Merged DDWFTTW in a “Real” Wind

[humber]

Yes, add that to the long list of things I 'didn't note', such as:
The sun came up this morning

TAD Logic^TM1) The Sun will rise in the morning
2) The Sun will not rise in the morning.
Therefore there is only a 50/50 chance that the Sun will rise.

Gravity is still in effect

Busily behaving like a spring.

Time did not stand still.

BB does, and a lot.

ETA: NEWSFLASH!!!!!!!!!!! Unanchored potato chip bags blow downwind (still)

Beats Blackbird!!!!

We leave the obvious stuff for you and humber to note.

What do you call failure?

 

[3point14]

But then why consider a CVT?

They didn't.

I asked what effect that would have.

 

[Jack by the hedge]

If we remove the pushing, the cart's average speed is 8.5mph. Slower than the wind.

And if you remove the B-29, Chuck Yeager didn't break the sound barrier in 1947. Thankfully, neither record was for accelerating from a standstill to top speed.

 

[humber]

They didn't.

I asked what effect that would have.

To make it even heavier.

 

[humber]

And if you remove the B-29, Chuck Yeager didn't break the sound barrier in 1947. Thankfully, neither record was for accelerating from a standstill to top speed.

With pushing. How about all the way? The chart says that the cart is pushed above WS. A lighter cart would be easier. Hey, >WS. Call the press.
With pushing included, average speed 18.5mph.
I like that you chose to make the comparison with Chuck Yeager, rather than with Supermarket Sweep Stakes.

 

[EHocking]

If that is done by rotating the axle assembly, so the mountings can be re-used, that reverses the direction of rotation of the wheels

Ayup, in that configuration, it will.

 

[ThinAirDesigns]

With pushing included, average speed 18.5mph.

Damn that's scary -- we should have let it sit a bit longer before we took off on that run so we could have kept that average below 10mph.

I hear that the average speed of a top fuel dragster through the quarter mile is something around only 0.01mph after they work on it all day. Now *that's* figuring out how to race without danger.

JB

 

[humber]

Ayup, in that configuration, it will.

Which is what I said the first time. What configuration did you have in mind that involves a 180 rotation of the axle, that will not do the same?

 

[humber]

If the instantaneous velocities did not sum to zero then there would be a net drift velocity. A zero average is in no way incompatible with Brownian motion.

Afraid it is.
Funny. There are rather a lot of molecules in even a small amount of air, and their motion is described statistically. RMS is the root mean square of all that.

You are being deliberately obtuse (and ridiculously pompous) in order to avoid facing the fact that you are wrong. The transform, you will observe, is from a finite square to a finite cylinder. It is trivial and it happens before your eyes. What does "Why is the air not in it?" even mean?

Then what about the new surfaces at the ends? When a new surface is created, energy is released.

If it helps, you may consider the "yacht" and "ocean" to be a model. The model demonstrates the principle of the sail driving the yacht downwind faster than the wind. This is possible because of the sail's component of velocity perpendicular to the wind, which does not depend on the earth being flat.

It's ridiculous.

 

[humber]

Damn that's scary -- we should have let it sit a bit longer before we took off on that run so we could have kept that average below 10mph.

And the 1min 40 seconds it spends below walking pace in the Jenkins video.

I hear that the average speed of a top fuel dragster through the quarter mile is something around only 0.01mph after they work on it all day. Now *that's* figuring out how to race without danger.
JB

A bucket would beat that pile of junk.

 

[mender]

Actually, there have been quite a variety of responses over the last 2 years as to why so many would keep responding to claims "full of sound and fury and signifying nothing." I'll concede the hypnotizing train wreck has oft been mentioned. However, given that this has been going on since 11/08, we're talking about the most extended, slow motion train wreck ever to enter the cloud of physics. Even a "type A cubed" personality like you, who has set a world speed record flying like a bird with a rig you designed, can't resist watching. You, who built Blackbird, and spork who helped design it, still can't really avoid reading Humber's prevarications. Doesn't most great humor contain elements of truth? And as I've mentioned several times, what about Feynman's sprinkler? It ain't always cut and dried despite appearances. Is it? They ALL claimed it was elementary physics.

Apparently Booger robbed us of the will to leave.

 

[I Ratant]

I've got the breakout rolling friction on the latest down to .5 oz.
Should be movable in the low level winds... I hope.

 

[3point14]

And the 1min 40 seconds it spends below walking pace in the Jenkins video.


A bucket would beat that pile of junk.

Tell me, do you know the meaning of the word 'wager'?

 

[Jack by the hedge]

Then what about the new surfaces at the ends? When a new surface is created, energy is released.

What irrelevance are you on about now? You, yes even you, can bend a square sheet of paper to form a cylinder. You do not need to create a new surface to achieve this.

Instead of focusing on irrelevant nitpicking, please try to grasp the point of the animation which is to demonstrate the mechanical equivalence of the first and last states. I cannot believe that even you can fail to grasp this, though I am increasingly sure that you will never bore of pretending to do so.

 

[I Ratant]

If I'm reading this right, are you talking about a freewheeling propellor only?

In one instance mounted so that it spins CW and in another instance so it spins CCW?

If the same cart and the same propellor, direction of spin will make no difference to the speed generated by this "spinning sail" (think of a rotor on a gyrocopter - unpowered, but the spin generates lift).

If you're talking about a CW vs CCW spinning prop driven by the wheels, gearing b/w prop and wheels will determine cart direction wrt tailwind.

.
Oh, yeah, I've found that out, and mentioned a million pages back or so.
That's what bothered me.
The friggin' prop wants to go the "wrong way" when left to its own devices.
Hooking it up to the wheels prevents that.. for the propellor to be thrusting after the vehicle gets to windspeed.
The sail effect goes away.. also mentioned in the past... a whole couple days ago.
Prettified that chart. Got the usual dismissals from the usual sources at the time.

 

[Jack by the hedge]

Afraid it is.
Funny. There are rather a lot of molecules in even a small amount of air, and their motion is described statistically. RMS is the root mean square of all that.

You are confusing two different properties: The speed of a typical molecule and the movement of the air en masse. As I originally suggested, you and SZ were talking at cross purposes.

 

[ThinAirDesigns]

.Hooking it up to the wheels prevents that.. for the propellor to be thrusting after the vehicle gets to windspeed.

Of course as you're aware (but like to pretend otherwise), the propeller doesn't wait for wind speed to begin producing thrust. If it did, the vehicle could never reach wind speed on it's own.

The sail effect goes away.. also mentioned in the past... a whole couple days ago.

You can mention it all you wish, but the blades of the spinning rotor act as sails from standstill to full speed -- this never changes nor stops happening at *any* speed from zero on up.

JB

 

[mender]

If you consider the prop blade to be a wing, it starts out stalled wrt the wind direction and as the cart moves and speeds up becomes un-stalled and operating at a normal angle of attack. The "sail effect" is the stalled condition and is quite inefficient compared to a normal AOA.

The important thing to remember is that the prop never changes its mode of operation from stalled to unstalled, just its efficiency in generating lift (thrust).

 

[Jack by the hedge]

With pushing. How about all the way? The chart says that the cart is pushed above WS.

And then continues to accelerate, all the way to 2.8x windspeed.

A lighter cart would be easier.

Irrelevant.

With pushing included, average speed 18.5mph.

Average speed is also irrelevant.

 

[mender]

I've got the breakout rolling friction on the latest down to .5 oz.
Should be movable in the low level winds... I hope.

You may find it helpful to pull the cart up to a portion of windspeed because of the stalled condition of the prop when the cart is stationary.

My cart takes about 3 grams to start it rolling; roughly 1/5th of yours.