I would like to build a keyboard instrument based on the Savart wheel
for our science museum.  A Savart wheel (physicists always feel obliged
to assign a proper name to every possible demonstration) is nothing
more than a rotating toothed wheel.  You push a card against the
rotating teeth to make a sound of a particular pitch.  Multiple wheels
produce chords that are quite pleasing.  I envision keys that would
push a plectrum down to each wheel and that would connect mechanically
to a sounding board or a resonator of some sort.

I think that the motor drive would be fairly straightforward to build
(a synchronous motor would be ideal, and I should be able to get one of
those, but the wheels are another matter entirely.  I know the ratio of
frequencies that should work: 44-47-49-52-55-59-62-66-70-74-78-83-88,
says a physics demonstration manual I saw.

But the machining of the wheel teeth is pretty much beyond my
capabilities.  We have a vertical mill and a rotary table in our shop,
but while I've seen these used elsewhere, I'm not confident that I can
get the correct number of teeth without coming to grief as the circle
is completed.

I don't think that there would be any sort of size limitation for the
instrument; we have lots of room in that place.  Thus I might try
large, fairly thick plywood disks with round-headed tacks pounded
into the edges, though I do worry about the stored energy in such an
arrangement; if it gets loose there would could be damage to museum
visitors, and most certainly damage to Kinsler from the exhibits staff.

I think heavy sheet steel should be adequate for gear material, I'm not
sure of what a long-lasting 'plectrum' or card material might be made
of.  I would also like to try wheels made with different shapes of
teeth in order to obtain different "stops," but that would come later.

As might be expected, the budget for the prototype of this project will
be somewhat limited.  I'm guessing an 11 note version will make an
adequate prototype.  If it works well, the museum may budget enough
money for a bigger version, perhaps with 88 keys.

Gears with the appropriate number of teeth aren't available from Small
Parts Inc, and it's quite possible I might have to use a gear train
to obtain the correct frequencies for some notes.  Given my limited
skills, I'd rather not try to build such a gear train.

I have a few ideas, such as drilling holes near the edge of the wheel
instead of trying to carve teeth, but ideas from this group would be
exceedingly valuable.  I know it's asking a lot, but I figure that this
group of craftsmen might be able to help me get started.

Mark Kinsler
Lancaster, Ohio, USA
tel.: 1-740-687-6368
http://home.earthlink.net/~mkinsler1

 [ "E.T.", the cute alien, used a rotary saw blade!  -- Robbie