US company Null Winds Technology is seeking Kickstarter funding for its swivelling Spoke Fins: nylon plastic fairings that are designed to cut spoke drag in both headwinds and crosswinds.
Fairings for your spokes? Uh-huh!
“Optimally streamlined Spoke Fins reduce the spoke drag coefficient by more than 50% in the critical, faster-moving, drag-inducing region located nearest the wheel rim,” says Null Winds Technology. “Since round spokes have relatively high drag coefficients — thereby becoming the major contributor to overall wheel drag — reducing critical spoke drag also reduces total wheel drag. Spoke Fins are also tapered lengthwise to reduce drag principally on the critical uppermost spokes, where wheel drag most retards vehicle propulsion.
That’s not all.
“As the wheel rotates, Spoke Fins automatically adjust their streamlined alignment for the changing orientation of the effective wind vector impinging on the spoke. Spoke Fins swivel to reduce pedalling effort under any wind condition, becoming especially effective on typical recreational bicycles with higher spoke-counts.”
So, that’s it in a nutshell. There are enough wheels about with bladed spokes; why not just go for a set of those?
“Bicycle racers know that bladed aero-spokes quickly become ineffective in crosswinds,” says Null Winds Technology. “Spoke drag quickly increases when impinging winds are directed crosswise across the flat blades. In a direct headwind, the common round spoke develops more wind drag than does a bladed spoke. However, against a crosswind the bladed spoke can actually produce much more drag than a round spoke.”
Null Winds Technology doesn’t present any wind tunnel data relating to Spoke Fin-equipped wheels. To be fair, that’s understandable because wind tunnel time is very expensive.
The Spoke Fins do, though, seem to fall foul of the UCI’s technical regulations. Article 1.3.011 says, “Any device, added or blended into the structure, that [is] destined to decrease resistance to air penetration or artificially to accelerate propulsion, such as a protective screen, fuselage form of fairing or the like, shall be prohibited.”
Null Winds Technology are seeking US$30,450 (£19,908) to buy the eight-cavity polished steel injection mould it needs to produce Spoke Fins.
Assuming the target is met, a set of Spoke Fins will cost you from US$20 through Kickstarter, although they’ll ship to the US only via this campaign.
For more info go to Kickstarter or www.nullwinds.com
41 thoughts on “Introducing Spoke Fins: swivelling fairings for your spokes”
spokey dokeys
spokey dokeys
mylesrants wrote:spokey
Have had a makeover……..
This is an idea that has
This is an idea that has popped into my mind a lot recently, but I’d need to see wind tunnel test data to show that adding to something with such a small cross-section actually reduces drag (significantly)… especially compared to bladed spokes. That said, they would be cheap, could give them a go and bin them if they don’t seem to help.
I’d be more interested in a similar thing for tyre valves, it could even simply screw onto the valve shaft?
I can’t imagine how the
I can’t imagine how the blades will point sideways in a crosswind with the centrifugal forces and air flow that the revolving wheel will generate, what this means is that the crosswind will have to be faster than the speed that the spokes slice through the air.
Also the picture shows that the blades trail behind each spoke, so if you picture the top of the wheel to start with, as the wheel rotates in the direction of travel the fin is behind the spoke but as this spoke approaches the bottom of the wheel towards the ground, the air flow is now coming from the opposite direction in relation to the fin, so as the fins are free to move they will then be pushed by the air and rotate to point back towards the bike frame, and as this particular spoke approaches the vertical position again it will have to spin round again to its first position.
I wonder how noisy that will be?
Darren C wrote:I can’t
The airflow is always in a positive direction (i.e. only acts head on to the spoke). When you say it is in an opposite direction, it is in fact actually at 0.
As the bike moves over the ground at, let’s say 20 mph, the circumference of the wheel travels at 20mph. So, at the top of the wheel’s rotation the velocity is +40 mph (speed of bike, 20mph+speed of wheel relative to bikes movement, 20mph) and at the bottom of the rotation the airspeed is 0 (speed of bike, 20mph+relative speed of wheel, -20mph).
You have then got to think about when the spokes are horizontal, but in this case the airflow is acting at a tangent; when it moves from horizontal into the downwards position, the incident tangential airflow should be negligible (so the fairings would be unlikely to rotate the opposite way).
A cross wind is often only 10mph @ 50/60 degrees, so the relative airflow at the top of the wheel is near enough head on. This means the only time that these spoke fairings are useful is when the wheel is nearing the bottom of it’s rotation (i.e. the slowest) as this is the only time the crosswind component is overly significant.
It’s a lot of hassle for such a small gain. I’d chose aero spokes over fairings (regardless of their poorer x-wind performance).
But into a stiff headwind…
But into a stiff headwind… say 15+mph at say 30º? Do you think there’d be any chance of them turning to the point of causing a negative effect?
I’m especially wondering what happens if you’re on a 5%+ climb into the wind and these things effectively start flapping back and forth.
Null Winds are the idiots who
Null Winds are the idiots who were trying (apparently still trying) to sell the “un-fender” wheel farings, optimized for making crappy bikes more aero while keeping no amount of water off of you and probably rubbing against your wheel/tire regularly. http://www.nullwinds.com/products-fairings.html
Centripital force.
Centripital force. Centrifugal force doesn’t exist. You’re not pushed outwards, you’re actually pushed inwards. Anyway. …
All sailors know of somrthing called apparent wind. It’s the combined vector of your vehicle’s speed and any additional environmental winds.
I agree that the rotation of a spoke (esp over the top) is a much higher velocity than any other vector, except if you live in Holland or Norfolk I suppose
could be useful for a RTW, lejog or RAAM rider?
Maybe this is what Liz Dimmock was waiting for to start her RTW ride?
slam that stem
Thanks for the correction, I’ve not heard of centripital force before!
Well at least I’ve learnt something today!
B-)
Just to play devil’s
Just to play devil’s advocate…
That Mr Newton taught us that every force has an equal and opposite, so if centripetal force exists, so too must it’s opposite…
slam that stem
Centrifugal force is a perfectly good concept. If you make the legitimate choice to look at something from a rotating viewpoint, then you will see a centrifugal force that pushes everything outwards. If you choose a non-rotating viewpoint then there is no centrifugal force. It’s a ‘fictional force’ like the G-force that pushes you back into your seat in an accelerating car, or the coriolis force that changes how things move on the rotating earth.
Simply construct newton’s laws in a rotating system…
Centripital force.
Centripital force. Centrifugal force doesn’t exist. You’re not pushed outwards, you’re actually pushed inwards. Anyway. …
All sailors know of somrthing called apparent wind. It’s the combined vector of your vehicle’s speed and any additional environmental winds.
I agree that the rotation of a spoke (esp over the top) is a much higher velocity than any other vector, except if you live in Holland or Norfolk I suppose
could be useful for a RTW, lejog or RAAM rider?
Maybe this is what Liz Dimmock was waiting for to start her RTW ride?
You say tomato, I say tomato.
You say tomato, I say tomato. You say centripital, I say centripetal.
Don’t worry Darren, whether it’s centrifugal force or inertia that throws you across the road, you still end up in the gutter.
Wheel drag retards? Oh.
Wheel drag retards? Oh.
Now I know how some of you
Now I know how some of you rabid disc brake haters feel.
the fairing is interesting in
the fairing is interesting in the same way as the spoke fairings. The actual element might be more aero – but the fittings really wont be! Either the slab plates, screws and nuts on fairing, or the ends of each of these ‘fairings’. Not convinced without some data to back it up.
The centripetal force is what
The centripetal force is what stops flowers from just falling apart. I’m more interested in the centrifrugal force, which is what keeps pulling me back to Lidl for my weekly shop.
chokofingrz wrote:The
Chapeau! :)) =D>
And these will cause how much
And these will cause how much fatigue as they move around on the spokes?
Municipal Waste wrote:And
Probably bugger all but they might take off the finish on your black spokes.
It’s interesting to note that
It’s interesting to note that a proper NACA aerofoil has a comparable drag to a circular profile ten times less wide. So I can fully see how it might reduce drag by 50%. And indeed the fairings will orient themselves to the combined vector of spoke through air and cross wind. I suspect they will tend to ‘follow’ directly behind the spoke as I can’t see a cross wind’s vector being significantly stronger than that of the spoke through air, particularly at a ‘competitive’ speed.
CharlesMagne wrote:It’s
As someone pointed out earlier; as the spokes come back down, once they are past horizontal, they are slowing in reference to the airflow vs. forward speed. Now, I’m no physicist, but at some point, they will be effectively in dead air before they start re-accelerating towards the top of their rotational cycle. I imagine in the right conditions, especially at lower speeds, such as steep climbs into strongish winds, you’d get these things flipping back and forth.
If nothing else, I could see that possibly being quite annoying at best, counterproductive at worst. If they can’t flip around as fast as the airflow changes from the top to the bottom of the cycle, they’ll possibly be creating even more drag.
I’d imagine they might be beneficial for indoors or dead winds, but I don’t know that I’d want them when riding into a 20kph+ headwind.
Instead of a wind tunnel,
Instead of a wind tunnel, they could set up a cheap magnet based speedometer, spin them up to high rpm, and plot graphs of time / speed equivalent as they slow down, both with and without fairings. Yes, it’s not the same as a wind tunnel but it would be sufficient to demonstrate principal.
Without even such basic data made available, I am skeptical. 😕
Instead of a wind tunnel,
Instead of a wind tunnel, they could set up a cheap magnet based speedometer, spin them up to high rpm, and plot graphs of time / speed equivalent as they slow down, both with and without fairings. Yes, it’s not the same as a wind tunnel but it would be sufficient to demonstrate principal.
Without even such basic data made available, I am skeptical. 😕
Instead of a wind tunnel,
Instead of a wind tunnel, they could set up a cheap magnet based speedometer, spin them up to high rpm, and plot graphs of time / speed equivalent as they slow down, both with and without fairings. Yes, it’s not the same as a wind tunnel but it would be sufficient to demonstrate principal.
Without even such basic data made available, I am skeptical. 😕
I don’t think this will work
I don’t think this will work in the real world. Probably looks like a good idea on a computer screen, all that that extra weight and swivelling will soak up e energy.
Also I bet it rattles like a pissed off snake.
I don’t think this will work
I don’t think this will work in the real world. Probably looks like a good idea on a computer screen, all that that extra weight and swivelling will soak up e energy.
Also I bet it rattles like a pissed off snake.
I don’t think this will work
I don’t think this will work in the real world. Probably looks like a good idea on a computer screen, all that that extra weight and swivelling will soak up e energy.
Also I bet it rattles like a pissed off snake.
I don’t think this will work
I don’t think this will work in the real world. Probably looks like a good idea on a computer screen, all that that extra weight and swivelling will soak up e energy.
Also I bet it rattles like a pissed off snake.
I don’t think this will work
I don’t think this will work in the real world. Probably looks like a good idea on a computer screen, all that that extra weight and swivelling will soak up e energy.
Also I bet it rattles like a pissed off snake.
I don’t think this will work
I don’t think this will work in the real world. Probably looks like a good idea on a computer screen, all that that extra weight and swivelling will soak up e energy.
Also I bet it rattles like a pissed off snake.
Make them retro-reflective,
Make them retro-reflective, and I might be interested. (Not for racing.)
I’m sure this was tried years ago though, and didn’t take off then.
I am surprised that people
I am surprised that people actually thinking about the possibility that this product could improve performance in any shape or form. Did any of you bought the power balance bracelet a couple of years ago?
I am surprised that people
I am surprised that people actually thinking about the possibility that this product could improve performance in any shape or form. Did any of you bought the power balance bracelet a couple of years ago?
This looks like a nightmare
This looks like a nightmare to keep clean so they spin freely.
Forward facing surfaces are
Forward facing surfaces are far more critical to aerodynamics (hence the effectiveness of “Kammtail”, laminar flow wings which have the thickest section nearer the trailing edge, etc) than trailing, so adding a fairing to the back with a circular leading edge (spoke) transitioning messily to the fairing is almost certain to increase drag.
Last I checked, CFD models
Last I checked, CFD models don’t even bother with spokes because they make basically no difference. They *do* matter when they are large spokes, but as long as there is the same number of spokes (ie 16-24), they are not considered relevant in the aerodynamics.
There’s a very good report by a woman who compared CFD for several different mainstream wheels and she gave a very good reason for excluding spokes in her computational models. She also correlated with existing real test data and concluded that they were not relevant. I can’t find it, but it’s out there for those who like to read extremely long and technical articles.
Now as to adding mass and increasing their size, you are basically taking something that is irrelevant and making it more relevant… probably in a bad way.
The added volume will not decrease turbulence. It *might* increase turbulence, but the Reynolds numbers are just not anywhere near the level where something like this could actually make a difference. Best bet is to just leave your spokes alone.
Dascinating … I’ll await
Dascinating … I’ll await its adoption by the pro-peleton.
Can I fit these on my bladed
Can I fit these on my bladed spokes….oh…wait….
Another whacky kickstarter
Another whacky kickstarter campaign.
Even if they work we are talking about a product that delivers marginal performance gains and would be illegal for anyone interested in such marginal gains (racers). Seems like another solution looking for a problem.
This is nonsense without at
:)) This is nonsense without at least some realistic testing e.g. with wind speed regulated fans, strain gauges to measure drag force at the axle mounts and a variable speed wheel drive with power consumption meter to also measure drag force.
I’d also query how quickly the blades can actually move and how long before they break off, and possibly cause a brake fail or wheel stall!
I’ll bet that the bladed spokes in my Mavic Crossride wheels are better in most conditions than these toys, including energy savings from better bearings and wheel rigidity; I haven’t needed to tweak the spokes at all!