Bicycle with oddly shaped wheels

Weird-Bike Guan Baihua of China made this nifty bike with a rounded triangular wheel and a rounded pentagonal wheel.

(Here's a video of a trike with square wheels.)


  1. Looks like the wheels are based on Reuleaux polygons.

    But my understanding is that you’ll get a smooth ride only if the axles are mounted eccentrically, and also has some backwards and forwards play, which may be the purpose of the rollers, but I can’t tell, and might be way off the mark. I would like, nay, NEED to see a video of this in action!

  2. ouch is right! i suppose maybe he didn’t have a way to cut round pieces so he cut polygons and shaved the edges? i mean, if that were the case, why not just keep cutting the corners til he at least got a twenty sided piece. Oh, wait, i know! he wanted to get on boinbgboing!

  3. Finally a bike that doesn’t need a pothole to drive its seat up my butt. 18 months well spent.

    #1, if someone rode this enough to bive themselves a bad back… Well lets just say that seems unlikely.

  4. Note that these shapes are constant width curves. like the UK 50p, and a few other coins around the world I expect. (coins have to be a constant width to work in vending machines).

    Note also that the design of the frame exploits, if that’s the right word, this aspect of the wheels, and the weight of the rider is suspended (on those rollers) on the upper rim, i.e. the top of the wheel. Additional mechanisms allow the hub to float with respect to the rest of the frame.

  5. Looks to me like the bike frame is actually riding on rollers at the top of the wheels — under the the olympic logo and the back luggage rack. It should have a fairly smooth ride, since those shapes are always the same height.

  6. @ #1: Forget about the chiropractor, that guy’s gonna need a good urologist to reconstruct his shattered testicles.

  7. My money is on this being a perfectly smooth ride. Both wheels appear to measure the same height base to top at any orientation. The bike rides on the top of each wheel, rather than from a fixed axle point. Fantastic!

  8. I remember reading an SF story long ago about some folks who needed to move a heavy engine across some distance, but were stranded on a planet that had religious prohibitions against the use of circles. They constructed rollers based on the Reuleaux triangle, which make great rollers, but not so great wheels.

  9. A Times article today by Marcus du Sautoy discusses this bike. [Who he? – Ed][He a maths prof who in October 2008 took over from Richard Dawkins as Simonyi Professor for the Public Understanding of Science at Oxford].

    “He believes that people will be drawn to the bike because it requires more work to cycle and therefore will provide more exercise for the cyclist than a conventional bike.

    “Those who have tried it have been surprised at how smooth the ride is.

    “That is because the edges of the pentagonal and triangular wheels are not perfectly straight. The sides of the shapes bulge outwards in such a way that the wheels share an important feature with the circle: the diameter across the shapes is the same which ever way that you measure it.”

    Someone in his comments said that to exercise more you could ride a normal bike for longer.

  10. Surely, nobody would build that without creating reduction geared hubs to make it roll smooth?

  11. So this is art, right? Doing something so incredibly wrong it’s clear you’re well aware how to do it right? Challenging our button-down rat-race plastic reality in the Cult of Newton? Resisting the oppressive tyranny of the circle?

    Sometimes there’s a fine line between art and trolling.

  12. @#6: Wait a second, you sit on your testicles while you ride a bike? You’re doing it wrong!

  13. Wild Wacky Action Bike! The bike that’s hard to ride!
    Goin’ to try to ride all day long, but I’m goin’ to fail ’cause it’s Wild Wacky Action Bike!Can’t ride it! Can’t ride it! Wild Wacky Action Bike!

  14. @#6: Wait a second, you sit on your testicles while you ride a bike? You’re doing it wrong!

    Well whose testicles SHOULD I be sitting on?

  15. @#10; I remember the story as well (I think it was a novel??) Anybody remember the name/author?

  16. Why do people think it’s clever to say “That’s dumb, it would be bumpy”? Would that be clever even if it were true? The whole point is that it isn’t bumpy. It’s a smooth ride. As a fan of both bicycle-hacking and geometry, this is officially wicked cool.

  17. If you want to use more energy than riding a normal bike, you could:

    -Ride faster.
    -Ride longer.
    -Pick a hillier or rougher route.
    -Carry more weight.
    -Use under-inflated tires.
    -Drag a small parachute.

  18. @13 Lobster:

    So this is art, right? Doing something so incredibly wrong it’s clear you’re well aware how to do it right? Challenging our button-down rat-race plastic reality in the Cult of Newton? Resisting the oppressive tyranny of the circle? Sometimes there’s a fine line between art and trolling.

    Hmmm… Or sometimes art it challenging your preconceptions about what is “wrong” and what isn’t. I assume by now you have read all the comments describing why this would actually provide a completely smooth ride after all?

  19. Triangle wheel better than pentagonal wheel; eliminates 2 bumps per revolution. Marketing copy = “40% less bumpy than the 5-sided wheel!”

  20. thanks to people for pointing out that it’s supposed to be a smooth ride, which i wouldn’t have seen without help.

    let me point out that the gear ratio is nearly 1:1. Which means you have to spin these these pedals crazy fast to go anywhere at all. The whole thing in motion must look like Fred Flintstone.

  21. Alright, I see the rollers. I understand that if the seat and frame and handlebars and everything else was attached to them this would provide a smooth ride.

    However it also seems like the bike frame is attached the centre of the wheel. The front one looks like it has some kind of little bit in between the thing that holds the wheel onto the bike and the roller, so this may act as suspension but the back bit looks (from the badly angled photos) like it’s just attached straight on.

    I’m willing to be proven wrong here if someone can show me different photos or a video. To me it looks like you’re in for a bumpy ride rollers or no rollers until you put some kind of suspension in place (which would further decrease the efficiency [which seems to be the point?]).

  22. I remember being awed when I first saw this principle in action. I was rather young and it was fairly long ago.

    Oh, Don Hebert, we need more wizards like you.

  23. @ITSUMISHI: The bike has no seat stays (which would run from the seat to the rear axle), so I deduce the chain stays are hinged at the bottom bracket, allowing the rear wheel to move up and down relative to the frame. That’s how suspension mountain bikes do it. If they are not, the rear wheel will jam against the rollers on top and not turn at all. Looking at their construction, the wheels are obviously the result of some very detailed engineering to get the curvature of the sides exact. That shape appears to be precisely the shape that would be demanded geometrically in order to produce a smooth ride if the bike does indeed ride on the top of the wheel via the rollers. (each side is a radial curve centered on the corner opposite)
    So while I would dearly love to see video, I am entirely confident in my deductions about how the bike functions. It’s the only way it makes sense (odd sense though it may be), and there is no way someone put in the crazy amount of work this bike would require for something that looks like it would provide a smooth ride in a weird way, but actually doesn’t function at all. It must provide a smooth ride in the weird way it appears to.

  24. Ooh, I get it. When the pointy, longer end of the wheel is down, the rounded, shorter end is up. You never have a point where the distance between the ground and the top of the wheel is different, thus they bike doesn’t go up and down and the ride is smooth. Brilliant!

  25. So what you’re saying is that in this photo the bit that attaches the wheel to the frame has a hinge between the two parts? Again the angles in the shot are terrible so it’s hard to tell.

    The first shot also has his foot in the way, the second has the pedal part covering it up and the 4th shot doesn’t show the back wheel in the slightest.

    Someone needs to provide more photos to make this shit clearer!

  26. …smooth ride…

    It has no tires. It is not a smooth ride unless you ride it indoors.

    Also, why? As far as I can see these are the features of this bike relative to a normal one:

    – It can’t use tires, so it is uncomfortable to ride

    – It has a gear ratio of 1:1, so it is slow and hard to ride

    – It has more moving parts, so it breaks more often and is harder to fix

    – It rides on rollers on top of the wheels, so if the wheels become the slightest bit skewed you can’t use it until they are replaced.

  27. Since several people have asked about an SF story using this same idea:

    “The Three-Cornered Wheel” by Poul Anderson, 1963.

    (I can’t believe that with all the trivia-crammed brains among Boing Boing readers, I’m the first person to post this info.)

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