Slow Motion Walter
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Links to photos - see text below for description.
Slow
Motion Walter is an automated marionette who strums his guitar and bobs
his head when the music is on. He's meant to accompany a musician at a
live performance and he belongs to a musician friend named Arthur II. One
day, Arthur asked me to help him make Walter dance so we got together and
discussed what it would take. The project has so far involved the use of
some Meccano parts, the sound sensor from a dancing flower, the motor and
baseplate from an old personal cassette player, a plant stand and a host
of other household items (not to mention Walter himself who was hand crafted
by Arthur).
Crankshaft
I started out with the idea that I'd have a small electric
motor drive a rotary crank system to pull strings up and down which would
then operate Walter's various movements. Initially, I bent a coat hanger
into a crank shape but the problem with this was that once made, there
would be no room for later adjustments. For my next attempt, I designed
a series of separate cam elements which would be mounted on a shaft. These
cams could have their eccentricity, phase relative to each other and axial
position on the shaft adjusted individually, giving much more freedom in
other aspects of the design. For a photo of these first attempts, click
here. Note the use of Meccano parts in the picture. I prototype a lot
of my mechanical designs using Meccano. It can be very useful. Also seen
in the picture is a means of coupling the drive motor to the crank. Since
a coat hanger has a smaller diameter than a Meccano axle, I tried a few
different items to mate them together and finally settled on using a rubber
hose and a few layers of shrink tubing (the type used to insulate soldered
electrical connections). This worked, but it was not necessary when I dismissed
the coat hanger idea (see the upper crank in the image). The second design
with adjustable cams required the use of a threaded rod as the shaft and
the cams would then be attached to the shaft using nuts. This turned out
to be the idea that worked but the first cam design needed a bit of work.
It didn't provide enough eccentricity (throw) so I designed a new
cam from scratch and made the necessary parts from a wooden pole, some
pressboard and a plastic separator for hard drive discs.
Motor and Other Electrical
By this time, I now knew that I had to supply 3 cams
(one for each hand and one to make his head bob). Watch a 3 second video
clip (580K AVI file) of the cams in action. Things were moving along
well so it was time to include the sound activation section. For a sound
sensor, Arthur provided one of those flowers that danced when you made
noise near it. We took the microphone and circuit out of the flower base
and I connected the Meccano motor to the output of the circuit. When power
was hooked up, it worked! We had one problem though. It ran much too fast
for our needs. Poor old Walter would be dead tired after a session at that
speed, so I used a potentiometer to add speed control. This solved that
problem - sort of. When the speed was lowered to a reasonable level, the
motor had difficulty starting each time it stopped - a problem known
as stiction. To deal with this, I added another stage of pulleys and increased
the power to the motor (hoping to overcome the stiction with a bigger jolt
to the motor each time it turned on). The problem with this was that one
more stage of pulleys also added more friction to overcome and any benefit
was canceled (it also took up more space). I then decided to dig into one
of my junk boxes, looking for an old personal cassette player (Walkman).
I took the base plate, motor and one dual pulley from it and used that
instead of the Meccano motor and two of the pulley stages. This worked
and two views of the setup can be seen
here. The whole motor/crankshaft setup is mounted
on a wooden platform with a battery box, the small sound sensor circuit
as well as an on/off switch, mic jack, DC in jack and the speed control
potentiometer. It has been configured so that it can be powered by 4 D-cell
batteries or an old 6V calculator adaptor which will disconnect the batteries
when plugged in. On the underside of the platform I attached a pair of
clips from an old foldup TV dinner table to make it easily installed or
removed from the stand.
Stage
The drive was not the only thing that needed to be built
for Walter to dance. He needed a stage to perform on as well. This was
constructed from a foldable plant
stand. Since the stand was narrow and the sides were parallel, it made
the usable space too small. To fix this problem, I made plywood
platforms which slide onto the existing shelves and hook into the lugs
where the shelves normally would. The end result is a stage
for Walter to play his guitar on that can be seen from a wider angle. Other
details include the white crossbar at the top of the stage
which was fashioned from the weight at the bottom of a set of mini-blinds.
The weight has a good cross-section to offer strength while being lightweight.
At its ends, I installed a pair of the eyebolts that are used to hold bicycle
fender stays to the fender. To put the crossbar in place, the eyebolts
are simply slipped into the opening at the top of the pipes that make up
the plant stand sides. This crossbar helps hold the sides of the stand
open the right amount for the stage platforms to slip into place. The microphone
used for the sound sensor was mounted in a pen cap making it look like
a lapel mike. It was then given a small guage coax cable with a 1/8" (3.5mm)
mini phone plug which plugs into the mike jack on the electrical platform.
Putting It All Together
The design also has to meet two more requirements. It
must be lightweight enough to be transported by someone on foot and must
be easily assembled and disassembled on site. In it's present state, the
complete weight (including Walter and his carrying case) is less than 20
lbs (9kg) and can be set up in about a minute. However, as you can read
in the next section, there is more work to do.
Protection From The Elements
Since the completed project will be used in an outdoor
environment, there is the possibility that poor old Walter could get caught
in an unexpected rainfall. For this reason, certain vulnerable parts have
had protective covers made for them. The first
cover protects the electronic circuit and other wiring and has been
made from the tray from a frozen lasagna. After cutting off most of the
flange around the top edge of the tray, other cutouts for wires and the
switch/jack panel and the tray was mounted in an inverted manner and held
in place with two screws in the remainder of the flange. More work was
needed to make and install the second cover. This one is to protect the
motor and drive pulleys and is made from the plastic container that nails
or screws come in. The fold-up lid of the container acts as an openable
hood so that drive belts can be replaced if necessary without having to
take the whole thing apart. The extra work that was done in order to make
this cover possible involved re-mounting the supports for the large pulley
in such a way that its drive belt was not locked between two supports.
Compare the new arrangement with cover
with the previous arrangement. This
cover was held in place by bolting it to the support next to the large
pulley.
Other details
Attention has been paid to other details of the finished
product as well. For starters, a label
was made for one of the panels at the back of the unit. This label indicates
on/off, speed and +6v DC input and was printed on a standard inkjet label.
To keep it from fading and being damaged by moisture, it was wrapped with
a layer of packing tape before the components were remounted on the plate.
A similar label will be made for the microphone jack. The stage platforms
have also been painted flat black to give them a more complete look.
To be continued...
Since this is a work in progress, I still have a few
things to do. For starters, Walter must be connected to his strings and
each string calibrated so that the movements appear smooth and realistic.
The drive platform seen at the top of the stage
image might be moved down about 6 inches (15cm) because it doesn't need
to be as high as it is. If I move it down, I can add a valence across the
top to hide this mechanism from view which would make the whole setup look
more like a real stage. I am also going to add wheels so that it can be
pulled along like a suitcase when the whole setup is packed up for transport.
The best wheels to use would be the dual type seen on some baby strollers.
A pair of these wheels on each rear leg of the stand, set up so that they
engage the ground when the whole unit is tilted backward would work well
I think. I will also have to include a means of attaching all of the parts
to the folded up stand during transport so they don't have to be carried
or packaged individually.
What's In A Name
You may be wondering where the name Slow Motion Walter
came from. Well here's the story as I've been told. Someone (who's identity
is unknown to me) mis-interpreted the words to the Deep Purple song "Smoke
On The Water". In the song, the line "Smoke on the water, fire in the sky"
was mistakenly thought to be "Slow Motion Walter, the fire engine guy".
So that should explain it.
Comments or Questions
I hope you have enjoyed my description of Slow Motion Walter and his stage.
If you have any comments or questions, please contact me at johngdguard-web@yahoo.ca.
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This page was last updated on March 18, 2005.
