Merged DDWFTTW in a “Real” Wind

[humber]

.
I don't care about this.
One insoluble problem at a time, until the weather improves and I can go outside and play with my toys.
I have not yet seen a sensible description, without acrimony and injured egos, listing the process from the start. What the prop does, what the wheels do, what are the limits... that would cause me to doubt my version.

It's more what is wrong with the claim from first principles. According to Spork, a generator can be attached to the wheel, to drive a prop, which drives the cart. But a brake should work.
That will provide a "retarding force" just like the generator does. A great deal of heat can be produced by a brake, and at very high temperatures, so has potential for high thermal efficiency. That heat could be used to evaporate water and drive a steam turbine to drive the prop. That will then drive the wheel, to drive the prop to generate more heat. A clear case of over-unity.
PM.

ETA:
It's all in complete accord with the model of the NALSA submission. Where they asleep?

The overall efficiency of that model is, 0.85*0.85*0.85 = 61%. That is easily achieved with the steam turbine. Even large power stations achieve that. The ratio of cart and air speeds, the "air lever" will still produce the net force. With this cart, to accelerate, press on the brake.

 

[humber]

Look at the "Under the ruler" video I posted. You're making the same mistake as Coco, who thinks that the cart won't move at all because the motion of the blue wheel opposes the motion of the other wheels. And yet the cart does move, faster than the ruler, precisely because of this opposition.

The large blue wheel is an idlerwheel.

http://en.wikipedia.org/wiki/Idler-wheel

It transfers the same same ruler motion to the smaller diameter wheel, but reverses it. The "amount" of wheel that passes under the ruler, is the same as the "amount" of wheel that engages with the smaller diameter wheel.


It is our old friend, the "over the top" reel.

These ideas are intellectually immature, and were long ago shot down. The bogus trial has been used to support the bogus theory.

The example of the brake and energy, is exactly why you don't want these characters anywhere near the effort to produce energy which you or your children may be relying upon.

ETA:
Perhaps you are thinking it should be this

Well, yes, but remember about the balance of forces that causes the reel to move one way or the other? They don't care if the "surface" is the ruler or the table. It's "all things are relative" but with the unavoidable bias, that we all share.

 

[Michael C]

For the more technically minded carteers here .... might it be correct to think that - prior to reaching steady-state - the whole cart mechanism can be likened to a 'slipping clutch' on a car? That is, the expected speed cannot yet be calculated simply by multiplying rpm x gear ratio?

Just curious.

Yes, we could liken the mechanism to a slipping clutch.

In fact there is always some slippage with a propeller, but first let's imagine an idealised cart with no friction, no drag and a theoretically perfect propeller. When this propeller has reached its ideal speed through the air, it is screwing its way through the air without disturbing it at all (impossible in real life: this is an idealised prop!). In this situation, when it makes one full turn it advances a certain distance, called its pitch, through the air. I'll use p to represent this distance.

There is fixed-ratio gearing between the prop and the wheels: for each full turn of the prop, the wheels turn by a certain amount and so the cart moves a certain distance over the ground. I'll call this distance d.

If we know the ratio between p and d, we can calculate what the steady-state speed of the idealised cart will be for any particular wind speed. Ill leave you the fun of doing the algebra: let w be the speed of the wind and v the speed of the cart and try working out v in terms of p, d and w (if you don't find algebra fun, I'll give the answer later!).

For the real-life cart, there will still be some slippage of the propeller even at steady-state speed. The amount of slippage will depend of several factors: the design of the prop, the aerodynamic drag from the chassis, friction in the bearings, the actual wind speed..., so calculating the steady-state speed of a real cart will be a complex affair.

 

[Michael C]

The large blue wheel is an idlerwheel.

http://en.wikipedia.org/wiki/Idler-wheel

It transfers the same same ruler motion to the smaller diameter wheel, but reverses it. The "amount" of wheel that passes under the ruler, is the same as the "amount" of wheel that engages with the smaller diameter wheel.


It is our old friend, the "over the top" reel.

[qimg]http://www.internationalskeptics.com/forums/attachment.php?attachmentid=21576&stc=1&d=1301218136[/qimg]

These ideas are intellectually immature, and were long ago shot down. The bogus trial has been used to support the bogus theory.

The example of the brake and energy, is exactly why you don't want these characters anywhere near the effort to produce energy, that you or your children may be relying upon.

Humber, as usual, is wrong. I have absolutely no interest in trying to engage him in any sort of discussion, but I'll just point out for the others: the cart that he thinks is the "same as" my ruler cart would move in the direction of the ruler, slower than the ruler.

The "Under the ruler" cart moves faster than the ruler. In fact it moves at exactly the same speed as a simpler cart without the blue wheel where the ruler passes under the centres of the cotton reels. The blue wheel serves to reverse the direction of rotation of the cotton reels.

 

[humber]

Humber, as usual, is wrong. I have absolutely no interest in trying to engage him in any sort of discussion,

I can understand why.

but I'll just point out for the others: the cart that he thinks is the "same as" my ruler cart would move in the direction of the ruler, slower than the ruler.

And how is the ruler different from the table? Aren't all things relative?

The "Under the ruler" cart moves faster than the ruler. In fact it moves at exactly the same speed as a simpler cart without the blue wheel where the ruler passes under the centres of the cotton reels. The blue wheel serves to reverse the direction of rotation of the cotton reels.

It's a 2:1 gear, just like the cotton reel, and like that reel, the work you do is the same, but the force is doubled. Top speed is limited by power. Always is.
The force is applied at the wheel, no matter how long the ruler is. Like a dog on a leash. The length of the leash may change, but the force is applied at the collar.

 

[jduffy77]

It's more what is wrong with the claim from first principles. According to Spork, a generator can be attached to the wheel, to drive a prop, which drives the cart. But a brake should work.
That will provide a "retarding force" just like the generator does. A great deal of heat can be produced by a brake, and at very high temperatures, so has potential for high thermal efficiency. That heat could be used to evaporate water and drive a steam turbine to drive the prop. That will then drive the wheel, to drive the prop to generate more heat. A clear case of over-unity.
PM.

Is there anyone who would not find this stuff entertaining?

 

[Modified]

It's not really being "pushed" by the wind any more than an airplane flying downwind is being pushed by the wind. It's pulling itself through the air using a propeller - same as the airplane.

I could go either way on that one, just as I'd have no problem saying that the drfttr cart was being "pushed by the ruler" though it may be more correct to say it is "pulling itself against the ruler".

 

[GlennB]

Yes, we could liken the mechanism to a slipping clutch.
.....

Thank you. No need for the algebra (unless you really enjoy it ), the general priciple is good enough.

I recalled a couple of motorbikes I had many moons ago with clutch problems. There were times when it seemed that reducing the power (throttle) would also reduce slippage and improve speed. Intuitively this makes sense to me, but I don't really know whether it's sound mechanically or just an impression I got at the time. Going easy on the gas pedal to reduce wheel spin on snow seems to be a similar idea.

 

[spork]

I could go either way on that one, just as I'd have no problem saying that the drfttr cart was being "pushed by the ruler" though it may be more correct to say it is "pulling itself against the ruler".

I think this is different in an important (but perhaps semantic) way. You can say this is being pushed by the air (that's the same question as to whether a wing is being pushed up from the bottom or sucked up from the top). But I don't like to say it's being pushed by the wind because...

It's outpacing the wind. This is what leads to confusion for so many. They all want to invent theories in which the prop produces a big air cushion for the wind to push against, and this is simply not happening. There is no difference at all between what happens with this prop vs. what happens with the prop of a Cessna flying upwind, downwind, cross-wind, or in no wind.

Would you say that a Cessna was being "pushed" by the wind when flying down-wind? I wouldn't. I'd say it's pulling itself through the air while also drifting with the wind. The wind does not provide any sort of "pushing" force on the plane.

 

[humber]

Is there anyone who would not find this stuff entertaining?

Want to tell me where it goes wrong?

You wrote plenty enough about the details of the trial.

 

[humber]

I think this is different in an important (but perhaps semantic) way. You can say this is being pushed by the air (that's the same question as to whether a wing is being pushed up from the bottom or sucked up from the top). But I don't like to say it's being pushed by the wind because...

It's outpacing the wind. This is what leads to confusion for so many. They all want to invent theories in which the prop produces a big air cushion for the wind to push against, and this is simply not happening. There is no difference at all between what happens with this prop vs. what happens with the prop of a Cessna flying upwind, downwind, cross-wind, or in no wind.

Would you say that a Cessna was being "pushed" by the wind when flying down-wind? I wouldn't. I'd say it's pulling itself through the air while also drifting with the wind. The wind does not provide any sort of "pushing" force on the plane.

Yeah, yeah. All very good.

I would like to see you tell this forum about the steam cart. Because of its "unconventional" engineering, I have called the BB, The Makey-Breaky cart, bit now it seems that Brakey-Breaky cart is more appropriate.

The model using the motor and generator has bee published, so I would like you to explain why the brake-driven cart will not work. If yours does, it will too.

 

[humber]

I could go either way on that one, just as I'd have no problem saying that the drfttr cart was being "pushed by the ruler" though it may be more correct to say it is "pulling itself against the ruler".

Are you sure there isn't something other than ruler that has been pulling itself, Modified?
That steam cart....

 

[Myriad]

That steam cart...

...would work fine, IF it were going downwind, IF the machinery produced the correct ratio of prop advance to ground speed, and IF the whole thing were efficient enough. In that case it would not be over-unity.

In practice, your handwaved figures notwithstanding, the efficiency would be so low that it is probably not possible in practice for that design of "steam cart" go downwind faster than the wind, with any currently available "steam" technology. It is, however, possible with more efficient means of power transfer from the wheels to the prop, such as a geared shaft or a spool transmission.

If you had a steam cart that was efficient enough to work going downwind, but it was not going downwind, then at any nonzero ground speed the work done by the brakes on the cart per unit time (braking power) must exceed the work done by the prop on the cart per unit time (thrust power) so it would only slow down. A velocity difference between the ground and the air is necessary for the latter to exceed the former, thus extracting the necessary power from the wind. So, it would not be an over-unity device.

Respectfully,
Myriad

 

[I Ratant]

It's more what is wrong with the claim from first principles. According to Spork, a generator can be attached to the wheel, to drive a prop, which drives the cart. But a brake should work.
That will provide a "retarding force" just like the generator does. A great deal of heat can be produced by a brake, and at very high temperatures, so has potential for high thermal efficiency. That heat could be used to evaporate water and drive a steam turbine to drive the prop. That will then drive the wheel, to drive the prop to generate more heat. A clear case of over-unity.
PM.

ETA:
It's all in complete accord with the model of the NALSA submission. Where they asleep?

The overall efficiency of that model is, 0.85*0.85*0.85 = 61%. That is easily achieved with the steam turbine. Even large power stations achieve that. The ratio of cart and air speeds, the "air lever" will still produce the net force. With this cart, to accelerate, press on the brake.

.
I knew an engineer who responded "Yes" to the statement that "heating up a car's brakes would cause it to move".... as they got hot slowing it down, the reverse should work.
And another who opined that a rocket, like a Saturn V left its c.g. on the launch pad.
But this downwind cart although it works, it has no use.
Folks long ago fingered out how to extract energy from wind, and the extractor need have no more mobility than the ability to point into the wind.
The mountains north of me have 1000s of these, taking advantage of the favorable westwinds at that location. It's so windy up there there are few branches on the west sides of the trees.. they get blown off before they can grown.
The cart merely keeps artificers off the streets and out of the bars and the clutches of loose women, and consume material and efforts, and Internet band width.
And attracts the attention of those who tinker with collections of random parts and have in interest in assembling to do things with wind.
I have a house full of that crap.
And only occasional contact with loose women. (Sob! )

 

[I Ratant]

Humber, as usual, is wrong. I have absolutely no interest in trying to engage him in any sort of discussion, but I'll just point out for the others: the cart that he thinks is the "same as" my ruler cart would move in the direction of the ruler, slower than the ruler.

The "Under the ruler" cart moves faster than the ruler. In fact it moves at exactly the same speed as a simpler cart without the blue wheel where the ruler passes under the centres of the cotton reels. The blue wheel serves to reverse the direction of rotation of the cotton reels.

.
I amuse myself with the reel, pulling it up the incline with the thread spooling off the top, and off the bottom..
It really isn't "intuitive" what happens, until you take the time to do it.

 

[I Ratant]

Yes, we could liken the mechanism to a slipping clutch.

In fact there is always some slippage with a propeller, but first let's imagine an idealised cart with no friction, no drag and a theoretically perfect propeller. When this propeller has reached its ideal speed through the air, it is screwing its way through the air without disturbing it at all (impossible in real life: this is an idealised prop!). In this situation, when it makes one full turn it advances a certain distance, called its pitch, through the air. I'll use p to represent this distance.

There is fixed-ratio gearing between the prop and the wheels: for each full turn of the prop, the wheels turn by a certain amount and so the cart moves a certain distance over the ground. I'll call this distance d.

If we know the ratio between p and d, we can calculate what the steady-state speed of the idealised cart will be for any particular wind speed. Ill leave you the fun of doing the algebra: let w be the speed of the wind and v the speed of the cart and try working out v in terms of p, d and w (if you don't find algebra fun, I'll give the answer later!).

For the real-life cart, there will still be some slippage of the propeller even at steady-state speed. The amount of slippage will depend of several factors: the design of the prop, the aerodynamic drag from the chassis, friction in the bearings, the actual wind speed..., so calculating the steady-state speed of a real cart will be a complex affair.

.
And toss in the mechanics of the various frictions on the cart, all of which will reduce the actual speed from the computed no-slippage no-friction situation.
It will still move, as we see.
That much should be understood.
Arguing about the how's it do that... to the point of personal attacks it reaches here.. disgusting.

 

[humber]

...would work fine, IF it were going downwind, IF the machinery produced the correct ratio of prop advance to ground speed, and IF the whole thing were efficient enough. In that case it would not be over-unity.

Braking the cart, accelerates it? The efficiency can be at least as high as the existing cart.

In practice, your handwaved figures notwithstanding, the efficiency would be so low that it is probably not possible in practice for that design of "steam cart" go downwind faster than the wind, with any currently available "steam" technology. It is, however, possible with more efficient means of power transfer from the wheels to the prop, such as a geared shaft or a spool transmission.

Heat engine. Carnot Cycle

n = 1 - Tc/Th
Tc = cold side ( ambient temperature)
Th = hot side ( brake disk temperature)

Any gas may be used to transport the heat.

If you had a steam cart that was efficient enough to work going downwind, but it was not going downwind, then at any nonzero ground speed the work done by the brakes on the cart per unit time (braking power) must exceed the work done by the prop on the cart per unit time (thrust power) so it would only slow down. A velocity difference between the ground and the air is necessary for the latter to exceed the former, thus extracting the necessary power from the wind. So, it would not be an over-unity device.

Respectfully,
Myriad

Nothing changes in any respect, other than the generator is replaced with a brake. A generator is a transducer, converting mechanical energy to electrical energy. The heat engine is another type of transducer.

The BB is, and always was, a claim for over-unity. It is Spork who has the "hand-waving" and no mathematical support.

A trial where he changed and controlled all the rules, has been used to claim that the cart works, but in fact, it remains the over-unity machine it always was.

ETA
And it applies to the cart as is. Increased output from the generator will produce more thrust ( the thrust always increases more than the wheel drag) which would drive the cart faster and so forth.
That is because the idea is bunk.

 

[zooterkin]

But this downwind cart although it works, it has no use.

Is anyone claiming it has a use?

 

[Myriad]

That's what it was intended to do, but.... BFD.. that's -all- it can do.
Like the Boing, configuration changes are needed to come back home.

Respectfully,
Myriad

 

[I Ratant]

Is anyone claiming it has a use?

.
Probably as much a use as living in a town with a championship sports team, which apparently elevates the average sports fan there to championship status without the fan having to capable of anything the members of the team can do.
Or as mentioned, as important as owing the world's largest collection of ball-point pens.
Ego boo to some, but yawn material to most others.
It has to do with wind, and being an aerodynamicist and life-long airplane nut, it's interesting to me.
I did enjoy watching the Tour de France when I was actively cycling, getting a feel of some of what those guys were doing with their bodies.. far in excess of anything I could do with mine.
Greg LeMond was interesting until the whining started.
And Lance... well, there is that problem (or not) with doping.
But cycling is probably the only sport I would walk across the street at most, to observe... did that last year when the Tour of California came through Palmdale on their way up to Big Bear. I've ridden parts of their route... It would take me weeks to do what they did in about 6 hours!