Torque Twist

[Paul Arden]

I will certainly try that Merlin, to be honest I don’t think it’s rod dependent, on the same way that pull-back pre-RSP is not. But rods do behave differently of course; for example with pull-back I prefer a softer rod.

Sorry I meant to shoot some video today of the loops. I’ll try tomorrow - no Xmas shopping time necessary tomorrow

I think there are quite a few things involved. Greater acceleration prior to the stop, it’s certainly a very abrupt stop. How much the actual torque in the rod plays a part I have no idea, not as much as the other things in my view. But I have no idea

Cheers, Paul

[sms]

A overall spine is usually not much stiffer than the 90degree side. The spine typically is corkscrew around the blank, but the overall spine is just a sum of it.

For a strong anisotropy/asymmetry (ie oval rod cross section) the rod would not go only up and down, but would also go from side to side. Which would not be good for tracking. And symmetric rod does not stiffen from twist. At least the rod I tested. And I do not believe any symmetric rod does (and the non-symmetric ones stiffness just move in the coordinate system, not truly stiffen in the coordinate system that follows the piece itself).

[Merlin]

Ok so let's consider that the spine of the rod does not interfere. There might be a possibility related to biomechanics. We need the help of someone knowledgeable in that field. Could there be an induced deceleration coming from the TT? Such phenomenon (induced acceleration or deceleration) is mentionned in multiple joints motions.

Then it could be something individual, I mean that the intensity of that extra deceleration would be dependent on the caster's physical capabilities.

Merlin

[Paul Arden]

What causes the S-shape? Is this a result of the loading or unloading phase? I can only remember seeing it on a 170 Cast in Spain (I don’t know why it happened there and I can’t remember seeing it on the log video - I’ll have to check!), I’ve seen it on all pull-back videos (filmed many times now) and now the Torque Twist videos.

I know that after the original pull-back video I uploaded from my cycle tour of Oz there was disagreement as to why it works. I think the three options were more force input, forced output, greater tension in the bottom leg - or a combination of these.

I suppose the other question is, is the S-shape a catalyst or a separate result. For example we do something (pull-back, torque twist) creates S-shape, which then results in higher line speed OR we do something and it results in both S-shape and higher line speed independently?

In other words for me I find TT and pull-back rather similar in both feel and result. I think that they should be categorised under the same heading, but I don’t know what that heading should be

Cheers, Paul

[Merlin]

Hi Paul

Your last sentence lighted a bulb somewhere, and I gave another look at the video. I can identify a pull back coming from your forearm. My best guess is that you twist your wrist at the same time you PB. The S shape comes from the PB, just like for a snap cast, the rise of the rod butt moves away from the rod tip. This S shape disappears as the rod counter flexes. It is likely that TT or PB have the same nature, a TT being a PB with a twist of the wrist. Have a look at the pics below:

TTa.JPG (56.74 KiB) Viewed 4010 times

TTb.JPG (57.63 KiB) Viewed 4010 times

TTc.JPG (54.64 KiB) Viewed 4010 times

What I call "tiny follow through" is just the end of the rebound of the rod due to CF. The stop is pretty hard, but the rebound is inevitable.

Merlin

[Paul Arden]

Ok thanks Merlin. That’s makes quite a lot of sense to me. When I pantomime TT my hand travels upwards. I’m on the lake for the next few days and will try to film some more. It also gives me a few ideas to play with.

Thanks, Paul

[sms]

No TT here:


S-curve is about conservation of momentum I think.

Here’s also a slight S-curve and no TT at about 1:00.

[Paul Arden]

While running through some threads on the old Board here is the one with the 170 backcast I mentioned. http://sexyloops.co.uk/archivedboard/vi ... 28#p256428

Anyway is not the point that sometimes it happens and other times we force it to happen? There is quite a bit of physics on the old Board on pull-back that goes over my head Still if I am lifting the butt with Torque Twist then it is not similar to pull-back; it is pull-back! And quite a neat way of doing it.

Going fishing for a couple of days with Sri. I’ll get some more video!

Cheers, Paul

[Graeme H]

Here's one possible option. I haven't fully thought it through yet, but on first consideration, it might work.

We know that when we make the 3 wide waves in a "wiggle mend" for the MCI test, we do it without making the rod wiggle about a node on the blank. It's just a wide sweep of the rod and the tip moves slowly and widely.

We also know that to produce the 6 narrow wiggles, we need to oscillate the rod rapidly so that the blank wiggles about a node on the blank. The tip moves very rapidly back and forth when we do this.

The pullback and TT both induce that wiggle about a node on the blank, shown as an S curve in Merlin's third photo above. The forced wiggling about that node makes the tip move more quickly than if we don't wiggle the blank about that node (i.e. no pullback) so there is a final ramp-up of tip speed over a short distance.

The side effect of this is to also reduce the distance the tip is moving (as in the comparison between the 3 and 6 wiggles in the MCI exam). That reduction in distance moved helps tighten the loop because the tip stops closer to the line path.

How does that sit with people?

Cheers,
Graeme

[Merlin]

There are many ways to make harmonics pop up, but it occurs as the rod is stopped, or eventually pulled back. In that case there is a physical constrain on the butt of the rod magnifying the S shape since tip is moving forward on its momentum and butt is moving backwards. That can happen without pullback if tip momentum is large (the case for the Daiwa 18 foot I think) and if the butt of the rod is kept immobile.

In the sea trout event, higher harmonics show up after line release, they come from the rod response to the caster’s input. Neatly stopping the butt corresponds to sending a sharp pulse into the rod which responds with a combination of harmonics. In a clamped-free condition (hand holding strongly the handle) the second mode has a node in the tip and sometimes the third mode pops up with another node in the butt close to the middle of the rod). If you hold the rod in a relaxed way, there are other harmonics appearing which are part of a “free-free” condition. With a slightly lower frequency than the second mode mentioned above, there is the first “free-free” mode with a node in the tip and a node in the butt, located in the handle if your tackle is correctly balanced with the reel. In that case you can easily control that mode, and produce the desirable wig-wag condition during an MCI test. The second free-free mode is close to the third mode of the clamped-free condition, with three nodes along the rod shaft and a pretty high frequency (e.g. 20 Hz).

TT, PB or Whuuump are various ways for “shocking the rod”, forcing its unloading, and getting some advantage from inertial effect (if you want to feel that one, take a cane rod) and tip trajectory (smaller loop corresponding to a higher mode as explained by Graeme, I am on the same page incidentally ). In terms of speed S shape is just a lottery: you can win or lose depending of the phasing in between the various modes. It’s always small anyway.

Some years ago we talked about PB (without twist), and analyzing the role of possible influential parameters (starting point, duration, intensity) showed that it was not so obvious to get the best of it. Here are some quotes from Paul:

It would be interesting to compare a variety of different initial force inputs followed by pull back since I think that the initial stroke itself can be gentler and that this usually works best.

That seems to say that one should avoid too sharp a PB to keep the rod on the fundamental mode as much as possible. It speaks to me when I think about striking white fish with a long pole. As a teen ager, I used to compete for white fish with long poles and very thin lines with floater and lead shots. Striking correctly with my long soft glass rods was possible if I used my forearm to strike and not my wrist. With the wrist the rod was set on its second mode immediately and the tip dived down before breaking the thin leader as it moved back up.

For me I get tighter loops with a small amount of pullback and use it for this purpose when I use gentle pull back, But when I really force it to form tucks and overpowered curves the loops are considerably wider to begin with.

I guess this is the effect of a forced counter flex which is emphasized by an intensive PB.

It feels to me - and of course that's subjective - that my pull-back is somehow in synch with the rod.
With a softer rod I get a very pronounced feel with pull-back

I think Paul gets more feel with a soft rod since his hand can better detect the bending in the butt. It is interesting to see that he starts his PB pretty soon, nearly just at MCL. It means that Paul uses a very fast tempo for the rod, his deceleration starting early during the casting motion. Maybe it is possible to detect when maximum rotation speed occurs with a better version of the video, which would help analyzing the cast for sure. If you have one available Paul, thanks to send it to me so that I can give a look. The quick tempo gives a “catapult” effect to the rod. Imagine you have a soft rod and that you cast without PB, you can load the rod and decelerate it completely before the rod is unloading. The unloading takes place as the rod butt is stopped (this is typical of the behavior of slow parabolic cane rods). With a modern fast rod, the same phenomenon is possible, the needed tempo is just faster. Paul adds a PB motion as the rod starts unloading so he forces the rod to unload faster, in synch I would say: the rod is unloading on its own and he forces the tip to unload with the backwards motion of the butt. The PB ends approximately at RSP1, which is difficult to detect given the S shape of the rod.

Merlin