The change of direction has to do with killing the vibration on
one side of the stick or the other. Nothing to do with angle of
ribs, balance of propeller, etc.

I do not know a technical physics answer for the phenomenon. I
have made many for give aways and kid things. Lot of fun to
perplex "smart guys". Another favorite to make is a "snapper".
You tube:
http://www.youtube.com/watch?v=XVKJh...eature=related

--
~~~~~~~~~~~~~~~~~~~~
DanG
Keep the whole world singing . . .


"DoN. Nichols" wrote in message
...
On 2010-11-20, engineman wrote:
Last night at a meeting I was introduced to the
Gee-Haw-Whammy-Diddle.
It is a simple device that has been around for a long time but
I
hadn't heard of it before. It is a wooden stick 5/16" dia. and
5"
long. The one I was given has 8 notches on it 5/16" apart and 1
/16"
deep.It has a simple propeller- like spinner on one end 1-1/2"
long.
When you rub a wooden stick or similar object along the notches
the
spinner rotates. The faster you rub, the faster it rotates.the
direction of rotation is determined by where you place your
fingers.
Can anyone tell me how it works?

IIRC, the trick to controlling the rotation direction is the
angle of the rubbing stick relative to the notches which causes
the tip
where the propeller is mounted to move in a circle in one
direction or
the other. The rest depends on the imperfection of the
propeller.

Or -- you can rotate the notched stick so one side or the other
of the notches is higher relative to the rubbing stick.

I searched extensively on google and found a lot of references
to it
but no one seemed to know what makes it work.

I suspect that if you had a perfectly balanced propeller, it
would not work -- but given the (lack of) precision of a hand
whittled
one, that imbalance is pretty likely.


http://bobscrafts.com/bobstuff/geehaw.htm

Also I'm wondering if it would work if made of aluminum?

Don't make it too heavy -- and don't make the propeller too
precise -- and it should work.

Enjoy,
DoN.

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