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October 1, 2009

Pedal power

Filed under: Tech Corner — mtbguru @ 7:51 am

A power sensor has always been on my gadget wish list, as a bona fide bike geek should. However, the prohibitive cost of such things and their non-portability has always kept it in quarantine there. Portability may not matter to some but it does a lot to me as I’d love to experiment with singlespeed vs geared, 26 vs 29, road vs mtb etc -and swapping wheels or crankset doesn’t really work here. Of course, the main requirements are accuracy and consistency – this means so far I’ve been stuck with the – non-portable – crank or hub option. I could give the iBike the benefit of the doubt (a device that basically measures wind speed and inclination and hence the power demand, in order to estimate the power put in), but it just doesn’t cut it for me (it may be great in conjunction with a second power sensor on the bike though).

What would work well for me is a sensor that can be either mounted (a) in the shoe (b) on the cleat or (c) in the pedal. And which produces an accurate and consistent signal, of course. I’ve been thinking about this for a long time and was about to embed some piezoresistors in a shoe or cleat myself, but it now seems a very promising effort is underway – and close to market. In fact, a number of such approaches have been tried out or are being developed; the late Microsport Technologies tried a sensor integrated in a shoe, the Brimm Brothers are working on a cleat sensor, but the Metrigear Vector, presented at the latest Interbike, looks now to be the first one to launch. It seems to be based on silicon piezoresistors (which I always thought would be better than traditional strain gauges, since they’re more sensitive and you can more easily measure the different components of the force vector), in conjunction with an accelerometer to measure cadence/crank position (the latter is an absolute requirement for pedal/cleat/shoe based sensors), and is integrated in the spindle of the pedals. Bikes and MEMS, right in my backyard!

Metrigear is also a local (to me) startup, and led by a guy that climbs Kennedy in 30 minutes flat – though he used a crossbike ; ) – so they must be serious about their cycling! The device is ANT+ compatible, so it will work with e.g. a Garmin 705 as head unit, it will come initially as a modified set of Speedplay pedals (mainly for road) but is promised to become available in different types later. Dan Connelly (from low key hillclimb fame) is doing a nice job in discussing the device in more depth and there is lots of chatter and talk about this on the Wattage Google/usenet group. There are still many questions, about the battery, durability, sealing, signal processing and availability etc but I’m for sure hoping this works as well as advertized!

One Response to “Pedal power”

  1. Californication » Blog Archive » Vermogen Says:

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