Walter & Group..........
This message from David Lambert, MCI :-
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Gordy:
Dennis' fly swatter is a great new concrete casting concept (excessive
alliteration? I know). Very evocative.
Regarding the hammer image: In large classes, especially with
beginners, a hammer and nail may be the quickest concrete visual to help
students understand the much discussed but often unclear concepts of
translation and rotation (not that I'd ever use those terms on anyone
but experts).
"Hammer a nail at eye level." Make the hammer image concrete by using a
hammer, not pantomiming a hammer stroke. Bang it into a piece of wood
at eye level. It's simple to set up; simple to carry. Make some noise;
it's an effective attention getter. You can transfer some complex ideas
on timing and physics with the hammer (or the fly swatter). Minimal
verbiage, needed, too.
Students quickly get that you can't efficiently push a hammer toward a
nail and expect to drive it home (with no wrist/rotation at the end of
the stroke). They also get that if you employ the wrist early in the
stroke, you won't have the power to drive the nail; if you do employ the
wrist too early, you're just pushing a hammer toward a nail. The hammer
visual conveys the concept of stop, as well. Again, minimal verbiage
needed.
If we're going to teach casting effectively, we must first learn to
teach effectively. Visual is memorable; visualizing often isn't. Be
dramatic; drama is what students remember -- not drone. Be Mel Krieger,
not Ben Stein. You're teaching, not conceptualizing. Casting is
physical. Use physical concepts to teach it.
RE: pull/push, also note: You are in fact pushing forward at the point
in the forward stroke where the rod butt passes perpendicular to the
line of the cast, eh? I don't see how that can be construed as pulling.
David Lambert
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Another one is the example made by throwing ("casting") paint from a paint brush on to a wall. If you have only rotation of the brush handle with no translation, you'll throw paint all over the place. This is one of Lefty's teaching tricks. It also holds that when you do this, if you don't have a, "stop" at the right place, you'll even throw paint on the ground. This is made even more obvious if you try to cast that paint to a circular target drawn on the wall.
I've actually done that when helping a friend paint his garage. Too messy for most teaching venues, but you can make the point though less dramatically by using water.
Same concept when throwing darts at a dart board.
Gordy
Gordy