■ FIGURE 7. Completed
circuit board and
Building the Circuit
and Control Panel
The circuit is constructed
on a piece of 5-1/2 inch by
2-7/8 inch perfboard using the
point-to-point wiring technique
following the schematic. All of
the parts necessary for the circuit are listed in the Parts List.
The control panel is
constructed using 1/16-inch
thick aluminum and can be
mounted directly to the circuit
board. A suggested metal
cutting and drilling template is
shown in Figure 6. Mount the
potentiometer, indicator LEDs, and
switches to the control panel and then
fasten it to the circuit board. Use two
position terminal blocks on the board
where the capacitor bank, battery
pack, fire switch, and accelerator coil
are connected. The completed circuit
board with control panel attached is
shown in Figure 7.
capacitor bank as shown in Figure 9.
The length of these wires may be
different, depending on what type of
stock you decide to build. Coat all
of the capacitor leads and solder
connections with RTV silicon rubber or
Plasti Dip for safety. The completed
capacitor bank is shown in Figure 9.
Barrel, and Breech
lating material as shown in Figure 5-F.
(I use a product called Plasti Dip that
is available at most hardware stores.)
The final step in completing the
transformer is to add the E-cores to the
bobbin. To prevent the two halves of
the cores from touching when they
are in place, three air gap spacers
need to be constructed. Cut three
pieces of electrical tape to a size that
is slightly bigger than the end of each
of the three legs of one of the cores
and then stick them on. Place the
cores on the bobbin and tape that
in place with transformer tape as
shown in Figure 5-G. The transformer
is now complete.
■ FIGURE 8. Capacitor energy
storage bank wiring diagram.
Build the capacitor bank using 10
1,500 μF, 200 volt capacitors wired
according to the diagram in Figure 8.
This capacitor configuration gives a
total capacitance of 600 μF at 1,000
VDC. Solder a 12 inch piece of high
voltage wire to the positive side of the
capacitor bank and a six inch piece of
HV wire to the negative side of the
The barrel consists of a 14 inch
length of styrene tubing with an inner
diameter of 7/16 inch. You can use
any sort of light plastic or nylon tubing
material that can be obtained at most
hobby shops. Wind 300 turns of #20
AWG magnet wire, in six layers of 50
turns each. Start winding the coil one
inch from the end of the tube. Cover
each layer of 50 turns with electrical
tape to secure in place and then wind
the next layer on top. Use two plastic
or cardboard discs glued to each end
of the barrel on both sides of the coil
to add support.
Fabricate a breech loading device
to move the projectile into a position
where it is partially seated in the coil.
You will need to experiment with the
initial position of the projectile to
achieve the highest velocities. The bolt
of the loading mechanism that I put
together contains a small magnet that
holds the projectile in place when the
launcher is tilted, but does not have
enough magnetic strength to interfere
with the pulse created by the accelerator coil. The completed accelerator
coil, barrel, and breech loading
mechanism are shown in Figure 10.
Pistol Grip and
■ FIGURE 9.
The trigger switch used is a
microswitch type but any momentary
contact switch can be used. The pistol
grip can be configured however you like,
just as long as you can mount a fire
switch. A general pistol grip construction
template is shown in Figure 11 and can
be fabricated out of plastic or aluminum.
Cut two identical pieces of plastic