Proyectos

675 Monk 01:Evil Genius

4/5/11

6:03 PM

Page 1

CHAPTER

1

Coil Gun

PROJECT SIZE:
SKILL LEVEL:

Medium

★★★✩

THIS COIL GUN (Figure 1-1) will fire a small metal
projectile at up to 30 miles per hour. It is portable,
being powered by batteries, and is guaranteed to
strike fear into the enemies of the Evil Genius. On
dark evenings, the Evil Genius likes to strapflashlights to the heads of his minions and make
them run around the Evil Genius’ Lair while he takes
potshots at them. Oh, how they squeal in panic!
A coil gun works in a similar way to a
photographic flash gun. Capacitors are charged up
over a few seconds, and then all their electrical
energy is released extremely quickly. In a flash
gun, the energy is released through a flash tube,
and in acoil gun it is released into a coil of wire.
This creates a powerful magnetic field that will
cause any iron object near the coil to move.

Figure 1-1

Since the coil is wrapped around the tube from a
plastic pen, and the iron projectile is inside the
tube, it will fly along the tube towards the coil. As
all the energy from the capacitors will be spent in a
matter of milliseconds, thecoil should ideally be
turned off by the time the projectile passes its
center and exits out the other side of the tube.
A similar, but less attractive analogy to the coil
gun is a toilet cistern. In this case, the tank is like
the capacitor, except that it is filled with water
rather than charge. The tank charges over a period
of a few tens of seconds. When the toilet is
flushed, all thewater rushes out.
The gun is controlled from a single threeposition switch. When in its center position, the
gun is off. When pushed forward, it starts to charge
and the charging LED comes on. When fully
charged, the LED goes off and the gun is ready for
firing by pulling the switch back like a trigger.

The coil gun

1

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Page 2

15Dangerously Mad Projects for the Evil Genius

What You Will Need

WA R N I N G !
This is not a real gun. You could probably throw the
projectile as fast as it comes out of the end of the
gun. In addition, the projectile is lightweight.
However, this project has a number of dangerous
aspects.
High currents. These are not high voltages, but
the currents are very high and produce strongmagnetic fields, so do not build this project or use
it anywhere near anyone with a pace-maker.

The components for this coil gun are all readily
available. It’s worth shopping around for the
capacitors; eBay usually has a good selection of
suitable ones if you search for “electrolytic
capacitors.” You’ll need the parts in the Parts Bin.
You will also need the following tools listed in
theToolbox.

Do not short-circuit the capacitors when they are
charged up. You may melt whatever you are
shorting them with, which means there will be small
quantities of molten metal flying around.
And do not place your eye or anyone else’s in
the line of fire of this gun.

TOOLBOX
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Soldering equipment
Hacksaw
Wood saw
Drill and assorted drill bits
Epoxy resin glue orhot glue gun
Multimeter

PA R TS B I N
Part

Quantity

Description

Source

Firing tube

1

Disposable transparent ballpoint pen about
5
⁄16 of an inch (7mm) in diameter

Coil retainers

2

Plastic brackets cut from a plastic food
container (see the following description)

Projectiles

2

Iron/steel nails 1⁄8 inch (3mm)

Hardware store

18 inches (45cm) lengthof 5⁄8" × 11⁄4"
(18mm 33mm) wood

Hardware store

Lumber
Plastic drink bottles

1

Plastic insulating tape

Hardware store

Coil wire

13 feet (4m) of 20 or 21 AWG enameled copper wire

Farnell: 1230984

Batteries

4

Budget PP3 9V batteries

Battery clips

4

PP3 battery clips

Farnell: 1183124

C1-8

8

4700µF 35V electrolytic capacitors, or any set
of 35V...