Gordy,
At the risk of beating a dead horse:
Bruce's diagrams are carefully drawn and are 100%
correct but I think it might be worth pointing
out again that he has
reduced the examples to rod motion only. As such, they are
conceptual
only and not necessarily a depiction of the real
world.
If we get into a mind set that says if the butt
end of the rod moves through space we must have
translation taking place then we may be
mistaken.
If we hold the wrist rigid and rotate the lower
arm and rod combination about the elbow we will
get
something that looks very similar to Bruce's
drawing depicting a mixture of translation and
rotation,
i.e. the rod will rotate and the butt of the
rod will move through space, but the motion will be rotation only.
I've taken the liberty of attaching a modified
version of Bruce's spreadsheet showing what I hope
are some clarifications regarding rotation and a
mixture of translation and rotation. Bruce
was very careful to show that the axis of
rotation (the point that the rod is rotating around) is
the very butt end of the rod. As you can see
there will be a subtle difference when the axis
of rotation is moved to the elbow and we take
away translation - the butt of the rod will move
in a circular path, not a straight path - but the
outside observer could think they are seeing a
combination of rotation and translation when no
translation exists.
I came across a fairly good discussion of
translation vs rotation at the following web site:
I'm curious - I haven't heard a response from you
regarding my question of whether it is
possible to pick up 30 feet of fly line plus
leader using translation only. Did you get my
email?
I could make it more of a challenge and ask
whether it is possible to pick up 50 feet plus
leader using translation only...
Again - I fully agree translation and rotation
are not subjects for most students. I do find them
helpful when discussing the difference between
arc and stroke.
Thanks
Walter
----- Original Message -----
Sent: Wednesday, September 03, 2008
8:30 PM
Subject: Rotation / Translation / my
error
Walter & Group..........
Bruce Richards sent us a spread sheet graphically depicting TRANSLATION,
ROTATION, A MIXTURE OF THE TWO AND DRIFT WITH TRANSLATION AND WITH
ROTATION. I've included these as an XL Spreadsheet attachment.
Here is his message:
Good points by both Troy and Walter. Walter has keyed on complex
rotations
caused by wrist/elbow/shoulder motions. To me, that is style.
If we
concentrate on what the rod actually does things get much simpler,
and that
is how we need to define motions, in terms of the rod... Below
I've
attached a simple Excel sheet I use to help people understand
rotation and
translation... The last tab shows 3 kinds of
drift.....
(See attached file:
Rotation-Translation.xls)
Bruce
Scientific Anglers/3M
4100
James Savage Rd.
Midland, MI 48642 USA
Tel:
989-496-1113
Fax: 989-496-3374
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Allow me correct an error I made in one of our previous
messages.
I stated that max loading of the rod coincided with max rod tip
velocity. I WAS INCORRECT
!
Max. rod tip velocity occurs at RSP (Rod Straight
Position). MAX ROD LOAD (MAX. ROD BEND) OCCURS ABOUT ONE TENTH OF A
SECOND BEFORE THIS AT NEGATIVE ACCELERATION (THE STOP).
Putting it in different words: The greatest bend in the rod
is when the rod is loaded the most. This happens at or close to the
STOP. Between the STOP and the Rod Straight Position, the rod
tip is moving fastest.
At RSP, the loop begins to form. This marks the end of the casting
stroke (as many of us look at it.)
RSP is the point at which the rod UNLOADS.
Gordy
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
From Troy Miller:
I
like Dennis' overall approach, in attempt to speak a language that students
can understand. I almost NEVER use the word translation with a
student, unless it's a CCI candidate. I say "move the hand from here
to here" while demoing.
I
could not disagree more with this statement:
If there is rotation during
translation it’s not translation !
Why can you not have other things happening to the object while it's
moving spacially? Shoot, on an atomic level, the electrons are doing
their own thing at the same time the macro-object is translating,
right?
Regards -- TAM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Troy...
Yes .... the atoms keep twirling and the subatomic particles at a nano
level are doing their dance whilst we circle our sun and the whole solar
system hurtles through space on to some sort of infinity !!!!!!
Bruce Richards and I both felt the same way. Perhaps Dennis
was thinking of a different concept when he typed that.
I, now, interpret his statement to mean that if there is rotation
during translation, that it is not PURE TRANSLATION.
With that, I'd agree. His prior statements support my contention.
I find that most casts have a combination of translation and
rotation.
I, also, agree with you and Dennis that the use of the terms, TRANSLATION
and ROTATION have no place in teaching early casters. In fact, I don't
use them except when coaching MCCI candidates or in discussing casting
mechanics with very advanced casters who are interested in the details.
Gordy
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Speaking of infinity:
I'm reminded of a time we had Ogden Nash as a guest. We challenged
him to come up with a rhyme for each word we chose. He was incredible
at doing that. I came up with the word,
INFINITY. His answer:
Dogs have fleas and pups
have fleas
and fleas have fleas that
bite-em.
The smaller fleas have lesser
fleas
and so ad infinitum
!
Gordy