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March 2001
April 2001
May 2001
March 5, 2001
I have decided to patch up the sparker hole and spend 15 bucks (hopefully from the SRDF Fund) on a good igniter. Hopefully I can patch it with just heating up a piece of the ABS and molding it into a strip to glue over the hole.
Things to try (from the Pyro's diary) (http://www.armory.com/~spcecdt/text/doap.14.html): denatured alcohol as a fuel, and a funky design ( in the above URL ).
I no longer fire my gun in the city.
April 15, 2001
Success!!! The day before yesterday I installed a lighter- a real one from Home Hardware for a BBQ, and the SRDF (Starch Resource Deployment Facilitator) fund paid for it, the fund is part of the demonmoo army. Unfortunately the fund is now closed. I installed it by putting two screws into the chamber and attaching the electrodes to the screw heads. That way I could put the lighter wherever it was handy to push and it is more reliable. I also put a screw in to keep the potato from falling into the chamber. I went into Hardwood lake for the day yesterday and walked in for about an hour because the logging trucks there are ripping up the road so much it is no longer passable in spots by car. At first the gun didn't work but then I put in 5 squirts of ether and it went, really loud. We met the neighbors on the way up there and he seemed like a nice guy so I didn't want to bother him and went to the creek, which is in like a valley. Here are some things I learned on the trip.
Propane
First it didn't work but then I did some experimenting and found that if I make sure there is nothing but air in the chamber and hold the Propane can so that the container is to the side of the chamber and the nozzle of the can is about touching the bottom of the chamber, then open the nozzle for about 1-1.5 seconds (start with one second, then add more if you need to) with a potato in it will work after 20-30 seconds with 80-90 percent reliability, may be more. Unfortunately there is some skill involved, and I would prefer to use syringes. If I lose the knack of putting in the fuel, I have to try to put propane in little by little, starting with a small amount and working my way up, same with ether. If there is no potato, you may have to put more in. Holding the can of propane at the right angle is important because that way it sounds different, a harder hissing sound, almost a bubble because there is some liquid propane coming out. Keep the gun horizontal when fueling, that way the fuel doesn't run out or anything, since it's heavier than air. If it still doesn't work, add more. If you think you've added to much, turn the torch on low so only the gas is coming out, put it into the chamber and light it (be careful) to burn the propane in the chamber. Then hold the gun so that the hot exhaust gases escape and go up, out of the chamber. If there is a potato in it, blow into the chamber so that you can smell only the fresh smell of that Awesome Black Stuff, ABS. If there is no potato, hold the gun as close to vertical as practical and blow five times into the barrel to air it out. You should smell only ABS. Then start again.
If you want to get the potato out for any reason, push it out as far as you can with the push stick then spin the gun by the chamber to make centrifugal pull out the potato. For this to work, obviously you can't stick the potato in too hard.
Ether
You actually need a lot of this stuff, that surprised me. Spray three times for a total of about 1.5, maybe 2 seconds with your finger, not tapping it. You may want to start low and add more. You should be able to smell strong ether fumes (don't smell them too much!). I have only tried this without potatoes so you may want to add less. One method I had success with for a dry fire with was putting about two squirts in the chamber and one bigger one down the barrel, this worked rather well but of course won't work with a potato. I haven't tried putting it in this way then putting a potato in. I also found out that you can ignite sap, like from pine cones jut by firing at them at close range. I haven't practiced as much with using ether so it's not as reliable to me as propane. Use the same tactics as propane to burn up the stuff inside and start over if you need to.
FINALLY
If it works, say a prayer of thanks to the potato gun gods and even if it doesn't, say a prayer anyways, asking for it to work next time.
I also threw together a smaller gun with some scraps I found around the shop, it almost always gives a reaction, so it's not boring but I'm not sure if it would ever fire a potato well, it was just for fun, I was bored.
Yesterday, We went recruiting for the Demonmoo Army and found a potential recruit and one almost definite one and one dud. We went to Davy's field and fiddled around for a bit and showed the new potential citizens spudguns. I brought the gun I made when I was bored, now dubbed "the noise maker". We also had a short demonmoo meeting. Today, however, I had great success with spudding again when we went to Hardwood lake. The roads are drier and better now, we got in most of the way with the car until snow stopped us and we walked the rest of the way. There were people who stared at us from their dock but they didn't bother us otherwise. I found out when I fire the potato into the water it shreds it into bite sized pieces for the fish. My friend's gun worked OK and he lit a fire by the water and we shot at it to put it out. I hit it and scattered it into the lake. I also found that rocks go farther than potatoes, with a potato backing, at least usually. We also had car trouble and I think dad blew a head gasket, that's what he said, which did stuff to the coolant which I won't detail here. We didn't have much time there (left ~12:10 came back ~5:30.) and we had to walk in part of the way so I didn't do much experimenting. When I got back I did one shot and found out that 160cc works rather well. I just did some more testing and found that even 100 to 240cc works. At 240 it didn't work the first two times I clicked the lighter but the third time it did and wasn't exactly quiet. I can't get it to burn rich and quiet so unless I can find a good way to measure ether, I still can't fire it in the city. I wish the neighbor wasn't so bitchy, then I could do some more experimenting but I'm afraid she'll call the police. Looking back at the experiments in the table, I have come to the conclusion that a good sparker is a necessity. I suppose I should just build a smaller gun. It was windy too, at hardwood lake, so I didn't have to air it out every time, just hold it the direction of the wind, it gives more oxygen too since it's not your breath.
I just fiddled today, putting propane in an apple juice can and in a beer can and lighting it. Neither worked great except when I let the apple juice can sit for along time then put in 60cc of propane. It didn't blow up the can but it bent it out of shape. My dad showed me that Canadian Tire sells cans of oxygen in exactly the same kind of can as propane, I'll try to get some tomorrow (Monday). I just found out that oxygen is under a lot more pressure (~5 atmospheres vs. ~40 atmospheres) so I probably won't be able to use a propane regulator thing on it.
Yesterday (Friday) we (Demonmoo) went down to Martins Field and did stuff after school but my small gun wasn't ready yet. I saw Jake's gun, which is two lengths of 2 inch pipe joined to a y joint then the barrel attached to one piece of the 2 inch pipe. He put the Coleman flint twist lighter into the dead end on the y joint and put in a drainage plug so that he could take out the lighter and replace the flint The lighter was attached to the drainage plug. A "drainage plug" is just the screw on cap for the ABS gun but since it's used in plumbing for draining the pipes, that's what it's called. His gun also has changeable barrels but I didn't see them. It was really quiet and I was wondering why but from today's experiences I think it's just because it has so little power, and it didn't go far either I suspect that the flint lighter promotes slow combustion. Pat also "fixed" my lighter by making the gas flow much lighter. It could be good or not.
Today I finished the gun. I turned that little "noise maker" into a real gun by putting a sparker in, plugging up the whole in the side and getting an end cap for it. I also replaced the duct tape that held on the barrel with the flex-joint reducer. The gun now has a really long 1/2" barrel and a shorter, 3/4" barrel. When I showed a friend the longer barrel we fired The gun with 30cc of propane and a rubber bullet made from some rubber tube with the whole plugged and a screw in the end like a dart. It went through a cardboard box and was really quiet. Later we took it down to the field (it disassembles too) and fired potatoes out of it. It didn't work very well with potatoes. It could be because of the friction of the long, corroded barrel or it could be, as dad said, when it explodes, the potato bulges out, jamming it in the barrel and making more friction. I thought that maybe the barrel is too small (diameter) and restricts the gas flow too much. That would explain Jake's gun as well since he had a small barrel too. When I got back I tried it again with the large barrel and found that it makes a much louder bang which may mean that it is more powerful, I can hope. Another way to look at it is that you can only get so much energy out of 30cc of propane. Next time we go spudding, I'll bring the shorter, wider barrel. I also found out that if you almost light the lighter (the "fixed" one) but don't make a spark a few times, the chamber fills with butane which burns up when you make a spark. Butane seems to burn hotter that propane. I just went and did some experiments with propane in a mortar like thing. I took the chamber of the small gun and just filled it with 40cc of propane and put the end cap on and light it with the sparker. I bet if you put a potato in it would launch it a fair distance, something else to try. Something strange I found was when I tried the mortar by not putting the end cap ( so it's just an ABS tube with a sparker) on and just holding the end against the table and it is much quieter for some reason, it doesn't make a rattling noise as with the end cap. First I thought the end cap was loose but it wasn't. Another mystery. I also tried it without either end blocked up and it just comes out both ends without making much noise.
I've been trying to make a silencer for the smaller guns since Jake got arrested. Here are some details about the smaller gun I mentioned before: The chamber is made with some leftover 2" pipe and some copper pipe, a 2' to 1.5" flex reducer (those rubber reducers) and an end cap for the two inch (abs) pipe. The only part I had to buy was the end cap for about three dollars at Canadian Tire the end cap was one where it doesn't fit over the 2" pipe but the outside diameter of it is the same as the pipe. I needed a regular coupler piece for a 2" pipe and you attach the end cap with that. I used half of a 2" coupler to plug the hole in the side of the chamber (the chamber used to be that of the "noise maker". The sparker is the actual piezoelectric sparker I took out of a gas match, the one I replaced in the large gun with a real barbeque lighter. so...
Small Combustion Gun
Since I don't know what some of the parts cost, and they were free for me, I'll put Free as the price.
End cap $3
2 couplers $1.38
2 to 1.5" flex reducer Free
2" pipe(16") Free
3/4" copper pipe(23") Free
Barbeque sparker (butane) Free (otherwise $2)
Total: $4.38
You may wonder how I attached a 3/4" pipe (and a 1/2" one) to the 1.5" end of
the flex reducer. I made two wooden circles as round as I could since I don't
have any machines to make them with, I just used a chisel. You can make them out
of any wood you want. Since I needed to make mine as circle with a chisel, I cut
about 1 and a half inch slices off the end grain of some basswood and redwood.
One has an outside diameter to fit into the 2" inch pipe and the other has an
outside diameter to fit into the 1.5" part of the reducer. Both have a 3/4 (or
1/2") inch hole in the middle. I attached them to the barrel as such: the barrel
is the stick in the middle and the two other lines are the pieces of wood.
The 1.5" piece of wood is the one to hold the barrel in place and the other one is just to keep the barrel straight in relation to the chamber. Put them about like in the picture and glue them in place with a hot glue gun.
Then slide the reducer over the end of the barrel and attach it to the gun with the reducer. Since the flex reducer is held on with hose clamps, you can take it off and have interchangeable barrels too. Stick on the end cap and put two screws into the chamber to attach the electrodes to from the sparker. Adjust the screws for the sparker until it goes every time. You're gun should look about like in the diagram.
Click for a larger image.
The gun takes about 30cc of propane once it is warmed up if you're firing it for the first time or will let it cool down for some reason, just put in about 45cc of propane, until it is warmed up. You could put in 45cc all the time but it won't burn as fast as 30cc. You might want to put a strap on for carrying or just collapse it and put it in a backpack.
To air it out, I just swing it round by the barrel about five times or if there isn't enough space, blow into the barrel about three times, with the end cap off of course, hold the gun with the chamber pointing up so the hot gasses can escape more easily. Attach the sparker any way you want, I haven't found a good way to do it yet. Most sparkers have crappy insulation on the wires and you have to not touch them or it will just zap you instead of the inside of the chamber. The sparker you extracted from the lighter will probably only have one wire attached to it. There should be another metal piece of some sort on the sparker and you can attach the second wire here to make the spark jump across the wires. This gun is still loud, you might not want to fire it in the city.
Yesterday, I went up to hardwood lake and took both the small and large combustion gun. With the big gun, I found that if you don't put a potato in, about 220cc makes an earth-shattering boom but with a potato in it hardly goes, with a potato put in about 150cc for good performance. You could still fine tune the amount to put in but 150 cc works great. I want to replace the silencer on it since it's getting pretty beat up. I might try different things like the three inch pipe for the outer covering instead of plastic sheet. I might just leave it off completely, or make a removable one. When I put a potato and all sorts of scraps in, when I fired it, the part where I plugged the hole in the side of the chamber up with came off. It didn't blow off but it cracked and came off easily afterwards. I guess the glue failed, I might try gluing it back on and putting a hose clamp on too. One cool shot I tried was going right up to a beer bottle and shooting it at about one foot range with a potato. It shatters the bottle and throws pieces about 15 feet. It's very cool but I don't think I'll try it again, since flying glass isn't much fun if you get hit.
I practiced target shooting with the smaller gun and got OK aim. I may want to fix the barrel, which is crooked because of the bad job I did on the wood ring things.
My dad mentioned something about a place to fire the guns near Burrits Rapids, the Ottawa Carleton Forest or something.
Today
I just tried putting a 3 foot long piece of 1.5" pipe for the barrel of the smaller combustion gun. It may work pretty good for launching potatoes, I put in 90cc of propane and it gave a large boom, and it vibrates the barrel too, sounding cool I don't want to try any more because it might be louder. Then I tried it simulating a potato in the barrel with a piece of tin foil between the barrel and the chamber, put in 45cc of propane and it made a slightly larger boom.
I just tried duct taping a ten foot long piece of 1" metal pipe on for a barrel and it makes a very large bang with 45cc of propane. The story of the guy with the 18 foot (I think) gun who fired golf balls over a mile and then blew his fingers off came to mind.
I was doing some experiments with a silencer and I tried stuffing up one end of a pipe with rags and the other end too with just enough room for the barrel. Basically I shot into a tube with rags stuffed into each end. I used a 4" carpet tube and then a 3" ABS tube, about 10 " long. It is very quiet, you can hardly heard it and the rags come out when the gun is fired, The thing is of course, you still have to get the potato out and I wonder if it would greatly effect the power of the gun. Still, a silencer that comes apart each time, and is easy to put back together gain, may be the answer. Maybe I could just duct-tape the fabric in and it would still work.
Yesterday, I did some experiments with a cardboard silencer and they worked out really well. On the 3/4 inch barrel, I rolled up a piece of corrugated cardboard the same length as the barrel, about 19". That way it fits into my backpack while giving the most silencing. The longer the silencer the quieter it is. Here is how I made it:
-Take a piece of 19" long by 16" cardboard (along the corrugations), or however big you want just remember the bigger, the quieter. I haven't experimented with the width of the silencer. Remember my silencer is as long as the gun barrel. The piece can have a damaged part on it where the flap of the box folded but I assume it would be better if it didn't (mine has the damaged part).
- take your barrel and roll the cardboard around it, tightly. Then duct tape the silencer to itself so it doesn't unroll. Be generous with the tape.
- Find a nail about 1/4 inch in diameter that isn't twisted or anything and cut the head off. This will be your drill piece. This is important, a regular twist bit will rip up the cardboard too much and the projectile will get stuck in the middle of the silencer.
- Drill at least 3, maybe 4 rows of holes, lengthwise along the silencer. Make them about 1 inch or a bit less apart for each hole. For the rows, distance each so that they are evenly spread out and drill them so that the drill bit passes through the hole in the middle of the silencer. The more holes, the quieter. I haven't experimented with different sized holes.
- Find a hose clamp and put the silencer on the gun, just slip the end of the barrel into the hole in the middle about 2 or 3 inches. Now take the hose clamp and tighten on the part of the cardboard that is around the barrel to make the silencer stay on better.
- You should be able to easily take the silencer off for loading, just pull on it.
- My silencer attached to my barrel looks about like this:
The first few times I fired it, the sound is very deceiving, you hear this little fwump and the potato flies away at very near normal speed. Now I can have fun firing it in the city, finally.
I learned another lesson yesterday. I already had it happen once but I learned not to stuff all sorts of stuff down the barrel. One potato is enough. I stuffed a potato, lengthwise so it was about a 4" slug and then stuffed down wet leaves. The gun blew the barrel off, where the rubber flex piece holds it on. You may recall the time I did about the same thing with the bigger gun.
This long weekend, I am going up to a camp out of the city to fire the potato gun. I have to pack my stuff and thought it would be convenient if I just made a checklist for future outings as well.
syringes
small gun-all 5 parts (both barrels, chamber and 2 silencers)
large gun
propane, rubber piece for propane measuring device
stuff sticks - 3
ammo
a lighter
possibly ether
screwdriver
duct tape
pliers
earmuffs?
**Editors note: From here on, it's mostly more about pyrotechnics than spudguns, that's just the way my interest shifted.
I tried stuff that wasn't really about spudguns but Making smoke bombs, using a coffee grinder to grind up the powders really fine and not melting the powders. I tried magnesium powder mixed with the smoke bomb and it works great, lots of bright flashes. I want to try copper to get a green light now. Putting copper dust in the smoke bomb doesn't produce green, it slows down the burning. It doesn't produce green when mixed with magnesium either. The formula for a smoke bomb is about 3 parts potassium nitrate and 2 parts sugar, use confectioners sugar since it's finer.
Fuse: add some flour to smoke bomb- very little
more sugar: slower combustion
more nitrate: incomplete combustion.