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Contributions of lever, spring and inertial acceleration

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sms
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Contributions of lever, spring and inertial acceleration

#1

Post by sms »

I don’t know if this has been dealt with before already but here we go.

So, modeling experts - what are the proportional relative contributions of rod’s lever, spring and inertial acceleration? That’s to line’s KE.

With the inertial acceleration I mean the KE compression to smaller and smaller part of the rod when it is straightening - the “whip effect”.

Of course it depends on rod, but let’s consider a long or fairly long cast. If we would be able to compare:
- very tip action SH rod (maybe 9’?)
- comparable much more through action rod (maybe also heavier)
- tip action DH rod (maybe 15’? and “scandi/hooting head rods tend to be like this)
- comparable much more through action rod (maybe also heavier)

Is it easy to do this analysis or just possible? Or already done?

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gordonjudd
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Contributions of lever, spring and inertial acceleration

#2

Post by gordonjudd »

With the inertial acceleration I mean the KE compression to smaller and smaller part of the rod when it is straightening - the “whip effect”.
Sakke,
The impedance of a rod and line are so different that I don't think there is much flexural wave energy from the rod that gets imparted to the line.

Different casts and rod will have different values, but just comparing the KE of the Line at MAV and then near its maximum value near RSP1 the nominal number is 80% lever and 20% rod spring.

There a several topics on the old board that deal with this trade off.

Gordy
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Merlin
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Contributions of lever, spring and inertial acceleration

#3

Post by Merlin »

Hi Sakke

I have data for 9 foot rods which I used in the old board. Up until now I did not model a cast for a DH one. The model is restricted to overhead casting, do not expect anything in spey casting. If you remember we discussed about very long rods (18’) maybe I can use the model rods I derived from that to answer your questions. For sure one uses more lever effect with a long rod.

There is a difficulty in spltting the energy in the line along the various mechanisms involved, it is not purely additive, especially in between lever and spring, but that does not prevent analyzing the situation.

Merlin
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sms
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Contributions of lever, spring and inertial acceleration

#4

Post by sms »

I just don’t really see any other clear reason for S-curve that occurs even without pullback (albeit pullback is just a an integral of the deceleration going to the minus side).
It is very visible with long rods (the parts moving fast are relatively heavy in relation to line being accelerated.

Yeah, the rod does not know if were doing overhead or spey, just the line mass being accelerated and direction.

I’m recovering from ACL surgery I had yesterday so I don’t go to upstairs to get a rod to take a video why it seems reasonable why this effect might be bigger contributor than what I previuosly thought, but is perfectly in line with “heavier rod straightens faster in casting”.

-Sakke
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VGB
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Contributions of lever, spring and inertial acceleration

#5

Post by VGB »

Get well soon Sakke
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grunde
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Contributions of lever, spring and inertial acceleration

#6

Post by grunde »

Excellent question m8!

Also I don’t know the answer :pirate: Jason used to call this inertial acceleration “the load shift” when we discussed this bend profile moving up the blank during the stop.

Would be a cool modeling project.

Get well soon!
Grunde
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Paul Arden
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Contributions of lever, spring and inertial acceleration

#7

Post by Paul Arden »

Is this tied with the self-deloading mechanism (or whatever it is called)?

What’s up with your leg, Sakke?

Cheers, Paul
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sms
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Contributions of lever, spring and inertial acceleration

#8

Post by sms »

Paul, maybe. Depends on the defenition. Tore my ACL playing floorball late Oct. Now it has been repaired. Expected to be in terrible pain and dizzy as fudge from the meds (opioids at this first stage), but neither has happened. Which absolutely marvelous.

It is quite easy to get S curve to the rod with just stopping. No line, no pullback. Just hard deceleration.
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grunde
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Contributions of lever, spring and inertial acceleration

#9

Post by grunde »

And you don’t have to stop hard to get it either.
"Essentially, all models are wrong, but some are useful."
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Paul Arden
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Contributions of lever, spring and inertial acceleration

#10

Post by Paul Arden »

I’ve seen it on my “stopless” 170 backcasts. Is this tied to the phenomenon that if you accelerate the rod forward away from a wall for example, that the tip will move back and contact the wall before moving forward?

Ouch. I hope you’re fighting fit soon mate.

Cheers, Paul
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