• Quick note - the problem with Youtube videos not embedding on the forum appears to have been fixed, thanks to ZiprHead. If you do still see problems let me know.

Down wind faster than the wind

Boy - I forgot how “touchy” you guys are. Did you really not realise I was joking? Perhaps I should have used a little smiley emoticon.

I have actually tested a ball bearing on a treadmill by the way. I wanted to see if there was any “advantage” close to the bottom roller. There wasn’t that I could see. The tread didn’t have a nice smooth surface like the turntable so the ball slowed more quickly. The ball running on the tread was very smooth however and I’m confident I could raise the bottom end of the treadmill so the ball could be made to hover almost indefinitely. This has absolutely nothing to do with DDWFTTW however and suggesting doing it this way was a joke and a “cheat” (not a real cheat because the “rules“ specified didn‘t forbid it).

Hope this will cheer you up - Initial tests of my new cart design on my roughly repaired, hand spun turntable have been very impressive. The single sided cart prototype develops enough thrust to travel against the spin of the turntable at quite an amazing speed. The turntable doesn’t have to be revolving very fast for the cart to move against it either so the design is quite efficient. I found (as others said) that a single prop works better than two. I will build a new motor driven turntable and double sided cart before beginning testing. Results will be filmed and posted. In the meantime . . . go outside and smell a tree, hug a flower.
 
Michael C said:
Here's a question: can you design a non-motorised machine, as small and as light as Spork's cart, that does not use the thrust of a propeller powered by the wheels, that touches only the belt of the treadmill, but which will stay in the same place on the running treadmill for more than a minute?
Click to expand...

ynot said:
Here’s an answer: Yes of course I can. A ball bearing will do this if I angle the treadmill downhill towards the front the correct amount so the ball will hover (not against the rules you set).

Holiday travelling is over and am starting to build my new turntable and cart for testing.
Click to expand...

I see you're looking for loopholes instead of giving an honest answer. The point of the question, of course, is to to ask what other phenomenon other than the thrust of the propeller could account for the cart staying on the running treadmill so long. I'll rephrase the question:

Can you design a non-motorised machine, as small and as light as Spork's cart, that does not use the thrust of a propeller powered by the wheels, that touches only the belt of the treadmill, but which will stay in the same place on the treadmill belt running perfectly horizontally or angled uphill for more than a minute?
 
ynot said:
Hope this will cheer you up - Initial tests of my new cart design on my roughly repaired, hand spun turntable have been very impressive. The single sided cart prototype develops enough thrust to travel against the spin of the turntable at quite an amazing speed. The turntable doesn’t have to be revolving very fast for the cart to move against it either so the design is quite efficient. I found (as others said) that a single prop works better than two. I will build a new motor driven turntable and double sided cart before beginning testing. Results will be filmed and posted. In the meantime . . . go outside and smell a tree, hug a flower.
Click to expand...
Ynot, congratulations. I suppose you must have rid yourself of any remaining doubts about steady state, have you?

I have some more to ask about this, but I'll use the other thread you started for it.
 
ynot said:
Boy - I forgot how “touchy” you guys are. Did you really not realise I was joking?
Click to expand...
-
Ah yes ... more of that "I'll make a statement as if it's a fact and when called on it I'll claim the 'spot the flaw' strategy".

JB
 
ThinAirDesigns said:
This is a perfect example of your lack of depth when it comes to testing. It will be far more difficult than you imagine to keep a BB within the length of a treadmill belt without running off one end or the other.
Click to expand...

No it won't. Just put one of these under the treadmill and that pesky BB won't be going anywhere. (except perhaps through the belt)
 
Jadebox, check out the link to my website. It contains a document that describes how a vehicle can go ddfttw. It doesn't assume the reader has any familiarity with these vehicles. And it doesn't assume the reader is an aeronautical engineer. It explains it in pretty plain language and if you read it, odds are you should at least have a basic understanding of how it works, and realize it does in fact work.
 
Archangel said:
Really you can?

Ok please demonstrate how you can tell which is which in the following example:

Alien Space Bats transport you from your home in the middle of the night whilst you are asleep.

You wake up in the "morning" in an exact replica of your house, the only difference as far as you can see is that you've landed in what appears to be a grass savannah.

The sky is bluer than you've ever seen before, and there are no clouds in the sky nor can you see the sun, yet strangely the area is illuminated.
Every time you try to walk further than 1 mile from your house, no matter the direction, you are instantly transported back to your house and you're still unable to see anything other than grassland.
Barring these minor differences the world is exactly the same as the Earth.


All that you can see around you is grass blowing in the wind and a windsock at the front of your house that is standing perpendicular to its pole and pointing to the right parallel to your house as you face your house.
You have a wind gauge that is telling you that the wind is moving at the rate of 10mph.

Is it possible that this house is actually:

a) Stuck to a giant grassed treadmill, moving towards the left side of your house as you face it?
/ \ >
___|__|__|__
<- Belt travelling this way

b) Stationary with a 10mph wind blowing from the left side of your house towards the right side?

Wind travelling this way
-> / \ >
___|__|__|__


c) either of the above.

If you've answered b) please provide proof of how you can determine this with the tools at your disposal (ie a Windsock, a featureless savannah and a wind gauge).
Click to expand...

Your flow diagrams are wrong. Period.

The test:
Introduce blue smoke into the air flowing past the observer moving with the belt and red smoke over the belt at the cart end, and then tell me you can't tell the difference
 
Christian Klippel said:
Hello,

i'm not sure that the combination of battery, generator and motor is feasible. Same goes for a flywheel, but to a lesser extent. The problem i suspect comes with the added weight, additionally with the charge required in the case of a battery. If the course is not that long, it might take too long to just accelerate the whole thing, especially when a rather big flywheel is used. In case of a battery/generator/motor combination, one would need a rather long time to charge the battery to any useful level.


One might use a bank of super-cap's instead of a battery, which would <snip>
Click to expand...

Flywheel Christian? You will be able to usefully recover no more than 50% of the energy stored in the capacitors, I'm afraid. Keep it in the flywheel.
 
Dan O. said:
This website? http://www.greglondon.com/tumbleweed/
Click to expand...

Well, here's the first and last thing I read that Greg London published ( http://tinyurl.com/8gc9qy ). It is really fairly humberistic in that it is caustic toward the people that have tried to explain it to him, condescending, and really truly astonishing in it's wrongness. Greg explained to us that we don't know how our own cart works, and that he is a real engineer that requires a much higher level of rigor (because a mistake on his part would result in many people dying in horrible fiery deaths). He apologized for having and holding others to his own high level of rigor - and then presented the design in this document.

Note that this is not only a design that DOES NOT work - it's a design that CANNOT work. He went on to explain that he had no need at all for testing it, because his high level of engineering analysis showed it clearly to be workable. Since Greg didn't see the need to test his design (high level of engineering rigor and all), we went to the trouble to build and test it for him. You can see our test here:

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

So by all means, people should feel free to read his further analyses, or even his primer on classical physics. I have no desire to read any more of this. If you read the attached I think you'll agree there's no reason to read any further.
 
Last edited:
humber said:
The test:
Introduce blue smoke into the air flowing past the observer moving with the belt and red smoke over the belt at the cart end, and then tell me you can't tell the difference
Click to expand...

I saw this with amazement! I read it with jubilence and excitement. Then I got to the punch line: "and then tell me you can't tell the difference"

That's not how it works humber. YOU have to tell us what the difference will be. HINT: there will be no difference.
 
spork said:
I saw this with amazement! I read it with jubilence and excitement. Then I got to the punch line: "and then tell me you can't tell the difference"

That's not how it works humber. YOU have to tell us what the difference will be. HINT: there will be no difference.
Click to expand...

It is a palpable demonstration of a condition that cannot exist in the real wind. The emphasis then shifts from that, to the capacity of the observer to appreciate that difference. That is what I meant.

ETA: I look forward to seeing the tests of your tumbleweed design.
 
Last edited:
humber said:
It is a palpable demonstration of a condition that cannot exist in the real wind. The emphasis then shifts from that, to the capacity of the observer to appreciate that difference. That is what I meant.
Click to expand...

Without the poetry or rhetoric, perhaps you can tell us what we should expect to see in the real wind, on the treadmill, and how they'd differ.

D'OH!!! There I go again asking questions that suggest I might expect a responsive answer.
 
Michael C said:
Humber, Spork and Archangel: please could you use the appropriate thread for discussions of treadmills, "real wind" and other problems of basic physics?
Click to expand...


On the one hand... my bad. I'm old and easily confused.

On the other hand.... "humber, spork and Archangel..." Really!? You put our names right there with humber? Is that our punishment for misbehaving? :D
 
As Michael C notes, there is a thread for discussing general physics and the comparison between treadmills and wind. Please use it.
Replying to this modbox in thread will be off topic  Posted By: Cuddles
 
It is really fairly humberistic in that it is caustic toward the people that have tried to explain it to him, condescending, and really truly astonishing in it's wrongness.
Click to expand...

Spork, the very first post on this entire thread says that you got two other threads on DDFTTW locked because of your behaviour. Getting an admonishment from you about being condescending is like getting lessons on ettiquette from John McEnroe. You cannot be serious.

if anyone is having trouble understanding how a machine can go DDFTTW and are getting sidetrack by spork's relentless confrontations, try taking a look at my writeup on my website. see #3108 for a link.

It explains how such a device can work, and doesn't rely on issues such as whether or not a treadmill is equivalent to moving in the wind. Also, my ego won't be bruised if you read my explanation and you still don't understand it or doubt whether it can work. Which can really help with follow up questions.
 
GregLondon said:
Getting an admonishment from you about being condescending is like getting lessons on ettiquette from John McEnroe. You cannot be serious.
Click to expand...

Your first paper was clearly condescending and showed a picture of the debate that was not even close to the one I have seen so I can't see your point at all.
 
You must log in or register to reply here.

Back
Top Bottom