YouTube Classics, Part Deux

[nsaspook]

 

[nsaspook]

 

[etotheipi]

 

[skyshrimp]

 

[nsaspook]

 

[etotheipi]

what the f*ck has happened to my youtube recommendations

 

[etotheipi]

 

[Jarvis323]

 

[nsaspook]

All you can eat is back in Vegas.

 

[Ivan Seeking]

 

[Ivan Seeking]

I think I know the key to how it works. Anyone want to explain?

 

[jbriggs444]

I think I know the key to how it works. Anyone want to explain?

Check out this thread in the Classical Physics sub-forum.

https://www.physicsforums.com/threads/ddwfttw-looking-for-the-least-confusing-explanation.896869/

I recommend reading the entire thing before attempting to add anything. Pretty much everything that could be said has already been said.

 

[Borg]

Here's the tree outside my door and the endless noise associated with it. This has been going on for several weeks and seems to be at a peak right now.

 

[nsaspook]

 

[nsaspook]

Remembering your friend on a Youtube channel.

 

[nsaspook]

 

[nsaspook]

Standard disclaimer inserted. Death, injury , etc ... don't do this at home.

 

[DaveC426913]

I think I know the key to how it works. Anyone want to explain?

The TL;DR version:

Three key facts:

1. A sailboat can sail downwind off wind faster than the wind. (i.e. on a broad reach, it is possible for a sailboat to beat a drifting balloon. (07m30s)
2. This effect can be utilized, although not on the way one might expect. (8m05s)
3. The propeller is not driving the wheels. (This is the key key.) In fact, the wheels are driving the propeller. The propeller is what is pushing the vehicle forward - which is why it can exceed the wind speed. (10m58s).

 

[Ivan Seeking]

The TL;DR version:

Three key facts:

1. A sailboat can sail downwind off wind faster than the wind. (i.e. on a broad reach, it is possible for a sailboat to beat a drifting balloon. (07m30s)
2. This effect can be utilized, although not on the way one might expect. (8m05s)
3. The propeller is not driving the wheels. (This is the key key.) In fact, the wheels are driving the propeller. The propeller is what is pushing the vehicle forward - which is why it can exceed the wind speed. (10m58s).

Let me state that another way: Calculate the maximum speed based on the initial wind speed V.

 

[DaveC426913]

Let me state that another way: Calculate the maximum speed based on the initial wind speed V.

I don't know how I would do that, but wouldn't you need to know how the gadget works (to know what forces are involved) to figure that out?

Anyway, they managed to achieve a much higher v than I assumed. They managed to reach 2.8 times wind speed!

 

[Ivan Seeking]

I don't know how I would do that, but wouldn't you need to know how the gadget works (to know what forces are involved) to figure that out?

Anyway, they managed to achieve a much higher v than I assumed. They managed to reach 2.8 times wind speed!

You simply assign variables for air friction, road friction, blade size, design, and pitch, etc... If you really understand how it works, you can set up the problem. The actual numbers are irrelevant.

The key is to determine precisely how energy is added to the system.

 

[jbriggs444]

You simply assign variables for air friction, road friction, blade size, design, and pitch, etc... If you really understand how it works, you can set up the problem. The actual numbers are irrelevant.

The key is to determine precisely how energy is added to the system.

If you have thrust to drag ratio for the airfoil, that should be enough.

Friction with the ground is irrelevant since one can make the craft as massive as is required to obtain the requisite traction. Friction with the air is irrelevant since one can make the prop as large as required (ignoring materials issues). Blade size, design and pitch are irrelevant if one can distill the performance down to thrust versus drag.

 

[Ivan Seeking]

If you have thrust to drag ratio for the airfoil, that should be enough.

Friction with the ground is irrelevant since one can make the craft as massive as is required to obtain the requisite traction. Friction with the air is irrelevant since one can make the prop as large as required (ignoring materials issues). Blade size, design and pitch are irrelevant if one can distill the performance down to thrust versus drag.

I have seen two pages of arm waving over this and not one equation.

Is this a bar or Physics Forums? Perhaps I took a wrong turn. ;)

Oh yes, and they have to adjust pitch.

 

[jbriggs444]

Is this a bar or Physics Forums? Perhaps I took a wrong turn. ;)

This is General Discussion. In particular, "YouTube Classics, Part Deux".

 

[Ivan Seeking]

This is General Discussion. In particular, "YouTube Classics, Part Deux".

And a thread was linked. ;)

 

[nsaspook]

 

[collinsmark]

Here's an update on the faster than wind, downwind vehicle. For technical discussions, there is already a thread in place for this here: https://www.physicsforums.com/threa...the-least-confusing-explanation.896869/page-3

 

[nsaspook]

 

[Ivan Seeking]

Here's an update on the faster than wind, downwind vehicle. For technical discussions, there is already a thread in place for this here: https://www.physicsforums.com/threa...the-least-confusing-explanation.896869/page-3

Fantastic! He really nails it intuitively in the demo with the wheels and board at the end. And in the first video linked above, she nails it down as to WHAT "gear ratio" is in play.

 

[Ivan Seeking]

It was cool to find this original version of David Bowie singing Space Oddity.