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Getting a handle on your cannon

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Getting a handle on your cannon

Unread postAuthor: feral_patriot » Wed Mar 28, 2007 11:38 pm

After seeing the numerous configurations for triggering mechanism/handle set-ups, and questions about how to attach a handle, I’ve decided to share what I came up with for our own spud guns.
You’ll need:
An old drill body
Clay
Regular craft style hot glue gun, nothing special
Masking & electrical tape
A small can of minimal expanding spray foam sealant
Some old newspaper
Dremel or equivalent tool for material removal
Popsicle sticks or the like
A hacksaw
A suitable blowgun nozzle
Hose barb wrapped with a minimum of 6wraps of Teflon tape
A small hose clamp
Hose clamps capable of @ 6” or so, @3, or enough to connect several together
A 6”-8” section of suitable hose
A screwdriver
Now, I’ve managed to find ways to use this method for air as well as combustion. Here, it will be for pneumatic, to keep it simple and since this is just as a tutorial, since once you’ve tried it a few times, you’ll be like a dog with a ball.
I tend to use old cordless drill bodies since I tend to go through them a bit.
First, gut it out and clean the grease, oil, dirt, etc. out of the plastic inner area.
Plug in the hot glue gun and set aside.
Next, take the blower nozzle and attach the prepared hose-barb to it (minus the hose & clamp). Then take the nozzle and try to figure out about where in the area of the drills trigger cut-out area the nozzle will lay while still providing enough room to activate the button/lever as a squeezeable trigger mechanism once it is mounted solidly in the handle. Once you get a good idea of that get your dremel set up for material removal (I use a coarse sanding drum), and start removing the appropriate plastic dividing/support fins from either handle side to allow the blow nozzle to be set where-ever you decide is best.
You may have to grind away screw hole poles in order to fit your nozzle, don’t worry about it. Sometimes it is necessary to attach the hose in order to get the proper angle set of the nozzle.
Now take your blow nozzle and cut off the end of it so that it will not protrude up into the motor cavity of the drill handle sand it smooth, and round the edges a bit, then put some masking tape over the entire end, covering the hole.
Now, using the hot glue gun you can position the blower where it needs to be and squirt dabs of glue strategically around the nozzle (on one side if possible) while holding the two handle sides together with the hose out the bottom.
It may be helpful to temporarily tape the sides together with a wrap or so of masking tape while setting the proper position.
If and when you are satisfied that your glue dabs you’ve shot into the cavity will hold the nozzle, take the tape off and separate the handle halves. Once separated, squirt some glue around the base area at the hose point to prevent movement when the foam you’re about to squirt in to the handle doesn’t move your blower
out of position.
Don’t get carried away with the glue, as there needs to be ample space for the foam to sneak through and do its job.
Once you’re satisfied that everything will stay in place, tape the two handles together with electrical tape sufficiently enough to hold the handles together as though they were screwed together. If there are any areas where screws can be put back in and be effective, go ahead and put them back in now.
Fill any small vent holes with some hot glue, you can pry it out later if you desire.
At this point, hold the handle in your hand and look down either side of it as if you were holding a gun out in front of you. What you are looking for is approximately where you are going to cut down each side of it to create kind of a trough for the PVC to sit into much like a barrel on a rifle. As you’re looking down it as though siting in on a target, you’ll be cutting the side and back down low; perhaps to the lower 1/3 of a circle, and more-so out of the front and back. You’ll also be using the grinder to remove material inside this area to help the chamber to sit down inside. When you are satisfied with how the PVC and the handle fit together put masking tape (do not use any type of clear tapes) on the PVC in a linear fashion so as to create an apron all around where the handle meets the chamber.
Next, take some clay and form a ball like a big marble and fit that over the taped end of the blow nozzle in such a fashion that it will create an exhaust port forward to the muzzle end at the trigger area.
When done here, tape the opening up so that the foam won’t escape around the blow nozzle trigger/button.
Now, rest the pipe/chamber on the top of your handle and attach the screw clamps in a pattern of three spots, front, middle, and back. Pay close attention to NOT crushing the upper portion of the handle against the PVC. You just want to hold the two parts together to make the “form” for your chamber to sit in the handle.
There may be anywhere from 1/8” up to ¼” of gap in the front &/or the rear of the handle where you’ve ground out material, this is okay.
Now, if you haven’t unwrapped and set up your can of sealant/insulation, do so. Shake it up as necessary, spread out your newspaper, and get your Popsicle sticks.
Turn the handle upside down so the hose points up, stick the straw on the can down, inside the handle and start slowly filling in down as far as the straw will go. After a couple seconds let off the trigger and pull the straw out. Stick it back in at the front and rear of the chamber trough if no foam has shown up here yet. Fill a bit if needed. Go back up to the hose end, check the progress, and fill as needed.
A bit of over-fill is to be expected, don’t worry about it. Clean off the excess with the Popsicle sticks. As the foam sets up and cures, more foam will leach out. Be AWARE of what the foam is doing, it can get away from you and make for a big mess; and it will NEVER come out of your clothes. TAKE YOUR TIME WITH THE FOAM.
Once you’ve filled it and left at least an inch down from the butt end of the handle, set the project aside, hose pointed up into the air in a warm place to cure at least overnight. Look in on it occasionally to clean up any excessive over-foaming. It is okay to let it leak out an inch or so along the trough area, and little knobs of it here and there, as well as maybe @ a 1”-2” bulge around the hose (sometimes I trim at the hose, sometimes not).
The next day, trim off all the excess cured foam and GENTLY break away the handle from the PVC after removing the screw-clamps. The masking tape apron can be peeled off the PVC, clean up any residual glue that the heat of the curing foam may have caused to get tackier.
Untape the trigger area, pry out the hot glue from the vent ports if you want to, and clean out the clay & masking tape from your nozzle exhaust area.
Now you have a pneumatic trigger handle assembly that can be transferred to different launchers or left on one. The short section of hose allows for a male hose barb for a multitude of possible connection variants... I tend to install a mini ball valve so as to have a very effective safety, that way if the lever/button gets squeezed accidentally at an inopportune time nobody gets hurt.
This method of foaming up is the very same thing done with prosthetic limbs, only the foam there is mixed a bit stronger,but essentially the same formula. I’d have never have thought of this if I hadn’t taken a course in Prosthetics a few years ago.
I have some pics and am currently trying to get them to load onto this post...going on second attempt, tonight.
Also, these will be of my most recent spud gun( I build several a year). For some strange reason people see how I put these together with the handle and they're like little kids after that toy they gotta have before Momma can leave the store!
I'm gonna try to give y'all the url for the pics on this.... http://new.photos.yahoo.com/dawnjerrene/albums
My wife setup the photos and all, so I'm hoping you can scroll through them and see what you think. Feel free to leave comments there or, preferably here.
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Last edited by feral_patriot on Thu Mar 29, 2007 3:58 am, edited 2 times in total.

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Unread postAuthor: trae08 » Wed Mar 28, 2007 11:43 pm

just do with the picture source inbetween. nice how to tho
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Unread postAuthor: feral_patriot » Fri Mar 30, 2007 8:44 pm

Thank you for the heads-up on what to do; unfortunately, though we tried to do that, our 'puter argued with us and we lost. Again.
So, we did manage to get a URL thingy on the post that did take me back to some old family pics site where we posted the pics for this project.
On another note,THANK YOU for being the one person to give me some kind of feedback @ my post... 54 other people must of been afraid to say anything; at least they looked, though. :)
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