Bike Anti-Porn - When Things Go Wrong

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  • shame.

  • ^ noooooooooooo

  • So what is that Donhou actually for, assuming it's not just a trolling exercise? Some kind of motor-paced road riding?

  • 100mph attempt.

  • ...by someone who's not consulting any previous high-speed cycling record holders, aerodynamicists or engineers?

  • No. By someone that thinks that if the other people weren't able to do it, why bother copying them. Think outside the box.

  • Still ugly though.

  • No. By someone that thinks that if the other people weren't able to do it, why bother copying them. Think outside the box.

    er?

  • ...by someone who's not consulting any previous high-speed cycling record holders, aerodynamicists or engineers?

    You don't need a bike aerodynamicist to ride at 100mph+ behind a screen, if you design the screen right your drag should be slightly negative.

  • These things are hilarious, this thread brightened up my day.

  • is that what you wished to say?

    Wanted or meant. Not wished.

    #youstartedit

    if you design the screen right your drag should be slightly negative.

    You can design a screen that creates thrust?

  • dont ask, please

  • You can design a screen that creates thrust?

    Yes, you just need to create a pressure gradient, from atmospheric in the clean air well behind the pace car to below atmospheric immediately behind the fairing. In fact, you can do it with just a barn door, as you'll see if you watch what happens to leaves behind trucks - they get picked up from the ground (where they are stationary) and move along the road some before they get dropped. The trick is to maximise the thrust without destabilising the cyclist with the wake vortex.

  • So tester, how important is an aerodynamic bike/position when riding behind a screen? I'm ignorant about aerodynamics but my common sense tells me aeroness isn't as important behind a screen, but then you're not in a vacuum so you're still cutting through air. How does it work?

  • I'd say it's more riding position that aero.

    Think how much harder you can push when down in deep drops.

  • If you're effectively in a permanent net tail wind, drag coefficient should be raised as high as possible to maximise thrust. A spinnaker would be good :-) Position on a paced speed record attempt is about maximising power and stability, you don't have to worry about the aeros.

  • ^I covered this a while ago in the any questions answered thread.

  • Of course you want to be in a position that allows you to push hard but my question was in regard to the "aero" and "deeper rims" remarks.

    So let me get this straight: the screen generates suction* and the more aerodynamic your bike is, the less this suction* is going to pull you forward. So you would ideally want some kind of sail to benefit from that force as much as possible?

    *I'm sure this term is totally inaccurate in this context but a lack of proficiency in both physics and the English language prevent me from using the correct terminology.

  • Bear in mind that since the air is moving past you from rear to front, your aero calculations need to based on going backwards :-) The amount of thrust is modest (but essential - it wouldn't be possible to do 160mph on motorbike tyres on salt without some help, the rolling resistance sucks up more power than a cyclist can produce). You're probably looking at a CdA > 0.5m² for Rompelberg, adding a worthwhile amount more could be dodgy, because you also have to consider what happens when you pull out of the wake to slow down at the end of a run.

  • Is the photo angle deceptive, or has that been crashed at some point in its life?

  • think it's the angle...

  • shame.

    anyone got a different link? I cant see that, 403 error

  • anyone got a different link? I cant see that, 403 error

    The server must have you on its naughty list


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    • IMG_4743.jpg
  • ^it's not really worth seeing

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Bike Anti-Porn - When Things Go Wrong

Posted by Avatar for flickwg @flickwg

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