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Fulcrum

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sms
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Post by sms »

No Paul, I am not saying that the ground is the fulcrum. I am just saying that from physical POV it is the sensible to have the framework tied to the ground.

Jürgen,

Then I can say I am fulcrum casting regardless how I cast. And I can also say that bottom hand is always the fulcrum. I just decided that I fix the framework to the bottom hand. Or I can say the fulcrum is always at the top hand if I fix my framerork there. Or I can fix my framework to the tip top and say that it the butt moves, not the tip - in that framework.

So, the whole point of the framework is that it must sensible - and the same for all casts regardless of style. We are casting in relation to planet earth, so it is sensible to fix the framework to it. If I was casting inside a speed train for example, then it would be sensible to change the framework so that the train is stationary in that framework. Otherwise I could say I cast 400m for example.
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Post by grunde »

sms wrote:But, back to business. I understand the different styles, I just do not buy that there would be the most effective way to bend/cast a DH rod since the forces are the same regardless of the way the work is done from physics side. But, of course, different styles suit different people and there are physical limitations to what human body can do. So, if there really are some advantages with bottom hand dominant style with top hand elbow pretty much locked, it should come from human motorics - and that I do not know anything about basically. All I can say is that I feel that most easy way to cast for me is to use about 50/50 top and bottom hand - high tip speed with low hand speeds.
This make a lot of sense :-)
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Post by gordonjudd »

In a quest for data, on a scale of one to ten, how patronising do you think an opening statement like "I try to be patient and informative..." sounds?

Magnus,
From my point of view it is sincere.

My questions to you are intended to be condescending however, so you are correct to feel that you are being patronized in these pointless back and forth posts.

If we cannot play nice, then I enjoy pointing out the discrepancies in someone's arguments as much as anyone so please sort this out for me.

Since you do not want to distinguish between a rotating bearing and a fixed fulcrum lets get back to your locating the "fulcrum" in the casting robot at the hub of the stepper motor.

In a lever, isn't the fulcrum supposed to be located on the rotating bar? You seem to agree that in the casting robot the source of the rotating torque is far removed from any point on the rod. Therefore, using you definition of a lever, how does the stepper hub become the "fulcrum" in the casting robot since it not located at a point on the rod?

There is a rotation center in the robot, and yet it has no fulcrum. Thus it follows that the rod does not meet your requirements as being part of a mechanical lever when it is being used in the robot. The same would apply when the rod is used by a great tournament caster like Chris Korich who uses his shoulder and elbow to provide most of the rod rotation in his accuracy casting style.

When the rod rotates without the use of a fulcrum what does it become? For me it is still a flexible lever, but to meet your requirement you must have another description in mind.

What is it?

Gordy
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Magnus
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Post by Magnus »

Great stuff Gordy :D

You have a curious way of trying to pose condescending questions but failing to answer the same type of question.

In a lever, isn't the fulcrum supposed to be located on the rotating bar? You seem to agree that in the casting robot the source of the rotating torque is far removed from any point on the rod. Therefore, using you definition of a lever, how does the stepper hub become the "fulcrum" in the casting robot since it not located at a point on the rod?


Simple answer is - because the motor is clamped in place, is grounded, but the armature on one end and the arm holding the rod on the other are free to revolve.

Gordy the robot arm fitted to the hub and any fly rod fitted to that arm are moving as one unit. That's a rigid system.

So, I drill a hole though a metal bar and fit an axle around which the bar can rotate. That axle serves as a pivot or fulcrum in my world. Push one end down and the other lifts, make one arm shorter and a small input movement becomes a big one.

The armature of the robot motor is forced to move, revolving the axle and the arm holding the rod rotates with axle. No sarcasm, no nonsense, I have no problems at all viewing the bearing holding that axle fixed in place as a fulcrum.

So, I take a wheel and fix a rod in plane with the wheel to two points on the circumference of the wheel. Apply force to the wheel and it turns around the axel and the rod rotates about the axle. If I fit the rod so it sticks out my input motion is magnified - the rod tip moves farther than a point on the wheel.
Now I fit the rod so it can rotate around one point on the circumference and a spring at the other end which pulls that end of the rod towards the center of the wheel while I rotate the wheel. (I'm thinking of a double pendulum type arrangement.) The path of the rod tip in that system does not describe a circle - something like a parabola I suppose.

My point is simply that I can break down the component parts into two simple machines. Two simple rotating machines both of which use leverage in the same way.
I really don't give a damn if in your world those two axles or the bearing which hold them in place qualify as fulcrums - call them whatever pleases you - there are however two points around which parts of the system are turning at the same time.
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Post by gordonjudd »

In a lever, isn't the fulcrum supposed to be located on the rotating bar?
and
That axle serves as a pivot or fulcrum in my world.

Magnus,
At least we are getting somewhere even if you chose to dodge a simple question.

Does this mean that in your world the fulcrum does not need to be on a line that connects two point on the bar (or rod) as it does in a classical lever?

What you are describing sounds like a source of rotation. That is much different than requiring the rod to have a support fulcrum that must be located on the rotating bar to be a true classical lever. If that is the case then we are on the same page.

So when your fulcrum (my rotation center) is not located where it would be if the rod was acting as part of a "true" mechanical lever what do you want to call the rod in the real world where the torque that causes it to rotate is not necessary located on the rod itself?

If "no fulcrum"="no lever" is still operative then you have the honor to come up with a new description for how the rod provides some mechanical advantage in the cast.

I am comfortable expanding the description of a flexible lever to simply be a way of magnifying the distance one end of it moves for a given rotation angle. I really don't care where that rotation source is located with that description as the d=r*phi relationship will hold regardless of what r (the distance from the rotation center to the tip of the rod) happens to be.

Since that rotation center relationship goes against your grain, then what do you want to call the rod when its rotation source is not located on the rod itself?

Like it or not Sakke's observation:
So, in my opinion, the traditional lever definition for rod needs to go out the window.

is true. I am all for expanding what is meant by the mechanical advantage of using the rod as flexible lever. If you want to hold on to your no fulcrum-no lever view then pick a new term, as in general there is no fixed (or moveable) fulcrum that is located on the rod.

Rotation center yes, classical fulcrum no.

Gordy
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Post by Bernd »

grunde wrote:
sms wrote:But, back to business. I understand the different styles, I just do not buy that there would be the most effective way to bend/cast a DH rod since the forces are the same regardless of the way the work is done from physics side. But, of course, different styles suit different people and there are physical limitations to what human body can do. So, if there really are some advantages with bottom hand dominant style with top hand elbow pretty much locked, it should come from human motorics - and that I do not know anything about basically. All I can say is that I feel that most easy way to cast for me is to use about 50/50 top and bottom hand - high tip speed with low hand speeds.

This make a lot of sense :-)

To cast our fly efficiently to the target we need:

a) tight loops
b) proper speed level (not max speed) for the length of line, the loop shape and circumstances (wind etc.)

Which elements help to form tight loops and match the line speed:

1. slack line kept to a minimum
2. good timing
3. smooth acceleration to an abrupt stop
4. rotation at the right time
5. adjust arc, stroke + force application to the length of line + rod stiffness

Short line = short movement
Long line = longer movement

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.

For my teaching I don't need a method to calculate how much force is added via top and bottom hand exactly. I am sure I can see differences with my eyes and know immediately if there should be made improvements or not.
Watch this one again:
http://vimeo.com/32786264
Who can't see the difference in force application of each hand compared to each other between fc & bc?

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Bernd
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Post by Magnus »

Gordy

I doubt we are on the same page.

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?

I'm assuming you think the classical definition of a lever means a straight rigid rod? Like this perhaps?

Image
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Bernd
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Post by Bernd »

Morning everyone :)
I looked up the meaning of the word "lever" on wikipedia:

http://en.wikipedia.org/wiki/Lever

lever (in English) = Hebel (in German)

http://de.wikipedia.org/wiki/Hebel

In German language the word "lever" seems to be used much more flexibel than it is in english language.

Hebel (Physik), ein mechanisches Kraftübertragungssystem, meist verwendet als einfaches Maschinenelement
= similar to lever in english

Hebel (Kampfsport), eine Technik im Kampfsport
= a technique in material arts

Hebel (Derivat), eine Kennzahl von derivaten Finanzprodukten
= a measure of derivative financial products

Hebel (Schach), eine Stellung beim Schachspiel
= a position in chess game

Hebel (Wabern), einen Ortsteil der Gemeinde Wabern (Hessen)
= part of a town in the state of Hessen

In German language I wouldn't really find a problem to define a lever for fly casting :). Sometimes new fields of using a given word are neccessary, aren't they?

Wasn't the "flexible lever" already defined here on Sexyloops?
Shouldn't we establish instead of question it?

Greets
Bernd
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Post by Paul Arden »

Hi Gordy,

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

Or have I misunderstood this (yet again!).

Cheers, Paul
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Post by Stoatstail50 »

If the arm is a system of articulated levers with a real tangible fulcrum at the shoulder, the elbow, and the wrist then the IC of rotation of the whole system during a casting stroke is very unlikely to co-occur with one of these points on the body.

So for each individual element of our system, the "fulcrum", as we would usually use it in the context of a single lever, and the IC of rotation of the entire system combined are two completely different things.

In addition if you examine one lever in the system, ie. the rod, in isolation, then the complexity arising from the coupling of levers and their sequenced use throughout the cast is totally lost.

Sadly, from a naming point of view, all casts are fulcrum casts, its just that the coupled fulcra are dominant in different phases throughout the casting stroke, especially if two articulated systems (arms) are used to move the rod.

So, lets say on the basis that it is theoretically faintly possible, that, for a very brief period at the end of a casting stroke, the top hand acts as the only fulcrum in the system and it is after this very very short passing moment that the cast is named a "Fulcrum" cast, this is completely fine by me... its just a name..so is it OK if we also call a cast where, for an equally brief moment in time, the top hand is dominant and the only fulcrum is at the bottom hand a "Fulcrum" cast too.... ??
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Post by Bernd »

Hi Mark,
can you think of this name resulting in tons of missunderstanding what is really happening during the cast?
Because I think this already has happened when reading this whole thread!

In our lesson...
"I am going to show you the fulcrum style now. Well, actually it's not about a fulcrum, but let me exlain..."
I have a feeling we might be in (unneccesary) trouble here :D

The top hand does not work as a fulcrum as I understand it after reading thru this thread (and I have already changed an article on my website on dh casting).
So I want to explain this in an easy way but not saying something which is simply wrong?

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Bernd
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Post by Stoatstail50 »

Its just a name Bernd...I can't see why we should be in any trouble.

Anyway..there are different fulcra in use in varying degree throughout a casting stroke. These fulcra are are biomechanically fixed, you can't slide your elbow up and down your forearm... :)

In this sense either the top or bottom hand may operate as a fulcrum on the rod at some stage during the cast.

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.

I'm interested to see if Gordy and/or Magnus are prepared to agree on that.
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Post by springer »

I dont use the term Fulcrum Flycasting but I can see why others do, I also dont see any reason for it to be complicated or not accepted as professionally correct.

Of course there are potentially 2 fulcrums at the point of contact with the rod depending on the leverage type you are trying to apply, top or bottom hand. Equally there are fulcrums within our joints but from a teaching point of view all pupils have the same joints so I think that part is less relevant.

The fulcrum style as taught by Peter Anderson and followed closely by the likes of Toft/Gilliespie and many other good casters works on the premise of a top hand fulcrum and class 1 leverage from an active bottom hand effort point of view

That is all the pupil needs to know, it doesnt need to be any more complicated than that IMHO.

I have in the past used the term 'passive top hand' which I think describes the motion very well but Im not looking to name it such. So long as the pupil understands that the bottom hand does the majority of the work and what the benefits are of this then the job is done.
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Post by victor »

Physics meets fly casting, fantastic. Just call it variable COR ( Centre Of Rotation) casting dependent on which hand is dominant. Upper COR, bottom hand dominant. Lower COR, upper hand dominant or mid COR, both hands equal.

Mark, I nearly understood your post, thanks.

Mike
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Post by gordonjudd »

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.

I'm interested to see if Gordy and/or Magnus are prepared to agree on that.


I can certainly agree with that as that is what I have been saying all along. We use different sources (rotating joints) that apply torque to rotate the rod such that its ICR changes throughout the cast.

Those centers can be located some distance from the hands that are are holding the rod especially when the extension of the different joints results in more translation velocity of the butt of the rod than producing angular rotation velocity.

A rotation center that can be located anywhere and thus is a different animal than a fulcrum that has to be located somewhere on the rod itself. I hope everyone (including Magnus) can see the difference.

Gordy
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