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Author Topic: Directorly Downwind Faster than the Wind  (Read 148428 times)

ramset

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Re: Directorly Downwind Faster than the Wind
« Reply #60 on: April 02, 2010, 04:53:47 AM »
Greg
my favorite part is when he stalls the telltales and keeps on truckin.
makes my head explode!

Seems like it really wouldn't need any wind,  dare I say
"It can make its own"

http://en.wikipedia.org/wiki/Apparent_wind

Chet

sparks

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Re: Directorly Downwind Faster than the Wind
« Reply #61 on: April 02, 2010, 05:56:30 AM »
Sailing was explained to be as the action of squeezing an oiled jellybean.  It pops forward if the hull is shaped correctly.
Pullup the centerboard in a boat on what is called a reach or when the wind is perpendicular to the hull and you start sliding sideways in the water slowly.  Instead of decreasing drag on a vehicle perhaps we should actively manage it.  Put a big funnel and drive the apparent wind through a turbine.  The drag will turn into more useful production.  Instead of the car creating a low pressure vortex or draft behind it which the car always wants to go back into the low pressure area is set up in front of the main body of the car in the shelter of the turbine.

TechStuf

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Re: Directorly Downwind Faster than the Wind
« Reply #62 on: April 02, 2010, 08:19:30 AM »

Quote
Instead of decreasing drag on a vehicle perhaps we should actively manage it


Spoken like a tried and true Schauberger afficianado!


I would even go so far as to say that micro-management is in order.


I'll have a double Schauberger to go....and make it snappy....


I've got places to go and people to see!









Cloxxki

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Re: Directorly Downwind Faster than the Wind
« Reply #63 on: April 02, 2010, 09:13:42 AM »
The cart makes its own wind, perhaps, but it's the apparent headwind powering it past the wind speed.
The prop sitting ON the cart must be scooping up air at a modest rate. To high a rate, and the drag of the prop will slow down the wheels, or they lose traction.

I have some sketches here also, funnel shape with a large prop front, small prop rear. It can do what we want, but will the tailwind be sufficiently impressed to push the cart out in front?
Without wind, from standstill there is just a massive wall or air in front, and no thrust. And at 10mph kick started speed, generating a little bit of power on the funnel, we can't expect the system of props to generate more more than Mr Hand used to get the system to 10mph. For, that's what we need to do away with nature's wind input. That's a lot of wind to make from scratch!

If one builds the little cart Spork offers building vids for, it may be interesting for those who smell OU, to try some gearing and kick start speeds, to see if it'll keep going. The smartest guys in this field, Spork's team, are not betting on this. They go for actual wind, however weak, and build a low-drag cart that can use the mechanical advantage to get better speeds than a ballloon.

If ice racers do 5x the wind speed...(200mph, is that in Guinness??) it would be interesting what a DDW cart can do. A prop may be less efficient that an airfoil, but when geared well, at least it has not frontal drag, it pulls harder than it pushes.

With a refined system of foldaway airfoils and props, a cart could on a windy day set repectable lap times around a typical car racing circuit. Only but: wind must be blowing.

For the slow acceleration up to wind speed, I would recommend a simple sail. Like a projector screen, it rollsup into a frame tube when the wind speed is matched :-) A set of small support points would make it an efficient sail shape.

Requiremensts for a DDW race cart:
- big prop (unless an over-geared small prop can be substituted, I doubt it)
- tiny cockpit
- all other parts reduced to minimum resistance : structures, wheels, everything.

The amount of force at a given wind speed acting upon the cart from behind, with it's self-backspinning rotor, minus the drag on all the parts, is what's left of acceleration.

Yes, lots of research into prop, yet not giving the actual wind movement relative to the ground much thought, we are after all making air speed, not ground speed? I also have a sketch here of an airship dragging a heavy cart, to get mechanical movement transferred. A really better idea for the feedback loop, I do not have.

Could we make a track of reppeling magnets, the other set in the vehicle, for maglev?
With wind, the magnets running by each other would be like a turning wheel, this could be extracted. We have to use it for a low-tech prop however, can't let another wheel turn faster, as we'll only end up with resistance greater than gain. At low apparent wind, the prop is just marvellous thing for lift vs drag.
Can you see it? A levitation craft, with a prop on its tail. It needs a magnetic track though, or it'll crash down. When you add vertical lift airfoil, and pedals, you have what I one dy intend to build, a human powered ground efect plane. These have existed (cross the Channel) in the bi plane variety, and worked, but I want something smaller and faster.

Cloxxki

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Re: Directorly Downwind Faster than the Wind
« Reply #64 on: April 02, 2010, 05:09:34 PM »
@Rapadura, I seem to have mis-read your post above I responded to, or maybe your edited it. Anyway, my apologies.

Rapadura

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Re: Directorly Downwind Faster than the Wind
« Reply #65 on: April 02, 2010, 09:02:07 PM »
No, Cloxxki, I didn't edit the post.

I did not say that the vehicle works this way or that way. I just said what the inventors were claiming. I don't  know the extent to which the inventors are correct.

Anyway, your answer was welcome, no problem with it.

Rapadura

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Re: Directorly Downwind Faster than the Wind
« Reply #66 on: April 03, 2010, 01:16:16 AM »
Unfortunately, this thing doesn't work (at least not the way the inventors claim).

Look these videos:

http://www.youtube.com/watch?v=RBjDPhLoPJY

http://www.youtube.com/watch?v=WXk5g-fS3pY

At the end of the videos, we can see that, when the vehicle is separated from the truck that was pushing it, the propeller quickly slows down.

It seems to me that these videos where made in a place with low speed enviromental wind. And with low speed enviromental wind, this thing don't work. The thrust created by the rotating propeller is not sufficient to compensate the friction in the wheels. So, the friction make the wheels slow down, and with the wheels slowing down, the propeller slows down too.

This might work if the RPM of the propeller were sufficient to create enough thrust to keep the vehicle at a speed at which the rotation of the wheels were in the same RPM of the propeller. I think it may depend of the size of the wheels, gear ratio, etc... Maybe bigger wheels could be better...

sparks

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Re: Directorly Downwind Faster than the Wind
« Reply #67 on: April 03, 2010, 01:50:21 AM »
   I am tired of wasting time and money traveling to work.   Now if I could anchor myself to this one point.  My job would come to me at a 1000mph.  But oh oh the Earth is moving 60,ooo mph relative to the Sun so if I anchored myself to just this one spot then the shop would kinda get to me a little faster than I could let go the anchor.  Oh oh the solar system is moving around the galactic cores and I'm not too sure how many miles an hour this is so I could end up letting the anchor go and find myself way down the road from the shop.  Damn it the galaxy is moving too.  No idea how fast the old milky way is going.  My rear end could end up in Jupiter when all I wanted to do was save a little time getting to my job.  If there is such as thing as a fixed point in the Universe and time doesnt dialate and there is an aether to reference then my job would be moving somewhere else at over a million miles an hour.  No wonder alien craft move so fast.  They just no how to get stuck.

gmeast

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Re: Directorly Downwind Faster than the Wind
« Reply #68 on: April 03, 2010, 03:37:44 AM »
Unfortunately, this thing doesn't work (at least not the way the inventors claim).
Look these videos:
http://www.youtube.com/watch?v=RBjDPhLoPJY
http://www.youtube.com/watch?v=WXk5g-fS3pY
At the end of the videos, we can see that, when the vehicle is separated from the truck that was pushing it, the propeller quickly slows down.
......................................................................

Oh my ... I just know there are aerodynamicists both professional and 'armchair' that are just shaking their heads.  Number one, the L/D of the props they are using is far from optimum and certainly only in the mid 80% efficiency, at best.  Oh yes, and they are transferring power between the wheels/propeller far less efficiently with that belt drive than they think.

I don't know why people just aren't seeing that this is the most incredible adaptation of wind to mechanical energy (I've seen anyway).

As an example: take a hydroplaning catamaran and place a prop on a pivoting mast that allows you to always 'aim' the prop into the wind.  Put a collective pitch control also on it.  Drive via a 90deg gearbox vertically down to another 90deg gearbox and out the back of the vessel to a high aspect prop in the water to drive the vessel forward (like a regular power boat).

You can go any direction you want.  No polished sailing skill needed ... go up wind, down wind, cross wind (I think that's it).  You would have a very respectable 'effective' sail area.  Now get to where you want to sip your champagne, drop anchor, let the propeller keep turning but now running a generator that's keeping batteries charged up to run the lights, galley, an oh yes, that ultra-efficient electric motor also linked to the prop shaft (you'll never be dead in the water).

For close maneuvering near the docks the propeller folds, you now run electric also with electric bow thrusters, etc.

How cool would that be?

Greg

sparks

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Re: Directorly Downwind Faster than the Wind
« Reply #69 on: April 03, 2010, 04:54:19 AM »
What I always dreamed of doing is setting up a fleet of sailing ships.  Those elgant creations that came before the smoke spewing steamboats.  Ply them up and down the tradewinds with built in hydrolizers.  When they had a full load of solid hydrogen aboard bring her into port.  Then go on back out and sail the seven seas fishing for energy.  This is how dumb people are.  The average whaling ship which was not optimized for speed could achieve over a thousand horsepower.  They neglected this scource of energy in pursuit of animal fats they could burn.  They spent more energy chasing the whales and killing them loading them etc than the whale catch produced.

gmeast

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Re: Directorly Downwind Faster than the Wind
« Reply #70 on: April 03, 2010, 06:37:07 AM »
What I always dreamed of doing is setting up a fleet of sailing ships.  Those elgant creations that came before the smoke spewing steamboats.  Ply them up and down the tradewinds with built in hydrolizers.  When they had a full load of solid hydrogen aboard bring her into port.  Then go on back out and sail the seven seas fishing for energy.  This is how dumb people are.  The average whaling ship which was not optimized for speed could achieve over a thousand horsepower.  They neglected this scource of energy in pursuit of animal fats they could burn.  They spent more energy chasing the whales and killing them loading them etc than the whale catch produced.
.

I hate the whaling industry.  I can't imagine the agony those poor creatures suffered after being harpooned.  Even with the modern grenade tipped harpoons, the whole thing is disgusting.  I'd like to send one of those whalers running on foot and fire my spear gun into his back then yank his ass to the ground and see how he likes it.

I'll bet you can't tell that topic gets me all bothered.  The things we humans have done ... sometimes I'm ashamed to identify myself as human ... hey wait a minute, that's right ... I'm an Alien ... got six toes, six fingers and ... oh darn, still only two of them things.

gmeast

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Re: Directorly Downwind Faster than the Wind
« Reply #71 on: April 03, 2010, 06:49:15 AM »
----------------------------

Man, you sure lucked out landing your handle "sparks", especially for an alternative energy forum.

Congrats

Cloxxki

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Re: Directorly Downwind Faster than the Wind
« Reply #72 on: April 03, 2010, 01:00:06 PM »
Unfortunately, this thing doesn't work (at least not the way the inventors claim).

Look these videos:

http://www.youtube.com/watch?v=RBjDPhLoPJY

http://www.youtube.com/watch?v=WXk5g-fS3pY

At the end of the videos, we can see that, when the vehicle is separated from the truck that was pushing it, the propeller quickly slows down.

It seems to me that these videos where made in a place with low speed enviromental wind. And with low speed enviromental wind, this thing don't work. The thrust created by the rotating propeller is not sufficient to compensate the friction in the wheels. So, the friction make the wheels slow down, and with the wheels slowing down, the propeller slows down too.

This might work if the RPM of the propeller were sufficient to create enough thrust to keep the vehicle at a speed at which the rotation of the wheels were in the same RPM of the propeller. I think it may depend of the size of the wheels, gear ratio, etc... Maybe bigger wheels could be better...
Those vids were taken before the successful lake bed ones. Some last-day adjustments were made, I think. I did not see inventors claim any speeds in still wind. I can see that any vehicle will have a minimum level of wind it operates in. Rolling resistance (they claim its way low) must first be overcome. In the case of thise DDW cart, the drive system from the wheel to the prop is part of the initial drag, it's a fixed ratio connection. With a foldaway sail and manual clutch, it would not need the truck's push.
It would be interesting to learn of their dyno tests, at which speed the prop offers which thrust. In their cart's case, the wind first needs to bring it there. As often said by the team, acceleration up to around wind speed, is very slow. This might be due to the prop blade style chosen? Anyway, this is not a drag race.

I happened to know (or claim to know) a thing or two about wheel for low-power, low weight, off-road applications. I am a recovering mountainbike tech weenie.
I can tell you, but vast majority of cyclists didn't start believing this until recent years and most still don't, that larger wheel are (almost) universally better for performance. A little bit more so if it's no drag race.
In this DDW application, traction oddly is a factor. They want a light craft, but it must offer sufficient traction to have the wheel slip from the wind forced on the prop.
How does one improve mechanical traction without just throwing on lead weight on the vehicle?
- reduce tire pressure (depending on surface conditions, rolling resistance might go up or down)
- softer tire tread rubber
- thinner tire casing
- don't use an innertube, seal up with tape, liquid latex and slime
- but really, increase wheel size

Larger diameter (not width per se) wheels, will have a longer and narrower contact patch with the surface. This is already visible when going from 22.5" to 25" diameter rims (26" vs 29" wheels) with otherwise identical tires. The traction is noticed in braking and climbing.
Furthermore, lateral stability is greater, as is cornering grip.

Would the team go from 26" to 29" MTB wheels, all other factors remaining the same, they'd reduce rubber interface rolling resistance and more importantly : traction. Slipping wheels, drag. Even if the wheels are trying to spin faster than the vehicle (might happen with that prop attached).

As their cart is not really bike-light though, I like the changes of using 36" wheels. Tires available are pretty much motor cycle quality (being relatively draggy), but their pure size makes them insane rollers. I once rode such a bike on an exhibition floor, and it was just utter silence and peace. Friends of mine have taken my designs, and make them reality, 36" wheels MTB's. They report unreal traction, from the super low tech tires. And, over rough terrain, it just outrolls everything, even when the smaller wheeled bikes are fitted with suspension system to smoothen their ride.

I wrote to Spork to look into large wheels, hidden inside the prop's support structure. It would be a 30 or 37" by 3" aero shpaed casing. Narrower above the wheel. Like with recumbent bikes, the tire would barely peek out from under the wheel casing. Little aero drag for stunning tire traction and rolling performance.
I'd rather bet my life on 36" wheels when crossing a salt lake at 150mph, than 26". Especially when power input is limited and speed is the goal. Supsension helps a vehicle run smootly, but just sucks out kinetic energy. There is a reason why carriage wheels were man-tall, or better.

I am a bit questioning the 3-wheel setup though. Although the steering is relatively simple, the balancing is more challenging (tipping over is game over). A 4-wheel setup would allow a very aero setup, wheels inline on either side. Usually, more wheels engaged, actually reduces rolling resistance. This at least goes for uvicycle vs bicycle, and for inline skates. I tested my inline with 2, 3 and 4 wheels in each, and the difference is clear. More wheels rolls faster. On asphalt hard to explain (in softer terrain you dig in less deep with more wheels spreading the load), but hey, all inline skates see is asphalt. Maybe is does compress under the wheels...

If it would be my project, I'd have most trouble figuring out the prop setup itself. One naked large one like this, multiple small ones parallel, or even in series, with or without ducts around them.
I support all would need to be tested for trust at various gearings, and them eventually incorperated into the final design.
I'd like a basic delta shape flat chassis, front wheel fully enclose of course. Rear wheel just sticking out the sides, and very thin aero blades making for the top part of the prop support. Preferably sitting well in front of behind the prop itself, unless they could double as air duct to improve prop efficiency. I could even imagine the prop being only halfway (bottom part) enclosed. The structure is handily there to provide some.

ramset

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Re: Directorly Downwind Faster than the Wind
« Reply #73 on: April 03, 2010, 02:45:08 PM »
Well
Very Cool that it was scaleable!
It seems to be an old school prop design , but there "must" be something special there!

Gotta be something special to over come all that drag and still make power to move?

@Clo
A Tiny replication?
I'll play![gotta be cheap]

Chet

 PS
Greg Do you remember the guy that had that "3 winged" sail rotary
Configuration?
About 15 /20 years ago?
Had it on a "BIG" catamaran ,was supposed to be the future,you
could drive it like a car,I don't know about going "Into" the wind.

Hmmm....... I do know someone that Should know, I'll ask him on Monday.

gmeast

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Re: Directorly Downwind Faster than the Wind
« Reply #74 on: April 03, 2010, 05:38:42 PM »
Well
Very Cool that it was scaleable!
It seems to be an old school prop design , but there "must" be something special there!
...................

The prop is 'old school' in the sense that it is for relatively low speed (tip velocity) and lifts (like a wing), or produces a thrust force almost all the way to the hub ... like the Wright Flyer (Wright Brothers, Kitty Hawk 1903).