I find it to be fun and creative to take consumer fireworks items
from the fireworks store, and assemble them into larger and more impressive assemblies. Fireworks cone-fountains
can be hung upside down in a line to form a waterfall, and they can also be used as drivers in this large wheel.
"Drivers" provide the force to make the wheel go round.
Chromatropes are a traditional fireworks display exhibition pieces. They are simply composed of two counter-rotating
wheels, each of which is a basic assembly of wooden crosses with the drivers attached at the ends of each arm. They
produce the kind of effect shown below.
Chromatrope
The device shown above has 8 pairs of crossing fountain-sprays, or 16 drivers. This would be 8 drivers per wheel,
and with 1 driver at the end of each cross-member, each wheel would have 4 cross-members. We'll build a simpler
version, with two wheels, each having 2 cross-members and 4 cone-drivers.
Here is an illustration of a chromatrope out of Weingart's Pyrotechnics.
You'll notice in both the photo and the illustration that the drivers are mounted at a 45 degree angle to the arms,
and will shoot their spray out at that angle. This angle also diminishes the amount of force with which each driver
will drive the wheel. I'm going to mount the cone-drivers at less of an angle to increase their force when turning
the wheels, since the cones are not as powerful as handmade drivers.
Here's a very simple pictorial essay on this consumer fireworks model. The hubs that the bolt-axles go through are
simply 3 inch long 3/8" threaded tubes/nuts/washers, available at a hardware store in the lighting
department.
I have cut 1-Inch x 2-Inch x 8 foot pieces of lumber in half to produce 4 foot long arms, and I've cut steep angles
on the ends of each arm.
Then I drill 3/8 inch holes in the center of each arm, insert the threaded tubes, put some wood glue between the arms,
and tighten the nuts and washers.
I've removed the wrapping paper from the cones and drilled some mounting holes in their hollow bases. I've also
installed some extra scotch-tape to insure that the fuses are secured in their tops.
I then mount the cones to the arms with iron wire, and I install buckets and quickmatch to fuse them together. I have
clipped the cone visco fuses on an angle to get fresh powder exposed, and I've glued and tied the buckets to the
cones to insure that they don't slip off.
I've assembled a T-support with 4x4 lumber and reinforcements. This insures that the wheels don't hit the vertical
support during operation.
I've assembled the wheels so that they are driven and turn in opposite directions. You'd be surprised how easy it
is to mess this detail up.
On the day of the show, I'll tie the two wheel ignition points into one leader so that both wheels will light at
the same time.
I always test at least one of the wheels with the cones you want to use to make sure that they are powerful enough
to get the wheels spinning once they are lit.
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