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  • I'm gonna have to be drunk for this. So, I guess; it is still the same old TR.

Topic: Direct Down Wind Faster Than The Wind (Read 14125 times) previous topic - next topic

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  • F X
  • The one and only
Re: Direct Down Wind Faster Than The Wind
Reply #825
You are making it complicated.  A reference point is simple.  If the treadmill was really long, you simply paint a white dot on it, and place the cart there.  You have picked a point that is going to be accelerating for a moment, but after the treadmill is up to speed, that dot is a valid point.  It's moving, but not moving. From the POV of that point there is wind.  There is also a cart that is going to move away from the point (because of the wind) and leave that point behind.

You seem to picking a point that can't exist in reality.  Or, you are using the cart itself as the reference point.
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

Re: Direct Down Wind Faster Than The Wind
Reply #826
FX, I can't tell you how happy I am to see you picking up the baton for absolute motion. It always bothered me a bit that the cart thread was the one thread on TR where you appeared to be a rational person. I'm glad to see that's no longer the case.

Re: Direct Down Wind Faster Than The Wind
Reply #827
You are making it complicated.  A reference point is simple.  If the treadmill was really long, you simply paint a white dot on it, and place the cart there.  You have picked a point that is going to be accelerating for a moment, but after the treadmill is up to speed, that dot is a valid point.  It's moving, but not moving. From the POV of that point there is wind.  There is also a cart that is going to move away from the point (because of the wind) and leave that point behind.

You seem to picking a point that can't exist in reality.  Or, you are using the cart itself as the reference point.

Nope.  Your really long TM is a good example.  Let's assume it's 100 miles long (so length isn't a factor) and running at 10 mph wrt to the ground and we have a white dot on the belt which is moving from the front to the rear at 10  mph.  The air is still with respect to the ground upon which the TM chassis sits.  Let's use your dot as the origin for the IRF.  Since the white dot is moving with respect to the ground, there is a 10 mph wind over it (because the dot is moving at -10 mph wrt to the ground). 

But a cart operating a Vminhover (10 mph), it is still with respect to the ground and air, moving at 10 mph with respect to the dot, and thus is operating in still air.  If it goes up the TM (with respect to the ground [DDWFTTW]), it has a headwind, if it backs up with respect to the ground, it has a tailwind[DDWSTTW].  The reference point is the dot which is receding behind the cart at 10 mph.  The cart is moving wrt to the dot and at Vminhover of 10 mph, is still with respect to the air and ground the TM chassis is sitting on.

Windgrins :grin:
Lunatic Fringe, I know you're out there.  You've got to blame someone for your own confusion.

  • F X
  • The one and only
Re: Direct Down Wind Faster Than The Wind
Reply #828
But a cart operating a Vminhover (10 mph), it is still with respect to the ground and air, moving at 10 mph with respect to the dot, and thus is operating in still air.  If it goes up the TM (with respect to the ground [DDWFTTW]), it has a headwind, if it backs up with respect to the ground, it has a tailwind[DDWSTTW].  The reference point is the dot which is receding behind the cart at 10 mph.  The cart is moving wrt to the dot and at Vminhover of 10 mph, is still with respect to the air and ground the TM chassis is sitting on.
None of that is in dispute. What does that have to do with the original argument?  I mean saying the cart is not moving in reference to the ground?  The actual unmoving ground isn't involved when it's on a treadmill.  The treadmill is the ground. Our dot is a still point on the ground, and the cart is moving in regards to the reference point.

Of course it's not moving relative to an unmoving observer, if it is exactly the speed of the treadmill.  And of course in regards to the air it's not moving if it is exactly the same speed as the treadmill.  From the POV of the cart, the air isn't moving, but the ground it is on (the treadmill) is moving.

What does that have to do with the point? 

Let me try another way.  WEe create a wind with fans, a long track of them, to create an artificial steady 10mph wind (wouldn't that be great?).  When we turn the fans on, one could claim it is the same thing as the ground moving.  But just the ground where the wind is, the solid earth where we have no wind is still.

Can you see why somebody might object to the claim?  That creating a wind is exactly the same as moving the ground?  This is the same thing as saying the treadmill is exactly the same as the wind blowing.  A moving platform is not exactly the same as wind blowing.

For the cart it makes no difference of course.   The physics are exactly the same.  Wind or moving platform, it still behaves exactly the same. 

It must be a semantics thing.


"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

Re: Direct Down Wind Faster Than The Wind
Reply #829
But a cart operating a Vminhover (10 mph), it is still with respect to the ground and air, moving at 10 mph with respect to the dot, and thus is operating in still air.  If it goes up the TM (with respect to the ground [DDWFTTW]), it has a headwind, if it backs up with respect to the ground, it has a tailwind[DDWSTTW].  The reference point is the dot which is receding behind the cart at 10 mph.  The cart is moving wrt to the dot and at Vminhover of 10 mph, is still with respect to the air and ground the TM chassis is sitting on.
None of that is in dispute. What does that have to do with the original argument?  I mean saying the cart is not moving in reference to the ground?  The actual unmoving ground isn't involved when it's on a treadmill.  The treadmill is the ground. Our dot is a still point on the ground, and the cart is moving in regards to the reference point.

Of course it's not moving relative to an unmoving observer, if it is exactly the speed of the treadmill.  And of course in regards to the air it's not moving if it is exactly the same speed as the treadmill.  From the POV of the cart, the air isn't moving, but the ground it is on (the treadmill) is moving.

What does that have to do with the point? 

Let me try another way.  WEe create a wind with fans, a long track of them, to create an artificial steady 10mph wind (wouldn't that be great?).  When we turn the fans on, one could claim it is the same thing as the ground moving.  But just the ground where the wind is, the solid earth where we have no wind is still.

Can you see why somebody might object to the claim?  That creating a wind is exactly the same as moving the ground?  This is the same thing as saying the treadmill is exactly the same as the wind blowing.  A moving platform is not exactly the same as wind blowing.

For the cart it makes no difference of course.  The physics are exactly the same.  Wind or moving platform, it still behaves exactly the same. 

It must be a semantics thing.

As you stated:

"For the cart it makes no difference of course.  The physics are exactly the same.  Wind or moving platform, it still behaves exactly the same."

Which was the original point.  So, for those of us in the know, when demonstrated on the TM traveling up the TM, the point was proven.

Windgrins :grin:  
Lunatic Fringe, I know you're out there.  You've got to blame someone for your own confusion.

  • F X
  • The one and only
Re: Direct Down Wind Faster Than The Wind
Reply #830

"For the cart it makes no difference of course.  The physics are exactly the same.  Wind or moving platform, it still behaves exactly the same."

Which was the original point.
Not really.  I had read an old Humber post where he was trying to explain that moving on a platform isn't exactly the same as a real wind, which is true.  Real wind can vary, and you can't duplicate that with a treadmill (for a person, not the cart of course).  A person would know they were moving, because when the ground changes speed , you know it.  It isn't exactly the same as being in a variable wind at all.

But as we know, for the physics of how the cart works, it does not matter a bit.

"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

Re: Direct Down Wind Faster Than The Wind
Reply #831

"For the cart it makes no difference of course.  The physics are exactly the same.  Wind or moving platform, it still behaves exactly the same."

Which was the original point.
Not really.  I had read an old Humber post where he was trying to explain that moving on a platform isn't exactly the same as a real wind, which is true.  Real wind can vary, and you can't duplicate that with a treadmill (for a person, not the cart of course).  A person would know they were moving, because when the ground changes speed , you know it.  It isn't exactly the same as being in a variable wind at all.

But as we know, for the physics of how the cart works, it does not matter a bit.

Yep.  Real wind tends to be variable.  But the TM is exactly the same as a steady wind and those do occur.  So as long as one can go DDWFTTW in a steady wind, then the concept is proven.

Windgrins :grin:
Lunatic Fringe, I know you're out there.  You've got to blame someone for your own confusion.

Re: Direct Down Wind Faster Than The Wind
Reply #832
Congratulations windgrins, you have a whole new humber to play with.

Yep.  Real wind tends to be variable.

The air moving relative to the treadmill belt and the air moving relative to the ground are both real wind.  If my treadmill belt was miles long you'd notice plenty of variability in the wind above it as well. 

  • F X
  • The one and only
Re: Direct Down Wind Faster Than The Wind
Reply #833
Yep.  Real wind tends to be variable.  But the TM is exactly the same as a steady wind and those do occur.  So as long as one can go DDWFTTW in a steady wind, then the concept is proven.
Yep.  The maker of the YT cart noted how long it took to get a steady wind in the right direction to be able to do a real world test.

https://www.youtube.com/watch?v=aJpdWHFqHm0

He had a remote controlled brake and steering and ran it all while filming and riding a bike next to it.  It shows a cart going ddwfftw powered only by the wind, but that didn't convince a lot of people.

spork actually drove a huge one ddwfttw and that didn't convince some people.  The treadmill test didn't either.

Makes you wonder how hard a really complicated bit of technology and science would fare in this modern world.
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

  • F X
  • The one and only
Re: Direct Down Wind Faster Than The Wind
Reply #834
If my treadmill belt was miles long you'd notice plenty of variability in the wind above it as well. 
I believe that, but why?  What would cause the still air to change just because the belt is longer?


"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

Re: Direct Down Wind Faster Than The Wind
Reply #835
Been waiting nearly a month now for Grins or Spork to answer your question above, FX. Makes me wonder if you have them stumped. In our brave new, post-truth reality, I'm awed that some remain so certain they are right about the outcomes of tests never run, like the cart on a much longer belt.

  • MikeB
Re: Direct Down Wind Faster Than The Wind
Reply #836
Must be some miscommunication regarding this.  There is no reason that longer treadmill belt length would cause airspeed variability above the belt.  Very near the belt the boundary layer of air may move more in the direction of belt movement with a longer belt but I wouldn't think this is what Spork meant by variability.



Re: Direct Down Wind Faster Than The Wind
Reply #837
Must be some miscommunication regarding this.  There is no reason that longer treadmill belt length would cause airspeed variability above the belt.  Very near the belt the boundary layer of air may move more in the direction of belt movement with a longer belt but I wouldn't think this is what Spork meant by variability.

How large would a treadmill have to be before you could not tell you were on one?

  • MikeB
Re: Direct Down Wind Faster Than The Wind
Reply #838
Three?

Re: Direct Down Wind Faster Than The Wind
Reply #839
Must be some miscommunication regarding this.  There is no reason that longer treadmill belt length would cause airspeed variability above the belt. 

In a large enough space there are pretty much always air currents - even if there's not a net wind direction.   It's not the longer belt that causes any airspeed variability.   Inside the hangars at Moffett Field near my house it sometimes rains.

Air moving relative to a surface or surface moving relative to the air is the same thing - not a similar thing.

That being said, the issue of gusts is a red-herring.  Even if I created a perfectly steady wind with a treadmill - it's still a real wind.
  • Last Edit: July 19, 2017, 07:54:09 PM by spork

  • MikeB
Re: Direct Down Wind Faster Than The Wind
Reply #840
I knew there was a rational (tr) explanation.  Natural convection winds within a large enclosed space.  FX and Arpie are fired (Trump told me).

Re: Direct Down Wind Faster Than The Wind
Reply #841
@RidgeRunner: Hope you're getting set for running your tests in the steady winds of September there in Utah. I'm really looking forward to seeing your TM cart outrun the packing foam, smoke, or whatever.

Re: Direct Down Wind Faster Than The Wind
Reply #842
I gave a talk at SRI today.  Pulled the wool over their eyes for sure. :)

Re: Direct Down Wind Faster Than The Wind
Reply #843
I gave a talk at SRI today.  Pulled the wool over their eyes for sure. :)
SRI?

  • F X
  • The one and only
Re: Direct Down Wind Faster Than The Wind
Reply #844
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

Re: Direct Down Wind Faster Than The Wind
Reply #845

  • F X
  • The one and only
Re: Direct Down Wind Faster Than The Wind
Reply #846
How content free of a post.  Congratulations.
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

Re: Direct Down Wind Faster Than The Wind
Reply #847
ditto

  • F X
  • The one and only
Re: Direct Down Wind Faster Than The Wind
Reply #848
Carts is serious bizness.
It's hard to believe the original spork threads about this are now over ten years old.
"If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man."
― Mark Twain 🔭

  • MikeS
Re: Direct Down Wind Faster Than The Wind
Reply #849
Quote
Or could it be, that they just simply found themselves wading in a seemingly bottomless pit of boredom... and when they finally reach their lowest level, they decide to log-in at TalkRational.org
That's a perfect fit for me!

Will Heinz be resuming his spirited rebuttal of Faster-than-the-wind-downwind wind-powered vehicles?
Being somewhat serious here, Heinz should open a basic Physics thread first.  The DWFTTW portion is a distraction to his more basic mistakes of the past.
  • Last Edit: September 21, 2017, 04:07:29 AM by SkepticTank