Friday, June 28, 2013

Reinventing the wheel?

    To agree with one of the developers' dodgy claims, Shark Wheels really are a revolution in wheel technology. By "revolution," I mean their products tend to revolve around a central axis. Outside of this simple prerequisite for the word "wheel," I can't see much advantage these wobbly-looking things would provide over the 5,500 year old tried and true "circle" models.

Photo: sharkwheel.com


    The skateboarding world is rife with market-minded inventors promoting gimmicky products to children. Every now and then, however, some of these products find their way into mainstream acceptance. Thanks in part to a highly successful kickstarter campaign, one LA-based startup has already begun production on their Shark Wheels, advertised as the SQUARE skateboard wheel that shreds! As a lifelong skateboarder with a physics degree, I found the initial claim suspect. I seem to remember most wheels I've encountered as having a much rounder shape, but one look at the kickstarter page will suggest that these Shark Wheels are squares, circles, cubes and sine waves ALL AT THE SAME TIME.


    Aside from a shaky perception of what a perfect cube is, the video is convincing. The strangely shaped wheel actually rolls! Boardwalk testimonials are positive! The inventor has the same goatee as Tony Stark! Though, of the many claims of superiority attributed to the sine-wave design, few are backed up with convincing evidence. I'll address them one-by-one.

It's a perfect cube
    No, it's not. Very obviously not. Not by a longshot. And contrary to what they say, they don't look like squares from the side. Nine-of-ten pictures show them from a three-quarter angle that gives the illusion of flat sides. Viewing them along the axle, you can easily tell it would contact the road smoothly in a circle. That's the entire reason it rolls.

Screenshot


Shark Wheels are faster
    I don't see any side-to-side races between the shark wheel and a traditional wheel. The speed of the wheels on the board relies almost solely on the quality of the bearing within that wheel, sold separately. The reduced contact area argument applies, but any traditional wheel with straight grooves (picture stacked donuts) would have the same advantage. There's no need for the sine wave here. 

Alternating center of gravity allows for superior high-speed stability, eliminating speed wobble-
    This is stated on the company's website, sharkwheel.com, and is just plain wrong. Speed wobbles, with which most skateboarders are frighteningly familiar, occur at high speeds when your center of gravity begins to oscillate away from the lengthwise axis of the board. If you don't stay low and push your weight forward, the wobbles can worsen until you find your face not-so-gently caressing the pavement. This has nothing to do with the centers of gravity of the wheels themselves, which are fixed in the center and don't alternate

    Furthermore, any extra stability these wheels may provide is probably due to their increased width to accommodate all the extra winding urethane. The same extra wavy width that must slightly hinder aerodynamic properties. 

Phenomenal grip-
    Grip is a mostly a function of how soft the wheel is, usually rated on the durometer scale for skateboarding. Lower durometer wheels are softer and grippier compared to the harder, higher durometer wheels used in street skating. By comparison, Formula 1 cars have wide, soft, smooth wheels because they are proven to grip dry roads best. 

Perfect rain/gravel wheels-
    Perhaps a bit of truth can be extracted here due to the grooves pushing water and sand into the negative space. Though, for rougher surfaces, I'd like to know which direction the grooves are facing at all times so they don't randomly fit into the wrong crack (or coping) and stop me cold. If you're off-roading, there are plenty of inflatable treaded tire wheels available that would do a fine job rolling over wet gravel.

All criticism aside, the custom color combinations and variable durometers are intriguing. I'll give 'em that.

But wait, there's more! From the kickstarter:

We plan on going into every market with a wheel. It is just a matter of time and money. From military vehicles to bicycles to wheelchairs, we want the Shark Wheel to be identified as the only non-circular wheel in existence.

Please watch the video below to see their bike prototype moving very slowly in a straight line. Riding, let alone leaning into a turn on that thing at speed looks dangerous. I can't wait to see what pseudoscience makes it work!


17 comments:

  1. Agreed. No proper demos of any superior performance, and no science to back any of their claims. Glad someone wrote this up.

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  2. You are just slamming them because you did not invent it. They also make racing wheels for bikes. Stop your crying.

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    1. Ignore the physics and just accept the developers' claims because you didn't invent the product? It's this gullible mentality that allows a pseudo-scientific campaign like this to thrive.

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    2. lemme guess you think steel skyscrapers can get damaged by weak fires? check open air kerosene temperature and the critical point of steel.

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    3. Oh wow. What a surprise you immediately bring up 9/11

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  3. Racing wheels for bikes? I don't buy it. Video or it didn't happen.

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  4. http://www.rongeitgey.com/sculp_pages/circlesinewave_b.html

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  5. Great post. I'd really like to see some independent testing, especially with some well-known pros, to get some honest thoughts on them. Every video I've watched is either filmed by the inventor or features their web address at the beginning and/or end, so...yeah, of course it's going to look like the best thing since sliced bread. ;)

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  6. Great post. We linked it to a page for an art-skate-science project we have been running in houston (a theme of it is the power of experiments and testing things out yourself - your post fits that bill).
    https://www.facebook.com/Sk8labHouston

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  7. I stumbled across your posting and as the inventor I know that you are studying this from a very narrow viewpoint and set of data and tests. I normally don't respond to these things because I would just rather people find the answers on their own but here are a few clarifications:

    1. Bike wheels and any wheel that leans is NOT our market and we will not be entering those markets with the standard design for obvious reasons. That said we have a double helix design coming later that would work in those areas but I still hate those markets for our wheel. It is not the right fit.

    2. The wheels as used in the skateboard configuration are significantly faster then a wheel of the SAME overall width and SAME durometer. We put down a smaller footprint during a full revolution and are therefore faster. LOTS of tests showing this in detail will come later. It is simple physics on this point.

    3. The wheel is a perfect CUBE. A SINGLE wheel fits inside a cube FLAT against all 6 sides of the cube. It is ALSO a perfect circle and a perfect sine wave. It is all 3. Don't say it isn't a cube because in 3 dimensional space it most certainly qualifies as a CUBE. The whole concept of it being square looking from the sides is real but the flat planes exist along the 3rd dimensional plane.

    3. The wheels are superb over gravel and rough surfaces compared to a normal wheel. The sine wave pattern moves over rough surfaces MUCH better then a conventional wheel simply because it does not have to steam roller over it all. Again this is simple physics and is easily proven in real world tests and opinions of everyone who tries them.

    4. Speed wobbles - Our SINGLE wheel when spinning gets MORE stable as speed increases with our design. At speed it feel like you are traveling on a wide track like a tank tread, very flat and resistant to movement along the horizontal axis. The gyroscopic effect at the hub is spread very wide and is GREATLY reduced. UCLA showed this effect in a HUB analysis they ran and that we are using for industrial analysis of the wheel.

    4. Grip. Our design with the 3 lips provides a smoother breakaway then a traditional wheel. Our grip numbers are virtually identical to a normal wheel in barrel tests until the wheel loses traction. Once traction is lost on a normal wheel it ices and that is it. Our breaks away in stages and doesn't ice until the very last moment. This is the equivalent of a car with neutral handling to one with snap oversteer. We break away smoothly and controllable. Honestly not sure if it is the lips or the sine wave pattern that makes the effect most pronounced.

    I am eager to get more tests out there to quite the naysayers but we exploded with millions of orders and my life is all about production right now. Appreciate any dialogue you might have in response. I am an open book and know where we have faults and advantages. Bikes suck. Everything else is kid of fair game!

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    1. Though I am skeptical, I'll withhold judgment on the performance claims until I see some unbiased test results. But PLEASE stop saying it is a "perfect cube," because that is ludicrous. "A SINGLE wheel fits inside a cube FLAT against all 6 sides of the cube" is not the definition of a cube. It is the definition of something that fits inside a cube. A hexagon fits perfectly inside a triangle, flat against all sides of the triangle. A hexagon is not a triangle.

      What you have created is a wheel with sine wave treads. It looks cool and it may even have some benefits. Can't that be enough? Why flout 9th-grade geometry along the way?

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  8. It seems like the way the the "tread" makes contact with the surface should help push material into the spaces in between. Shouldn't that help over surfaces where you have patches of sand or gravel?
    I have no idea if this wheel will the awesome, just ok, or a "gimmick". I thought your idea is certainly interesting and worth supporting so I backed your project. I look forward to giving them a try.

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  9. Coming from experience riding a longboard with Gullwings and Dave's Shark Wheel, I can say there is a noticeable difference to riding my stock Sector 9 from the local skate shop. With the Shark Wheel grip is especially there when attempting to power slide, yet extremely smooth when heading full speed over dimpled manhole covers. I didn't have a lot of time with the wheel but did take it through water, rocks and sand, down driveways, sidewalks and launching off curbs. After taking them for a spin I can say I'm thoroughly impressed. I'm no pro boarder but I will say as a skate veteran who loves to surf, I'd trade up my existing wheels for a set of Shark Wheels any day. Tread patterns are essential to dominating various terrain and weather conditions. These wheels work very well at doing that!

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  10. I'm not going to withhold judgement.

    There's zero real physics demonstrated in the videos. No tests. And they are not cubes. The only thing they might do is give you more traction because they have increased area and varied angles for grip. It's vaguely possible that the wheels may be faster on perfectly smooth surfaces due to reduced contact area. Big deal, nobody is trying to shave three tenths of a second off their track time.

    It doesn't hold up to scrutiny. Enjoy your novelty wheels, I hope you feel faster and "grippier." I'd be caught dead buying them.

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  11. "David Patrick" above (October 16, 2013 at 5:15 PM) counts out the six benefits of Shark Wheels as: 1, 2, 3, 3, 4, 4.

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  12. Have any of you actually ridden one? I don't know about physics but I rode one today and it definitely feels faster than my 70mm long board wheels of the same durometer.

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    1. use a higher quality ball bearing between your board and wheel and u have the same effect

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