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Fluent wheel may not be shocking, but it is shock-absorbing

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May 7, 2014

SoftWheel's Fluent wheel replaces spokes with shocks

SoftWheel's Fluent wheel replaces spokes with shocks

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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.

The shocks remain rigid when going over smooth surfaces, but compress when the wheel takes...

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?

Source: SoftWheel via Wired

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
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16 Comments

Amazing.

Julie Long
7th May, 2014 @ 03:46 pm PDT

It's interesting how inventions spark at around the same time. Loopwheels and ShockWheel are also pretty recent. This idea would not have made sense back when bicycles still used rim brakes but tis possible with disk brakes mounted on the hub.

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.

Daishi
7th May, 2014 @ 07:53 pm PDT

Good point there Daishi,

Also there is another issue that will pop up during taking a sharp turn.

The banking forces will try to induce axial force trying to incline the wheel.But nevertheless a beautiful idea,does have potential.

SumoDes
8th May, 2014 @ 12:13 am PDT

SumoDes makes a valid point when they say that side forces will present a problem in keeping the wheel rotating in the same plane as the bike frame. This will become more pronounced as the suspension system loosens with wear.

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.

Mel Tisdale
8th May, 2014 @ 01:59 am PDT

This idea is completely retarded.

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.

hawkinspeter
8th May, 2014 @ 03:58 am PDT

these have been ''invented'' over and over again for at least 100 years.

expensive

weak

heavy

energy-wasting

no road bike needs shocks, period

wle

wle
8th May, 2014 @ 08:52 am PDT

SumoDes and Mel -- in normal operation, the wheels on a two-wheeler (unless it uses gyroscopic stabilization) don't experience much sideways force. There's a little bit when entering and exiting a turn, but during most of the turn, the bike's lean exactly compensates for its lateral acceleration. The force on the wheel is strictly radial. If this were not so, the bike would fall over!

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.

SLB
8th May, 2014 @ 09:00 am PDT

Looks like another case of a solution looking for a problem.......

Michael Logue
8th May, 2014 @ 09:05 am PDT

Bound to be a little loopy after loosening up but a nice design nonetheless. Maybe best on small diameter or slower moving wheels where torsional play and centripedal forces won't cause a sort of self-steering phenomenon.

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.

Mirmillion
8th May, 2014 @ 09:37 am PDT

I wonder about the distance between the hub and the wheel, and what forces may be applied to the shocks. Longer distance equals greater forces. Loopwheels are 20" and made with folding bikes in mind. On the video the Softwheel doesn't look much larger so maybe it won't be an issue. Taller Loopwheels are a possiblilty, and Sam Pearce said he might have something new in 2014. I would favor the Loopwheels based on simplicity.

Bruce H. Anderson
8th May, 2014 @ 12:38 pm PDT

Fine on a wheel chair but lousy idea on a bicycle. Imagine coming down hill on a bridge with a high angle of decline. Obviously as speed built there would be a huge problem with an axle not in the center of a wheel. I would expect an epic, bone shattering vibration because the axle would not be centered in the wheel.

Jim Sadler
8th May, 2014 @ 07:17 pm PDT

My money is on Loopwheels for now. :)

Where I do see the potential for this is by incorporating a small amount of sag (as do the loops) and combine that continually oscillating motion as the wheel rotates with high speed linear actuators in the shocks to reinvent our notions of what a hub motor looks like.

Mike J Singleton
9th May, 2014 @ 05:57 am PDT

SLB,

.

Lateral stiffness is very important for bicycle wheels because there are large lateral stresses during normal competition oriented operation.

.

The thing that you are missing in your analysis is that it is often advantageous for the rider to have their mass not centered over the frame.

Check out some pictures of riders who have had to leave the saddle pedaling up steep inclines and you will see there is a significant about of lateral load on the wheels.

Also note that riders will keep the bike more upright in certain turns, while leaning their body inboard, but pushing the outside handlebar. This type of cornering allows you the possibility of recovering/staying on your bike if traction should give way, whereas if you are centered over your frame and leaning inline with your frame, when traction gives way you are going to hit the dirt/pavement.

.

If you still have doubts, look at the differences in rear wheel builds on decent custom built wheels. Notice how the right side must compensate for the decrease in dish, sometimes having twice as many spokes, but more commonly resorting to three-cross while the left side can be radially spoked. If lateral loads were as light as you say, it wouldn't matter, they could just lace up a single row straight down the middle of the hub/rim...but they don't even do that on walmart bikes.

BGriffin
9th May, 2014 @ 11:16 pm PDT

Stupid.

The list by wle is spot on except the for the bit about road bikes not needing suspension in that not all roads are made equal.

The video one SlowWheels, sorry SoftWheels, is marketing BS and it is pretty telling that they are not showing one thing that really calls for suspension - notice how they only drive down a curb for instance and that they aren't exactly running the smallest of tires.

If one needs to make a folding bike more comfy I'd recommend getting a suspension seat post. Cheaper, lighter and not a component where absolute precision is critical.

BZD
11th May, 2014 @ 02:39 am PDT

Can this wheel run in reverse without making a high torque transition at the hub? Wheelchairs do back-up, bicycles not so much.

Steve Springer
12th May, 2014 @ 07:53 am PDT

Definitely a bad idea for a bike tire.

I do have an ME degree, but the folks prior have made as good of comments as any engineer would make and I agree with them. I would like to add one key point of "badness" that hasn't been mentioned.

Any bike suspension system has to have a small amount a sag when the rider sits on the bike. This means when any of the three shock absorbers are on the lower half of the wheel they will be compressed and when they are on the upper half of the wheel they will be extended. Shock absorbers, by definition, absorb energy as they extend and contract. So, with every revolution of the wheel each shock absorber will go through a contract-extend cycle and absorb energy, which will have to come from the cyclist. This makes the wheels innefficient. The better they get at absorbing shock, the more innefficient they will be.

Mistro
14th May, 2014 @ 01:16 pm PDT
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