Sunday, December 9, 2007

Sprints with the PowerTap

I mentioned some oddities I experienced with the powertap I currently have on the bike I'm riding a few posts ago - ya'know, the whole exact same power readings during a sprint deal.

Here's a a screenshot from the download of yesterday's file where I was doing some sprints:

one thing to note is that when I stopped pedaling, I then glanced at the PT head unit as I was coasting - it kept reading the same value for a bit - and this observation is reflected in the download.
So, this observation would suggest that the PT is doing some unknown filtering in their data acquisition. This could be good, or it could be bad - in the case of short efforts , it appears that it's doing some weird things as it relates to reality.
Not that this sprinting observation really matters in the grand scheme of things (it's been kind of refreshing for the past couple weeks not to give any credence to the flashing numbers on the power display!) - but it is a worthwhile thing to note.
Speaking of power meters - did y'all see the dueling press releases from ergomo/gita this past week?
Guess that is a partial explanation as to why I never got an ergomo to evaluate from the "important folks" at ergomo-usa. Then again, the excuse I continually got was that "there just isn't any availability right now for demo's" - or words to that effect - which from the sounds of the Gita position is a factual statement...
Anyway - I reckon my original thoughts on the ergomo still have some relevance:
-measure one leg and double it and all the doubt that that brings up
-ease of installation
-reliability of "zero-ing" out the unit prior to riding
-measure one leg and double it and all the doubt that that brings up
did I mention "measure one leg and double it and all the doubt that that brings up" ;-)
Seriously, though - I reckon if a gadget helps you ride your bike more intelligently/purpose/reliably then that's a good thing.
I used to keep training logs back in the day where I'd actually write things down - that was a good tool to make sure I was doing what I had set out to do on a given day. Nothing like the satisfaction of writing down HR's and times and distances and RPE's in that journal entry for the day!
Downloading a power meter file can have a similar effect on training, in my experience.

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2 Comments:

Blogger TnA said...

I think something's amiss with your PT. I've never observed that type of thing with mine in sprints. Also, the second sprint in your plot looks like it had a dropout at the end of it since the speed trace goes to zero for one record as well (I'm assuming the blue trace is speed).

Check the batteries in the hub, check your contacts at the head unit, check the spacing to the receiver, make sure you have the latest firmware in your head unit (2.21), etc., etc.

December 13, 2007 5:19 PM  
Blogger kraig said...

What you suggest is a possibility, Tom Anhalt - so, what is your opinion on the topic - blame the user? or blame the tool?

Kinda silly to have "issues" with a gadget (one of which required sending the unit back to the manufacturer - which to their credit they solved quickly) this quickly/often - ya know I've done less than 25 rides on this sucker since the day I acquired it.

Good news, though, is that I received the SRM Cannondale spindle in the mail yesterday from Craig over at www.wiredbike.com ! That means that I might have an SRM online by the end of the weekend. Thanks Tom, for the opportunity to give a shout out to Craig over there on the left coast for his help on this project!

December 13, 2007 8:23 PM  

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