Directorly Downwind Faster than the Wind

[gmeast]

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

Congrats

[Cloxxki]

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]

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]

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).