DDWFTTW Turntable Test: 5 Min Video - Is It Conclusive?

[rcgldr]

Now Atom Man knows that if his strategy is to be successful he must be sure that the drag from his generator is less than this amount, so he decides to use only half of this extra thrust in powering the generator.

But this isn't the case. What Atom man needs to know is the power output versus power input for a propeller, and the minimal amount of thrust required to overcome the aerodynamic drag from a small apparent headwind on the cart and the rolling resistance from larger apparent head speed from the ground (rolling resistance) to obtain a specific maximum speed. Chances are that the prop chosen will generate more thrust than is minimally needed, but this will be opposed by the wheels that drive the prop, and the ratio of opposing force / thrust is < 1 if the prop and related gearing are efficient enough. So the ratio of opposing force / thrust remains about the same, but since the drag related factors remain about the same, the ratio (thrust - opposing force) / (drag factors) increases with prop thrust.

Let’s use those heavy air molecules you mentioned that weigh 1 kg each and let’s start out at wind velocity of 10 m/s and we need to throw 10 of those molecules back every second, so n = 10. That will be (1kg) (10m/s) (10 molecules/s) = 100 Newtons of Force.

The speed of the molecules thrown back doesn't need to be 10 m/s. 4 m / sec would probably be sufficient. The cart is only attempting to go DDWFTTW, not twice as fast as the wind. So restated:

(1kg) (4m/s) (10 molecules/s) = 40 Newtons.
KE = 1/2 mv^2 so at 4 m/s the KE is 8 Joules.
power output = Energy/time or Energy x n = 8 J x 10 = 80 watts.

Assume the cart is moving at 12 m/s down wind.
Assume prop and gearing efficiency to total about 69.4%.
So power input needs to be (1/.694) = 1.44 times power output = 144 watts.
At 12 m / s, the required driving force = (144 / 12) = 12 Newtons.

So we have 40 Newtons of thrust opposed by 12 Newtons of force related to driving the prop, leaving 28 Newtons of force to compenstate for the opposing aerodynamic drag of the apparent 2 m/s headwind, and the rolling resistance from the 12 m / sec forward speed of the cart.

 

[schroder]

Thrust = (10 kg/sec) * (10 m/sec) = 100 N
Power required = 1/2 * (10 kg/sec) * (10 m/sec)^2 = 500 Watts
Power Available = F v = (100 N) * (10 m/sec) = 1000 Watts

Where's the problem with that Schroder?


So it's even better this time wouldn't you agree?

You and Vanesch should get together and write some joint effort fairy tales! Between his “propeller that does not require any Force” and your “power available” you two can rewrite the book of physics, as long as it is in a Fairy Tale! Please remember to start you stories with “Once upon a time” so the reader will know what to expect.
You write this, and ask me what is wrong with it?

Power Available = F v = (100 N) * (10 m/sec) = 1000 Watts

Where's the problem with that Schroder?

Do you mean that you do not know what is wrong with it, or are you just testing me?
The power required to turn the propeller is clearly 500 Watts from your own calculation:
Thrust = (10 kg/sec) * (10 m/sec) = 100 N
Power required = 1/2 * (10 kg/sec) * (10 m/sec)^2 = 500 Watts

Now where is the power available coming from? You mean the Total power expended in the isolated system of the propeller and the air as the propeller works on the air and vice versa? And to what part of the system is this expended power available, pray tell? I can answer that for you: The power is expended; it is no longer “available”, GONE, FINISHED, and KAPUT!

But that is not all! You still have not shown where the 500 Watts is coming from to throw those heavy air molecules around. You and Vanesch are playing a game here, thinking that maybe no one is out there who can see through it. I find this extremely boorish and just plain stupid. If DDWFTTFW means that much to you, that you will come on here and post blatant lies and falsehoods, and if this Physics Forum is so afraid of coming out and challenging these lies, then this Forum is losing credibility steadily. I know there are people on here who can see that what you are posting is garbage. You cannot show a source of energy for the cart at velocity greater than wind velocity, so you resort to this type of circular argument, which any first year physics student can see through. It is getting OLD and TIRESOME.

My plan is to continue investigating the heterodyne. I generally think it is best to take notice when numbers crop up on their own and then try to see if those numbers fit any meaningful known relationship. When the ratio of 2.4 came up, I automatically thought of the first carrier drop out of a Bessel null, and when 1.41 came up I naturally think out peak and RMS values. Also, from experience with rotating machinery I am very familiar with beats, harmonics and vibrations. All the indications are there for some sort of heterodyne. Looking at Swerdna’s video, the cart first advances in one direction until it stands still momentarily on the tread with the linear velocity of the wheel exactly the same as the linear velocity of the tread. That is the very definition of a beat frequency and it cannot stay there for long! One of them, the cart or the tread, must drop out of that beat and of course it is the cart. The drop out is very similar to a carrier drop out at a Bessel null. If you have ever done a carrier drop out you would immediately see the resemblance here in the mechanical system. Now the cart starts running in the opposite direction at a ratio of 1 : 2.4 which is the modulus of a first Bessel null! I am not making any of this up, these are the actual numbers obtained by analyzing the video. I cannot ignore these numbers. Do I have a complete theory or a complete explanation of what is happening here? No, obviously not. The combination of the cart and the turntable is very interesting and I intend to look into this until I understand it completely. In the meanwhile, I will no longer respond to your and Vanesch’s blatant falsehoods as they are not worth one more moment of my time.
When I have my heterodyne model complete, I may post a link to it here, or I may not. Meanwhile feel free to lie and hoodwink your way to fame on myth busters, but I seriously doubt they are still interested in DDWFTTFW, especially after I fill them in.

My turn to roll on the floor laughing!

 

[vanesch]

You and Vanesch should get together and write some joint effort fairy tales! Between his “propeller that does not require any Force” and your “power available” you two can rewrite the book of physics, as long as it is in a Fairy Tale! Please remember to start you stories with “Once upon a time” so the reader will know what to expect.
You write this, and ask me what is wrong with it?

Power Available = F v = (100 N) * (10 m/sec) = 1000 Watts

Where's the problem with that Schroder?

Do you mean that you do not know what is wrong with it, or are you just testing me?

There is of course nothing wrong with it. What do you think is wrong with it ?

The power required to turn the propeller is clearly 500 Watts from your own calculation:
Thrust = (10 kg/sec) * (10 m/sec) = 100 N
Power required = 1/2 * (10 kg/sec) * (10 m/sec)^2 = 500 Watts

Yes, that is correct. We need to have 500 W to feed the motor of the propeller/throwing machine/...

Tell me, a generator that DELIVERS 500 W and is powered by the axle of a wheel that rolls at 10 m/s, HOW MUCH DRAG FORCE DOES THAT CAUSE ?

(answer: 50 N).

Other question: if you want a drag force of 50 N by BRAKING, how much POWER do you dissipate in the brake if the car is going at 10 m/s ? Could you, pretty please, answer that question ?

In the meanwhile, I will no longer respond to your and Vanesch’s blatant falsehoods as they are not worth one more moment of my time.

I fully understand that. The mechanics is so evident, and the proof so easy, that it becomes embarrassing to try to talk yourself out of it, that's it ? You don't want to enter again in something like your 10 + 2 = 8 debacle, I understand. Who was it saying that you are the kind of person that would even maintain that 1 + 1 = 3, rather than admit to be wrong ? In fact, you warned us from the start: "I cannot accept to be wrong", you said a while back. You know, sometimes, even though it seems insurmountable, admitting that you've been wrong all the time can be a liberating experience. You should try it. We all know it now here. There's no point trying to hide it. It will give you probably a great sense of relief.

In the mean time, in as much as you are the engineer you claim to be, you should ponder about the question of the brakes... How much heat must I be able to evacuate from a brake that gives me 50 N of drag on a car that runs at 10 m/s... If you have that one wrong, then you might make a lot of professional errors. Now, maybe you wouldn't make an error there if you could liberate yourself from your mental block.

 

[vanesch]

My plan is to continue investigating the heterodyne. I generally think it is best to take notice when numbers crop up on their own and then try to see if those numbers fit any meaningful known relationship.

You mean, that if a phone number contains 31415, that you think that you're calling a circle ?

BTW, tell us when your turntable is ready, and when your 3 tachymeters are installed, to compare it to my prediction T3 = R/r (T1 - T2). I'm "curious"

 

[spork]

You and Vanesch should get together and write some joint effort fairy tales!

I honestly don't know if you can see the irony, or you're really that misguided.

You and Vanesch are playing a game here, thinking that maybe no one is out there who can see through it. I find this extremely boorish and just plain stupid. If DDWFTTFW means that much to you, that you will come on here and post blatant lies and falsehoods, and if this Physics Forum is so afraid of coming out and challenging these lies, then this Forum is losing credibility steadily.

If you look at this simply as a numbers game, it should be perfectly clear that everyone but you sees Vanesch's posts for what they are - accurate and truthful. It amazes me that you continue to dig a deeper and deeper hole for yourself.

My plan is to continue investigating the heterodyne.

By all means. Please also investigate HHO, pyramid power, crystals, and coriolis as an explanation for the cart's performance.

I generally think it is best to take notice when numbers crop up on their own and then try to see if those numbers fit any meaningful known relationship.

Better physics through numerology.

The combination of the cart and the turntable is very interesting and I intend to look into this until I understand it completely.

In that case I hope you're a young man - and have lots of schooling ahead of you.

 

[ThinAirDesign]

Meanwhile feel free to lie and hoodwink your way to fame on myth busters, but I seriously doubt they are still interested in DDWFTTFW, especially after I fill them in.

Well, I can only *hope* that you will do as you say and "fill them in".

Since I fear that you're quackery will get lost amongst all the other quackery that the MythBusters get inundated with (see their own forum for examples), I have an offer for you: Write up your paper or whatever it is that you are going to "fill them in" with, post (or PM) it and I will make sure it gets to the appropriate Executive Producer. We have an actual dialog with these folks and we can make sure your particular form of quackery get's it's due with them.

Truly schroder -- every good episode needs a foil and if you're credentialed and as experienced as you say, if your position has the support of the "Academy" as you say, and the thought of making us look like the boobs you believe we are holds any appeal, we need each other. We need to produce a skeptic who comes off as smart, educated and convincing, who is also willing to take an *on air* stand on this -- so far the people willing to criticize haven't met those filters.

JB

PS: Remember, when it comes to your referenced "fame on MythBusters", neither spork no I even expect to be mentioned on any such show -- the right skeptic however would likely actually get the on-air "fame", not us. After all, everyone remembers the pilot who said the plane wouldn't take off on the POAT episode.

 

[The Dagda]

I cannot ignore these numbers. Do I have a complete theory or a complete explanation of what is happening here? No, obviously not. The combination of the cart and the turntable is very interesting and I intend to look into this until I understand it completely. In the meanwhile, I will no longer respond to your and Vanesch’s blatant falsehoods as they are not worth one more moment of my time.
When I have my heterodyne model complete, I may post a link to it here, or I may not. Meanwhile feel free to lie and hoodwink your way to fame on myth busters, but I seriously doubt they are still interested in DDWFTTFW, especially after I fill them in.

My turn to roll on the floor laughing!

That comes off as very arrogant you are aware of the level of education of some of these people, they're not fobbing you off with pseudoscience, this is standard physics for a very good reason.

Still can't say I'm surprised, when in a hole...

 

[spork]

Remember, when it comes to your referenced "fame on MythBusters", neither spork no I even expect to be mentioned on any such show -- the right skeptic however would likely actually get the on-air "fame", not us.

Agreed, but that's fame I could do without.

 

[Subductionzon]

Schroder, I seriously suggest that you look at the recent posts of vanesh again. It still irks me when I watch spork's video for his Mythbusster's challenge when I hear one of my quotes trying to debunk Jack Goodman's video. You have left so many crazy statements that they could haunt you for years.

 

[mender]

My plan is to continue investigating the heterodyne. I generally think it is best to take notice when numbers crop up on their own and then try to see if those numbers fit any meaningful known relationship. When the ratio of 2.4 came up, I automatically thought of the first carrier drop out of a Bessel null, and when 1.41 came up I naturally think out peak and RMS values.

(snip)

I am not making any of this up, these are the actual numbers obtained by analyzing the video. I cannot ignore these numbers. Do I have a complete theory or a complete explanation of what is happening here? No, obviously not. The combination of the cart and the turntable is very interesting and I intend to look into this until I understand it completely. In the meanwhile, I will no longer respond to your and Vanesch’s blatant falsehoods as they are not worth one more moment of my time.

Schoder, you might save yourself a lot of trouble if you can get Ynot to repeat his test at a couple of different turntable speeds and then see if the data still holds the pattern that you're looking for.

I'm curious, you really don't know that the energy to run this thing is coming from the wind? I think I can help you work through that issue if you are willing to go step by step.

 

[spork]

It still irks me when I watch spork's video for his Mythbusster's challenge when I hear one of my quotes trying to debunk Jack Goodman's video.

Sorry about that. We just pulled out a few of the classic quotes at random. I don't think I could tell you who said anyone of them.

 

[Subductionzon]

Sorry about that. We just pulled out a few of the classic quotes at random. I don't think I could tell you who said anyone of them.

No problem, it keeps me humble, not humber

 

[ThinAirDesign]

LOL Sub ... I'm the guy who picked though and pulled out those quotes and until now I had no idea one of those was yours.

JB

 

[spork]

LOL Sub ... I'm the guy who picked though and pulled out those quotes and until now I had no idea one of those was yours.

Well, it's a good testimony to considering new real-world evidence and keeping an open mind even when you start out with strong intuitive feelings on the subject. Imagine if everyone was willing to do that.

 

[Subductionzon]

Well, it's a good testimony to considering new real-world evidence and keeping an open mind even when you start out with strong intuitive feelings on the subject. Imagine if everyone was willing to do that.

Then we would have hardly any fun at all. Where would threads like this be without schroder, humber and now 3bodyproblem? Of course these people have possibly served a good purpose keeping this topic alive for others to find and worry over.

 

[vanesch]

Still 55 (now 54) posts to go to reach 1000... Hope we'll get there :shy:

 

[atyy]

Still 55 (now 54) posts to go to reach 1000... Hope we'll get there :shy:

Ok, here's a little help. I probably missed it since your equations were spread out over many posts. What is the justification that 0<k<1 physically exists?

 

[swerdna]

I put my TT and cart together again to show a visiting friend and made a video with the TT running at a slower speed for those that want to compare calculations at different speeds (as suggested by mender post #940). I have also replaced the “large” tether arm with a thin bar. Are there any other tests anyone wants done while it’s together again? (that don’t involve me having to buy tachometers).

 

[vanesch]

Ok, here's a little help. I probably missed it since your equations were spread out over many posts. What is the justification that 0<k<1 physically exists?

Thanks

K is a design choice. It comes in v_out = K v_cart

v_cart determines the rotation speed of the wheels, and through some gearing, the rotation speed of the propeller, and the propeller has a pitch. So with a certain rotation speed of the propeller (and hence, rotation speed of the wheels, and hence, speed of the cart on the surface) corresponds a certain velocity of the outgoing air flow.
You can make K as big or as small as you want by changing the gear ratio between the wheel and the propeller, by changing the diameter of the wheel, or by changing the pitch of the propeller.

Note that v_out = K v_cart is an approximative model of a propeller, because v_out might
1) be influenced by the incoming velocity v_in
2) the relationship might be somewhat non-linear (in that case, the model v_out = K v_cart is still useful, but as a local linear approximation, and K can vary with the working point).

For a turbine in a closed tube, the relationship v_out = K v_cart would be much more exact (there's only one velocity that "gets through" the turbine without hitting the blades).
v_in will change the amount of work that needs to be done but it won't influence (much) the final velocity. I don't know in how much this applies to an "open" propeller.

The point was just to have a plausible model that shows that the device can work in principle, not really to get numerically very accurate outcomes. Given that there are large margins, a small model change won't change the qualitative conclusion.

By lowering the gearing ratio, you can make the propeller run as slowly as you like, and hence make K as small as you like. Actually, the relationship 0 < K < 1 is too severe. You can have K values outside of that range and still have the thing working. But if K really is too large (say, K = 5), then the device will not work. It is as if Atom Man was throwing his molecules too fast. The propeller would then require more work than can be delivered with a drag force on the wheels smaller than the trust by the propeller ; in other words, the overall force flips sign.

 

[vanesch]

I put my TT and cart together again to show a visiting friend and made a video with the TT running at a slower speed for those that want to compare calculations at different speeds (as suggested by mender post #940). I have also replaced the “large” tether arm with a thin bar. Are there any other tests anyone wants done while it’s together again? (that don’t involve me having to buy tachometers).

Nice ! I don't know if it is just changing a switch or if this involves more work, but a whole set of TT speeds would be nice (from very slow where the thing probably doesn't work, to whatever you consider reasonable). To be able to exclude all the zeros of the whole family of hypergeometric functions
(or, who knows, to find a "resonance" peak... )

A few other (silly) experiments would be to disconnect the propeller, and see how the thing behaves without it (haha). You could also place a sail on it, to have an idea of the actual "wind speed" (maybe some air gets dragged along the table).

Finally, you could maybe place a visible dot on the small wheel so that we can see it turn and make a close up image of when the cart comes by (at low speed so that the video can capture it).

 

[mender]

Thanks, Ynot, that helps to have another set of data. I get 10.2 ft/s for the turntable in one direction and 2.1 ft/s for the cart going the other way just before the end of the video. Did the cart speed up much from that point?

That's 12.3 for the cart, 10.2 for the turntable and a ratio of 1.21 - another coincidence? 11 x 11? How often does that number pop up? Of course that's just a number.

Ynot, could you try it again with some fresh lube on the cable and any other appropriate spots? According to shroder's theory, a small change in friction shouldn't be enough to upset a null but according to everyone else, it should result in an increase in speed, providing it does reduce the drag a bit.

 

[vanesch]

That's 12.3 for the cart, 10.2 for the turntable and a ratio of 1.21 - another coincidence?

1.21 GigoWatt (sic) was the power needed for the car in Back to the Future, no ?

OMG, swerdna, be careful, you might just be projected in another era !

 

[swerdna]

I think the cart had reached terminal speed before the end of the video but maybe not. I try to keep the videos short because uploading to Youtube takes forever.

Wish it was as simple as changing a switch but it involves having to take the drill drive apart and fit a different size wheel each time. Would it be okay if I just fitted a different size wheel to the cart? If the prop wasn’t in the way I could just shorten the length of the tether arm.

Before slowing the TT down I filmed the cart with the same TT speed as this video -

Not sure if it was just more “run in” or because I re-washed the bearings but the cart is running more efficiently in this video -

In the first video it takes about one and a third revolutions of the cart before it “hovers” while in the second video it takes less than one revolution. You should find the TT speed is the same in both videos. The terminal speed in the second also seems much faster to me but I haven‘t measured it.

 

[vanesch]

Would it be okay if I just fitted a different size wheel to the cart?

That's even better, because that changes the effective "gear ratio".

 

[swerdna]

That's even better, because that changes the effective "gear ratio".

Do the videos have to show the start-up period or can I just film when the cart is up to speed?

 

[spork]

Would it be okay if I just fitted a different size wheel to the cart?

That's a good set of data to get, but it's very different from running the TT at different speeds. Changing the size of the wheel changes the cart's advance ratio. The advance ratio is the primary design feature that governs the carts theoretical speed relative to the wind. As the advance ratio approaches 1.0 the cart tries to go an infinite multiple of the wind's speed, but will fail to work at all if the real world losses don't become incredibly small.

When the advance ratio goes above 1.0 it becomes an upwind cart. That would be a great experiment to show.

 

[ThinAirDesign]

Do the videos have to show the start-up period or can I just film when the cart is up to speed?

If it were me and uploading were a problem I wouldn't show startup --- just a long enough clip of each different test to be able to time the TT revs to the cart revs.

JB

 

[mender]

I agree with spork and jb, for the first set of tests different speeds would be best with just the final steady state speeds shown. The next round could be with different wheels though.

My tests showed a different break even speed for different advance ratios, so a different size wheel should also take the cart out of the "null" ratio.

And thanks again for building your turntable and doing tests. I still plan on doing one but I plan a lot of things!

 

[spork]

My tests showed a different break even speed for different advance ratios, so a different size wheel should also take the cart out of the "null" ratio.

Yup, I think you can expect higher minimum turntable speeds as the advance ratio gets closer to 1.0. The extra energy is required for the effectively higher "leverage".

 

[schroder]

Not sure if it was just more “run in” or because I re-washed the bearings but the cart is running more efficiently in this video -

In the first video it takes about one and a third revolutions of the cart before it “hovers” while in the second video it takes less than one revolution. You should find the TT speed is the same in both videos. The terminal speed in the second also seems much faster to me but I haven‘t measured it.

You are back to a perfect 2.4 again! In the first video after putting the TT back together again, it is obvious that you are not getting a clean drop out of the forward revolution of the cart. This is a perfect analogy to a partial carrier drop out and the ratio can be almost anything at all. You need a clean and complete drop out of the CW rotation of the cart, a sharp transition, as we see in this last video. A very nice mechanical heterodyne!
Can you please give me the distance from the center of the TT to the center of the track of the wheel as well as the diameter of the small wheel? Thanks!