TOY INVENTOR’S NOTEBOOK
Make a Diving SpudMarine!
INVENTED
AND
DRAWN BY
Bob Knetzger
HERE’S A FUN AND FAST WAY TO CREATE
a homemade version of the classic cereal
premium toy, the baking powder-powered
diving submarine. Instead of plastic, we’ll
make one out of a potato. It works well —
and when you’re done, you can eat it!
First, cut a potato into a ¾"– 1" diameter
cylinder, about 3" long. Use a piece of
¼" brass tubing as a plug cutter. Press the
tube all the way into the potato to make
3 through-holes evenly spaced along its
length. This will reduce the mass of the
potato for better diving. Enlarge the bottom
of the center hole to make a flared conical
opening (see #4). This will create an air
chamber for the bubbles.
Next, make a periscope. Cut a thin piece
of wood about ¼"× 1" and drill a ¼" hole in
the center. Cut a 1"-long piece of ¼" wood
dowel and push it through the hole, so
there’s an equal amount of dowel exposed
on each side. Insert the periscope into the
middle hole in the potato.
Time to test it! Place the SpudMarine in
a tall pitcher or vase of water. If it floats,
cut off some of the periscope and try again.
If it sinks fast, trim off some of the potato
and try again. If it sinks very, very slowly,
it’s ready! The sub should be just ever so
slightly heavier than neutral buoyancy for
best diving action.
Remove the sub and shake it dry. Pack
some baking powder (not baking soda) into
the bottom of the center hole. Use another
piece of wood dowel to tamp it in tightly.
Gently lower the sub back into the water
and let it sink. Then watch it bubble, rise,
breach the surface and “burp” its bubbles —
and sink again! How many cycles will your
sub do before reloading the powder? ;
e
1. Cut
through-holes.
2. Make
periscope.
3. Insert
into center
hole and
test for
buoyancy.
4. Pack bottom
of center hole with
baking powder.
5. Dive!
Bob Knetzger is an inventor/designer with 30 years’
experience making all kinds of toys and other fun stuff.
164 Make: makezine.com/26
