Powertap for wheelchair ?

Discussion in 'Power Training' started by SolarEnergy, Sep 20, 2006.

  1. SolarEnergy

    SolarEnergy New Member

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    Did I dream or did I really see the SL's typical yellow display mounted on a wheelchair ? (A competitive wheelchair)
     
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  2. freewind

    freewind New Member

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    So has anyone seen or heard of a power meter used on a wheelchair?

    Any idea which power meter would be suitable for a sports wheelchair?

    Cheers!
     
  3. grahamspringett

    grahamspringett New Member

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    Don't forget the CPU is also a wireless speedo, which is probably what the wheelchair user was using it for.

    Current power meters are designed to measure power through the transmission so none would be suitable for a wheelchair. That would need some kind of strain gauge on the wheel grips.

    That said, power through the arms would probably be a lot less than the legs, plus there's no consistent flow of torque, more like regular pulses plus lots of freewheeling.
     
  4. Alex Simmons

    Alex Simmons Member

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    A PT could still work but you'd have to set it up with a fixed gear converter and have the drive wheel attached to the "cog" of the PT, rather than directly to the wheel. Also it could only be set up for the right hand side wheel.
     
  5. SolarEnergy

    SolarEnergy New Member

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    So maybe I didn't dream after all :)

    I'd encourage any wheel chair racer to at least drop an email to Saris.

    I sometimes train along with Chantal Petitclerc (5 golds in Beijing), I'll ask her if she's ever heard about something and report back to this thread if I got anything interesting to report.
     
  6. freewind

    freewind New Member

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    Thanks everyone for the input!

    Actually, I am sure it would work on racing wheelchairs, but i was thinking of other wheelchair sports like rugby and basketball where most of them do not have a separate hand-rim...

    Alex, would you know what's the best way to get a used PT in Melbourne?

    SolarEnergy, look forward to your reports! :)
     
  7. Dietmar

    Dietmar New Member

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    No, a PowerTap would be entirely unsuitable for measuring power on a wheelchair, simply because the torque at the hub is always exactly zero (well, except for a little bit of friction, which is minuscule). Short answer: Forget it.

    P.S.: Sorry, I overlooked this post:
    Yes, that would work, in principle, but there's quite a few caveats. The cog that the drive wheel would have to be attached to would be subject to significant non-axial moments, which might cause a noticeable measurement error. The fact that you are measuring torque on one side only is problematic, too, whenever the driver is not going straight. Plus, making this contraption work properly is not so easy...
     
  8. Alex Simmons

    Alex Simmons Member

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    flea-Bay I suppose.

    Check with Richard Sawris at wheelbuilder.com about fixed gear conversions for Powertaps and whether you still need an old style (no longer sold/serviced) PT model or if you can use an SL model. Wireless would probably be better for this if Richard has a fixie converter to suit those hubs but wireless is more expensive. Just not sure on a wheelchair where you'd mount the pickup (I don't have a racing chair to look at).

    rigging up a drive wheel to a "cog" that can screw onto the PT could be done by a local machinist/engineering shop. I have fortunately landed myself with an excellent local guy that is beginning to fabricate some special items for my prosthetic - a cleat attachment adapter. His main game is chainrings and cogs and if you go down that path and can't get something suitable made, let me know. he had made custom frames for many years but no longer. I've had several frames from him over the past dozen or so years. Still ride one of them, steel, and a favourite training steed.

    Sure there might be some issues on whether it would accurately report power and the differences between left/right won't be known but if you can get the parts for not too much and are willing to experiment, I think it's worth a shot and if it works OK it could bring many of the benefits of training with power to wheelchair athletes.

    If it doesn't work, well you can always sell the PT.
     
  9. H46Driver

    H46Driver New Member

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    Was it a standard chair or a hand bike?
     
  10. SolarEnergy

    SolarEnergy New Member

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    Unfortunately, it's really been a while. It wasn't a bike this is for sure, but I can recall the exact design of the chair.
     
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