarbo] [ In reply to ]
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I see that I'm moved back to the front, so that helps. The old format didn't work that way, so I assumed that all was lost.
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