• 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

humber said:
What is the one thing that connects all together. No wind. There is no "equivalence" what you are seeing is a toy on a belt, doing what a toy would do if it were on a belt.
Click to expand...

"Wind" is the speed of the air relative to the surface. The speed of things other than the air and surface do not matter. Why would they?

You do realize that we are all on what is effectively a giant belt right? The earth is spinning.
 
humber said:
Remember Mr Newton "for every action there is an equal and opposite reaction"
Click to expand...

Yes, I remember. I also remember that the cart is not the only thing being acted on here - there is also the belt and the air, which you seem to have forgotten.

Changing the orientation of the propellor, will simply change the amount of drag, and therefore the amount of energy absorbed from the belt.
The two forces will always be in balance, not only because of that law, but that the sum of the two forces is that derived form the belt.
Click to expand...

So you think if I aim the propeller straight up the cart will remain motionless on the belt. I suggest you think again, and if you find that difficult, imagine the propeller is encased in a container full of thick viscous oil. If there is any resistance in the propeller - which there always will be in still air unless it's not rotating - there is a torque on the wheels. It's precisely like braking a car.

The propellor is not a motive force, but a dissipator of energy.
Click to expand...

That must make it difficult for propeller planes to fly, mustn't it?
 
humber said:
That's how planes convert the engine's power to motive force. So, there you go, you now understand a little bit more.
Go play now.
Click to expand...

So you're going to ignore all the substantive question I asked you? Evidently that means you believe cars can't brake?
 
Thabiguy said:
my_wan,

I'm genuinely pleased that we've been able to clear up some misunderstandings and move forward. Now, there's one significant thing to resolve.

I underlined the problem here. Correctly, the situation would be this:

Craft = -1 mph wrt ground, right to left.
Wind = +8 mph wrt ground, left to right.
Prop air = +0.5 wrt craft but craft = -1 wrt ground therefore:
Prop air wrt ground = -1+0.5 = -0.5 mph wrt ground.

The important thing to realize here that the prop air speed, wrt craft, is linearly dependent on the ground speed wrt craft (i.e. the propeller will slow down if the cart slows down wrt ground). It can't possibly stay constant, such as +2.

Are you with me so far?

(P.S.: I'll be AFK for a couple hours.)
Click to expand...

What you have done is changed the gear ratio to make yourself right again. I admitted and fully explained that you can change sporks specifications to do this for real. I also explained in detail why sporks design as he specified is not geared this way, i.e., 1 to 1 rpm ratio and wheel diameter less that prop diameter. Read the rest of my response for more detail.
 
sol invictus said:
So you're going to ignore all the substantive question I asked you? Evidently that means you believe cars can't brake?
Click to expand...

Now you're getting there. The propellor is a brake. It impedes the cart's motion. Why? Because it would otherwise move with the belt, so it impedes its motion to stop that happening.

You're keen on experiment. Take the propeller drive shaft and move so that it is now vertical, rather than at the rear. The cart will perform the same.

The wheels take energy from the belt, to drive the fan in air, so that it can impede the cart's motion. Orientation makes no significant difference.

You see, I know you can't cheat this, because without it, there is nothing to see. You must balance the forces to avoid the embarrassment of it going backwards. Go ahead. You can do MHazes experiment at the same time.

ETA:
Just to make it crystal clear. Balance will be achieved, because what ever the drag the propellor
causes, is taken from the belt. The balance does not involve any 'thrust'. Therefore the smaller the fan, the less torque will be measured, but it will still hover about much as it does. You can also demonstrate the effect of changing the belt speed, much the same will occur.
 
Last edited:
humber said:
That's how planes convert the engine's power to motive force. So, there you go, you now understand a little bit more.
Go play now.
Click to expand...

To see you addressing the likes of Sol in a condescending manner is literally painful for me to watch.
 
humber said:
Now you're getting there. The propellor is a brake. It impedes the cart's motion. Why? Because it would otherwise move with the belt, so it impedes its motion to stop that happening.

You're keen on experiment. Take the propeller drive shaft and move so that it is now vertical, rather than at the rear. The cart will perform the same.

The wheels take energy from the belt, to drive the fan in air, so that it can impede the cart's motion. Orientation makes no significant difference.

<snip>
Click to expand...

Holding the cart stationary and orienting the fan upwards will create a force orthogonal to the force from the treadmill. The cart will move in the direction of the treadmill once it is released.

That is a significant difference.
 
humber said:
Now you're getting there. The propellor is a brake. It impedes the cart's motion.
Click to expand...

Good - so you admit you were wrong before when you claimed the forces always balance. We're making progress.

Next question: when the propeller is spinning in still air (as opposed to inside a can of oil attached to the car, for example), is the only force on the car due to the torque from its wheels, or is there another force?

Remember - we're working in a frame where the car is stationary, the air is stationary, the ground is moving, and the wheels are spinning.
 
Modified said:
"Wind" is the speed of the air relative to the surface. The speed of things other than the air and surface do not matter. Why would they?

You do realize that we are all on what is effectively a giant belt right? The earth is spinning.
Click to expand...

Do you think then, that if you put a fan in closed box, the box will move?
 
sol invictus said:
Good - so you admit you were wrong before when you claimed the forces always balance. We're making progress.

Next question: when the propeller is spinning in still air (as opposed to inside a can of oil attached to the car, for example), is the only force on the car due to the torque from its wheels, or is there another force?

Remember - we're working in a frame where the car is stationary, the air is stationary, the ground is moving, and the wheels are spinning.
Click to expand...

See the top line? That's called tautology. Saying to me what I said, but in a different manner.

I do not accept that you are qualified to judge my answer. Do the experiment. The previous posts, indicate what you must do.
You have yet to supply any supporting calculations, because you can't do them, so we must resort to seeing is believing.
 
humber said:
See the top line? That's called tautology. Saying to me what I said, but in a different manner.

I do not accept that you are qualified to judge my answer. Do the experiment. The previous posts, indicate what you must do.
You have yet to supply any supporting calculations, because you can't do them, so we must resort to seeing is believing.
Click to expand...

OK, humber, I guess that's that then. I've demonstrated what the forces are, that they don't always sum to zero, and that there are no physical principles that forbid the cart from outrunning the wind. Others have done the experiment and very thoroughly documented it. All of us have shown considerable patience in trying to help you through your basic confusions about physics.

Given your attitude I'm not interested in continuing any further.
 
Ivor the Engineer said:
Holding the cart stationary and orienting the fan upwards will create a force orthogonal to the force from the treadmill. The cart will move in the direction of the treadmill once it is released.

That is a significant difference.
Click to expand...

Scarcely. It is rather a matter of balancing the torques. If there is an imbalance, of what you see as thrust, then the nature of the trick will be exposed. A weak push or pull one way or the other.
It could be rigged to show it going backwards, but then I would simply ask them to show that it could be otherwise. The obvious facility of such changes, and the lack of torque, would make the banality of the idea, obvious. It's only useable output, is the torque imbalance. It really is parlour trick dressed up in a lot of talk of inertial frames.

I have no fear of saying this, because it is so easily demonstrated to be guff.
There are no "calculations" and if there were, they would confirm my and other critic's assertions. It wastes energy from the belt so it can stay were it is. The slight progress is due to simple imbalances. The small momentum of the propeller, serves to keep it in the one direction, but that is happenstance rather than anything else.
 
Last edited:
sol invictus said:
OK, humber, I guess that's that then. I've demonstrated what the forces are, that they don't always sum to zero, and that there are no physical principles that forbid the cart from outrunning the wind. Others have done the experiment and very thoroughly documented it. All of us have shown considerable patience in trying to help you through your basic confusions about physics.

Given your attitude I'm not interested in continuing any further.
Click to expand...

Mission accomplished. Yes, yes, yes. No documentation from you, though.
 
Last edited:
You are right of course, but this is not about the plane thing, but a direct claim concerning this rather silly cart, so the burden of proof was upon them, but apart form a lot of the usual, there was no acceptance of what were blinding flaws in the whole concept. There is nothing to explain. It is what it is.
 
humber:
Do the experiment.
Click to expand...

I *have* done the experiment and have succeeded.

"I have built, and will demonstrate on demand, a vehicle which travels directly downwind, faster than the wind, powered only by the wind, steady state."

Those who "know" we are wrong and actually have the committment that humbers *states* he has should get the escrow paperwork started and send a note to spork -- he's just dyin' for some little fishy to dart at the shiny hook.

Unfortunately, humber only *states* the committment -- he doesn't actually have it or escrow would have already been executed.

JB
 
sol invictus said:
Good - so you admit you were wrong before when you claimed the forces always balance. We're making progress.

Next question: when the propeller is spinning in still air (as opposed to inside a can of oil attached to the car, for example), is the only force on the car due to the torque from its wheels, or is there another force?

Remember - we're working in a frame where the car is stationary, the air is stationary, the ground is moving, and the wheels are spinning.
Click to expand...
There is another force.:) Just as a side note I've never said it's impossible. You just can't do it with the plans for this cart because of the propeller.
 
Last edited:
You must log in or register to reply here.

Back
Top Bottom