Fulcrum

[Magnus]

However in a complex system the IC of a single part of that system is not fixed and its not at all the same creature as a fulcrum.

Yep - no problem with that.

[gordonjudd]

In your world a layman is held to a rigid meaning for the term fulcrum while you bend the meaning of the the word lever.

Is that a double standard Gordy?

Magnus,
I don't know if it is a double standard, but it saves having to rip out certain pages in my casting books.

I think I know the difference between a fulcrum and a rotation center so it does not bother me. I also like to look at the force and distance the rod applies to the line as it results from its use as a flexible lever that relates to the spring of the rod.

Considering the rod to be a forced cantilevered spring connected by a stiff torsional spring at its driven end might be more technically correct (that is how Haun analyzed it), but somehow I do not think that description is going to find much use in fly casting books.

However, whether the rigid part of the lever is straight such as a pry bar or curved such as your crow bar example the fulcrum on the bar has to be located at some point on the bar itself to be a supporting fulcrum to meet the classical definition of a lever. If you can find something different, it would be a big help to ending this pointless semantics exercise.

Let's just cut to the chase and agree on a simple, direct concept that you keep avoiding. This is the third time (and counting) that it has been asked in one form or another.

In a lever, doesn't the fulcrum have to be located somewhere on bar to provide a support point for the rotation?

Gordy
P.S. You posted while I was preparing mine.

Yep - no problem with that.

Good for you, I was not expecting that.

Digging a bit deeper into that answer are you still holding on to your dictum that:
No fulcrum = No Lever
and therefore it follows that:
Good lord! All the textbooks that give a fishing rod as an example of a type of lever now need to be re-written.

Gordy

[sms]

Short line = Andersson style = clearly dominant bottom hand
Why is it so effective?

Because good casting is not only about how we create the proper amount of tip speed as effective as possible!
It is also about a small arc and an abrupt stop.

If we pull our bottom hand into the stomack it stops immediately. To add less force via top hand helps to stop it faster as well as it helps to control the small arc matching the short line.

In regard of the bc (which I am almost totally missing in all the analyses in this thread) I think most casters bring in more top hand because pulling something to our body is easier than pushing it away from our body.
It also helps to control the anchor if little more top hand is used in the bc. Using too much bottom hand easily blows the anchor.
See again it's not only about effectively producing high speed.
It's about controlling and matching all elements of a good cast.

Hi Bernd,

I think that abrupt stop is only needed to reduce loop max height for given arc. Btw, did you see my video of MPR in a cup, where it is free to move forward when the stop torque would step in:
http://www.youtube.com/watch?v....o_title

I match the arc to needed line speed and line mass (includes lenght and density).

I have a friend, who uses very much bottom hand with his DH back cast, it is really weird looking. He has gone thru the underhand casting route. It works for him, at least with short lines. The danger of lower hand dominated back cast is that it is aimed way too low and you get very long anchor or "double anchor".

I would call different styles just bottom hand and top hand dominated and 50/50. And then I would tell the pupil that they describe roughly which hand moves most (does most work, but not effort) during power application.

I don't know which is more efficient for us, pushing something away from us or pulling something towards us with the forces and velocities that we need in fly casting. That's something I would like to know thou.

[Stoatstail50]

If we think about the rod as a part in a complex system with a connection at two points, each point being a place where the rod can pivot, how many fulcra exist on the rod ?

[Magnus]

Yes Gordy a fulcrum makes contact with the lever.

[gordonjudd]

Am I right the The IC doesn't actually tell us how the rod was rotated in the two hands.

Paul,
That is correct.

The rotation does not necessarily come from the contact forces on your two hand. You could hold the rod rigidly with your hands and lock your wrists so they would not rotate (and thus turn the force from your hands into internal contact forces on the rod that by definition can do no work), and still rotate the rod by rotating your elbows or shoulders.

If I dragged the rod forward and then applied all the rotation with the bottom hand to finish in the exact same position as rotating the rod forward throughout the CS, then wouldn't the IC be the same?

If I understand this fully, the answer is no.

Your motions in that case would involve translation and rotation in the first case and pure rotation in the second. Translation can cause the ICR to move a great distance away from the rod if the rotation rate is small.

As an example take a look at the ICR flow that Lee Cummings produced in his single handed distance cast. As he drags the rod forward there is very little rotation going on. When the rod had a slight clockwise angular velocity then the ICR was out of the frame of the camera on the bottom of the video. When he drifted the rod so the angular velocity was counter-clockwise then the ICR jumps out of frame to the top of the video. As a result the ICR jumps around all over the place since the rod was being translated with little or no rotation at the start of the cast.

Even for the short period of time where Lee turned on the rotation rate, he was still producing high translation velocities in that cast (look at how much translation there is in his upper body). As a result, the ICR never gets close to his elbow at MAV as is typically the case in most of the casts I have analyzed.

The frame rate in that video makes for a very choppy result. I would like to see where the ICR actually was at MAV using some high speed video. The 25 fps rate in that video does not do justice to the speeds Lee produced in that cast.

If the rod was being constantly rotated about one place (the shoulder for example) while all the other joints were locked in place to produce all of the rod rotation then the ICR would always be fixed at the shoulder throughout the cast,

The flow you get with high translational velocities is much different than if the rod is undergoing pure rotation. The ICR location does include the impact of both types of motion so it is still a useful concept to look at the overall result that comes from a mix of the two types of movements.

Gordy

[gordonjudd]

Yes Gordy a fulcrum makes contact with the lever.

Magnus,
Thanks, that is a good first step in resolving our semantic differences.

Soooo... Is the concept that the rod acts like a flexible lever in casting sill a useful concept in your book or not?

Good lord! All the textbooks that give a fishing rod as an example of a type of lever now need to be re-written.

I'm trying to salvage your casting library here.

Gordy

[Paul Arden]

It's not just casting libraries, if you look up examples of lever on the Internet the fishing rod appears as often as the wheelbarrow! Thanks for the explanation Gordy, I'll charge up my laptop so I can follow the links.

Cheers, Paul

[Malcolm]

What happens if the forces on the rod are exactly the samebut applied from a different direction: Here is an image showing what I think most (but not all) would agree is a simplified path of the rod handle with the rotation about a series of points - the points varying according to the point in the stroke.



However, I can apply those forces to the rod handle in different ways. I can stand with my arms outstretched in front of me and move my hands clockwise and anti clockwise and if I were strong enough apply the same forces to the rod.

I could have the rod facing me and draw the upper hand towards me and push the lower hand away - effectively reversing the stroke (Ok I do realise that only part of the stroke could be completed

Am I right in thinking that although we are applying exactly the same forces to the rod that the ICR would change?

[Will]

Couldn't resist jumping in on the drawing-fest!

I'm confused about this fulcrum definition thing. Just assume that we have a different kind of see-saw (below).

Gordy/Magnus, where is the fulcrum?

Cheers

W.

[Will]

Next Question!

Does the amount of force needed to move the lever, applied at pt A, change as the pt. of rotation moves (see below)?

Cheers!

W.

[Stoatstail50]

On a two handed rod there are two points of contact, each one is a "pivot" or "fulcrum".

The rod can be moved in varying degree around one, the other, or, most likely both together.

Whatever we choose to do they both remain a "fulcrum" and the rod remains a lever, working in a linked system coupled with the other levers in our arms and, simplifying things a little, connected across the shoulders.

Rotate any one bit in the system and you'll move the rod. If we add all the rotational options in the system together then the rod can be rotated and translated at the same time, which is where Frank got his old "translation is part of rotation" argument from.

If we choose to move the top pivot point forward and the other back, a coupled force, we generate a turning moment in the rod to make it rotate.

This will cause the rod to rotate around a point somewhere between the two pivots. Vary the force between top and bottom and this point will move up and down the perpendicular line between the two pivots where the two opposing forces go to work on the rod.

The mix of forces that drive the centre of rotation of the rod closest to the upper pivot point is being called "Fulcrum" casting, even though you could just as easily argue that the mix of forces that drive the centre of rotation of the rod towards the lower pivot point is "Fulcrum " casting too....

I dont understand what the fuss is about, its just a name...

Is there a fulcrum in the top hand ? yes, but there's one co-existing in the bottom hand too, whatever we do.

Can you vary the forces applied ?, yes you can

Is one way of moving the rod more bio-mechanically, or even just mechanically, efficient than another ?...

..maybe... but fkn hell...lifes too short to do the maths...surely...

[sms]

Will,

Yes, the green triangle is the fulcrum. But, your lever is not straight, basically the black part is your lever, the yellowish brownish part is not part of the lever.

Mark,

Yes, the forces can be varied, but they are, of course, always in balance. For same KE for line, the bottom hand dominant style you need to move the hand more (longer distance), thus the forces (on both hands) are smaller than with same setup and top hand dominated (shorter moves with more force).

[Will]

Will,

Yes, the green triangle is the fulcrum. But, your lever is not straight, basically the black part is your lever, the yellowish brownish part is not part of the lever.

Mark,

Yes, the forces can be varied, but they are, of course, always in balance. For same KE for line, the bottom hand dominant style you need to move the hand more (longer distance), thus the forces (on both hands) are smaller than with same setup and top hand dominated (shorter moves with more force).

Gotcha! So the lever has a V shape in it! Brillliant!

So effectively we have a dynamic lever in which the V changes its dimensions as we move through the cast.

W.

[sms]

Yes, levers do not have to be straight.

For example, you can swap between 1 and 4 in the below and it works the same.