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Spanish experiment

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Merlin
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Spanish experiment

#1

Post by Merlin » Wed Jan 23, 2013 7:48 pm

Ok we restart the discussion about the experiment that Aitor is aiming at. First let’s recall the context. Although this has been debated many times and that a foolish number of poor engineers have succeeded in modeling the problem, there is nothing but experience to confirm why a bendy rod is useful. After describing what a first experiment could be using a brick on a table and a falling weight, Aitor has the ambition to make the same type of experimental check with a trebuchet and a couple of rods (flexible, rigid) made by Alejandro. That is a promising perspective.

The problematic is not far from the casting modeling although it does not exactly fit to the problem, but nevertheless what we are interested in demonstrating the usefulness of a spring. Some of us modeled Aitor’s experiment so we have the means to guide him for the experiment.

Image

Image

As a representative of the foolish engineers club I confirm that the usefulness of a spring is that the basic mechanism is to move some force along a large distance and not to store elastic energy in the rod which is supposed to be feed back into the line.

Many times the question comes up to know whether using a spring is minimizing the amount of energy a caster has to use, but we have to recognize that we engineers are failing to convince readers this is real. In fact we are relying to our (good) models but suspicion is the rule. The lock up comes from the fact that readers are not accustomed to physics laws and this makes the dialogue very difficult. At the end of the day there is no miracle: the caster has to provide the energy that will be nicely provided to the line by a smartly designed fly rod.

We are not discouraged (in both camps) so we encourage Aitor to test his concept until we can get a visible evidence of what the engineers’ club is arguing about; and what the “I believe what I see” club is convinced about.

I may be provocative in suggesting to Paul that any contesting argument which appears to be wrong should entitle its creator to give some money for a good cause supported by the SL forum. Not sure this is a good idea; it may dry up the discussions…

Aitor, we rely on your willingness to succeed in making your experiment real. We are ready to help you for the design and wish you all the best.

Now I have some doubt coming to my mind: even if Aitor can demonstrate the usefulness of a spring in casting, how many people will believe this is true? I may well have a too much tortuous mind...

Merlin
Fly rods are like women, they won't play if they're maltreated
Charles Ritz, A Flyfisher's Life

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Paul Arden
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Spanish experiment

#2

Post by Paul Arden » Thu Jan 24, 2013 7:46 am

I may be provocative in suggesting to Paul that any contesting argument which appears to be wrong should entitle its creator to give some money for a good cause supported by the SL forum. Not sure this is a good idea; it may dry up the discussions…
No I don't think this is a good idea, not least because I have a very long history of being wrong on the Board!! :p

Cheers, Paul
It's an exploration; bring a flyrod.

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Spanish experiment

#3

Post by Unregistered » Thu Jan 24, 2013 9:07 am

Merlin wrote: Aitor, we rely on your willingness to succeed in making your experiment real. We are ready to help you for the design and wish you all the best.

Now I have some doubt coming to my mind: even if Aitor can demonstrate the usefulness of a spring in casting, how many people will believe this is true? I may well have a too much tortuous mind...

Merlin
I am thinking of how to devise the lead-weight / lead-spring-weight comparison and I have an general idea about how to devise it.

My doubt is of the same nature as yours: if the experiment demonstrates that both weights cover the same distance with the same enrgy input from the lead, how many engineers will believe this is true? :D

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gordonjudd
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Spanish experiment

#4

Post by gordonjudd » Thu Jan 24, 2013 4:27 pm

As a representative of the foolish engineers club
Merlin,
As a long-retired EE, I think I am a charter member of that club as well, and have decided to adopt a portrait of our honorary founding president as my avatar. A new persona for the new board.

I don't know about you, but I thought I was voting for Alfred Eisenstein when I checked the Alfred E. box instead of the Isaac N. box to be the honorary president of the club. I guess that Alfred E. (Newman) was better known to the general public so we are stuck with a goofy looking founder. But then you have to be a bit goofy to think that the finger,spring, marble or car,spring,brick model has anything to do with fly casting, so in my case it is a good fit.

Gordy

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Spanish experiment

#5

Post by gordonjudd » Thu Jan 24, 2013 5:05 pm

I am thinking of how to devise the lead-weight / lead-spring-weight comparison and I have an general idea about how to devise it.
Aitor,
You might find that using a stretched bungee cord with the rod butt on a hinged pivot might be an easier implementation of your fixed input energy source than a more complex trébuchet arrangement. The bungee cord would produce a decreasing angular acceleration of the butt rather than the more constant (or smoothly increasing) value we actually apply in casting, but at least the initial PE source would be the same and that is the main constraint you are trying to impose with your experiment.

The trouble with this is in working out a "soft" stop to halt the rotation of the rod, although the hard stop shown here [vimeo]32605368[/vimeo] did not appear to snap the rod but did produce a lot of after-stop tip bounce.

Good luck to Alejandro in coming up with a tapered flexible rod that has the same MOI as a stiff broomstick having the same length. Getting those two rods to have the same KE (a non-negligible value in a real world spring that has mass) as the bendy or a stiff rod rotates would I think be nearly impossible to do. It is more likely you will have to measure those different MOI values and take them into account when you come up with your final energy values.
My doubt is of the same nature as yours: if the experiment demonstrates that both weights cover the same distance with the same energy input from the lead, how many engineers will believe this is true?
I think we agree that the distance and the same energy is being distributed in different ways in your experiment. However, the force applied to the brick over that distance will be different, and account for larger amount of work energy applied with the spring. I still owe you that plot, but will do so later today.

I am rooting for your success in doing this experiment, for as Feynman said:
It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.
Richard P. Feynman
Gordy

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Spanish experiment

#6

Post by Unregistered » Thu Jan 24, 2013 5:27 pm

gordonjudd wrote:
My doubt is of the same nature as yours: if the experiment demonstrates that both weights cover the same distance with the same energy input from the lead, how many engineers will believe this is true?
I think we agree that the distance and the same energy is being distributed in different ways in your experiment. However, the force applied to the brick over that distance will be different, and account for larger amount of work energy applied with the spring. I still owe you that plot, but will do so later today.

Gordy
Gordy,

No need for plots, I just prefer some plain words for everybody to understand.
If we have taken a brick as a simile for a fly line the only thing we are discussing here is wether the brick attached to the spring is going to cover a longer distance than the other one, for, in a real case scenario, the rod that is applying the larger amount of work to a line is going to shoot that line farther away.
So when I put the two bricks side by side the one driven by the spring and the lead will go a longer distance over the table, right?

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Spanish experiment

#7

Post by Unregistered » Thu Jan 24, 2013 5:30 pm

gordonjudd wrote:Good luck to Alejandro in coming up with a tapered flexible rod that has the same MOI as a stiff broomstick having the same length. Getting those two rods to have the same KE (a non-negligible value in a real world spring that has mass) as the bendy or a stiff rod rotates would I think be nearly impossible to do. It is more likely you will have to measure those different MOI values and take them into account when you come up with your final energy values.

Gordy
Alejandro told me that he has an idea about how to minimize that difference, although it is quite clear that the MOI of the rigid rod will always be higher. Anyway that is another advantage for the flexible rod and not the other way around.

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James9118
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Spanish experiment

#8

Post by James9118 » Thu Jan 24, 2013 5:53 pm

Aitor - what's the launch date for your experiment? I know a nice quiet spot near Neptune for it. You are doing it in space aren't you.... :D

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Spanish experiment

#9

Post by Unregistered » Thu Jan 24, 2013 6:01 pm

James9118 wrote:Aitor - what's the launch date for your experiment? I know a nice quiet spot near Neptune for it. You are doing it in space aren't you.... :D
Maybe, I have heard that Virgin is organizing some space trips already. :cool:

Anyway, after weeks of asking I don't have any clear reply to an easy question. Again and for the last time:
- Two identical bricks on a table
- Two identical weights
- One spring
- One inelastical string

One weight is connected to the brick by the inelastic string; the other one is connected to the weight by a spring. Both weights hang at the same height from the edge of the table, the spring is in equilibrium.
We release both weights and they reach the ground.
Which brick covers more distance over the table?
I don't know about work, nor about energy, I only know what my eyes see. If the spring combo transfers more energy to the brick this one will go a longer distance. Right?

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Lasse Karlsson
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Spanish experiment

#10

Post by Lasse Karlsson » Thu Jan 24, 2013 6:10 pm

Aitor wrote:
Anyway, after weeks of asking I don't have any clear reply to an easy question. Again and for the last time:
- Two identical bricks on a table
- Two identical weights
- One spring
- One inelastical string

One weight is connected to the brick by the inelastic string; the other one is connected to the weight by a spring. Both weights hang at the same height from the edge of the table, the spring is in equilibrium.
We release both weights and they reach the ground.
Which brick covers more distance over the table?
I don't know about work, nor about energy, I only know what my eyes see. If the spring combo transfers more energy to the brick this one will go a longer distance. Right?

Hi Aitor

The brick without spring has covered more table when the weight hits the ground....

Cheers
Lasse
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http://www.karlssonflyfishing.com

***Bring Mark back!!!!!! ***

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