Limited number of designs. The spider allows (in theory anyway) you to put a PM on any crank arm with a removable spider. Moreover, I suspect the arm would need to be aluminum for them to put in the arm.



I am surprised that no one has gone to Asia for manufacturing for something that amounts to a glorified bathroom scale. Perhaps the volume is to low but........... how many would buy an SRM system if they cost $500-$1000? Exactly............

The Asian manufacturing guys are mass-producing electronics that are way more complicated than an SRM or PT.

Starnut

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As I recall back in the day our good buddy Greg Lemond used a power meter that worked on the pedals but just for testing in the lab if I remember

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I heard something somewhere about shimano considering a power meter, I'm sure they could get a solid unit that retailed under $1k. I would buy one

I guaran-damn-tee you it'll be propitiary and will most likely work with a special headunit that is incorporated into the 7900 computer and drivetrain. Moreover, the shifters and the crank are $700 each.................... there is no way it'll be $1000. Additionally, it'll likely rely on more than one part of the drivetrain and thus be of limited use to anyone who does not use Shimano.


Starnut

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This is an interesting premise. Without taking the thread too off-topic, would you care to expound on your remarks, specifically the "glorified bathroom scale" comment?

My particular concern with the meters I've seen is that regardless of the strain gauges that measure accuracy to within a few percentage points, it only does so for one leg.

Imagine a cyclist trying to work out deficiencies and leg muscle imbalances without the proper information in terms of what each individual leg is doing.

Also, I see systems that are not exactly user-friendly. I'd like to see s system that is compatible regardless of what type of crank and bottom bracket a rider is using.

Also, where would the strain gauges need to be placed to get as accurate power readings as possible if you were to build one from scratch?(Yes, I don't know much about how these things work as you can tell, but the idea of utilizing this type of data is intriguing.)

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sure.

PMs work with starin gauges and bathroom scale work with strain gauges.

I have a bathroom scale the gets down to .01 lbs and it cost me $70. I have a PM that measures down to the .01 ft/lbs and cost $4000. One was manufactured in Germany and one was manufactured in Asia. Granted, the PM does velocity as well but so does a $40 cycling computer.

My point was/is....... I think a significant amount of the cost of a PM is (obviously) not technology, materials, or engineering.............. it's labor. I dare someone to tell me it's the cost of the programing and software .

My iPod has umpteen more MB memory than my SRM headunit and cost .02 as much. A Garmin can (all be it not as effective) be used as a headunit for ~$300 while a PCVI costs $1100 is you buy the HRM strap and the Pod. By all intents and purposes, an iPhone may soon be able to serve as a headunit.


Why do PMs cost so much?



Because they can and people will pay for it.


I seen the one legged argument and until you can prove it you blowing smoke. In fact, there is a well know power coach, with one leg, that race and trains with a PM. Because the crank is a system and energy is transmited via the spindle................. it's a single system.

Accuracy is not the problem.


Additionally, the muscle "imbalance" argument is trite at best. Recently studies from the UT and UUtah have determied that imbalances are caused more by biomechanics and not actual muscle composition or useage. If the latter were true we'd walk in circles and not beable to control it. Moreover, trying to correct a slight muscle imbalance is a futile exercise as you'd need to balance it in every part of your life that involves useing that muscle group. Further, this does nothing to express imbalances in other sports: XC skiing; speed skating (left turn only); NASCAR (left turn only with no power steering); Golf; football/soccer; etc. I have yet to find out why cycling is some much different than any other sport?

Moreover, what does a imbalance have to do with where a PM is manufactured? A PM is not even the best tool to do determine an imbalance.


Starnut

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Do it!

It think the biggest issue is that the market is small... just not enough potential sales to amortize the costs over. You might ask why any of these bike parts are so expensive. You can buy a fully functional bike at Walmart for less than a set of derailleur pulleys. Or look at tires... I pay as much for bicycle tires that last 2k miles (or less) as I do for car tires that last 50k miles.

The only one that did that was the Ergomo.



Powertap or iBike.

So I guess you are ok with the PM limiting your pedal choices to one? With any of these systems that measure torque it is obviously more efficient for the measuring device to replace parts on the bike. IMO this is not "user unfriendly".

BTW, all of the crank or hub based PMs could easily track each leg separately by tracking the crank position. If they aren't doing it, it is because they don't consider it important.

Sounds difficult to me. The arms are subjected to all sorts of bending and twisting loads. You'd have to make assumptions about the loads being applied and also track the arm position.

The beauty of crank and hub systems is that the driving torque is being applied in a single plane in those locations, so it is easier and more accurate.

That sounds like it's going to be PowerTap/SRM money then?

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You seem to have misunderstood. I said I wasn't sure how these contraptions work, so anything I point out was for the sake of discussion, not argument.


Again, you are taking a tone that is a bit out of line given my intent. Besides, my personal muscle imbalance issues are the result of a couple of accidents and resulting surgical procedures. Structurally my legs are the same length. Muscle atrophy is known to take place after surgery in some instances.


When did I ever make this connection? I took the time to ask a few questions that may have been a bit off-topic but still pertinent.

Regardless, thanks for the reply. Very informative.

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It does seem that market forces are now at work and I am hopeful that the price of power meters will fall into the £500 range in a year or two:

1. Increased competition with multiple devices being introduced into the market giving price / reliability / feature competition and generally driving innovation
2. Increased uptake allowing manufacturers to defer high fixed costs over a larger number of users
3. Introduction of common standards (ANT+) to allow modular use of components, creating an open system with choice of measurement, readout, and software modules, e.g. use a Powertap computer (I know that doesn't work yet) with a Qranq crank and Trainingpeaks software.
4. Patents coming to an end - IIRC some of SRM's patents are about to run out, which would lead to the possibility of generic 'Cateye' SRMs.

Currently my concern is that the startup companies building power meters do not have the business savvy or willing to get big. The chap that built a highly technical prototype in his shed is not the right chap to productionise on a big scale and take it to the masses. It seems a bit that the people who develop their baby want to hold on to it rather than using licencing agreements to get it out there to the masses. Maybe I'm wrong here but it looks that way to me.

I for one would love to see Shimano using SRM's patents to churn out identical-looking Dura Ace cranksets but with strain gauges and electronics integrated to a readout on a Flight deck computer. Similarly Campag and SRAM... In 2-3 years there would be an Ultegra version...

Looks like they will use piezoelectric sensors from the Danish company Noliac Ceramics: http://www.noliac.com/Default.aspx?ID=7901


They don't specify which type of piezoceramics they will use from Noliac. But it's probably either piezoelectric force sensors and/or piezoelectric accelerometers: http://www.noliac.com/Default.aspx?ID=7778


Technology: Axial and bending piezoelectric sensors: http://www.noliac.com/Default.aspx?ID=15

http://www.manufacturingtalk.com/news/hbm/hbm172.html

Fortunately new powermeter companies have a great track record. Oh wait. . .

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