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Thread: Carbon Fiber Racing Wheelchair

  1. #21
    Black Alloy

    No offense meant by my previous comment. I think what you are doing with Carbon is really cool. I look forward to seeing what you come up with in the future. There is still a lot of potential with composite materials that has not been explored by wheelchair manufacturers.

  2. #22
    Quote Originally Posted by nonoise View Post
    Is that a footrest? I've not seen one of those before on a racer.
    Quote Originally Posted by Black Alloy View Post
    Yeah, it's a footrest. I think the kneeling position is used almost exclusively these days.
    Quote Originally Posted by crash86 View Post
    I have never used a Racing chair but that actually looks fun. With my feeling I could never have my legs tucked up under me. Nice work.
    Quote Originally Posted by jheath View Post
    A lot of amputees and triathletes still use footrests.
    As Tanni Grey-Thompson says, kneeling is the "aspirational position", but plenty of people who are not necessarily elite racers are using the conventional (feet forward) position. I also know racers who used to kneel but who have switched to avoid pressure sores and damage to the knee joints.

  3. #23
    Quote Originally Posted by totoL1 View Post
    Normaly racer guys have two pairs of wheels, if the race is in a windy day they didn`t use disc wheels.
    In handbikes too, in a windy day a disc wheel could make you lost the race, so it`s better take with you an extra pair of wheels for if where you go is windy.
    It's my opinion that discs are the fastest wheel option in any conditions (for handcycles). In wind, you can definitely feel it pushing on you, but I don't believe it causes one to lose much speed. Much like the "skirts" and air dams that you see on 18-wheelers, it prevents "dirty air" around your bike. Essentially, the disc wheels can act as a fairing for the rest of the bike. Plus, the aerodynamic profile (looking from the front) for a disc wheel is very small. They definitely cut the wind as one would expect. On a bicycle, a disc is usually used on the rear. There, it is tucked back behind the front wheel, the frame, and the rider. On a handcycle, the discs are out there in the open. I think that discs are a greater advantage for handcycles than they are for bicycles. Their lateral stiffness and push-friendliness makes them the best choice for racing chairs, too. But damned if they aren't expensive!

  4. #24
    Quote Originally Posted by The_Wheel_Life View Post
    It's my opinion that discs are the fastest wheel option in any conditions (for handcycles). In wind, you can definitely feel it pushing on you, but I don't believe it causes one to lose much speed. Much like the "skirts" and air dams that you see on 18-wheelers, it prevents "dirty air" around your bike. Essentially, the disc wheels can act as a fairing for the rest of the bike. Plus, the aerodynamic profile (looking from the front) for a disc wheel is very small. They definitely cut the wind as one would expect. On a bicycle, a disc is usually used on the rear. There, it is tucked back behind the front wheel, the frame, and the rider. On a handcycle, the discs are out there in the open. I think that discs are a greater advantage for handcycles than they are for bicycles. Their lateral stiffness and push-friendliness makes them the best choice for racing chairs, too. But damned if they aren't expensive!
    Lateral wind.

  5. #25
    Great information and thanks to all for contributing.

    On this particular chair I chose feet forward seating for the easier transfer in and out of the chair. The project is a test platform for a number of variables and not initially set up for competition. I did provision for a kneeling position seat assembly that will be tested at some point.

    The disk wheels IMO were the best choice for the simple reason of handrim dynamics. Transferring push stroke energy from the handrim to the wheel rim through spokes would likely result in unwanted maintenance issues.

    jheath,

    no offense taken. There are many fine wheelchair builders out there. We're just trying to expand the options available.

  6. #26
    http://www.youtube.com/watch?v=Cr1zC60ytHo

    This has probably been posted before but may give you a few different ideas for the shape of your carbon racer. Towards the end Jeff spins it around and you can see how if differs from the traditional racers.

  7. #27
    Discs are not the most aerodynamically efficient wheel - they're only better than tri-spokes and some deep dish spoked wheels in a headwind with =/- 5 degrees of yaw - in any other wind condition, they create more drag than a lot of other wheels. Steve Hed did a lot of research on this, which is why his bike teams often ran tri-spokes front and back in TT situations.

    Discs are generally heavier, and it's debatable as to whether or not they're stiffer. I had some of my best races on tri-spokes.

    That carbon chair in the video was one of the stiffest and most aerodynamic chairs I built, and like Tman observes, we used the properties of the carbon to go away from the traditional shape and configuration of the racing chairs that are currently in the market.

    The chair in the video is 14 pounds, all in, with disc wheels that had an extra layer of s-glass on the outer skin because of how hard I hit. With my track setup (more minimalist steering and lighter wheels) it was under 13.

    Making something out of carbon that's exactly the same as a tubular metal construction isn't making the most of the material. With respect, copying a design and making it out of fancy material isn't really pushing the envelope very much - most of the aluminum chairs that are available commercially are in around 16-17 pounds anyway.

    Your everyday chair looks almost exactly like a Marvel without suspension, and your racing chair is a copy/paste of a Top End or a Draft - I'd like to see how either of them perform in a fatigue test.

    If you don't fatigue test your chairs to RESNA, please do not ever let anyone else use one in a real-world situation - an untested everyday chair that fails could hurt someone, an untested racing chair that fails could do worse.

  8. #28
    Senior Member DaleB's Avatar
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    Quote Originally Posted by JeffAdams View Post

    Your everyday chair looks almost exactly like a Marvel without suspension.


    I'm not seeing the resemblance. I think you may be thinking of the Carbon Black. Different company, iirc.
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  9. #29
    Sorry then - it looks just like an Invacare A4 or Eliminator, not a Marvel.

    Same comment. If it's not tested, please don't sell it.
    Last edited by JeffAdams; 06-14-2013 at 05:32 AM.

  10. #30
    Looks like a nice racing chair, myself I've never really had a interest in racing chairs because of the repetitive shoulder motion is not very healthy for the shoulder joints, that's why I ride a handcycle instead. I've got a pair of Corimas on the rear of my Freedom Ryder and a Zipp 404 on the front, I really like em. I gotta admit though, racing chairs can be fast, there was a guy in one in the recent Vermont City Marathon and I was just behind him for the first 5 miles or so and then he pulled away and took me on the hills and never looked back, I was surprised.
    "Life is about how you
    respond to not only the
    challenges you're dealt but
    the challenges you seek...If
    you have no goals, no
    mountains to climb, your
    soul dies".~Liz Fordred

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