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Author Topic: IQ² power meter for bicycles  (Read 3252 times)

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Offline Gilatabar

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IQ² power meter for bicycles
« on: April 02, 2018, 05:44:00 pm »
Hi all!

Long time follower of the Youtube channel, but first time on here.

I came across something today about bicycle power meters and it made me wonder if that thing would actually work (I'm thinking not). Let's ignore the additional length it gives to the pedal axles. :


Most power meters are either in the wheels, measuring the tortional force between the chain and the rims/tires, or are in the cranksets, measuring the strain on the spider holding the chainrings. Garmin and other brands are also making some in pedal forms, and I'm guessing they're measuring the deflection of the pedal axle. But this "new, revolutionary design" seems off. Would their strain gage actually measure anything?


Thanks!
 

Offline BrianHG

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  • Country: ca
Re: IQ² power meter for bicycles
« Reply #1 on: April 02, 2018, 07:50:12 pm »
The units inbetween the pedals and crank are load cells, or strain gauges and are very accurate if done right, that is if your call 1.5% error accurate for the usually 1k$ professional pedals.  Also, better check if the units are temperature compensated.  Strain gauges drift with temperature and the better pedals have compensation and specify their opperating temperature range.  This device, though not too clearly shown in the ad, is a strain gauge inbetween the pedal and the crank.  They also look so flimsy and weak needing to fit and be small inbetween your existing pedal and crank, that, if you pedal at low RPM and high torque, (My typically cadence is 17-35, but in highest gear going uphill indefinitely), these devices look like they will peak their readings and snap like I have broken many normal pedals and their bearings in the past.  If you pedal at the standard cadence range of >80, then they should be fine as this will be a more normal torque.

1. Before buying, search for it's sample speed and torque measuring error compared to other dedicated power meters like power-tap pedals which can measure and log torque both on the down stroke and up stroke on each pedal.  Check for error margins and which regulatory firm has validated these devices.  Example:
http://road.cc/content/review/171512-powertap-p1-pedals
http://road.cc/content/review/232788-favero-assioma-duo-power-meter-pedals
http://road.cc/content/review/235867-garmin-vector-3-double-sided-power-meter

You should also be asking not only their % accuracy over the life time of the pedals and unit to unit, get the sample rate as 100 is considered a minimum today.  The high end units sample 256 times a second as they need to capture the snap torque every time you shift your weight.  If none of this information is made available, then you know something hasn't been done to any quality control standards.
Prices have dropped significantly since the add links I posted above.  Also, search on ebay for used meters if you want a better price.
The PowerTap P1 is a good cross between price and quality.
« Last Edit: April 02, 2018, 08:03:09 pm by BrianHG »
 


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