Messages on acceleration of angular motion of the rod butt

Walter & Group............

This was my answer to Al Crise after reviewing the string of messages between members of his group and Bruce Richards.  (In this string, Bruce's comments are prefaced by, ****** ) For some reason, the graphs made via the Casting Analyzer didn't copy.

ol Al...

Interesting comments.  After discussing this with both physicists and engineers, I came to take back what I had said about, "accelerated acceleration".  I was just plane wrong about that.

I, now, agree fully with what Bruce said about linear acceleration (a constant rate of acceleration) as needed for best loop formation.  Work with the analyzer helps confirm that when those graphs are matched with videos of rod tip motion and loop formation.

In the not too distant past, many of us were not really clear on the differences between velocity and acceleration.  We've learned a great deal since then.

Gordy

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Tailing loop

Howdy Bruce
I do have to agree with 'After the RSP' effects the rod leg and
before path effecting the fly leg of the loop. Not sure on the
starting speed most of my students are too fast to start and can not
maintain that acceleration Causing the tip of the rod to rise then
feeling this they will sometimes Slam the power and tail or figure 8
the line.
******The perception may be that they are starting too fast, but I've never
seen it in hundreds of analyzed casts. Very easy to sart too SOON, but too
fast is rare as hens teeth.....

As for the line passing the rod tip while it is at RSP or if using a
thrust cast it is as it passes the tip. I see your point.
Acceleration is just 'speeding up' what we want is faster
acceleration in the last 10% of the casting stroke.
****Sorry, but that's precisely what we don't want. The rate of
acceleration should remain the same from beginning to end for best loops.
We want faster speed at the end, certainly, but not faster acceleration.
Here's an analogy. We want to accelerate a car from 0-60 mph in 12 seconds.
For most efficient operation we want linear acceleration, 5mph at 5 sec. 10
mph at 10 sec., 15 mph at 15 sec. and so on, gaining 5mph/sec for 12
seconds. That's how we want the angular acceleration of a fly rod to
change, to make best loops. What many drivers do (I used to!) is go 2mph in
the first 5 sec., 5 mph in 10 sec., 8 mph in 15, 14mph in 20, etc. finally
needing to go from 45-60 mph in the last 5 sec. That is also what most
casters do, believe it or not, accelerate too slowly in the beginning, too
fast at the end. Click on the picture below, this is a chart of a classic
example, but VERY common with almost all casters who aren't experts.....
I've never seen a chart where the rate of acceleration was faster early in
the stroke than at the end.

*** from Bruce Richards

(See attached file: tailing loop)

low rate of angular acceleration at the beginning of the backcast, then very rapid acceleration up to the stop.  Not very smooth, looks like a "HE-MAN" casting with brute strength.  In contrast, the forward cast looks a bit more uniform in the angular acceleration.  And the symmetry is not so good...  Rod loading looks rather poor, based on the rebound. Troy Miller

 

Good analysis Troy. Al, you should do a quick read on a physics site (there

are lots of good ones) on the definitions of speed and acceleration and

linear acceleration and related terms. You're getting yourself all messed

up due to terminology.

We've studied this extensively Al, there is NO QUESTION that linear

acceleration makes the best casts. When you get your analyzer the thing to

look for is the "smoothness" ratio, this shows how linear the acceleration

was. The lower the number, the more linear the acceleration, the smoother

the cast and the loops will be better, guaranteed!

Bruce

 

 

Thanks

  To me it still looks like the speed it much greater in the last part of the last part of the cast.

Like the last 10% of the cast time wise

ol Al

 

 

 

*****You're right Al, speed is greater, as I said. But look at the acceleration.

The steeper the line, the greater the acceleration. Notice how the line is

not steep at first (slow acceleration), but is very steep at the end? This

is what I mean. This is actually almost creep, slow early rotation,

followed by fast rotation. Look at the difference between that cast and

this one. (See attached file: Bruce.bmp)This cast made a very tight pointed

loop, the previous chart was for a cast that either tailed or nearly

tailed, and had a low bottom leg.

And yes, the second "blip" is rebound.

 

Bruce