Fulcrum

Magnus · Post by **Magnus** » Sat Dec 10, 2011 12:00 pm

Sakari

I'm casting with my elbow forwards - single handed rod.
My upper arm is rotating though about 30 degrees, rotating about my shoulder. My elbow is opening and closing about 20 degrees as my arm moves.

Both segments of my limb are being used as levers.
The sports medical stuff I've read talk about the arm as a series of segments - levers - with the muscles pulling and pushing - around a fulcrum for each.

Both those segments of my arm are inputting force when I cast, work is being achieved by both. There is no single fulcrum for my arm, however, logically I see no problem with the idea that there are fulcrums for each segment, usually at the joints.

(Incidentally, again logically, effort includes 'work' but also includes the applied force needed to hold something still, in equilibrium. Which is why Gordy's weightlifters can go purple with effort holding a bar stationary - no work but plenty effort.)

Paul Arden · Post by **Paul Arden** » Sat Dec 10, 2011 12:01 pm

So, in my opinion, the traditional lever definition for rod needs to go out the window. Otherwise we are moving quite fast standing still

Fascinating stuff. So is the flyrod now a fourth class of lever, one that has no fulcrum? Amazing that in 12 years of discussions that this has never come up. I'm lost for words. But I'm here to learn!

Thanks, Paul

sms · Post by **sms** » Sat Dec 10, 2011 12:28 pm

Magnus wrote: Both those segments of my arm are inputting force when I cast, work is being achieved by both. There is no single fulcrum for my arm, however, logically I see no problem with the idea that there are fulcrums for each segment, usually at the joints.

Hi Magnus,

Yes, they are acting as levers in reference to previous body part that provides the fulcrum (joint) point. The lever changes between 1st and 3rd depending on the direction of movement.

Magnus wrote:(Incidentally, again logically, effort includes 'work' but also includes the applied force needed to hold something still, in equilibrium. Which is why Gordy's weightlifters can go purple with effort holding a bar stationary - no work but plenty effort.)

sms wrote:But, even with totally stationary hand, it feels to us that we put effort in. Just take ie 4kg/8lb weight and hold it with horizontally extended arm. You are not doing any work (or effort, there is no energy change in the system), but it feels like you need to put in effort.

Ok, my bad, I though effort's definition was different as can be seen above.
If holding something stationary is effort, we put more more of it with the top hand in DH casting in regards to force. But I guess effort cannot be measured so it is subjective.

Paul Arden wrote:
So, in my opinion, the traditional lever definition for rod needs to go out the window. Otherwise we are moving quite fast standing still

Fascinating stuff. So is the flyrod now a fourth class of lever, one that has no fulcrum? Amazing that in 12 years of discussions that this has never come up. I'm lost for words. But I'm here to learn!

Thanks, Paul

Well, I truly think that the problem is just too narrow definition of word lever that includes fulcrum which we cannot have in any reasonable way in casting. At least I could not decide on any physical basis why we should fix the framework to bottom hand rather than to the top hand or vice versa in DH casting for example.

So, I still think that rod is a flexible lever, but not in the narrow definition including fulcrums. It is a lever with tree point forces acting on it (excluding the inertial stuff here).

edit: Please remember that I am not a native English speaker, so my understanding of words may not be 100% correct - just like my grammar. So, if something seems illogical, please ask if I did really understood what someone else wrote or if I meant what I wrote.

Paul Arden · Post by **Paul Arden** » Sat Dec 10, 2011 12:56 pm

Well I'm no engineer, and you are, so you're going to be right. I was of the belief that all levers had to have a fulcrum, and I'm completely lost now that this is not the case. I thought in the case of flycasting, the fulcrum moved in space. Walter even gave me an equation for a moving fulcrum so it did seem to back up my belief.

I just don't see how a lever cannot have a fulcrum, so maybe we can start there? I realise that the rod is moving through space, ie translation, but it is also rotating. Why in a SH rod is the butt of the rod not the fulcrum? Because it's translating through space? If I run along a moving train pushing a wheelbarrow the fulcrum is still the wheel.

Cheers, Paul

Magnus · Post by **Magnus** » Sat Dec 10, 2011 1:00 pm

Hi Sakari

Your English is great so no worries and my apologies if it seems like I'm tripping you up on English usage or grammar - not my intention.

You are using the physics concept of work - which is fine - well used here and easily checked online.
However effort doesn't have a technical definition for use in physics as far as I know? Effort force perhaps?

My point really was that opposing forces are common, well described in physics or engineering, and some of them hold things in balance.

From a subjective POV when I cast a DH rod Underhand style it feels like I am holding the upper at a constant distance from a centre and pulling the lower hand closer. I think that's essentially what Alan and others who invoke the idea of a fulcrum at the top hand are trying to communicate. (If you look at Alan's elbow in that clip he posted you can see what I mean - it remains bent.)

On the other hand

with a more mobile top hand it feels like the top hand is pushing away and the rod is pivoting in the bottom hand - which may well still be moving. (And you can end the stroke with a fairly straight upper arm - like the bamboo caster I posted earlier.)

sms · Post by **sms** » Sat Dec 10, 2011 1:04 pm

Paul,

Let's consider that the contact point is the fulcrum. Where is the effort then? At the same place. Now, is it 1st or 3rd lever? :p

Actually there is no one point. Just take a rod (or TV remote, piece of stick etc) and grab it loosely like it was a rod. Now move it back and forth (FC and BC) and you'll notice that you have at least three contact points (one on one side if you use just one finger around the grip and two on one side) - four more probably with normal grip. The same thing as with DH rod basically, just closer to each other.

Paul Arden · Post by **Paul Arden** » Sat Dec 10, 2011 1:12 pm

Let us take a see-saw. Fulcrum in the middle. We apply force to one end and Jill lifts up and flies through the air. Now we take that same see-saw and move it through space, and pull down again and Jill once again flies through the air. Has the fulcrum changed?

This is basically Alan's understanding and it was mine too. It may be wrong, but it needs replacing with the thinking that you guys have because I don't know what that is!

Cheers, Paul

Paul Arden · Post by **Paul Arden** » Sat Dec 10, 2011 1:15 pm

let's consider that the contact point is the fulcrum. Where is the effort then? At the same place. Now, is it 1st or 3rd lever?

Sorry that should have been rod butt and I corrected it immediately after!

sms · Post by **sms** » Sat Dec 10, 2011 1:21 pm

No worries Magnus, I did not get the impression that you would be trying to trip me on my English. Just reminded that sometimes there can be something lost in translation. Not rotation ;-)

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.

sms · Post by **sms** » Sat Dec 10, 2011 1:30 pm

Paul Arden wrote:Let us take a see-saw. Fulcrum in the middle. We apply force to one end and Jill lifts up and flies through the air. Now we take that same see-saw and move it through space, and pull down again and Jill once again flies through the air. Has the fulcrum changed?

Yes it has if the observer is still standing on the playground where the see-saw was. If the observer is still attached to the fulcrum, then no change. That comes down to the framework fixing issue. So, where should we fix the framework in fly casting then? Top hand, bottom hand (rod butt) or ground? I think ground. Otherwise it is not objective.

Regarding earlier, the rod butt cannot be fulcrum in SH rod since it is not touched (except in ie long back cast)

Magnus · Post by **Magnus** » Sat Dec 10, 2011 1:57 pm

Thanks Sakari. Incidentally that's not at all far from my own impression of Underhand casting. Personally I think I use more lower hand so maybe 40/60 for me. Since I'm not trying to tune my casting for max-distance what matters to me is how it feels and how I feel after a day fishing. Just seems easier and more relaxed.

We have a seesaw, Paul is off 'playing' with Jill so I place a second seesaw where she was sitting. How many fulcrums do we have?

Juergen Friesenhahn · Post by **Juergen Friesenhahn** » Sat Dec 10, 2011 1:58 pm

Paul Arden wrote:It may be wrong, but it needs replacing with the thinking that you guys have because I don't know what that is!

Cheers, Paul

Hi Paul,

I don't think, that your "thinking" has to be replaced.

The scienceguys only have another perspective.
If you will, have a look at my lousy "planetpainiting".

Your thinking/traditional perspective can be found in Pic 1.
Example 1 is painted static, but the planet can move somewhere else and the moons are always rotating around the planet.
Our earth flies on it's sunorbit, but our moon rotates around us.

Their perspective is in Pic 3.
They plot the (curved) tracks of the planet/moons,
they set the perpendicular bisectors on this tracks, and where this perpendiculars meet, there is the "instant centre of rotation".
Also called the "pole of planar displacement".

Just take my planetexample and replace:

Left moon: Bottomhand
Planetaxis: Tophand
Right moon: 1st stripperguide

Now we are back, casting!

BTW: This measurementmethod for the "pole of planar displacement" has strong limitations:

the results can easily be brought ad absurdum, by moving the "fulcrum" translational.
If one measuringpoint moves translational, the consequence is, that there is no center this point rotates around.
Means, the bisectors of the 3 objects can not unite, therefore, they can't measure an I.C. for this configuration.
The I.C. lies in infinity.

The "pole of planar displacement" of a twohanded rod moved with a translational fulcrum in the tophand can't be measured with this method!
(1st point of measurement: bottomhand, 2nd: tophand, 3rd: stripperguide)

The problem in this thread is I.M.H.O. rooted in the refusal of differerent perspectives.

Cheers

Juergen

sms · Post by **sms** » Sat Dec 10, 2011 2:07 pm

Magnus, for distance, my top hand becomes more dominant and I basically try to get the peak force higher with bottom hand.

Jürgen,
you are also discussing the framework, and I think, we should fix it to the ground as that is not moving in the space where we want to deliver the fly from point A to point B.

Paul Arden · Post by **Paul Arden** » Sat Dec 10, 2011 2:12 pm

Well difficult question Sakari, but since Alan doesn't straighten his right elbow I would actually place the fulcrum in the top hand. If he only straightened his top arm and didn't pull on the bottom I would place the fulcrum at the bottom hand. If he did both push and pull then I would place it inbetween. At least that's how I've always seen it, and from an instructors' POV I would have thought that would have been spot on.

But you're saying that the fulcrum is the ground. That's certainly a very different perspective.

Cheers, Paul

Juergen Friesenhahn · Post by **Juergen Friesenhahn** » Sat Dec 10, 2011 2:21 pm

Jürgen,
you are also discussing the framework, and I think, we should fix it to the ground as that is not moving in the space where we want to deliver the fly from point A to point B.

Hi Sakke,

surely, we all have frameworks we are judging through.
It is simply impossible without!

And yes, we want to deliver a fly from A to B.

Use the framework of a fixed camera on the ground and you'll get results like the "pole of planar displacement".

If somebody uses the "fulcrum-framework", he just uses a different perspective of the same happening.

There is nothing "untrue" or "more true".

And be sure, that guys, who use a fulcrum-framework, deliver the fly damned good.

Cheers

Juergen (with ue, instead of ü, if you don't mind

)

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