Build Your Own Launcher
Alright, you want build your own potato launcher. These
instructions will help you on your way to an effective yet simple
spudgun that should provide hours of enjoyment for you, your friends,
but probably not the old man down the street who gets mad when your car
backfires!
COPY AND PASTE THIS ENTIRE PAGE INTO WORD AND PRINT IT. No need to keep running back to the computer while you are trying to build your launcher.
A few things to note before proceeding:
- 1.
These instructions/procedures are provided as-is. No guarantee is made
that this device will function as well or better as I have experienced,
intend, or describe it to operate. In other words, your results may
vary, and they may even be very undesirable results, possibly resulting
in personal injury or property damage. Please review the site
disclaimer for more information. - 2. The wording and
statements/nomenclature pertaining to the construction and operation of
this potato launcher are intended as such to help ensure one attempting
to do this has a basic understanding of the equipment and materials
involved. If some of the statements seem 'Greek' to you or you do not
recognize some symbols or phrases, that is wholly my intent, and you
should obtain assistance from a trusted source or not proceed at all. - 3.
These instructions are intended for a beginer or someone that has never
built a spudgun before. The procedure outlined below is not necisarily
the method myself or another experienced spudgun builder uses. These
instructions will help guide you in building a "sound" piece of
launching hardware. As you gain experience, you may find that different
things may work better for you....but start simple. Thanks, and happy
spudding! - 4. The finished product should look something like this.
- Keep in mind that PVC pipe/fittings are not approved by the manufacturer to be used for the purpose of constructing spudguns.
Here they are, in the recommended order to check them out:
Step 1: Getting stuff to build it
This
materials list is to build a very simple starter model potato launcher,
with the intent to get the most bang from your buck (so to speak). By
no means is this the only way to build a launcher, or nearly the
coolest, but still able to provide hours of fun.
MATERIALS:
Obtain the following items: (qty 1 unless so indicated in [])
- 10" of 4" SCH40 PVC water pipe (chamber body)
- 36" of 1 1/2" SCH40 PVC water pipe (barrel stock) Or get yourself a piece of SGTC rifled barrel stock.
- 4" PVC coupler
- 4" x 1.5" PVC bushing (if not available combine two, like 4x3 and 3x1.5)
- 4" PVC FSxFNPT adapter (clean-out adapter)
- 4" PVC MNPT threaded plug
- PVC primer, one with dye in it if possible (purple, blue)
- PVC pipe cement, medium body is best
- [2] #8x2 1/2" flat or round head allthread machine screws, drive not important
- Two feet of 16g or lower stranded insulated wire
- Electrical and Duct tape (of course!)
- Red button BBQ ignitor/striker, a replacement found near new BBQ's (find one for a grill w/side burner if possible)
EQUIPMENT/TOOLS:
Suggested tools for building the potato launcher:
- Hand wood saw (or hacksaw, for cutting pipe, maybe you already got it cut at the store)
- Pocket knife
- Needle Nose Pliers
- Soldering Iron w/PbSn or Pb free solder (or just use tape and hope it works)
- Drill motor with bit 0.010" larger than machine screw shank
- Appropriate driving tool for machine screw (probably Phillips)
- Medium half round file for shaping pipe (or a lathe if you got one)
- Rag for PVC cement clean up (disposable)
Step 2: Preparing the materials for assembly
To
make sure everything goes together properly and smoothly, proper
conditioning and sizing of the materials is necessary. Pay particular
attention to the shaping of the pipe ends, as this is a major factor in
proper solvent welding with the fittings.
PVC PIPE SIZING
Cut
the two pipes to size, 10" and 36" with the saw unless you already did
so in the store. Using the file, take off the sharp corners on the
inside AND outside of the pipe. Radiusing the inside helps reduce the
amount of potato scud that can build up in the launcher, and breaking
the outside corner ensures proper solvent welding, if this is not done
leak paths may result. Cut ends should be as square as possible. To one
end of the 1 1/2" pipe it is suggested that the inside be chamfered
about 0.020" and the outside filed or turned down to almost meet the
inner chamfer, creating a blunt knife to help size the potato. It will
work without out this step, but a lot messier!
PVC FITTINGS
Inspect
the fitting for really bad weld lines or possible large dislocations
that may result in premature failure. Remove all paper tags or labels
by peeling, scraping, even using a bit of primer to clean off the last
adhesive. File off any sharp sprues that may hamper your ability to
grip the fittings firmly when assembling.
IGNITION SYSTEM
Cut
the wire into two equal lengths. Strip and twist each end about 3/4"
back. Taking the BBQ igniter, upon inspection you should find a plug on
the tail end (one electrode site) and close inspection should reveal a
very fine wire embedded in the side body of the igniter, close to the
button lip.(if you have a 2 pole ignitor -- side burner type -- this step will be much easier)
This fine wire is attached to the igniter nearest the button, as the
wire is just pressed into this slot which might be about 3/4" long.
Carefully extract the other end of the wire with the knife, removing
all but the last 1/4" or so from the slot. Carefully twist this wire to
one end of one electrode wire stripped previously. Immediately solder
this connection together taking care to not break or extricate the fine
wire from the plunger body. Cool with spit (really!), dry, and tape
this joint back against the body with electrical tape, using enough to
immobilize the wire with gentle tension.
Take the wire
supplied with the igniter, the one with the plug that fits on the base,
and cut leaving about 2" from the plug end that will fit into the base
of the igniter. Strip and twist this stub to the other electrode wire,
soldering, and taping over the solder joint. You now have an igniter to
make a 'remote' spark. Try it holding the two free electrode wire ends
about 1/4" apart--don't touch them! (your BBQ igniter may be a bit
different, the idea is to get both electrodes away from the igniter, so
you don't make a big hole in the launcher combustion chamber.)
Step 3: Assembling the Launcher
Now
you get to stick all the stuff together, using pipe glue and tape and
more solder if you like! Just don't breathe too much pipe glue
solvent...it'll make you nuts!
I Chamber Assembly:
Prime
both ends of the 4" pipe, also priming the 4" bushing, both 4" coupler
sockets, and 4" slip on the adapter. DO NOT get any primer on the
adapter threads! Immediately apply pipe cement to the three primed 4"
fittings, then LIBERALLY to both ends of the 4" pipe. Start both the
coupler and adapter fittings on the pipe, start the bushing in the
coupler, then right the assembly with the threads up, pressing it
together with body weight while twisting about 1/2 turn. Hold this
position for at least 30 seconds. The pipe ends should bottom each
about 1 1/2" inside the fitting socket. If they both do not bottom,
either apply more force IMMEDIATELY somehow to get it to, or you are
screwed and have to throw it out--start over with that. If the fittings
and pipe are properly conditioned this should not be a problem. Wipe up
any spilled glue with the rag, but leave a good bead at the external
pipe/fittings line. If any glue got on the threads get it out of there
as fast as possible! Any glue on your hands should just be left to dry
and then peel it off. Using solvent to remove it will just increase
your exposure to it.
II Electrode Installation:
Wait
about 10 minutes for the glue to set. Using the proper size drill bit,
put two radial holes 90deg apart about 1/2" back from the front edge of
the adapter fitting--the plastic here is about 1/2" thick as well.
Drive in the two machine screws nearly all the way, leaving about 1/8"
between the screw head base and the plastic. The ends may touch or be
far apart--the electrode gap will be calibrated after the electrode
wires are connected.
III Barrel Introduction:
Prime
one end of the barrel and the 1.5" socket on the bushing. If one end of
the barrel was chamfered to a knide, prime the square 'regular' end of
the pipe. Apply glue, liberally to the pipe, and press together, again
using a 1/4 turn motion to bottom. Hold for 30+ seconds. After
releasing place the unit upright for several minutes, to let the glue
set a little more. Solvent welding is more of a curing than a drying
process. Solvent is lost, hence the term drying, but the action of the
solvent effectively cures all those individual plastic parts into one
continuous physically joined piece of plastic. Properly done, solvent
welds are always stronger than bulk pipe.
IV Wire it Up:
Tin
the two free ends of the electrode wires if possible. With each end
bend it around the screw shank, just below the head, in a clockwise
manner (you may need needle-nose pliers if the wire is heavy). After
the wire is at least 3/4 turn around the shank, tighten the screw,
pretty good, biting the wire into the plastic a little. Liberally apply
electrical tape, rubber tape, or silicone RTV to the exposed metal
areas, as they will shock you all day long if not insulated properly.
Before taping tug on the wires a little to make sure they are firmly
gripped by the screw head.
V Electrode Calibration:
Setting
the gap is next. The two screws may be in a variety of relative
positions, depending on how straight and aligned the holes were
drilled. Wearing leather gloves, you now want to somehow create about a
1/4" gap between the screws. This gap does not have to be measured from
the very tip of the screw, and the spark will find the shortest route
possible. Bend only one screw if possible, and dont bend it around a
whole bunch back and forth, or it will get work hardened and break
sometime. DO NOT test the spark device yet, as there are still PVC
solvent fumes all over the place. Just wind sufficient tape around the
ignitor body to fully insulate all metal parts from your hand when you
grip it. Lash it to the side of the chamber if you like with electrical
or duct tape, just don't press the button yet!
Step 4: All put together...now you wait
IT IS HIGHLY RECCOMMENDED THAT YOU WAIT AT LEAST 24 HOURS FOR THE GLUE TO FULLY CURE AND SOLVENT TO DISSIPATE.
Many
of the unfortunate potato launching accidents occur due to over anxious
constructors/operators getting a little trigger happy a little too
early. Keep in mind that the solvent fumes are extremely flamable. A
few notable events include people chemically/thermally removing a
majority of the hair on their head, or rapidly separating the
supposedly single piece of PVC plastic back into its purchased
components (or even smaller pieces!) Just wait...it'll be worth it.
In
the mean time this is a great opportunity to gather what you may need
when you do start running this device. On the top of this list is
certainly a bag (or two...or three...) of good fresh potatoes. Never
use old sprouting, skunky potatoes, this is just bad form! Buy a bag
for $2 and relish in their crispness! Also a fuel, probably starting
with hairspray, the old mainstay. Traditionally the 'Aqua-Net' brand
has yielded to best results, but it will be mighty hard to find those
folks who grew up on that. Once you get more experience you might
graduate to propane...but wait a bit. A good location is also
required...don't use this device in the middle of your subdivision out
of your garage or you are guaranteeing that old grandpa down the way
will call the cops!
Step 5: Using the launcher
Again,
find a suitable location to deploy your potatoes, as the device can get
quite loud with a good fuel load. Out in the sticks is best, but just
not downtown!
- 1. After waiting the necessary time
for the solvent vapors to dissipate, now you can test the ignition
device. Depressing the plunger briskly should produce a good spark to
jump across the screw threads. If all connections were made correctly
and the gap is about 1/4" it should spark every time (or at least 9
times out of 10). If it doesn't check your connections, maybe set the
gap a little closer (never less than 1/8") but get it to work, or
potatoes are going nowhere (unless you throw them--boring!) - 2.
When a reliable spark is verified, test fit the threaded plug into the
adapter. It shold engage the threads at LEAST TWO TURNS. If not, check
for crud in the threads, and if clear, obtain a 60deg triangle diamond
file, and size down the plug threads a little. The threads are at a
60deg angle, so careful filing about the first few threads is ok. - 3.
With the cap off, load a potato! With the chamber on the ground, place
a potato over the muzzle of the launcher, and press it down with your
palm, shaving off the excess, creating a cylindrical potato plug. Make
sure the potato contacts the wall firmly all around, or it will not
fire or not that well. Loading the potato sideways is acceptable, as it
creates a more stable projectile anyway. Ram the potato down to within
2" of the breech of the barrel, using a smaller diameter PVC pipe or
broomstick. Don't push it too far or it will fall out into the
chamber...and just be subject to a short baking cycle. - 4.
With the spud firmly seated in the breech, pick up the launcher and
holding with one hand, dispense a few seconds of hairspray directly
into the chamber. Don't use too much; it will just make a mess. Quickly
close by screwing on the end cap hand tight, do not use a tool to
tighten to two turns or you will likely never get it off again. - 5.
Call out "Fire in the hole!", point the launcher in a safe direction,
and depress the BBQ plunger. That potato you rammed down there should
exit at a quite rapid rate with a sizable report, and depending on
where you aimed and at what angle you pointed, it went anywhere from 6
inches to ~200 yards from the muzzle. Pretty cool. If you clicked the
ignitor a few times and it didn't work, you are not alone, check out my
next section. - 6. If it worked, great! Remove the end cap
(this may require a tool), vent the spent gasses getting a fresh load
of air, and repeat as necessary!
Step 6: Debugging the Launcher
There
are a lot of reasons why your launcher may not be working. First and
foremost NEVER take off the cap and start clicking away at the igniter.
This again has led to human fires and that chemical thermal hair
removal thing again....
Hairspray in cold weather just
does not go well. Too much of the burnable stuff in the spray condenses
on the chamber walls, making it very difficult to burn. You might try
warming the chamber by the fire if you are camping or graduate to a
lighter, hotter fuel (propane....)
To 'defuse' a
misfire you need to take off the cap, while pointing it in a safe
direction. Allow the chamber to air out for several minutes, perhaps
longer, to get the fuel load out. After you are certain the fuel has
been vented, again verify the spark, just by turning the chamber enough
so you can see where the spark should be. Never point the chamber bore
directly at your face, or body, or anybody else. If it sparks then it
is a fuel mixture problem.
One of the most common fuel
problems leading to misfire is too much fuel! Not usually a problem
with hairspray, other richer fuels can be overloaded above their UEL
value, and they wont work. Always try less fuel rather than more fuel.
If
you still can't get it to work I invite you to peruse the many other
web sites that talk about how to troubleshoot your combustion launcher.
Again I have made a partial list, and sadly just don't have the time to
address every specific person to person launcher complication. I hope
you do in fact figure it out and experience many hours of safe
spudding.
DisclaimerAs with most other sites with cool and/or dangerous stuff, here we go. I'm not a lawyer, but take heed:
You view and interpret material from this web site SOLELY AT YOUR OWN RISK.
You
release ALL ENTITIES IN THE UNIVERSE, save yourself, from liability
from any occurrence as a direct or indirect result from material or
merchandise viewed, attempted, communicated, purchased, or otherwise
interpreted from this web site and/or domain. The communicative
material within this site is presented primarily for educational and
entertainment purposes only.
It should also
be understood that the use of plastic water pipe (PVC, ABS, or any
other) for spudguns is one of the MOST WRONG things you can do with the
pipe. Accidents are very rare however, as most people
follow generally accepted safe practices through proper solvent
welding, conservative fuel usage, and using only potatoes for
projectiles. Using 'high power' fuels such as acetylene and/or nitrous
oxide or pure oxygen as oxidizers is highly discouraged, especially in
plastic spudguns. Low environmental temperatures (below freezing) also
makes plastic pipe far more brittle, so accidents happen more
frequently in colder air.
Hey, have fun, play it safe, and if you have a question about something, ask someone before trying it.
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