After breaking his pelvis six years ago, Israeli farmer Gilad Wolf invented a new suspension system for wheelchairs that incorporates shock absorbers into the wheels. He's now a board member of SoftWheel, a Tel Aviv-based company that refined his creation into a product known as the Acrobat wheel. Although the Acrobat was unveiled in 2012, this year SoftWheel announced something new – a bicycle wheel that uses the same technology, known as the Fluent wheel.
Both the Acrobat and Fluent work in exactly the same fashion.
Three cylindrical shock absorbers radiate out from the hub to the rim, taking the place of spokes. They remain rigid when going over smooth surfaces, but compress when the wheel takes particularly big hits. This means that the hub temporarily moves downward within the wheel, that movement absorbing the energy that would otherwise be transmitted through to the rider.
Both wheels also differ from many regular suspension systems in that they react not only to obstacles that are passing directly beneath the bike, but also to those that it's meeting head-on, such as curbs.
According to a report in Wired, SoftWheel plans to start selling the Acrobat wheel in the fourth quarter of this year, priced at approximately US$2,000 a pair. There's currently no word on availability of the Fluent, although the company states that it will be compatible with a wide variety of existing bikes. It can be seen in use in the video below.
Many readers will no doubt be reminded of Loopwheels, a similar product that uses three looped carbon composite springs instead of cylinder-and-stanchion-type shocks. All you mechanical engineers out there, please weigh in with your thoughts – which system ought to work better?
I'm not a mechanical engineer but the biggest problem I see is that the outer rim must be made much more rigid to retain its shape without the support of rigid spokes or mags inside it. Even after that is factored if one of these shocks had just a slight difference in tension it would feel like driving on a bent rim because the hub wouldn't be purely centered. This would cause the effect of "high spots" and "low spots" almost like using a slightly oval wheel that would absorb some momentum.
I think the net result is probably heavier than fork shocks with a lot more cost. The only real benefit I see is that it has potential to shock absorb in multiple directions but unless you smash into a lot of curbs and stuff vertical shock absorption seems fine.
I see it as a gimmick that people might notice and point at as cool/different but I don't see it as an improvement over the existing design.
I am not at all sure that this is a sensible solution to the problem of shock absorption when one reads that it only comes into play "...when the wheel takes particularly big hits." A normal bike suspension operates on all surfaces, from the smooth to the "cor blimey."
Seeing as you are asking for votes, mine goes to the Loopwheels design. It is simple, durable, low/zero maintenance, rigid outside of the designed plane of rotation and, I suspect, a lot cheaper.
When you are driving a wheel from the hub, you need the wheel to be as stiff as possible to transfer that energy to the rim and the tyre and thus propel you. If you try to put any kind of springs or dampening between the hub and the rim, then you are losing energy compressing/decompressing with every single pedal stroke.
So, for only $2000 you can get overly heavy, poorly performing wheels that probably require a lot more maintenance than normal bike wheels. You'd be better off just putting a big cushion on your saddle.
However, this idea can work well on a wheelchair as you are providing the driving power from the rim, so shocks between the rim and the hub won't be a problem. Just don't ever put these on a bike.
\no road bike needs shocks, period\
wle
I agree, though, that the dampers in this design would have to be made to very tight tolerances. The advantage of using dampers over springs is that dampers can have a nonlinear response, where they don't move much at all up to a certain level of force; it's hard to do that with springs. These do seem to be a lot more expensive than the Loopwheels, though.
I'd be happier if this design had used a spiral array of carbon fiber blades which flexed from any angle of impact but also provided protection against side forces due to high lateral rigidity.