DWFTTW | Down Wind Faster Than The Wind

[Aaron]

vids showing concept

Hi Dingus, I never saw your post.
This is the user and he has 4 vids:

http://www.youtube.com/user/coolaun

[Aaron]

Making of the DDWFTTW cart

Part 1 YouTube - Making of the DDWFTTW cart (Part 1 of 3)

Part 2 YouTube - Making of the DDWFTTW cart (Part 2 of 3)

Part 3 YouTube - Making of the DDWFTTW cart (Part 3 of 3)

[Cloxxki]

Posting here, as I have an account here.

I may have figured out why, on top of Spork's own team research, why the drive blew up.

I made an X-Y graph,
X axis being ground speed of the vehicle
Y is for plotting the wind speed, relative speed of cart to the wind, and the amount of air the prop tries to work it's way through.

- Wind speed is a vertical line, I took value 10 on the X-axis.
- The "amount of air the prop tries to work it's way through." must go through (0,0), yet also great than "relative speed of cart to the wind". 1:1 with the X value might be safe, but possible not giving snappy acceleration.

In a fixed gear ratio, and fixed prop pitch...with the slightest over-gearing (steeper than 1:1) of the prop, it will start putting more and more torque on the drive system. This would be a diagonal line moving out above away from "relative speed of cart to the wind".
The slightest under-gearing would create a fixed equilibrium speed.

If an over-gearing (unavoidable I suppose if you want to go fast) coincides with with drop in tail wind or worse, it will stress the system quite a bit. Actual cart speed of course needs time to catch up.

The mis-match in prop speed and wheel speed will create skippage. This will become cyclic, it's what wheels do when they don't match their ground and turning speeds.

My best best for a reliable wind racer of this kind would be to have a variable, self-adjusting gear ratio. That, or the same for prop pitch.
You can't slam on the brakes in a fixed gear ration, the chain will feel it.

On the fly manually variable pitch could load the system greatl, and needs to be overrides by a slip clutch of sorts. It would however allow for momentary acceleration to overtake another vehicle more quickly, rather than waiting for the speed to materialize.

Any ideas? this stuff is just fascinating to me. Spork's team is looking to break the land record for wind powered vehicles with their next build. that now over 130mph I seem to remember. Already they have ~2-3x wind speed directly down wind, of course higher speed will makes this more challenging.
for a first attempt though, I think their result is amazing. 45mph in a mild ~15mph breeze, and acceleration until failure occured.

Their cart was very basic. What would you chance to the aerodynamic setup to get even more speed? Use a hull of sorts? A rang around the prop, or even a cylindrical jet style enclosure?

[Schpankme]

Sailing Against the Wind

Windmill Sailboat

The 36 foot catamaran, Revelation II, is powered by 3 20-foot long carbon fiber propellers on a 30 foot rotating mast.

[Cloxxki]

Windmill Sailboat

The 36 foot catamaran, Revelation II, is powered by 3 20-foot long carbon fiber propellers on a 30 foot rotating mast.

Yet, it has the prop turn the other way, losing out in DDW conditions. The Rev has a complicated sail as I see it.

The cart gets rolling with tail wind, DESPITE the prop being geared against the natural way it wants to turn. So, the prop is doing a great job immitating a garage door. Turning the expected way would be like offering few friction, only to spin it. Turning as it it wants to propel the cart, surprise surprise, it actually does. Any speed it turns, it accelerates the crt. It's geared such that it cannot scoop up less air than it hits as headwind.

We have a positive feedback loop here, boosting the efficiency of the prop from maybe 20% to closer to 80% or so (my guess). The prop itself, being geared faster than the headwind it faces, has negative drag, and huge thrust. The cart itself, barely offers drag.

You want a big prop, and small cockpit. 150mph will be breached, possible in 60mph or slower winds.

Wind has just become an auxiliary power source for all vehicles. Upwind it can go miracles, downwind the same. Side wind, we have airfoil wings. With a typical family car stationary on a windy parking lot, the airfoils (channeleing the air) and props can work together to fill batteries, and sell excess energy to the grid.
If I can pedal my bike to 55kph cruising speed in 90kph tail winds over beach (higher rolling resistance)... What would a 1m diameter prop behind my bike geared to the rear sprockets bring me? Could I cruise at 80kph, or even better?
It's well established that windmill cars can ride well against the wind, close to 100% the wind speed. This would be great on a bibycle stle vehicle as well. Why let ll that wind fly past, if energy can be extracted from it that offers more power than it generated resistance against direction?

[Cloxxki]

A mind teaser for y'all.

Could a cart with prop, geared similarly to a DDWFTTW setup, rolling down a slope from standstill, beat the gravity equasions as usually applicable to that slope?

Meaning : could a prop cart make it down the slope faster than a "perfect" cart, comprised of weightless no-rolling-resistance wheels, zero airdrag, yet substantial weight?

Gravity is a bit like vertical tail wind of 9.8m/s², right? At an angle though, contrary to wind, you go slower rather than faster.
And if you throw a press-papier out of the window with downward impulse (start-up velocity), it does not encounter gravital back draft.

So, can gravity be "overtaken" by a cart with a prop fed with by positive feedback loop from the wheels?

I'm not so sure myself yet. Leaning towards: yes, the prop cart can be faster. If true, just as mind-blowing as the DDWFFTW thing...

[eastcoastwilly]

Hi Folks,

I know this has been posted on this forum before, but wouldn't it be cool to implement the Dyson Air Multiplier into Peters idea for a funnel and input this into the multiplier.

If you could ever manage to achieve 10 X the airflow this thing would take off like a rocket

Will

[Cloxxki]

Hi Folks,

I know this has been posted on this forum before, but wouldn't it be cool to implement the Dyson Air Multiplier into Peters idea for a funnel and input this into the multiplier.

If you could ever manage to achieve 10 X the airflow this thing would take off like a rocket

Will

I'd not heard of the Dyson before!
Would its own thurst be a relevant figure, at a given input power?
It does like an interesting conbination with a fan behind it, even if it's more of a chaneller for air than a thruster.

[Cherryman]

I'd not heard of the Dyson before!
Would its own thurst be a relevant figure, at a given input power?
It does like an interesting conbination with a fan behind it, even if it's more of a chaneller for air than a thruster.

I used to work in the automotive industry, bodyshops etc. There simular concepts are used, we had air blow pistols with uses the same principle about 10 years ago.

- A hollow tube, feet air in from the side, and the airflow will drag in additional air, althoug u loose prerssure!

- Also with the introduction of aquapaint the common dry methode was using a lot of those to create directional airflow. We used to call them "venturi's"

[Peter Lindemann]

Full Size Model

Hi Folks,

Well, here is the full sized proof that the DWFTTW principle works. This machine was clocked at over 38 MPH powered by a 13.5 MPH wind!

Wind-powered car goes down wind faster than the wind

Enjoy,
Peter

[Harvey]

Hi Folks,

Well, here is the full sized proof that the DWFTTW principle works. This machine was clocked at over 38 MPH powered by a 13.5 MPH wind!

Wind-powered car goes down wind faster than the wind

Enjoy,
Peter

Very Nice!

Somehow using the wheels to turn the prop does bring back memories of a Go-Cart I envisaged at the age of 8 where big tires in the back drove smaller tires in the front but if we can use wind to tack a sailboat into the wind it stands to reason we could employ a feature of the force to accelerate faster than the wind.

How do we plot the force vectors on this

[Aaron]

output faster than input

Great find Peter! Very cool that Google is actually sponsoring them.

This pump I posted:

http://www.energeticforum.com/97309-post91.html

The output is WAY faster than the air leaving the diesel or electric
pump blowing air at the front of the pipe inlet. And everything goes
thru the pipe without touching the sides.

This kind of thing is definitely more than possible

[witsend]

You have a cart and the wheels are connected to a propeller. When you push the cart, the propeller turns and makes enough wind thrust to accelerate it faster than it was pushed

DWFTTW - Google Search

Directoryirectly Downwind Faster than the Wind - PESWiki

YouTube - DDFTTW

YouTube - Direct Downwind Faster Than the Wind #1 (DDWFTTW)

YouTube - spork33's Channel

Aaron - This thread has been teasing my mind and I'm recovering it from page 3 - I think?

I'm not sure of the thesis here. If the cart goes faster than it was pushed then is the extra energy coming from the wind? Therefore the cart is moving at some velocity that is the product of the force of the push, and the wind. Where then is the extra energy? And did you measure the force of the wind. Surely to prove this one needs to establish the speed of the wind and the speed of the cart. If the cart is exceeding wind velocity then indeed we have OU. Am I missing something? And did the velocity exceed wind speed? That would, indeed be impressive.

[Cloxxki]

No extra energy!!

NO OVER UNITY. Sail boats are not over unity either.

Just leverage, to get ALL of the energy from the wind.

A sail vehicle with open sail going 1x wind speed, is not having any force in the sail. It won't even blow up, but hang slack. Yet serious energy was put on the sail to get to that speed, think about it.

The frontal area of the cart being pushed through the air consists mostly of the cockpit and the pillars for the prop.
The prop itself is offering thrust, just likely less than there is kinetic energy in the wind (air moving).
The trick is the efficiency of a prop at low wind speeds to generate thrust, and the whole vehicle being pushed from behind by the FORCE of the wind. Wind speed is just that, and relevant with a garage door sail wide open.
BMX Oracle, a fast sailboat, can beat a balloon downwind to a finishline, it just need to zigzag for it.
All the prop changes, is having an angle on the wind (helical blade path). Like two little sails spinning an axis.

If it's hard to grasp the speed of the vehicle, imagine how much energy a 17 foot turbine could harness from 10mph winds. And how much it would take to push the cart less prop, to 10mph. You'll there IS energy left. And it's used for acceleration beyond wind speed. The wheels and prop (it is a specifically designed prop for the job) are geared to have the prop THRUST back at the wind at all times.

Notice how the cockpit is built to be TINY, while the prop is HUGE. There is a pretty obvious reason for this. A large garage door sail with a little prop on top, just isn't going to cut it.

All that limits such a cart to reach 10x wind speed, is prop efficiency, and prop size versus overhead frontal wind area. And yes, rolling resistance to some degree.

I envision transport systems being built that rely on wind power, and use some solar as well. I envision them being faster than regular trains, is mild winds.
I can see sailing races on railway tracks. Super low rolling resistance, lots of stability (especially with undergripping wheels). Sails can be huge, overhead frontal area tiny, efficiency optimal.

If Blackbird's first attempts were 2.85x wind speed, dead downwind, there is more to come for sure. Other teams will need to be formed. Races held.
If you can accept that races exist where similar carts race each other directly upwind over a narrow dike, you're halfway to understanding that with a prop in stead of turbine, the downwind can be easily beaten.

The Blackbird team have teamed-up with NASA to use their runways and educate their engineers :-)

One thing I'm still trying to figure out to be sure... Due to the cart making its own wind (moving through more wind that a fixed turbine will after see passing it by), might the cart in fact be harnessing more wind energy? This is a tricky one for me, and I'd have to read back to make sure what the team claims.

Really, it's all leverage. The part being leveraged has less drag than the wind is acting upon from behind.

[witsend]

No extra energy!! Just leverage.
The frontal area being pushed through the air consists mostly of the cockpit and the pillars for the prop.
The prop itself is offering thrust, just less than there is kinetic energy in the wind (air moving).
The trick is the efficiency of a prop at low wind speeds to generate thrust, and the whole vehicle being pushed from behind by the FORCE of the wind. Wind speed is just that, and relevant with a garage door sail wide open.
BMX Oracle, a fast sailboat, can beat a balloon downwind to a finishline, it just need to zigzag for it.
All the prop changes, is having an angle on the wind (helical blade path). Like two little sails spinning an axis.

If it's hard to grasp the speed of the vehicle, imagine how much energy a 17 foot turbine could harness from 10mph winds. And how much it would take to push the cart less prop, to 10mph. You'll there IS energy left. And it's used for acceleration beyond wind speed. The wheels and prop (it is a specifically designed prop for the job) are geared to have the prop THRUST back at the wind at all times.

Notice how the cockpit is built to be TINY, while the prop is HUGE. There is a pretty obvious reason for this. A large garage door sail with a little prop on top, just isn't going to cut it.

All that limits such a cart to reach 10x wind speed, is prop efficiency, and prop size versus overhead frontal wind area. And yes, rolling resistance to some degree.

I envision transport systems being built that rely on wind power, and use some solar as well. I envision them being faster than regular trains, is mild winds.
I can see sailing races on railway tracks. Super low rolling resistance, lots of stability (especially with undergripping wheels). Sails can be huge, overhead frontal area tiny, efficiency optimal.

If Blackbird's first attempts were 2.85x wind speed, dead downwind, there is more to come for sure. Other teams will need to be formed. Races held.
If you can accept that races exist where similar carts race each other directly upwind over a narrow dike, you're halfway to understanding that with a prop in stead of turbine, the downwind can be easily beaten.

The Blackbird team have teamed-up with NASA to use their runways and educate their engineers :-)

Thanks for this Cloxxki. I get it. WELL. ROLL ON WIND POWERED VEHICLES. There seems to be so many, many preferable alternatives to oil. Hopefully we'll get these into operation.