Merged DDWFTTW in a “Real” Wind

[humber]

No math required in this case. A speed difference between hand and spool does not imply that there's any acceleration happening. Zooterkin was right, you were wrong. If a=0, it does *not* mean the spool is stationary, as you claimed, just that its speed isn't changing. Sir Isaac worked this out centuries ago.

How more basic can your errors become?

An opposing force F at the ground, becomes 2F at the thread,because of the gearing. 2F - F =F. It can't stop accelerating. What actually happens, is dependent upon the ratio of the moment of the reel to the mass of the reel.

But, in the simplified case, acceleration stops when F net = 0, but the gearing simply prevents that. To keep a constant velocity, the force must be applied for half the time. One way is to not pull with a constant force as you watch the reel respond, and the other is to let it pass by so you can't apply force until you catch up with it, and pull again. The result is the same. Force is applied for half the time. V_avge reel = V_avge hand.

The cart is based on discredited notions of screwing props and cotton reels.
Exhumed, to repeat the mistakes of the past.

The first source was Ruina and his wheels and rails, just like the ruler cart. Then Drela. Spork's analysis was a version of that, with the "arbitrarily low" friction of .001. Steel on steel.
Now it's Smith, and the air lever....etc

 

[GlennB]

But, in the simplified case, acceleration stops when F net = 0, but the gearing simply prevents that.

How bizarre. My car has very nice gearing, yet I find it quite easy to proceed along at a constant speed. Many many physical systems achieve the same effect. My bicycle, my lawnmower, my Labrador, my fishing reel (have I mentioned PowerPro^tm braid?) .... too many to mention here really.

You have disproved Newtonian mechanics; may we call the new system Humberonian mechanics? Congratulations.

 

[humber]

So simple. You have a simple cart that you are towing behind you at the same pace as you. The force is F.
Apply 2F, by pulling on the rope, and it will accelerate towards you. Continue to do that, and it will overtake you. To stop that, pull at 2F, let is slow as you walk ( the thread will slacken) then when it is taut again, pull with 2F again. Average F, speed the same as you.
That is the only way you can avoid it overtaking you. Same with the reel.
Cotton reels have a complex set of behaviors, and will fool you.

And the bike and car are power limited. Pick up the most basic book that you can find, and it will show that gears are used to match the load to the engine's power band. Same as a bike.
All Carteers are invited to play the shell and pea game with me. You won't stop until your bank accounts are empty, because you will be SURE you know where the pea is.

 

[I Ratant]

It will move without a prop if there is sufficient wind. There can be no torque without drag, but the sail force is not the only force at work pushing the cart downwind.
...

.
Did that.
With no prop, the freewheeling cart wouldn't move in the available wind, but go briskly downwind with the prop fixed and not rotating, and briskly plus with it free to rotate.

 

[ThinAirDesigns]

.
Did that.
With no prop, the freewheeling cart wouldn't move in the available wind, but go briskly downwind with the prop fixed and not rotating, and briskly plus with it free to rotate.

So, let's get this straight -- while at all times *some speed* slower than *some wind speed*, the device went *some speed* faster and faster as drag was increased by *some amount*.

I can't imagine why we didn't start with such new and rigorous tests ourselves when on our quest to go DDWFTTW.

JB

 

[Jack by the hedge]

An opposing force F at the ground, becomes 2F at the thread,because of the gearing. 2F - F =F. It can't stop accelerating.

This is just embarrassingly wrong. I think you need to reconsider exactly what forces you mean, and where they are acting.

Better still, forget all about the forces involved and just apply a little bit of very basic geometry to the situation. You will see that the reel always moves twice as far and twice as fast with twice the acceleration of the hand pulling the thread.

So every time the hand moves 1m the reel moves 2m. It does not matter if the hand accelerates, decelerates or travels at a constant speed, the reel will follow suit.

It's amazing that just a few posts ago you said "assuming steady state for one, and not the other is a mistake" but now you're back to asserting "it can't stop accelerating". What nonsense.

 

[Jack by the hedge]

To keep a constant velocity, the force must be applied for half the time.

Wrong.

 

[humber]

So, let's get this straight -- while at all times *some speed* slower than *some wind speed*, the device went *some speed* faster and faster as drag was increased by *some amount*.

I can't imagine why we didn't start with such new and rigorous tests ourselves when on our quest to go DDWFTTW.

JB

Oh, that's rich, ThinAirDesigns.

Edited by Gaspode: 

Corrected spelling of user's name.

You started out with a dyno fitted with strain gauges, to measure the thrust at the prop, and the force at the wheel. I told you that your gauges would not work, and the basic design of the dyno made that problem pale into insignificance.

The gauges did not work, and neither did the dyno, but success was based upon how far the dyno moved, when tethered to a truck, as the prop tower wobbled until something broke. From that, you conclude that the prop is producing 200N, even though you pass by it, without even your remaining hair being ruffled.
The "prop momentum video" says that 200N is out by several orders of magnitude.

 

[Jack by the hedge]

So simple. You have a simple cart that you are towing behind you at the same pace as you. The force is F.
Apply 2F, by pulling on the rope, and it will accelerate towards you.

Until it reaches twice your speed, when the drag will balance the 2F pull. Then it will stop accelerating and follow you at twice your speed until you eventually run out of rope. Of course in reality the "rope" is the wind, so it doesn't run out.

 

[ThinAirDesigns]

The gauges did not work, and neither did the dyno, ...

No.

JB

 

[humber]

No.

JB

The rear wheels where driven by a 6hp motor. The front wheel was restrained by a small incline. The work needed to over come that is small, because the bulk of the mass is over the driving wheel. If the prop were to be producing 200N, the cart would fly off the dyno. a =200N/200kg = 1ms-2.

 

[ThinAirDesigns]

Poor humber - in over his head on damp pavement.

JB

 

[humber]

Wrong.

You can't tell me my cart won't work. If when pulled with constant velocity, the drag is F, then applying 2F for 50% of the time is an average of F.
I could do that while walking at a constant velocity, but tugging at the rope with my arm for a few seconds. The reel is no different.
The reel, the two carts and the ruler are impractical solutions to the problem; should that be possible.

But, it's a waste of time.
If I pull a simple 1kg cart 1m with a force of 1N, then the work is F*d = 1J.
But, for a 1kg reel that rolls that same 1m, but needs 2F, the work is 2J, but with the added problem of the angular work that is not present in the simple cart. The ratio of linear to angular force, rule the reel, but that is no important.

That extra energy of the increased work goes somewhere, and it is added to the KE of the mass. KE = m*a*d =mass*acceleration*distance.
Distance and mass are the same in each case, so acceleration is doubled.
Maybe I can turn that into 2V, but if I had the power to do that,
then I could tow the simple cart to 2V.

 

[humber]

Poor humber - in over his head on damp pavement.

JB

That dyno test looks like a sketch from Laurel and Hardy.
Wobble...wobble....boing!

The tests that I Ratant has done, are closely mimicked by those undertaken by Mender in his dungeon. He used a fan, as did I, and at least my conclusions are concordant with I Ratant's.

The Prop and Turbine race shows the turbine to be much faster from the gate, just as the un-geared carts are. It later slowed, but that may have been due to the rubber bands you used as tyres, or that the gearbox was limiting the AV of the rotor. If that ratio is set too low, the rotor will self-limit. I thank you for your attention, ThinAirDesigns.

Do not change a user's name so as to insult.

Replying to this modbox in thread will be off topic  Posted By: Gaspode

 

[Jack by the hedge]

You can't tell me my cart won't work.

But I can tell you your cart won't exceed windspeed, which is the object of the exercise.

If I pull a simple 1kg cart 1m with a force of 1N, then the work is F*d = 1J.
But, for a 1kg reel that rolls that same 1m, but needs 2F, the work is 2J, but with the added problem of the angular work that is not present in the simple cart.

The angular work is also present in the wheel sof your simple cart, but you disregard it. If the acceleration is low enough you can disregard it in the reel too.

KE = m*a*d =mass*acceleration*distance.
Distance and mass are the same in each case, so acceleration is doubled.

To go twice as far in the same time you must go twice as fast. Your acceleration would be double that of a cart which only went half as fast. So what does that prove?

Maybe I can turn that into 2V, but if I had the power to do that,
then I could tow the simple cart to 2V.

It's not the power to do so that is the real (reel?) trick, it's a mechanism to do so. And it's been done. And it's such a clever mechanism that some people still don't see that it can work.

 

[humber]

But I can tell you your cart won't exceed windspeed, which is the object of the exercise.

If you can claim that applying a constant force of 2N, gets you 2V, then so can I.

The angular work is also present in the wheel sof your simple cart, but you disregard it. If the acceleration is low enough you can disregard it in the reel too.

No, the cart's wheels are not related to the overall mass. The angular to linear ratio of the reel is determined by the moment, and so by the possible constructions.
But, if I wish away the angular part, I am no better off, because the lever always causes 2F, so twice the work is done for the same distance, so acceleration is doubled. Why not, there is twice the force.

To go twice as far in the same time you must go twice as fast.

Not quite. One mass is constant at 1m/s. The other accelerates from 0m/s to 2m/s over 1 second. Both have traveled 1m, and the average velocity is the same, but the final velocity is doubled.
.

Your acceleration would be double that of a cart which only went half as fast. So what does that prove?
It's not the power to do so that is the real (reel?) trick, it's a mechanism to do so. And it's been done. And it's such a clever mechanism that some people still don't see that it can work.

It is possible achieve a 2:1 theoretically. To cut a long story short, the solution results in zero force in the thread. A waste of time.

 

[I Ratant]

So, let's get this straight -- while at all times *some speed* slower than *some wind speed*, the device went *some speed* faster and faster as drag was increased by *some amount*.

I can't imagine why we didn't start with such new and rigorous tests ourselves when on our quest to go DDWFTTW.

JB

.
Do try to participate in the conversation, instead of being condescending.
There's enough of that.
I'm not duplicating what.. the much hooplaed.4th or so attempt to show ddetc?...I'm just looking at what is involved... what makes what move, and how. The wood framed cart from 2007 did the feat first.
Bigger doesn't make better.
I might find a longer free-run area to set both carts loose on, to see which moves faster, further, and what time might be involved for any overtaking.
The current results show the windmilling propellor cart takes off quickly, while the driven propellor cart starts slower.
I'd like to see what distance and time might be involved in it's catching up, or not, with the freewheeler.
But I can do something worthwhile instead of trying to put some information here on an insignificant and pointless "feat" which interests me.
Any land sailer can return to the point of release.
How much more cash will be needed to get the larger things to do that?
I've spent all of $6.23 to get closer to the same results as the supersized carts get.
And have to walk to bring them back to the starting point.

 

[ThinAirDesigns]

.
The wood framed cart from 2007 did the feat first.

No.

JB

 

[Llyricist]

I just hope I get the CD before RP/Humber get their's. So I can continue to be his worst nightmare.

 

[spork]

I just hope I get the CD before RP/Humber get their's. So I can continue to be his worst nightmare.

I have to guess that RCP requested the data from the Swedish consulate or something - because I never heard anything about his request. I imagine the data is on the way to you - because you were competent enough to actually request it.

And on the off-chance the RCP did manage to request it - and figure out how to give them a correct address to send it to... he still has to figure out how to make the drop so that humber can get access to the data without giving away his identity or leaving his quarters (cell?). And even if that works out, humber will have to figure out how to open the files. I figure you have a good 6 month lead on them.

But I'll warn you - it's really tedious and boring data. If I recall correctly, it has several runs we did over the two days.