DDWFTTW - Tests.

[spork]

Ynot, Michael C is correct in saying that your experiment shows the difference between static and kinetic friction. You're incorrect in stating that's all it shows. I can easily give you a scenario in which the block and surface have the same coefficient of friction for both static and kinetic, and yet they still show what your experiment shows - no self start, but it can sustain DDWFTTW if given a start.

You claim to have thick skin and broad shoulders, but you launch these silly attacks as you've done with your description of your poorly conceived experiment, and hope not to be corrected. The simple recipe for avoiding attacks is to not attack others. The recipe for not being corrected is to avoid saying things that are wrong. 'mmKay?

 

[ynot]

Ynot, Michael C is correct in saying that your experiment shows the difference between static and kinetic friction. You're incorrect in stating that's all it shows. I can easily give you a scenario in which the block and surface have the same coefficient of friction for both static and kinetic, and yet they still show what your experiment shows - no self start, but it can sustain DDWFTTW if given a start.

You claim to have thick skin and broad shoulders, but you launch these silly attacks as you've done with your description of your poorly conceived experiment, and hope not to be corrected. The simple recipe for avoiding attacks is to not attack others. The recipe for not being corrected is to avoid saying things that are wrong. 'mmKay?

Sure, but you don’t seem to realise that works both ways.

I don’t mind being corrected when I’m wrong, in fact I would be disappointed if I wasn’t. I do mind however (but not much) that I’m accused of being “incorrect” by way of a misquote - Saying ‘that’s all it was meant to demonstrate” is not saying “that's all it shows”. You seem to employ misquoting/misinterpreting attacks in an attempt to discredit others quite often.

I will let forum readers reach their own conclusion as to who does the majority of personal attacking on this forum.

 

[ynot]

Ynot, can you clear something up for me, please? I watched the little cart that could first, because for some reason the ..couldn't didn't load properly at youtube and I clicked on the other. Now, first of all, I thought that was fairly obvious that the cart would accelerate from that held position. It's being made to keep at windspeed, but should theoretically be producing enough thrust to accelerate. You let go. It does.

But, I then watched the little cart that couldn't, and it doesn't run long enough to reach steady state, or not long enough for me to judge that. I take it that it is the same setup exactly, and I also have to take it from your report that however long it ran, the cart never reached windspeed. Now, I can't for the life of me think of any other explanation than that provided by Michael, which seems to suggest that not only did the cart not beat the wind, it never really set off from being stuck (by that higher static friction) to the TT.

Now you might think of something to test that - like perhaps handicap the cart in another fashion - if you want to check. From the few seconds we get, it seems to move slightly, but does not even cross the index mark. I think you would have a strange anomaly if it had a steady state that was some fraction of windspeed when set off from a standing start, but a multiple of windspeed if set off from windspeed. The physics of that would be very odd indeed - it should have a favoured speed - above it, it will slow down - below, it will speed up. See?

So the cart that couldn't may have just been stuck like a brick on a slope, but one that, with a tiny push, would slide down the slope. It's also my experience that such an object can slide a little way, but not quite get going and stop again.

The same design can't be a cart that couldn't and a cart that could other than by some unusual effect like the static friction you have introduced into the system. This is why your idea of the cart possibly only beating the wind when held so that it gains enough thrust to accelerate was wrong, I think. It is not being held so that it is forced to create sufficient thrust by being held, but prevented from developing more by going faster. At any speed slower than that, it will be providing more thrust than is needed for the speed it's going, so it accelerates. It's being held back, and if it's being held back, it can't be the cart that couldn't.

You might be able to hold it back to something slower, and then let go. But you've already done a standing start right up to beating the wind. I think you must conclude that your idea of what it can do being increased by being held must have been wrong. One test design - maybe tricky to find the bits - would be a trailer with wheels that are turning, but have a lot of friction in the axles. Another simpler (and truer) method might be to fit a more inefficient prop, so that it goes, but doesn't beat the wind. If you hold that cart at windspeed, I'm confident it will just slow down immediately you let go.

ETA: Whoops, in all that I forgot to ask the thing I wanted you to clear up: wasn't your point that a cart that would not 'normally' beat the wind could be made to by being held at windspeed? If so, the video of the cart that could isn't any use unless it slows down again to lower than windspeed and is actually a cart that couldn't. It seems to be a cart that could, but again the video isn't very long. So, after both videos, I don't know which it is, a cart that can or one that can't. Oh yes, I do, it accelerated from windspeed, so it isn't going to slow down again in the same conditions. You seem to have a view that the forces will be different depending on how they used to be at some time in the past, which is getting dangerously close to humberism for my liking.

Keep up the good work.

It takes a long time to upload even short videos to Youtube so I try to keep them as short as possible. I tested the “cart that couldn’t” for quite a long time and I don’t think it would ever gain enough speed to advance against the turntable without receiving some sort of “prod“ to do so.

I’m not saying there’s anything wrong with a cart being helped up to wind speed as long as it doesn’t store excess energy in any way in the process. I once thought this might be happening but my experiments have proven (to me at least) it doesn’t. Other experiments I had seen didn’t prove this to me adequately and I have received feedback from others who also have been helped in this regard by my experiments. This is not saying that other experiments didn’t or don’t provide useful information.

My experiments have been so conclusive to me that I now pretty much accept that DDWFDDW is possible. I will always have an element of scepticism however for something that is so counter intuitive and will keep testing and may even build a cart for outside testing in actual winds or some form of wind tunnel. Have a ten speed bike design in mind as it would be cool to ride on the cart. Hope if others are doing the same thing they post videos of their results regardless of whether they are successful or not.

 

[Dan O.]

Because the efficiency of the prop is non-linear, it is possible for a cart that can travel DDWFTTW will not be able to self start. However, YNOT's videos don't clearly demonstrate this because the block in the two videos are in different positions. The can't-do cart has 15-20% more friction drag than the can-do card.

It is also possible for the block to start flying over the surface of the spinning disk much like the heads fly in a disk drive. Once the block takes flight, the friction goes to almost zero.

 

[spork]

My experiments have been so conclusive to me that I now pretty much accept that DDWFDDW is possible.

Have you posted video of any of these experiments? So far I think you've told us that everything you posted was a "find the flaw" game or specifically "not an experiment". Why haven't you tied weights to your cart and run them over pullies? Isn't that what you kept bitching at us for not doing? You were so upset that you would have to use your own time to perform your own experiments.

 

[spork]

Because the efficiency of the prop is non-linear, it is possible for a cart that can travel DDWFTTW will not be able to self start. However, YNOT's videos don't clearly demonstrate this...

D'OH! You gave away the ending. I'm sure ynot would have figured it out.

 

[ynot]

Have you posted video of any of these experiments? So far I think you've told us that everything you posted was a "find the flaw" game or specifically "not an experiment". Why haven't you tied weights to your cart and run them over pullies? Isn't that what you kept bitching at us for not doing? You were so upset that you would have to use your own time to perform your own experiments.

What a shame your main interests seem to be ego and limelight.

 

[ynot]

Because the efficiency of the prop is non-linear, it is possible for a cart that can travel DDWFTTW will not be able to self start. However, YNOT's videos don't clearly demonstrate this because the block in the two videos are in different positions. The can't-do cart has 15-20% more friction drag than the can-do card.

It is also possible for the block to start flying over the surface of the spinning disk much like the heads fly in a disk drive. Once the block takes flight, the friction goes to almost zero.

I filmed the “could” video first and when I did the “couldn’t” immediately after and the block spun in to the propeller with the centrifugal force (obviously). I tied a string from the side of the block to the center and made it too long by mistake. After filming I continued “playing” and did both “could” and “couldn’t” runs with the string attached. Same result each time and never any “flying“. Of course you will have to just believe me on this and I could be lying and cheating (again apparently).

 

[ThinAirDesigns]

What a shame your main interests seem to be ego and limelight.

Judging only by results, Sporks "main interests" of ego and limelight at least take second fiddle to making sure that test are what they seem to be.

Wish the same could be said for your tests. As he points out so far we have the following catagories of tests:

A: One round of trick "find the flaw" tests presented as real.
B: One round of tests that you have so little faith in that you introduce with "no claims are made" statements.
C: A last round of tests that pretty much everyone agrees don't demonstrate what you say they demonstrate.

JB

 

[ynot]

Judging only by results, Sporks "main interests" of ego and limelight at least take second fiddle to making sure that test are what they seem to be.

Wish the same could be said for your tests. As he points out so far we have the following catagories of tests:

A: One round of trick "find the flaw" tests presented as real.
B: One round of tests that you have so little faith in that you introduce with "no claims are made" statements.
C: A last round of tests that pretty much everyone agrees don't demonstrate what you say they demonstrate.

JB

The Spork & Co tag team strikes again. I will return to not responding to insults.

ETA - Let me answer your points first . . .

A: How is it possible to run a “find the flaw” test and not present it as real? That’s a question that isn’t rhetorical.
B: Not a lack of confidence but more an attempt to reduce insults. The attempt clearly didn’t work.
C: I don’t agree. But regardless, I never claimed to be perfect.

Lets see what Spork & Co have Offered . . .

A: Did they come up with the idea? No. it’s at least 60 years old.
B: Did they design “their” cart. No. they copied someone else’s cart.
C: Is using a treadmill their idea? No. They copied that idea as well.

But they have done very well to give this principle public exposure on several forums and boosting their egos and gaining some limelight in the process. It’s like you guys want something good to put on your CV.

At least what I’ve done has been fairly original.

 

[ThinAirDesigns]

The Spork & Co tag team strikes again. I will return to not responding to insults.

-
Now you're taking a simple statement of facts on record in this thread and calling them "insults".

JB

 

[ThinAirDesigns]

It is also possible for the block to start flying over the surface of the spinning disk much like the heads fly in a disk drive. Once the block takes flight, the friction goes to almost zero.

Same result each time and never any “flying“.

Unless you are prepared to show some pretty good resolution video to support that statement you're just barking on the wind -- not from a "lying or cheating" standpoint, but just from a "you can't know that so you shouldn't say that" standpoint.

The string on the front of the block angles up to the cart tether. Obviously this means that with tension the front of the block is receiving an upward pull. Once the boundary layer of air from the spinning surface gets under a ever so slightly raised surface, it would have a dramatic influence on the overall friction.

Only a very high resolution video taken from just the perfect angle could prove that Dan O's simple and perfectly plausible hypothesis is in fact not happening.

JB

 

[Dan O.]

I filmed the “could” video first and when I did the “couldn’t” immediately after and the block spun in to the propeller with the centrifugal force (obviously). I tied a string from the side of the block to the center and made it too long by mistake. After filming I continued “playing” and did both “could” and “couldn’t” runs with the string attached. Same result each time and never any “flying“. Of course you will have to just believe me on this and I could be lying and cheating (again apparently).

You would probably not see the flying because it is using ground effect. (<-= OMG, did humber write that!!)

To demonstrate if you have flight, spin it up so the cart & block are traveling faster than the wind then disconnect the drill so it will slowly spin down and watch for the sudden change when the block stops flying. Alternatively, tether the block to a force measuring device (without the cart) and look for a transition from low drag at high speed to higher drag at low speed.

[A simple force measuring device: hang a weight from the ceiling and run a horizontal tether from the weight to the block. Use a ruler to measure the displacement of the weight and calculate the force with simple trig.]

If you don't get flight with this block, try rounding the leading edge.

 

[ThinAirDesigns]

A: How is it possible to run a “find the flaw” test and not present it as real? That’s a question that isn’t rhetorical.

-
How is it possible to ever expect credibility after presenting tests as real and then days later, and only under challenge, admitting that they were intentionally flawed? That's a question that isn't rhetorical either.

B: Not a lack of confidence but more an attempt to reduce insults. The attempt clearly didn’t work.

-
Well, that's what you say *now*, days after the fact and again under challenge (see above)

Lets see what Spork & Co have Offered . . .

A: Did they come up with the idea? No. it’s at least 60 years old.
B: Did they design “their” cart. No. they copied someone else’s cart.
C: Is using a treadmill their idea? No. They copied that idea as well.

Wait, this is another game of "spot the flaw" and "I've left an important detail out that should be included" -- that detail is the flawless credit we've given to the designers who went before us. We throw credit around like Christmas candy.

JB

 

[ynot]

-
How is it possible to ever expect credibility after presenting tests as real and then days later, and only under challenge, admitting that they were intentionally flawed? That's a question that isn't rhetorical either.


-
Well, that's what you say *now*, days after the fact and again under challenge (see above)



Wait, this is another game of "spot the flaw" and "I've left an important detail out that should be included" -- that detail is the flawless credit we've given to the designers who went before us. We throw credit around like Christmas candy.

JB

You didn’t answer question A. When you have I will answer yours.

 

[ynot]

-
Now you're taking a simple statement of facts on record in this thread and calling them "insults".

JB

The old “my insults aren’t insults because they are facts” ploy.

 

[ynot]

You would probably not see the flying because it is using ground effect. (<-= OMG, did humber write that!!)

To demonstrate if you have flight, spin it up so the cart & block are traveling faster than the wind then disconnect the drill so it will slowly spin down and watch for the sudden change when the block stops flying. Alternatively, tether the block to a force measuring device (without the cart) and look for a transition from low drag at high speed to higher drag at low speed.

[A simple force measuring device: hang a weight from the ceiling and run a horizontal tether from the weight to the block. Use a ruler to measure the displacement of the weight and calculate the force with simple trig.]

If you don't get flight with this block, try rounding the leading edge.

The “block” thing is of no further interest to me. There are other things I may test and may start constructing a cart for outside wind testing. Or I may do something completely different with my time.

 

[spork]

What a shame your main interests seem to be ego and limelight.

Not only does that not follow in any way from the quote, there's nothing that suggests this other than your desire to attack us and our tests without expecting the same in return.

A: Did they come up with the idea? No. it’s at least 60 years old.

As I've said more than once - I did come up with the idea. I then learned I was not the first to have come up with it. Certainly that's common enough. I never claimed to have "invented" this thing. Nor have I ever claimed any different than the statement right here.

B: Did they design “their” cart. No. they copied someone else’s cart.

We initially copied Jack Goodman's cart to a large extent - and gave him full credit (watch our video). We then copied Mark C's cart to a large extent - and gave him full credit (watch our video). We never claimed any differently.

It’s like you guys want something good to put on your CV.

Really? You'd have to tell me what I plan to do with that. We've been completely up front with this from the start as well. We want to get the Mythbusters to do a segment on it.

At least what I’ve done has been fairly original.

Really!? By reproducing the tests the Bauer did many years ago? He put his cart on a turntable long before you copied him.

By the way - what Goodman did wasn't original. What Bauer did wasn't original.

The old “my insults aren’t insults because they are facts” ploy.

Facts are facts. If you find them to be insulting you should avoid doing things that are embarrassing.


I just hope you consider this entire post insulting - and therefore don't respond to it.

 

[John Freestone]

You would probably not see the flying because it is using ground effect. (<-= OMG, did humber write that!!)

No, but I'm fairly sure he's trawling this thread for new phrases he can punch in to his random word generator and spew over the other one. Actually, what am I saying, he's used that one all along - that the cart on a treadmill is lifted on the boundary layer, by its wheels!

You're doing very well, BTW. One day at a time!

 

[John Freestone]

It takes a long time to upload even short videos to Youtube so I try to keep them as short as possible.

I accept that, and I trust your integrity in honestly saying what you saw over a longer time. I think you may still misunderstand what I'm saying, since you haven't addressed the points directly. Maybe I was a bit quick to jump in and waffled a lot, and so confused you.

I tested the “cart that couldn’t” for quite a long time and I don’t think it would ever gain enough speed to advance against the turntable without receiving some sort of “prod“ to do so.

That's fine, but the point was whether this was because it was a cart that couldn't self-start, as was put to you. If you observed it for a long time, it probably should have dawned on you that it was pretty much not going anywhere w.r.t. the mark on the TT. It seemed to me that your earlier hypothesis was something like the following:

A cart might be blown by the wind to less than windspeed (as almost any would without cleverly designed props and stuff if it has wheels and a fairly low rolling resistance in a good enough wind), and remain there, not beating the wind. However, if held at windspeed, the same cart might then beat the wind steady state (or even, perhaps, beat the wind for a time and then return to slower than windspeed).

That's the kind of thing I thought you thought, and that you posted these last two videos genuinely to demonstrate. It seems that you were wrong, because of the difference between the static and dynamic friction. If you have the same cart not starting in one video, and beating the wind in the other, it isn't a cart that couldn't beat the wind, just a cart that couldn't self-start, and not only did the original claim of JB/spork allow for that, but it means that your hypothesis was wrong. It could help the whole study, other people's understanding of it, and relations with other experimenters, if you were clearer in your retractions or where you stand on these things.

I’m not saying there’s anything wrong with a cart being helped up to wind speed as long as it doesn’t store excess energy in any way in the process. I once thought this might be happening but my experiments have proven (to me at least) it doesn’t.

It is good of you to say that you changed your mind, but it is a different matter from the above, I think. But maybe we are a little at cross purposes. The phrase 'helped up to windspeed' is crucial: does it mean given a wee push to get over its static friction (or allow its prop to develop enough efficiency, as I understand is another possible reason not to 'start')? It sounds like it could be a way to try to bolster your earlier hypothesis, because another way to read it is as if it needed pushing all the way to windspeed, or holding at windspeed, for it to beat windspeed. You seemed to say that a cart that won't could become a cart that would by being held at windspeed. Clearly, your cart that wouldn't could be helped up to some small fraction of windspeed, if necessary, and continue to accelerate, beat the wind, and remain there steady state. That's a cart that could, to me, and could despite dragging a brick. Being held at windspeed had nothing to do with its success, and your experiment suggests, and you seemed to interpret it, otherwise.

Other experiments I had seen didn’t prove this to me adequately and I have received feedback from others who also have been helped in this regard by my experiments. This is not saying that other experiments didn’t or don’t provide useful information.

You're definitely right there about your main demo, IMO. As I said before, if someone looks at the spork pushing the cart backwards on the treadmill and has a kind of intuitive feeling that that could somehow make it 'bounce back' and accelerate beyond windspeed, then your minutes and minutes of steady state counter-rotation is one method of helping people get over that, as is putting the treadmill on a slope (but that is hard to balance, etc.).

My experiments have been so conclusive to me that I now pretty much accept that DDWFDDW is possible.

Gosh, reticence still!...

I will always have an element of scepticism

...Ah yes, of course, this is scepticism, and good on you for that. I "pretty much accept" there's no God, I'm going to die, and machines can be blown faster than the wind blowing them directly downwind. I could wake up and realise some of that was wrong! You don't have to ever be 100% convinced.

however for something that is so counter intuitive and will keep testing and may even build a cart for outside testing in actual winds or some form of wind tunnel. Have a ten speed bike design in mind as it would be cool to ride on the cart. Hope if others are doing the same thing they post videos of their results regardless of whether they are successful or not.

A ten-speed DDWFTTW bike - ace! You should turn some heads.