Merged DDWFTTW in a “Real” Wind

[humber]

That or a paper bag -- take your pick.

For once, humber got something right.

JB

I Ratant can readily change the gearing, by switching to the other crown gear on the axle.
Order of merit
1) Free wheeler (top speed)
2) Downwind Turbine. When free of the ground, the rotor rotates, and the wheels turn downwind. (possibly higher initial acceleration)
3) Failed upwind turbine (yours). When free of the ground, the rotor rotates, and the wheels turn upwind. Loser all round.

Paper bag beats (3). But not (1) & (2), but has a great price/performance ratio.

 

[383LQ4SS]

There's a damn good reason that this particular version won't be establishing any DDWFTTW records anytime soon.

[qimg]http://www.internationalskeptics.com/forums/attachment.php?attachmentid=21822&stc=1&thumb=1&d=1302820388[/qimg]

JB

I would think the prop is installed backwards? Also...who knows if the pitch is proper for this application. Pitch seems critical and this prop looks like it needs to be closer to flat. And the proper gear ratios seem important for maximum effect.

 

[humber]

.
The latest modified as if the cart was on the ground, facing downwind, (note: simulated ground position) shows the propellor rotation and wheels rotation matches the BB.
From the rear, the propellor rotates CW.
From the right side, the wheels rotate CW.
Up until the vehicle achieves the speed of the wind, the force the wind puts on the prop is a push force, from the rear of the vehicle.
At the transition from <wind speed to >wind speed, the propellor is supposed to become a conventional propellor, pulling the vehicle forward.
This is the stumbling point.
A propellor moving forward into a headwind, as it must be past the transition, doesn't have any thrust, it only drags, unless there is something to add the power needed to have more thrust than drag.
The wheels are supposed to do that.
But my buddy today finds that not possible. Without some source of power, the cart might be expected to get to the speed of the wind downwind, but no faster.
.
I expect my cart configured as shown will move downwind, with the propellor moving in the proper CW rotation.
I want to see it get faster than the wind pushing it.
The freewheeler will provide that indication, as there's no practical for me to get the speed of the vehicle, it being in essence just an unguided missile, going where it will.
If the driven cart can go faster than the freewheeler, I will be satisfied.
Getting it to that point has taken a lot of mostly unaided work by me.
Some helpful hints from mender and humber.

I suspect they are talking about this, I Ratant.
http://www.youtube.com/watch?v=nudBjrOF3LE
When free, the wheels turn into the wind.

 

[windgrins]

I Ratant,

I haven't built a cart and am not part of the team. So this is shooting in the dark. In the build videos, it says to ensure the larger gear is on the prop shaft-this means that every time the wheel axle turns, the prop turns less revolutions ( at the least a 1:1 ratio). This allows the wheels to have a mechanical advantage over the prop (leverage).

Also, in your explanation there is an issue. As soon as the prop starts turning, it produces thrust to push the cart downwind. There is no transition point below or at windspeed!!!

The faster the cart goes, the more thrust the prop creates due to the wheels turning the prop. At < wind speed, the prop is thrusting. At = to WS, the prop is thrusting more. At > WS, the prop is thrusting even more.

Cart guys, please let me know if I got this right. Thanks,

 

[recursive prophet]

Like Platt, it's an entertaining failure.

Which explains your joviality and encouragement, right?

 

[humber]

My comments have nothing to do with any graphics added to his picture.

His vehicle will lose to a paper bag because it isn't built correctly. Like Platt, he needs help. Like Platt, he's decided to go his own way. Like Platt he decided to insult the very people who can help him. Like Platt, it's an entertaining failure.

JB

Oh, it took years of training to make similar carts. A box of props from a flea market ( about $5), 6 wooden wheels/pulleys ( total $4). The most expensive item was the thread. Three types ( total $6).
Oh, the mental strain of figuring out how to connect one to the other.

 

[Subduction Zone]

My comments have nothing to do with any graphics added to his picture.

His vehicle will lose to a paper bag because it isn't built correctly. Like Platt, he needs help. Like Platt, he's decided to go his own way. Like Platt he decided to insult the very people who can help him. Like Platt, it's an entertaining failure.

JB

I agree. He started out with the wrong attitude and he hasn't changed much. And he probably has the same error that Platt had. But at least his propeller isn't made from popsicle sticks.

 

[Subduction Zone]

I Ratant,

I haven't built a cart and am not part of the team. So this is shooting in the dark. In the build videos, it says to ensure the larger gear is on the prop shaft-this means that every time the wheel axle turns, the prop turns less revolutions ( at the least a 1:1 ratio). This allows the wheels to have a mechanical advantage over the prop (leverage).

Also, in your explanation there is an issue. As soon as the prop starts turning, it produces thrust to push the cart downwind. There is no transition point below or at windspeed!!!

The faster the cart goes, the more thrust the prop creates due to the wheels turning the prop. At < wind speed, the prop is thrusting. At = to WS, the prop is thrusting more. At > WS, the prop is thrusting even more.

Cart guys, please let me know if I got this right. Thanks,

Hey!!! No fair citing resources that I Ratant purposefully ignored

 

[humber]

You will need to be very good to talk your way out of the failure of the geared
cart against the free-wheeler, boys.

 

[spork]

A propellor moving forward into a headwind, as it must be past the transition, doesn't have any thrust, it only drags, unless there is something to add the power needed to have more thrust than drag.
The wheels are supposed to do that.
But my buddy today finds that not possible.

Does your buddy believe bees can fly? I generally find real-world evidence more convincing than theory. That's how scientists do it.

Getting it to that point has taken a lot of mostly unaided work by me.
Some helpful hints from mender and humber.

Interesting. So you're saying that you're insulting the people that can help, not asking questions, and still they don't tell you how to do it!?

I Ratant,

I haven't built a cart and am not part of the team. So this is shooting in the dark. In the build videos, it says to ensure the larger gear is on the prop shaft-this means that every time the wheel axle turns, the prop turns less revolutions ( at the least a 1:1 ratio). This allows the wheels to have a mechanical advantage over the prop (leverage).

Also, in your explanation there is an issue. As soon as the prop starts turning, it produces thrust to push the cart downwind. There is no transition point below or at windspeed!!!

The faster the cart goes, the more thrust the prop creates due to the wheels turning the prop. At < wind speed, the prop is thrusting. At = to WS, the prop is thrusting more. At > WS, the prop is thrusting even more.

Cart guys, please let me know if I got this right. Thanks,

The new guy has it all figured out.

 

[ThinAirDesigns]

If a picture is worth a thousand words, in this case comparing two pictures side by side would be worth a few million of yours.

.
Done.

LOL -- hardly. You'll notice that I didn't merely say "post two pictures side by side", I said *compare* the two pictures side by side.

One of these things is not like the other.

JB

 

[windgrins]

I Ratant,

I do have one more suggestion. (Again, I have no dog in this fight!)

Since the cart guys actually know how to build a cart that can go DDWFTTW, I would suggest you suck it up and ask nicely "Would you please tell me how to modify my cart to make it work properly, folks?"

You obviously put a lot of work into your cart to make it work so I think you really would like to see it work as advertised.

I'm not part of this but since Spork and company really did build a cart that can go DDWFTTW, I think a positive attitude combined with a will to listen and learn would probably go a long way.

They have been pushed pretty hard by all kinds of idiots on this forum so I can understand why they are a little sensitive.

Also your aerodynamic explanation of the prop at <,=, and > WS is wrong. What they are telling you is that the prop acts always as a pusher throughout the entire regime--period. There is no transitional period except from 0 speed of the cart when the prop is not moving at all.

I hope this helps as you have a real opportunity to learn and elevate the conversation by taking this approach.

Thanks,

 

[ThinAirDesigns]

Also your aerodynamic explanation of the prop at <,=, and > WS is wrong. What they are telling you is that the prop acts always as a pusher throughout the entire regime--period. There is no transitional period except from 0 speed of the cart when the prop is not moving at all.

Windgrins, this is precisely the problem with I Ratant -- he's been told the above by about 10 other people on this list (including me) and he just scoffs it off.

You can lead a horse ...

JB

 

[humber]

Interesting. So you're saying that you're insulting the people that can help, not asking questions, and still they don't tell you how to do it!?

I think I Ratant's model-building skill are clearly evident. All nicely done.

The new guy has it all figured out.

Your monopoly is under siege, and damned if I can't calculate, Spork.

These kits are really good source of bits for making TM carts.

 

[spork]

I Ratant,

I do have one more suggestion. (Again, I have no dog in this fight!)

Since the cart guys actually know how to build a cart that can go DDWFTTW, I would suggest you suck it up and ask nicely "Would you please tell me how to modify my cart to make it work properly, folks?"

The new guy is still batting 1000. No sucking up needed really. Maybe just a slight apology - something of the form "hey - maybe I was wrong - perhaps there is something worth talking about here". He doesn't even have to ask all that nicely. But asking would be a big step up from telling us we've got it wrong.

We've got nearly infinite patience for people with genuine questions, and roughly zero patience for people that are insulting for no reason.

 

[humber]

LOL -- hardly. You'll notice that I didn't merely say "post two pictures side by side", I said *compare* the two pictures side by side.

One of these things is not like the other.

JB

The one on the left is a clumsy scrap heap, the other isn't.

 

[humber]

We've got nearly infinite patience for people with genuine questions, and roughly zero patience for people that are insulting for no reason.

You will definitely need to be good to tell me that I didn't make things correctly,
Spork.

 

[windgrins]

Humber,

I think this will be my one and only comment about Spork's "monopoly".

Spork and team built not just one, but many carts that can go DDWFTTW. They "wrote the book" on how to do it and I salute them. I especially liked the "oil drum world" explanation as it is a clear transform and extension of a previously demonstrated model of DWFTTW to DDWFTTW.

His team deserve the monopoly but have not claimed it as they seem pretty open to real questions. I haven't even built the small cart, but from a physics, aeronautics, and sailing perspective, this was a bit convoluted but a very clever demonstration of a principle. Consequently, they'll get no pushback from me since they went into the real world and put their ideas to the test and won! Great job guys!

To be clear, that's the attitude I bring to this forum.

 

[temporalillusion]

Discussing this thing with a long-time aviation nut... pilot's license, life-time spend in aviation, full-scale and hobbyist, sail boat enthusiast, he expressed concern about the situation.

I still have a text book from when I flew gliders that incorrectly describes how lift is generated (the same way that humber is wrong about how lift is generated).. not saying your friend has an incorrect model in his mind, but there are a TON of pilots out there that have the wrong idea concerning how lift is generated.

 

[humber]

Humber,

I think this will be my one and only comment about Spork's "monopoly".

Spork and team built not just one, but many carts that can go DDWFTTW. They "wrote the book" on how to do it and I salute them. I especially liked the "oil drum world" explanation as it is a clear transform and extension of a previously demonstrated model of DWFTTW to DDWFTTW.

His team deserve the monopoly but have not claimed it as they seem pretty open to real questions. I haven't even built the small cart, but from a physics, aeronautics, and sailing perspective, this was a bit convoluted but a very clever demonstration of a principle. Consequently, they'll get no pushback from me since they went into the real world and put their ideas to the test and won! Great job guys!

To be clear, that's the attitude I bring to this forum.

OK by me, Windgrins, but if they are so helpful and knowledgeable, why do they present their remarks to I Ratant in mocking riddles? It does sound like they want him to fail.

I have one for them. This cart goes up the TM belt, no prop, motors or tricks.