SPORTS POWER METERS

A post from the Brim Blog

News: Blowing our own trumpet

We’ve decided that it’s time to correct our “publicity deficit” by spending some time explaining what we’re doing, and more importantly, what you will be able to do with our power meter. Most of you have heard the fanfare of various new announcements and promises for new power meters over the past 6 months. Some of them have involved very big names, have got lots of publicity, and have generated high expectations. Meanwhile we’ve been in our test labs and at our desks working hard on the technical and commercial development of our cleat-based power meter, and as we read all the claims for what other products will do we thought “ours does that – and more”. So it’s time we made some noise.

The Brim Brothers power meter measures not just power, but also cadence and a big chunk of other details about what’s going on with your feet and your pedals. It measures forces, pedal angles, crank angles and speed of rotation 100 times per second and uses this to calculate torque, power and cadence. The pods on the left and right shoes make these measurements and calculations independently and then communicate directly with each other over the ANT wireless system. One of the pods acts as the master by combining the values and transmitting them to an ANT+ compatible display. It’s all just plug-and-play, with nothing to be configured. The pods automatically decide which of them is the master, so there’s nothing to be configured for that.

If there’s only one pod then it will automatically double its own power measurement (as an estimate of the power on the other pedal) and send that to the ANT+ display. That means that if you use just one pod instead of a pair you will still have a usable power meter. By the way, the pods on each side are identical so it makes no difference which way round you use them. Each pod automatically works out whether it’s on the left or the right shoe. A major design goal in developing the power meter was that it should be easy to own and use, with absolute minimum configuration and calibration (and I’ll talk about calibration in another post soon) so we’ve come up with clever ways for the pods to work out things for themselves.

While the main purpose of the power meter is to send torque, power and cadence data to an ANT+ display, the detailed data stream is extremely interesting to look at. This gives us extra ways to see what’s going on as you pedal. The simplest is to look at how you apply force as the cranks rotate. Theoretically a rider should apply the maximum push-down force as the crank is half way through the down stroke, but we could see in our realtime graphs that our test rider was applying force very late and then continuing in an attempt to stretch the cranks at the bottom. Seems like he might benefit from adjusting his pedaling style a little, particularly by moving the application of force to slightly earlier in the pedal stroke.

Watching these graphs in realtime while cycling on an indoor trainer is quite intriguing. You can see immediately the effect of trying to, for example, apply force earlier in the down stroke. During these tests we had a discussion about the mental drivers and triggers that set the way you apply pedal force, and we went on to discuss how a rider uses the beat of music when training indoors and whether this could be used to improve pedaling efficiency. From observation it was apparent that our test rider pedals such that the music beat occurs just after the crank passes the horizontal position, so we did a short unscientific experiment where he consciously changed so that the beat occurred just before the crank passed the horizontal position. The effect was immediately obvious on the realtime graphs – the point of maximum force moved back in the crank rotation. We didn’t do any experiments to see if this resulted in any measurable improvement in efficiency (how would we quantify that anyway?) but I’m sure there are lots of knowledgeable people out there who will do these experiments as soon as we deliver the technology to them.

There is lots more stuff I want to share with you, but I’ll leave that for another day (hopefully within a week or two). Two things to finish off today. First, we have a 45 second video introducing ourselves. It’s kind of a bland corporate thing so probably only of interest to you if you’ve only just found us (and I swear that’s the last time anyone will get me in front of a video camera). Second, you may notice a blog post here called “The problem with the Kionix KXSD9” that’s password protected. The article is a very technical explanation of a serious problem we had with a component, and is not open for public reading at the moment. If you have a particular interest in the KXSD9 contact me.

18 Responses to “Blowing our own trumpet”

  1. Peter says:

    Why is your previous blog entry “Tech corner : Protected: The problem with the Kionix KXSD9″ password protected so we can’t read it?
    What’s the point of a blog people can’t read?

  2. Victor says:

    Barry

    We are very excited about the powermeter and look forward to testing.
    I see it as an excellent tool for bicycle fitting as well as pedal efficiency training.

    Victor

  3. Eric Abbott says:

    I read your article with interest. In viewing your articles pictures, I was curious as to how the pods mount or attach to your Sidis. As a master’s program student, is your team using DFM/X and concurrent engineering in your design process?

    Keep up the hard work,
    Eric

  4. Matt says:

    The race is clearly on between you guys, the Look/Polar group and the Metrigear/Garmin group.

    There is a legion of people out there just like me, who have thier credit cards in hand ready to spash down for a pedal/cleat based powermeter.

    The sad fact is that the first to the market will be the winner, even if their product isn’t necessarily the best. Anybody remember betamax?

    So, the question on everyone’s lips is: when are you going to market?

  5. David Alyea says:

    I’ve been hemming and hawing over the Quarq S975 power meter setup, and then I see your latest blog entry. I sure wish you guys would hit the market soon! I love the idea. Comparing the Quarq Power Meter to what you’re doing, your methodology is a lot more desirable. Waiting for the blog post announcing the product release!

    David Alyea
    http://www.qbike.com

  6. Chris Cleeland says:

    I see that in the promo video the cleat/pedal system in use is the speedplay zero. Is your device inherently system-specific, i.e., will it have to be adapted and tested for every pedal/cleat system out there?

  7. Jeff Ingham says:

    How about switching shoes I want to be able to go from my road bike to my cross bike with different shoes/pedals.

  8. Derek says:

    Great update, the system sounds fantastic. There should be a market for several systems. Hope you are nearly ready to launch!

  9. Jim says:

    I have multiple bikes (mountain, road, TT, cyclocross) and multiple pairs of shoes (“ride” and “race” for each road/TT and mountain/CX). Am interested in how easy it would be to use this system for all combinations.

  10. Hammertime says:

    Presuming it works well, is available for the desired platforms, and is reasonably priced, there’s only three things which matter: When will it be available? When will it be available? and lastly When will it be available?

    On the other hand, better to not promise anything than to make promises you may not be able to keep.

  11. Rodrigo says:

    Hi. Are you guys measuring pedal forces or crank torque only?

  12. Anthony says:

    If you need any testers in America, please let me know!!
    Can’t wait to see your power meter.

  13. Gerald says:

    Hi Guys
    Great to see an update as I think a few people were starting to doubt you judging by the comments on Boards.ie
    I for one will be waiting cash in hand for the first pod available .
    Great Job .

  14. Barry says:

    So many questions, both here and by email! (and most them are “when?”).

    The answer to the “when?” question at the moment is simply that we’re planning for sometime at the end of this year. I’m very conscious that the history of power meter development is littered with broken deadlines, but that’s the best schedule we can give at the moment.

    Other questions about pedals and switching between shoes will be answered in future blog posts (soon). Stay tuned.

  15. Jason says:

    Well done guys, you’ve come a long way! I am looking forward to seeing your product go to market and hopefully being able to afford to buy it. Only advice I could give is don’t become too attached to your product. You can be credited with investing it but don’t be afraid to let go and sell the patents and information to one of the major bike companies who will be able to develop and market it beyond your capabilities. Not trying to discourage you guys, but this advice was the best piece of wisdom I’ve been given over my lifetime. Best of luck!

  16. Feliciano Ferreira says:

    Hello,

    The ANT+ will be compatible with the Ibike system? Did you already contact them? There is a good opportunity for you, I think. Best of luck, with all the partners…To me its seems the best approach so far.

  17. [...] an Ihrem in den Pedalplatten integriertem System und haben nun endlich mal einige Bilder und weitere Informationen herausgegeben. Konzeptionell unterscheidet es sich somit deutlich von den Polar/Look bzw. Garmin Vector Pedalen, [...]

  18. NapoleonD says:

    Looking forward to seeing what you come up with. I’ve been a powertap user for a coupl eof years now and am getting frustrated with being stuck to one wheel. Quarq and SRM are too pricey and the iBike is all over the shop and can’t be used on the turbo (i.e. useless).
    Come on fellas, keep beavering away :)
    (Oh, and make it cheaper than the others!)

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