Fettering Rotor for Bicycle

[BeggarsInSpain]

Hello,

I have been dreaming of a Fettering rotor for a bicycle. This device would impart the bicycle with wind power. I am not sure if I will have to power the rotor with electricity. I actually kind of think that because of the small mass of the rotor and the frictionless ball bearings that it will spin by pedaling the bike, giving it a kind of "wind-assist." I made the drawing to show how I might make the rotor attach to a luggage rack with a piece of wood that is counter-sunk for ball bearings. I made the picture so that the device has many rotors. Each rotor will drag and the amount of lift each successive rotor provides will be reduced from the first. So, it might be better to have fewer rotors. I think, that making the rotors taller changes the lift drag ratio.

It would be interesting to get a bike tuned to use a front hub motor and a Fettering Rotor. A bike that is capable of regenerating electricity from the wind and/or rolling down hills, so that it would get very good mileage.

From,
Tyler

 

[neptronix]

What is a fettering rotor? Google search turns up zero results.

 

[ebike4healthandfitness]

What is a fettering rotor? Google search turns up zero results.

Flettner rotor.

 

[amberwolf]

If you're trying to get the bike to move by taking energy from the wind of it's forward movement....it won't work, because you will slow yourself down by taking away that forward energy, and there are *always* energy losses in any conversion from one energy type or form of motion to another, so you won't even maintain speed.

If you are trying to do something else, you'll need to provide much more information, clear pictures of what you are trying to do, links to existing information about the ideas / parts, etc.

 

[Logic11]

Hmmm...
Unless this thing provides some sort of aero advantage and/or spins like crazy when the bike's stationary in a strong wind, it's basically a perpetual motion machine? and those never work.

 

[gromike]

A Felttner rotor bicycle? Maybe have all the tubes in the frame spinning optimally via some sort of Rube Goldberg apparatus.
Though, a handkerchief dangling from a pocket would probably negate any gain you would achieve from your efforts, (and then some.)

 

[amberwolf]

Assuming it is the Flettner Rotor being referred to by the OP, this video that I was coincidentally watching in the background just now

describes how they work, etc.

As far as I can tell, you have to apply some power to spin them in order to get the propulsive force in the direction you want, from the wind that is blowing past them. There's a specific relationship between wind speed and rotor speed given that I didn't catch, but it's fairly high; you'd need some form of wind speed sensor to control the rotor speed to maintain that.

Also AFAICT, they will also need to be vertical, not horizontal as shown in the OP's picture. There appears to be a scale ratio height/diameter that works well given the shapes I see in the different systems.

From what I can see in the various successful implementations of them in this video and in internet searches, they'll need to be tall enough to be above your wind shadow, so they will also create significant drag on the bike when the wind is not blowing as required, and they'll need to be stiff enough to probably add significant weight and change the handling of the bike, and make it a challenge to ride near trees or other typical objects near roads and paths.

Not something I have enough interest in to pursue further (no way for me to implement it; not enough constant wind in my rides to make it worth even testing; it's usually gusty or direction-changing), so that's about all the info I can provide.

 

[BeggarsInSpain]

What is a fettering rotor? Google search turns up zero results.

Sorry, Flettner Rotor. The Fettering Rotor would actually be near the Knuter Valve. So, the Flettner Rotor would generate lift, the Magnus Effect is caused by an area of low pressure that the rotation of the Flettner Rotor causes. The height of the rotor would be like determining the length of an airfoil. If you've ever seen world record, wind powered ice skates, that is a demonstration of highly engineered air foil for moving a person. I am just kind of coming up with the idea.

In my drawing, there are 6 or 7 rotors, 4 golf balls high. I suspect that the lift advantage would become negligible after a certain number of rotors in the peloton or rotor array, depending on wind heading and direction of travel, (the way fluids will behave near a Flettering Rotor are in the documentation,) or the lift might be perpendicular to the direction of travel. I also think that changing the height of the rotors will effect the lift to drag ratio, but I need to try to measure those things and learn to make it a practical device for varying wind speeds. Also, we have to take into effect the mass of the vehicle.

In order to make this not a perpetual motion machine, I will not insist that the ball bearings are frictionless and that the rotors would require small amounts of rotational velocity because golf balls really are not that massive. Instead, I will power the Flettering Rotor with a small electric motor and its own lithium ion, and small PV array ~36w.

When the wind hits that rotor and I am traveling down a hill with my direct drive front hub and I have a 20mph wind at my back, I will regenerate more electricity to the batteries than when the wind is 10mph down the same hill, if I use the same rate of descent. So, in that way, the Flettering Rotor would turn this bicycle into a wind turbine on wheels.

 

[BeggarsInSpain]

Also AFAICT, they will also need to be vertical, not horizontal as shown in the OP's picture. There appears to be a scale ratio height/diameter that works well given the shapes I see in the different systems.

The rotors in my picture were meant to be vertical. Horizontal rotors can work, especially if you are climbing a lot. The axis of the rotors is called the camber.

 

[BeggarsInSpain]

If I had a Flettering Rotor on the handlebars that had 100 golf balls at 45.9g per golf ball, their rotation would affect the gyroscopic precession while turning. That is why I use a direct drive front hub for when I am riding a stoppie down a mountain and regenerating wind energy to my battery.

 

[Sailing the high seas]

Hello BeggarsinSpain,

I was just performing a search on whether somebody had build a bike with a Flettner rotor and found your query in this forum.

Using the Flettner rotor on a bike might be a good idea.
It is a all known aerodynamic propulsion method.

@Logic11:
It might seem like a perpetual motion machine, but in reality it works in the same way that a sailing boat takes energy from the wind to make propulsion. If you sail in the trade winds on the ocean, you can sail for weeks with steady speed. So you are not violating thermodynamic laws of energy conservation. The energy is provided by the wind.

The Flettner rotor is just a sail of "a strange shape" (a rotating cylinder). It is capable of generating aerodynamic lift, because the rotation of the cylinder ensures a better lift (by altering the pressure distribution along the cylinder). This is well known in aerodynamics. If the cylinder would not rotate, it just causes aerodynamic drag. But when the cylinder rotates, it starts generating an aerodynamic force perpendicular to the direction of the wind (this is lift force, and can be used to propel a ship or any other vehicle equipped with the Flettner rotor)

The way any sail (or wing, or Flettner rotor) works is that the sail changes the direction of the wind. By Newtons second law, this induces a reaction force on the sail, and that propels the sail forward. If the wind comes from the side, the propulsion force is approximately in the direction you want to go, hence you reach the highest speed.

Ships with Flettner rotors have been tested and used. It works, but it does not work so good to have replaced ordinary sailing rigs. So apart from some experimental systems, Flettner ships have not gained commercial market acceptance.

To reduce the fuel consumption of big ships, better systems have been designed, and have become commercial:
See Econowind | Make shipping sailing again
The Econowind system reaches a very high lift coefficient, hence is more effective than a wing sail (of the same dimension).

Back to sailing with a bike.
In the Netherlands there is a commercially available sailing bike, see:

Whike

whike.com

So there you can buy a wind-powered bike and have great fun.

Should you want to experiment with building a Flettner Rotor bike, the Whike will be your benchmark. Under favourable conditions, the bike can reach speeds of approximately 60 km/h or some 37 mph.

The potential advantages of a Flettner rotor version of a Whike is that the rig / mast might be smaller for the same propulsion power. This might make the system more compact and lighter, and therefore of more practical value as a commuting bike, or long distance holiday bike.

The disadvantage is that the Flettner rotor must be rotated to work aerodynamically. This indeed takes some energy (but less than the aerodynamic energy the rotor harvests from the wind).

So when starting the bike by doing some pedalling, and spinning the rotor (by energy taken from the bike wheels), there comes a point where the aerodynamic propulsion power exceeds the drag on the bike, and the energy consumption for rotating the Flettner rotor, hence the bike will accelerate until it reaches a cruising speed where propulsion and drag are in balance.

To be of practical value, a wind-powered bike should still work when sailing close to the wind (what sailors call close-hauled sailing, at a angle of roughly 30 degree to the true wind direction). Sailing straight into the wind is not possible.

It would be a nice project for students at a university or polytechnic school to analyse this problem, and build the most optimum Flettner bike for racing.

Hope this helps you further. If you want to know more, please let me know.

 

[Logic11]

Hello BeggarsinSpain,

I was just performing a search on whether somebody had build a bike with a Flettner rotor and found your query in this forum.

Using the Flettner rotor on a bike might be a good idea.
It is a all known aerodynamic propulsion method.

@Logic11:
It might seem like a perpetual motion machine, but in reality it works in the same way that a sailing boat takes energy from the wind to make propulsion. If you sail in the trade winds on the ocean, you can sail for weeks with steady speed. So you are not violating thermodynamic laws of energy conservation. The energy is provided by the wind.

The Flettner rotor is just a sail of "a strange shape" (a rotating cylinder). It is capable of generating aerodynamic lift, because the rotation of the cylinder ensures a better lift (by altering the pressure distribution along the cylinder). This is well known in aerodynamics. If the cylinder would not rotate, it just causes aerodynamic drag. But when the cylinder rotates, it starts generating an aerodynamic force perpendicular to the direction of the wind (this is lift force, and can be used to propel a ship or any other vehicle equipped with the Flettner rotor)

The way any sail (or wing, or Flettner rotor) works is that the sail changes the direction of the wind. By Newtons second law, this induces a reaction force on the sail, and that propels the sail forward. If the wind comes from the side, the propulsion force is approximately in the direction you want to go, hence you reach the highest speed.

Ships with Flettner rotors have been tested and used. It works, but it does not work so good to have replaced ordinary sailing rigs. So apart from some experimental systems, Flettner ships have not gained commercial market acceptance.

To reduce the fuel consumption of big ships, better systems have been designed, and have become commercial:
See Econowind | Make shipping sailing again
The Econowind system reaches a very high lift coefficient, hence is more effective than a wing sail (of the same dimension).

Back to sailing with a bike.
In the Netherlands there is a commercially available sailing bike, see:

Whike

whike.com

So there you can buy a wind-powered bike and have great fun.

Should you want to experiment with building a Flettner Rotor bike, the Whike will be your benchmark. Under favourable conditions, the bike can reach speeds of approximately 60 km/h or some 37 mph.

The potential advantages of a Flettner rotor version of a Whike is that the rig / mast might be smaller for the same propulsion power. This might make the system more compact and lighter, and therefore of more practical value as a commuting bike, or long distance holiday bike.

The disadvantage is that the Flettner rotor must be rotated to work aerodynamically. This indeed takes some energy (but less than the aerodynamic energy the rotor harvests from the wind).

So when starting the bike by doing some pedalling, and spinning the rotor (by energy taken from the bike wheels), there comes a point where the aerodynamic propulsion power exceeds the drag on the bike, and the energy consumption for rotating the Flettner rotor, hence the bike will accelerate until it reaches a cruising speed where propulsion and drag are in balance.

To be of practical value, a wind-powered bike should still work when sailing close to the wind (what sailors call close-hauled sailing, at a angle of roughly 30 degree to the true wind direction). Sailing straight into the wind is not possible.

It would be a nice project for students at a university or polytechnic school to analyse this problem, and build the most optimum Flettner bike for racing.

Hope this helps you further. If you want to know more, please let me know.

I'm well aware that wind energy might be converted into forward motion while in motion, or at least some torque in that direction.
I posted about ...er... sprung wings over spokes likely helping to provide a bit of forward torque here somewhere.
(They would ameliorate the effect of side winds/gusts and improve wheel aero too)

I may even be convinced that a wind turbine on a long enough aero mast, to get it up where the winds is actually blowing, might provide some forward torque if the rest of the vehicle is low and in the slow wind.

But anyone putting a wind from 'straight ahead only' and 'down here with me' and especially a 'in front of me', has been smoking 'efficiency' pot!

Then; go stick a tall mast with a turbine on a bicycle and see how that effects handling!
All the wind powered ground vehicles have at least 3, widely spaced wheels and a lot of open space to be enjoyed in.
And if you want to go directly upwind; you'll be tacking. (nautical term)
That's not an option on a road.