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sailingsoul
SFN Addict
2830 Posts |
 Posted - 07/29/2010 : 19:44:32
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Who hasn't dreamed or laughed at, the concept of putting a propeller on a car to have the wind spin the propeller and drive the wheels. That's right, harness the wind to get you down the road, with no engine! Well that's what a team has done in record setting trials, earlier this month. One might wounder what about down wind, once you match the wind how could you go any faster, than the wind? Well this baby clocked 2.8x the wind speed, down wind. Wait a minute if this is possible why are we buying gas, on windy days?
From the ArticleThe DWFTTW cart traveled directly downwind at 2.8 times the wind speed.,,,, with the wind acting as an external power source that propels the cart faster than the wind itself
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SS
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There are only two types of religious people, the deceivers and the deceived. SS |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 07/29/2010 : 20:21:06 [Permalink]
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| Interesting. But I'm one of the disbelievers. Can't be done, says me, |
“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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Robb
SFN Regular
USA
1223 Posts |
Posted - 07/29/2010 : 20:49:02 [Permalink]
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The wheels turn the prop, which turns the vehicle’s wheels, which turn the prop, which turns the vehicle’s wheels. Cavallaro knows what you’re thinking.
“It sounds like a perpetual motion machine — but you’ve got the wind as an external power source,” he said. |
How can the wheels turn the prop if the prop is supplying all the energy for the car? What am I missing?
Somehow they are getting more energy from the wind than it takes to propel the car at that speed.
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Government is not reason; it is not eloquent; it is force. Like fire, it is a dangerous servant and a fearful master. - George Washington |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 07/29/2010 : 21:21:57 [Permalink]
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Seems odd to me. Have to wait until more info is available on how it works.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 07/29/2010 : 22:07:24 [Permalink]
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Mark Chu-Carroll explained this 20 months ago.
Basically, the wind doesn't turn the propeller. The propeller acts like a sail, instead, which provides forward thrust that turns the wheels, and the turning of the wheels spins the propeller to provide more forward thrust.
As Mark says in what is a big apology and correction,It should be obvious that there's some way to go downwind faster than the wind, because as so many people pointed out, sailboats do it. It was frankly stupid of me to even argue about this - it's really pretty boneheadedly obvious. The question never should have been "can it be done?", but rather just "does this device do it?"
And the answer to that is "Yes". This thing does do it. It's not magic, it's not perpetual motion. In fact, it's really astonishingly simple, once you realize that the behavior of things moving through air is quite different from the simple rigid system that it appears to be equivalent to. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 07/29/2010 : 22:23:40 [Permalink]
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I'd like to know whether, somewhere in that "massively heavy-duty transmission," there is a flywheel lurking. I can envision such a wind-powered vehicle building up energy from harnessing a following wind's energy into potential in a flywheel while stopped or at speeds lower than the wind.
Properly geared, such flywheel energy could build up potential to become quite powerful. And with good gearing, such stored flywheel energy might then be tapped once the vehicle gets to wind speed, propelling the vehicle faster than the wind itself. (The propeller would then either be feathered, or operate to push the vehicle against the slower wind at such speeds.)
That's my first guess as to what's going on. It would violate no laws of conservation of energy, and could account for what little we know of the feat.
It would also be a sneaky trick, not different in effect from having the vehicle sit at the starting line and operate an electrical turbine generator until a battery is fully charged, then using that charge to outrace the wind. |
“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 07/29/2010 : 22:47:51 [Permalink]
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| I missed Dave's post above. I am now reading and trying to understand Mark Chu-Carroll's explanation. |
“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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ThinAirDesigns
New Member
13 Posts |
Posted - 08/01/2010 : 20:27:04 [Permalink]
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Hi, I'm JB -- one of the two primary designer builders of the vehicle in question.
Originally posted by HalfMooner
I'd like to know whether, somewhere in that "massively heavy-duty transmission," there is a flywheel lurking. |
Journalists/bloggers always want to make something BIG or SUPER when doing a story. I have no idea why this one picked the transmission to 'super-size'. He of course never spoke to us nor did his research from our project blog (http://www.fasterthanthewind.org)
Our transmission consists of ordinary bicycle sprockets and chain.
http://www.fasterthanthewind.org/2010/01/next.html
http://www.fasterthanthewind.org/2010/02/last-circle-for-now.html
http://www.fasterthanthewind.org/2010/02/one-thrust-box-to-go.html
| I can envision such a wind-powered vehicle building up energy from harnessing a following wind's energy into potential in a flywheel while stopped or at speeds lower than the wind. |
The transmission is of the fixed ratio type -- we used the cassette to find the right ratio on the dyno, but there's no derailer and no shifting happens while on the run. (we haven't change ratios since we found the optimum one.
With a fixed ratio transmission, there is no way for any stored KE in the rotating parts of the drivetrain (prop, etc) to be used to accelerate the vehicle since slowing the prop also slows the wheels.
JB |
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Dave W.
Info Junkie
USA
26022 Posts |
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sailingsoul
SFN Addict
2830 Posts |
Posted - 08/02/2010 : 07:58:57 [Permalink]
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| Welcome ThinAirDesigns (JB). Congratulations on your results and record breaking achievement. I'm not surprised to hear the article comment about the transmission was a bit overstated because it makes sense any complexity would likely add undesired friction. SS |
There are only two types of religious people, the deceivers and the deceived. SS |
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ThinAirDesigns
New Member
13 Posts |
Posted - 08/02/2010 : 09:47:21 [Permalink]
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Hi Dave,
We have a few minor nits with his explanation (his "cushion" analogy isn't correct), but overall he did a decent job. Most of his mistakes were in his drawing with the gears and were pointed out in the comments.
JB |
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ThinAirDesigns
New Member
13 Posts |
Posted - 08/02/2010 : 09:48:30 [Permalink]
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Originally posted by sailingsoul
Welcome ThinAirDesigns (JB). Congratulations on your results and record breaking achievement. I'm not surprised to hear the article comment about the transmission was a bit overstated because it makes sense any complexity would likely add undesired friction. SS
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Thanks SS.
Yes, we spend a LOT of time figuring how to get rid of weight and complexity - net efficiency was everything.
JB |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 08/02/2010 : 11:50:37 [Permalink]
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It's pretty interesting, and after a little reading I think I understand at least the basic explanation.
You guys should start a wind-car racing league!
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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ThinAirDesigns
New Member
13 Posts |
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bngbuck
SFN Addict
USA
2437 Posts |
Posted - 08/02/2010 : 17:02:24 [Permalink]
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Practical Quiz on the Mechanics of Motion.....
If an airplane lands at 100 mph on a large conveyor belt running at 100 mph in a direction opposite to the direction that the airplane is landing, what happens? |
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ThinAirDesigns
New Member
13 Posts |
Posted - 08/02/2010 : 17:07:21 [Permalink]
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Originally posted by bngbuck
Practical Quiz on the Mechanics of Motion.....
If an airplane lands at 100 mph on a large conveyor belt running at 100 mph in a direction opposite to the direction that the airplane is landing, what happens?
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What happens? ... People on the internet argue about it for years. :-)
But other than that, not much as long as the tires etc can withstand spinning twice as fast as normal for a short time.
JB |
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A most counter-intuitive feat!
