ANTENNA
LAUNCHER  "Steampunk" Styling -
Sends tennis balls flying at 500 mph!

This is
the result of a week of creative spray painting. It has a copper and brass
steam boiler look. The style is coined: "Steampunk". There is
more aesthetic work planned for the
launcher.

After nearly throwing my arm out to
install my three band dipole, and only getting it elevated around 45' up.
I knew it was time to get a hold of a decent tennis ball
launcher!
These launchers use compressed air to accelerate a tennis
ball to 300 mph pulling a tow line as high up as 150-400' in the air to
allow for installation of ham radio wire antennas in the branches and tops
of nearby trees.

We've used them at Field Day before and I was impressed
with the results.
The problem was where to find one... Could I simply
make one? So I needed to do a little research.

Well... it turns out
that there is a great web site setup by a couple of hams just to satisfy
the above qestions:

http://www.antennalaunchers.com/antlaunching.html

A
great site that will educate you on the basics, intricacies and safety
issues of procuring, building and using pneumatic antenna launching
systems.

SAFETY
DISCLAIMER: Mike K4ICY and this site does not condone the
use of this or related device if used within a legally forbiding
jurisdiction or for inapropriate use that can and will threaten life,
safety and property. You build one at your own risk and are encouraged to
understand the many dangers associated with fabrication and use of any
device that accelerates a projectile. All responsibilities and liability
are that of the owner and builder.

How does mine differ from
the ones you can buy from Antenna Launchers.com?
• POWER!
My launcher has double the pneumatic charging volume and can launch the
projectile to 300' with 80psi.
• Less Cost... are you
kidding?!?!  Why pay $110 from someone, just to have to build it
yourself?
• Coolness Factor... (pictures soon) Mine has been
decorated to have what's called a "Steam
Punk" look. Styled after plausible technology of the late
1800's.

Oh yeah!  Everyone thinks it's made from real metal.  What
better PR device than a killer work of art at Field Day that is also
functional!

I am NOT currently buidling any, but will cave to
making one at least once a year.
If you choose to build one yourself,
please make good notes from many of the website that teach the building of
"Spud Guns" or "Tennisball Launchers"
There are companies that sell
parts such as barrels and valves.

I will not get into exact
dimentions and details. If you are able to build one, then you are apt to
figure out the nuts and bolts yourself.
There are two hurdles to
overcome in procuring parts: The valve modification and obtaining the
barrel material.

The barrel must one, be the exact size as the
diameter of a tennis ball (which varies) and be pressure rated.
The
best PVC pipe that I've found is called "SDR-21" and has an internal
diameter of 2.6"
I was fortunate to locate a supply at the local
EWING Irrigation supply house. You can also go to a local plumber or
plumbing supply house. NOT The Home Depot or Lowe's!
But you will be
able to readily find all the other required parts at those stores.
The
modification of the valve is easier than you may expect. These are simple
devices sold by RainBird, Orbit and others and work on simple
principles.
All you would do is provide a quick escape of diaphram
backside air pressure through a common air release mechanism to allow it
to do it's thing.

PHASE
1  Modifying the Sprinler System
Valve

Check out this YouTube video where there are
step-by-step instruction on how to do this for your launcher or spud
gun.
http://www.wonderhowto.com/how-to/video/how-to-modify-a-sprinkler-valve-for-use-in-a-spud-gun-212056/

Parts needed for valve modification. Available at
your big-box home improvement store.

PLEASE NOTE: RainBird no
longer manufactures this model type of valve and have moved to cheaper
Mexican production. I am currious to see how the new type could me modded.
But I'm sure you can do this to about every brand. Not all valves work
exactly the same. But you should try to only work with the diaphram model
and not the plunger version.

This is a common 1" sprinkle system valve found at most
hardware stores. You can get the connections in glue-in or
threaded.

These type are intended for residential use and have a 24
volt controlled solenoid for actuatiion. There is also a pressure release
control stem in the middle.
Bigger and better ones can be used,
especially if ridiculous amounts of "firepower" are needed. I do not
recommend using the smaller 3/4" version.

Take those two items off, unscrew
counter-clockwise, and discard them.

There are six long screws. With some downward
pressure to budge the screws, remove them and carefully remove the
cover.

PLEASE NOTE the contents and location of the inside parts.
Some valves have many. Generally just the spring, note its placement and
the placement of the rubble diaphram.

This is the inside of the valve cover. Note the
THREE small breathing holes:

The one to the left is for the
air-from-solenoid intake port. The adjacent hole on the side of the dome
is the air-to-solenoid port. The middle is the manual air-release control
port.
These holes are too small of adequate release of diaphram
equaliztion pressure.

Use a drill to widen the center hole. Start with a
smaller diameter so that the stress on the plastic will be
reduced.

With this model, the center area is perfect with a good
thickness to support the reducer connection.

Use a 1/8" NPT pipe thread tap. With level and firm
pressure, rotation of the tap should be done with a tap handle, but a
socket wrench works fine.

Ocasionally remove the tap to remove
excess shavings. Stop until 3/4th of the tap area is submerged. Tap lower
if the treads are two narrow for the brass fitting.

Ensure that the tap area is at least 1/4"
in depth. Many valves lack the thickness in their cases to hold the
fittings.

The fittings will be holding the weight and user forces
of the air-gun / trigger mechanism. And extra depth of high-strength
polycarbonate epoxied to the surface my be required.

1/4" tapped hole in the valve
cover.

Clean away any burs.

(Not shown) Brass NPT fittings are combined with
yellow (gas) teflon tape. I used a 1/8th" double ended coupler and
1/8th-14th" elbow.

Mix the two-part epoxy, A very small quantity
should do. Use a toothpick to spread it on the threads of both the cover
hole and the brass fitting.

Apply epoxy with a toothpick to the remaining
breather holes. They are not needed.

Carefully fill from both sides
and avoid excess.

Go ahead and mix a small plastic cup with more
epoxy... hey! Why waste money. ...Plus, it's kinda weired
looking.

This will ensure that there will be no escape of air after
future handling of the launcher and any possible unsticking of the
epoxy... A mis-fire could be fatal!

(Top with air tap connection and epoxy chamber
fill.)

Allow to set for 24 hours...  Re-assemble, alternating
screws (light at first) diagonally across valve cover. Then snug ensuring
that the diaphram is not unevenly pinched.
Ensure that there is no
debris or dust inside the top of the diaphram chamber.

Final
vintage faux copper & brass look applied:

See below for procedure on painting
PVC...

PHASE
2  Assembling Lengths of PVC
Pipe

Measure and cut all length of the diffrent sections
from only PRESSURE RATED PVC.

The overall look and performance of
the tennis ball launcher is up to you.  You can form any combination
of shapes and power level that your wallet will allow.
As long as the
air has a pressure tank to be stored in, an inlet valve, firing valve and
barrel.

Cap ends and reducer adapter links are used to
create the barrel and pressure tank.

RULE OF THUMB: The pressure
tank should hold at least twice the volume as the barrel.
Volume = Pi x  Inside
Radius squared x  length or
pipe
Though the barrel can be longer, and you may
see greater velocity. If the tank is smaller, you'll have less
acceleration of the projectile in the barrel.

(Adapter detail...)

(More detail)  USE ONLY "MEK" High Strength PVC
primer. Avoid using the time friendly cement, as a strong, air-tight bond
is required.

BEFORE GLUING finished pressure chamber to the rest
of the launcher,

drill, Tap and install the Schlader valve and
optional over-pressure protection valve and optional pressure gauge first
with yellow teflon tape.
Blow out any shavings or dust that can
contaminate the surface of the valves diaphram.

The barrel and pressure tank should be created first
them arranged in your chosen configuration.

PLEASE NOTE: If the
valve is the threaded type, ensure that there is enough clearance to
remove the valve if service is needed.

PHASE
3  Finalization

Since the barrel and tank were only connect by the
1" PVC length on the other end, it was important to shore them up to
prevent damage from shifting weight.

I used a stainless-steel vent
pipe strap for this model. The first model has an intricate stucture of
brass and steel that is more for show.

Attach the valve trigger, I used a common
pneumatic air gun.

You can route to another location by use of an
air hose or a fast release solonoid valve... whatever you wish. The faster
the release of air on the control side of the diaphram the more launch
performance you will get.

This is a tennis ball projectile. You may use other
projectiles such as a slug made from PVC links, golf balls, potatoes,
squirrels (don't!), etc...

The tennis ball is widely used by the
ham community because of it's safety when falling, where-as the
traditional methods, namely lead sinkers, arrows and wrenches are
dangerous!
Making the ball is simple: Cut a 1.5" gash in it with a
knife. Fill with a baggie of 30 pennies for good weight (which increases
velocity!). Make a few loops of 30-40 lb test weight mono-filiment fishing
line and seal the loops halfway into the gash with a adequate application
of Super Glue. I prefere the Gorilla brand rubberized Super Glue.
Cure
overnight...

Here is the final assembly. Two slight variations
are shown.

Certain brands of tennis balls are a tight fit but
provide improved velocity. A chuck should be made.

PHASE
4  Testing

It is very important
to test your launcher before field use!!!
• Fill air
chamber with 20 psi to begin testing for catastopic failure.
Submerge the launcher in the bath tub or place under a few towels as
shrapnel from exploding PVC can be leathal!
• Take out of
water and squease the valve trigger... It should make a "barking" barking
noise. I suggest using ear-plugs as the release of pressure and noise
decibel level can be harmful.
• Increase pressure by 20
psi until you reach the maximum. - PLEASE NOTE: You should be safe if you
never excede 1/3 of the max psi rating on the largest (thus weakest) PVC
pipe.

Since I'm using 3" pipe for the tank, and it's rated at 260 psi, I use 90
psi as my max... It does well. I can send a ball 400" (at a 45 degree
angle), so it should be sufficient for ham use.
• Take to
an open field and try the projectile by itself. Start off at smaller psi
incerements and gauge the height and distance that each level brings.
You'll notice that it is expontial.

DESIGN
NOTES:
• When
a thicker diameter ball is used and when more weight is added the
resultant back pressure will cause the projective to go farther and
faster.
• Be carefull to tighten connections and seals.
Loss in air pressure in the trigger line will cause uninteded
misfirings!!!
• 40 or 50 lb test fishing line with an easy
sun-catching day-glow color is recommended for the tow
line.

SAFETY RULES AND
PROCEDURES:

1) LEAVE BARREL
CHAMBER EMPTY
2) ONLY FILL TO SAFE PRESSURE LEVELS - DO NOT
OVERFILL!
3) POINT AWAY FROM PEOPLE, PARTS OF YOUR BODY, PROPERTY,
PETS, ETC.
4) NEVER - NEVER - NEVER AIM OR FIRE THE LAUNCHER WHERE THE
PROJECTILE OR TOW LINE CAN COME IN CONTACT WITH ELECTRICAL SERVICES
5)
FIRST POINT LAUNCHER STRAIGHT UP IN THE AIR, PLACE BALL IN AFTER. THEN AIM
SLIGHTLY HIGHER THAN TARGET TO ADJUST FOR DRAG.
6) WARN NEARBY
PEOPLE
7) DEPRESS TRIGGER QUICKLY AND HOLD

Launcher in action at the Jamboree On The
Air.

HOW TO PAINT PVC
PLASTIC:

1) First -
Clean surface with alcohol and lightly sand with a high grit to rough up
the surface.

2) Coat entire surface with a liberal application of
"Purple Primer"

This is an agressive solution of Tetrahydrofuran and Methyl
Ethyl Keytone. Very toxic to breath, but effective.

3) Within the
first few minutes after the excess liquid primer has evaporated - Paint
surface with a nuetral color Spray Paint formulated for PVC
plastic.
The spray paint
manufacturers claim that this paint will adhere to PVC. But in real life,
it usually peels off after a while.

4) Apply a new coat, once dry
to the touch, with the spray paint color of your choice. - Re-apply with
second or third coat later.

For a vintage finish there are paints
for that. Metal can be achieved by first applying a standard metallic
color. These usually have a flatter look.
Then patting on a
super reflective chrome-like version of the paint with a paper towel or
sponge.

Other effects, like corrosion or weathering, can be done
with diluted mixes of other paint
colors.