Spud cannons?

wbarnhill

wbarnhill

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I was wondering if anyone has built a spud cannon before, and their experiences with best choice of piping, pressure, etc.

Anyone? :D
 
I've only ever built a small one, but I've known a few friends who have done some crazy stuff with them. With normal fuel PVC is fine, but if you're going to work with more advanced stuff you want to get some kind of metal combustion chamber. I know a guy who tried to use some welding O2 and blew his up. I think it works better if you have a separate combustion chamber and barrel.

The other thing I've seen that's neat is an electric ignition. One guy I know used a gas grill lighter. One more inventive friend got a taser, took it apart, and used it for remote ignition. This is why he didn't die when his gun blew up after the O2 experiment.

Many people tend to forget that air is also required for combustion. We used an old bicycle tire pump to get some air in there, and air compressor is much less work if you've got one.

Many people use hairspray as fuel, I'm more a fan of brake cleaner. I've heard bug spray works alright, but I've never seen it done. As i said, be careful with anything more potent.

Now that I re-read your original post, it seems like you might be interested in an air-powered cannon rather than combustion. I've never tried one of those, just seen it done on Mythbusters.
 
4' long 4" PVC with a piece of 3/4" x 2.5" as a nipple at the closed end. Use a screw on end cap as oppossed to a slide on as the later will not hold during launch.
Or, for more specific instructions refer to: http://www.spudtech.com/
 
bluesky74656 said:
Now that I re-read your original post, it seems like you might be interested in an air-powered cannon rather than combustion. I've never tried one of those, just seen it done on Mythbusters.
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Yeah, I'm wanting to stay away from combustion, just in case. :D
 
I didn't build a spud cannon but I did built a tiny cannon out of one-inch steel pipe that shot marbles. A few firecrackers were used as propellant. It worked great!
 
KennyFlys said:
I didn't build a spud cannon but I did built a tiny cannon out of one-inch steel pipe that shot marbles. A few firecrackers were used as propellant. It worked great!
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Don't upgrade the propellant to cherry bombs. :hairraise::hairraise:

-Skip
 
My Brother used to work building rose floats for Cal Poly. They has this old cas cylinder (can't remember the size of it) that was out of hydro. The thing had an ID about the size of a coke can. So some brilliant engineer decided to cut off the bottom, attached an acetelyne fitting on the bottom, and plugged in a can of frosen water with enough tape to make a tight fit.

Fill the thing with enough Acetelyne until it goes off by itself, and voila. Instant Carbide cannon :hairraise:

Pete
 
I made a smaller potato gun by taking a 2' piece of 4" PVC pipe and reducing it to 2", add a 2' piece of 2" PVC. At the other end use a Y pipe and cap the end. On the other opening add a screw type pug that you can remove. Drill a small hole in the pipe near the Y and add a push button striker from a gas grill. Shove the potato down the 2" pipe until it is neat the reducer. Unscrew the cap add a fair amount of WD40 and replace cap. Point in safe direction and push the striker button. Potato will launch several hundred yards.
 
My big gun:
the power
the size

Dual combustion chambers, each 4" x 2.5'. Total of about 9 feet tall, mounted on a trailer using Right Gaurd as a propellant and a grill ignitor. It would recoil about 5 feet if we didn't anchor it. It has long since blown up (about a year ago).

I've built some others, I want to try to top the gun I posted with a massive air cannon.
 
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More to come, I've got one that uses compressed air, and I can get about 400 yards distance at a 45 degree angle....
 
wbarnhill said:
I was wondering if anyone has built a spud cannon before, and their experiences with best choice of piping, pressure, etc.

Anyone? :D
Click to expand...

Hot water PVC, Aqua Net hairspray and a BBQ lighter. If you really want to get trick, PM me and I'll tell you how to make it strong enough for Oxy & Acetylene or Propane, caution, extremely hazardous, but you can rock with this one.
 
High school physics teacher had a cannon in the classroom. A short length (< 1 foot) of steel pipe with a spark plug welded in one end. Quick shot of natural gas from the spigot on his desk, then shove a cork in the end of it. 15 kV from a convenient neon light transformer (we used it for lots of things) "to insure ignition" and away it went. First shot punched a hole in the ceiling. The cork was tethered with a length of telephone cord from then on. Ah, the 1960s. A teacher could get arrested for the stuff we enjoyed back then.
 
Henning said:
Hot water PVC, Aqua Net hairspray and a BBQ lighter. If you really want to get trick, PM me and I'll tell you how to make it strong enough for Oxy & Acetylene or Propane, caution, extremely hazardous, but you can rock with this one.
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Exactly. Hairspray works great. There are a few other great propellents.

We built one that shot a potato nearly 1/2 mile.
 
Start with a 1"X 24" piece of Iron water pipe, hone the inside with a brake hone until a 1" super ball will fit snugly. Drill a 1/8th hole in the center of a pipe cap and place a cherry bomb fuse thru the hole so the cherry bomb is in the end of the pipe as you screw the cap on the end of the pipe. Jamb a super ball into the pipe all the way to the cherry bomb.

Light it and roll it on to the gym floor during a basket ball game, and bail !
 
NC19143 said:
Start with a 1"X 24" piece of Iron water pipe, hone the inside with a brake hone until a 1" super ball will fit snugly. Drill a 1/8th hole in the center of a pipe cap and place a cherry bomb fuse thru the hole so the cherry bomb is in the end of the pipe as you screw the cap on the end of the pipe. Jamb a super ball into the pipe all the way to the cherry bomb.

Light it and roll it on to the gym floor during a basket ball game, and bail !
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Funny, but I don't think it would be worth the jail time. :D
 
This thread reminds me of the annual barbecue lighting contest that they had at Purdue University some years ago. The object was to see who could get a charcoal grill ready to cook on in the shortest possible time. As I understand it George Goble, a senior systems engineer, has the shortest time on record in the order of 3 seconds. He used 60 pounds of charcoal, a lit cigarette buried in the charcoal as an ignition source and then he poured several gallons of liquid oxygen onto the charcoal. See attached picture. :hairraise:

He used to have all of the details on a web site but I understand that the University made him take it down. It's also my understanding that the local fire department forbid him form doing anything like that again.

Someone else put details up on this site: http://blogs.msdn.com/gzunino/archive/2004/05/23/140092.aspx
 

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Might have something to do with the fact that Lox + Hydrocarbon can become explosive it it doesn't light right away. I beleive that early in the space program someone spilled lox on asphalt. It looked like the LOX evaporated, but instead it permeated the asphalt, and it exploded as a result.

This may be apocryphal, but the mix is definately not very safe.

Pete
 
vontresc said:
Might have something to do with the fact that Lox + Hydrocarbon can become explosive it it doesn't light right away. I beleive that early in the space program someone spilled lox on asphalt. It looked like the LOX evaporated, but instead it permeated the asphalt, and it exploded as a result.

This may be apocryphal, but the mix is definately not very safe.

Pete
Click to expand...

In his description of the event on his original web site he made mention of the fact that you cannot pour the LOX onto the charcoal and then light it. He said it would explode if they had done that. He also said the fire department considered it playing with explosives and forbidding future events for that reason. He did this several times and once using a $1.99 grill from Costco which was disintegrated immediately.
 
Maverick said:
This thread reminds me of the annual barbecue lighting contest that they had at Purdue University some years ago. The object was to see who could get a charcoal grill ready to cook on in the shortest possible time. As I understand it George Goble, a senior systems engineer, has the shortest time on record in the order of 3 seconds. He used 60 pounds of charcoal, a lit cigarette buried in the charcoal as an ignition source and then he poured several gallons of liquid oxygen onto the charcoal. See attached picture. :hairraise:

He used to have all of the details on a web site but I understand that the University made him take it down. It's also my understanding that the local fire department forbid him form doing anything like that again.

Someone else put details up on this site: http://blogs.msdn.com/gzunino/archive/2004/05/23/140092.aspx
Click to expand...

That would work well. I built a BBQ pit for one of the oilfield boats I used to run that had a spreader bar under the coals that I'd hook up to a welding O2 tank. The pit was 20' wide (there were 150 people on this boat) and 3' in diameter, and the coals would be ready to cook on in about 3 minutes from the time I'd first stick the cutting torch in to light the coals. First time I rigged it, people were leaving the deck and going inside...:rofl::rofl::rofl::rofl: wussies....
 
A college roommate and I made "the world's tiniest tater gun" out of some hobby shop brass tubing. At the time, they had just come out with little mini M&Ms candies. We found the right size of tubing, crushed it into an elliptical shape for a nice fit around the M&M, and silver soldered it to a sheet brass combustion chamber. A little electric igniter from a "clicker" grill lighter provided the spark. I was flying R/C helicopters pretty seriously at the time, so some 15% nitromethane heli fuel provided the kick.

That thing never failed us, and it was a lot of fun. I remember that we could take paint off the walls with it. We were such nice, responsible kids - unlike another friend who took a potato gun into the bathroom on the girls floor and blasted huge craters in the stall doors. (My ears are still ringing!)
 
A college roommate and I made "the world's tiniest tater gun" out of some hobby shop brass tubing. At the time, they had just come out with little mini M&Ms candies. We found the right size of tubing, rolled it into an elliptical shape for a nice fit around the M&M, and silver soldered it to a brass combustion chamber. A little electric igniter from a "clicker" grill lighter provided the spark.

I was flying R/C helicopters pretty seriously at the time, so some 15% nitromethane heli fuel provided the kick.

That thing never failed us, and it was a lot of fun. I remember that we could take paint off the walls with it. We were such nice, responsible kids - unlike another friend who took a potato gun into the bathroom on the girls floor and blasted huge craters in the stall doors. (My ears are still ringing!)
 
foka4 said:
- unlike another friend who took a potato gun into the bathroom on the girls floor and blasted huge craters in the stall doors. (My ears are still ringing!)
Click to expand...

I guess I never made the connection, but it was at the same friend's wedding reception a few years later that I remember sending sand-filled aerosol paint cans across a farm field from a little 16" cannon made from high pressure gas pipe. We clocked over 30 seconds of air time with some of the more potent loads ("Heck Andy, just dump in the rest of the powder and see what happens!"), with the 50+ lb. cannon doing several backflips from the recoil.

Those were the days...
 
Henning said:
That would work well. I built a BBQ pit for one of the oilfield boats I used to run that had a spreader bar under the coals that I'd hook up to a welding O2 tank. The pit was 20' wide (there were 150 people on this boat) and 3' in diameter, and the coals would be ready to cook on in about 3 minutes from the time I'd first stick the cutting torch in to light the coals. First time I rigged it, people were leaving the deck and going inside...:rofl::rofl::rofl::rofl: wussies....
Click to expand...

I have an mpeg file of him pouring the LOX onto the charcoal but I couldn't upload it. This site doesn't take mpeg files apparently.
 
foka4 said:
I guess I never made the connection, but it was at the same friend's wedding reception a few years later that I remember sending sand-filled aerosol paint cans across a farm field from a little 16" cannon made from high pressure gas pipe. We clocked over 30 seconds of air time with some of the more potent loads ("Heck Andy, just dump in the rest of the powder and see what happens!"), with the 50+ lb. cannon doing several backflips from the recoil.

Those were the days...
Click to expand...

We had a group in the Civil War Skirmish Association who made a mortar specifically designed to shoot bowling balls. Highly entertaining to watch. And when they stoked it up and put a "try ball" in it you could really hear the wind whistling in the extra holes. :D Wish I had a picture to post, but that was many years ago.
 
Here's a question, a stupid one, but I'd rather double check and look like an idiot than do something stupid and be an idiot.

Let's say I have a line pushing 100PSI. If I attach that line to a container (say a sealed off section of SCH40) will that section max out at 100PSI or will the pressure climb? My mind says it should max out, but I wasn't 100% sure. I want to attach a tank of high pressure air regulated down to 100PSI output to my charging barrel.
 
wbarnhill said:
Here's a question, a stupid one, but I'd rather double check and look like an idiot than do something stupid and be an idiot.

Let's say I have a line pushing 100PSI. If I attach that line to a container (say a sealed off section of SCH40) will that section max out at 100PSI or will the pressure climb? My mind says it should max out, but I wasn't 100% sure. I want to attach a tank of high pressure air regulated down to 100PSI output to my charging barrel.
Click to expand...

Problem is the expansion losses, if you want it to work, you have to be able to deliver the volume of the barrel at the rate you want the projectile to go. I used to hook 3000psi scuba cylinders to a 3" orange launcher, and the small passage in the valve would keep things in check without using a regulator.
 
Please, if you are going to play with pressure, stay away from PVC. You've been told, if you insist you are being the idiot.
 
Richard said:
Please, if you are going to play with pressure, stay away from PVC. You've been told, if you insist you are being the idiot.
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Duly noted. The only way I'd be using PVC is with pressure rated (240PSI or higher) SCH40, but I am looking at other options.
 
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