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Thomas Builds His Marshmallow Launcher
In this episode Thomas decides the only way to defeat the
evil Dragamont is to build a powerful marshmallow launcher.
He wanted something that looked safe enough for little kids.
He wanted something that would pack enough punch to scare
away a hormone crazed teenager. And, since the math works
out easier that way, he wanted more than one.
His team needs at least three launchers. Dragamont is a
powerful foe and we'll take Colin Powell's advice and make
sure we have enough people and firepower to do the job.
Thomas needs about $20 for his share of the kit. He rides
his bicycle to the cool tractor store with his list of parts.
Parts List For Launcher
Some things money can't buy. This marshmallow launcher
is one of them - you have to build it. But, money is needed
to buy the parts. Truth is hard to calculate...
Things To Buy For Some Launchers
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(3) one inch pressure rated ball valves $15.00
(3) Schrader valves (like in bike tires) $ 9.00
(1) one inch 10ft long PVC pipe pressure rated $ 5.00
(4) one inch end caps for above pipe $ 1.00
PVC primer and cement $10.00
Epoxy glue (for Schrader valves) $2.00
Bike pump (one can be shared) $15.00
Large size marshmallows (also can be shared) $ 3.00
-----------------------------------------------------
Enough parts to make THREE launchers $60.00
Why Did You Pick Those Parts?
Thomas knows that a Schrader valve is used on bike tires and
car tires (his dad told him). You see one every time you check
the air or pump up the tires. The ones with metal threads
designed to be screwed into something work best. We found
that tractor stores were more likely to have this part than
home improvement stores.
The one inch inside diameter pressure rated PVC pipe does
not cost much. Thomas thinks it's a good deal. Make sure you
get pressure rated pipe! Each piece is so darn long that it
does not fit into the car without sticking out the window!
Thomas knows to bring a saw because his dad forgot and
looked funny driving home with a pipe sticking out the window.
The one inch ball valve is bigger and heavier and more
expensive than expected but it should do the job. The valve
is a bit stiff and may be hard to operate for some people.
Thomas is worried about this but it's hard to explain in
words what you think.
The end caps are not expensive so we get an extra one. They
will get drilled for the Schrader valve. With an extra cap, one
"hole drilled too large" error is fixable. Thomas knows people
make mistakes when learning new things.
Making The Launcher
After each drilling or sawing step, cleanup the plastic junk from
around the cut. Good work habits make good projects. Thomas
is wise and already knows the value of brushing your teeth.
Thomas used a drill to make the hole in the PVC end cap for
the Schrader valve. Then he used pliers to "screw" the metal
valve into the plastic end. Finally he applied epoxy to the inside
and outside to make sure it holds real good. He should be
able to hang 150 lbs from the valve without it pulling out
of the plastic. (Thomas is careful not to mess up the inside
of the cap where a long piece of one inch PVC pipe will
go in a later step)
Drilling the right size hole and getting the valve threaded into
the end cap and well glued is the most difficult part of making
the launcher. If at first you don't succeed, throw away the
plastic end cap and try another one. We have an extra one.
Thomas feels there's a better way than having a valve sticking
out from the end of the pipe where it might get hit.
The barrel and air chamber are two pieces of pipe with a
one inch inside diameter. Thomas knows that's about the
right size for a marshmallow. Almost any saw can be used
to cut the PCV pipe to length. A baby could do this.
He made the air chamber about 26" and the barrel about 10".
Others have done the exact opposite. These numbers came
from inspired thinking during a football game and have no
mathematical basis. It worked and that means something.
Thomas gets a puzzled look on his face. He wonders what
really works best.
The end cap with the Schrader valve goes on one end of the
air chamber. The ball valve goes in the middle and connects
the other end of the air chamber to the the barrel. Duh.
The pressure rated PVC pipe takes a purple primer before the
cement to make a high-quality connection. There is enough
glue in each can to make a small house. We will have plenty.
Get together all the parts and fit them together before applying
the primer/glue. This is called "dry assembly". Thomas makes
sure all the parts fit together before opening the glue.
Gluing PVC is pretty simple but make sure you have good
ventilation as the purple primer and cement have quite a smell.
This is a "welding" process as the solvent melts the PCV pipe
into one solid piece. A little primer first then glue all surfaces.
Push glued parts together with a quarter twist. It's easy.
Leave it alone. Let the connection grow strong. Everybody
wants to try the gun on day one. Thomas says to get a good
glue connection you have to wait until day two. He waits.
Using The Launcher
Strategy: Keep face and fingers the way mom likes them.
Tactic: close valve - insert marshmallow - then pump it up.
Thomas found that the stiff ball valve was too hard for some
team members (including himself). The solution was to bolt
a wooden "extender handle" onto the regular valve handle.
Quite a bit of extra work but one more problem was solved!
Big size marshmallows can be used. Thomas says this
launcher solves a common problem. When you make
some-mores the chocolate candy bars go quickly. The
graham crackers are individually packed and can be
saved for breakfast. But, those pesky marshmallows
must be removed from the area ASAP! This launcher
will get them LONG GONE - with style.
Dried marshmallows can be rolled in your hands so they
will fit down the tube. A sticky marshmallow stuck in the
barrel could mean victory for the evil Dragamont. Keep
your "powdered marshmallow" dry.
Any bike pump can be used to pressurize the chamber.
A gauge can be used to calibrate distance. Making a chart
listing number of pump strokes vs distance is even better.
The launcher should be good for 100PSI and inexpensive
bike tire pumps can't create much more pressure than that.
Start with two or three pumps and go from there. Thomas
likes the idea of starting slowly.
Now it's time to close the ball valve and pump up the device.
Warning: Once the device is pressurized it's dangerous!
Whenever the valve is closed (handle goes across the pipe) it
might be under pressure! Point in safe direction until the valve
is back in the open position (handle in-line with pipe).
"Point it in a safe direction." Thomas will do his best to make
sure all team members realize this is important. No injuries.
The evil Dragamont has been seen over there. It's November
and Thomas is NOT willing to wait until spring for a test launch.
Let's send something white and yummy over by those trees.
WOW! It made a noise and a puff and the marshmallow
went really far! It took a while for Thomas to find that white
marshmallow with all the white snow on the ground.
About 100 feet seems typical. That's pretty good when you
think about how far you could THROW a marshmallow.
There is enough force to go thru foam or paper at ten feet.
Once you have seen a good shot, you will respect the power
of this launching device.
Thomas finds this project fun and easy to build. It may even
demonstrate some scientific or nutritional principle. Will it
be powerful force for the side of good? He is now ready to
get the team and try another "test" - this time on Dragamont!
Design Considerations From Dad:
Building an explosion based launcher like a SpudGun
sounded interesting but was maybe too much for
(anybody/small kids/me). It seemed worthwhile to
avoid any flaming spray that would be hard to explain
to mom. Even after entering the hardware store, the
project was simplified to keep cost down and
reliability up. (Still, could be better...)
The downside of a pressure chamber is that it's bigger and a
ball valve trigger is needed instead of a little spark. This bike
pump based project is powerful. I was surprised how much
force was in the pressure chamber. Take it easy. Have fun.
Store the launcher with the Schrader valve pointing up.
This wonderful project was inspired by:
Boy Scout Troop 765
A Spark SpudGun
Britney's Guide to Physics
Many other spudgun sites and movies...
 
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Project Done In November 2006 (Picture resolution goal 480w x 240h)
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