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12/13/06 Speed test results are posted here
12/12/06 Big Update: Got the new 8' barrel! Using Oxygen/MAPP at atmospheric pressure yielded a 25% increase in maximum range, now reaching almost 1000 feet.
There are a few new cool effects:
- You can hear a distinct "ssssss" whistle of the spud splitting the air. Not a crack (probably nowhere near supersonic yet) but it is a distinctive sound I never hear before.
- Interesting sound effect shooting at a brick building 200' away. Very distinct "POW pow-smack." That is the initial blast (POW), the echo of the blast (pow), then the spud hitting the building (smack). The amount of time between each sound was similar though closer together on the pow-smack, which tells me the spud averaged more than 1/2 the speed of sound. I know we can look at a digitized recording to measure the ms between spikes. Will do this some day.
- At least in the cold, makes a cool momentary white blast fog at the end of the barrel about 3' around and 4' long. Fog disappears instantly.
- A hard-packed snowball exited the barrel as a cloud of snow.
- It is no longer possible to track the path of the fired spud. It vanishes into the distance too quickly to follow. I measured range by watching lake surface for landing spot.
Several minor problems crept up:
- Loud enough now to need hearing protection. Really makes your ears ring.
- Low-flow valve was shooting a small 4" flame before snapping shut. I suspect that oxy/fuel mix was filling the general area of the valve, so for a split second combustion outside the valve was balancing the combustion inside the valve, thus preventing it from snapping shut faster. Was probably losing some potential chamber pressure.
- Weather was cold, around 28 degrees F. I suspect that this robbed huge amounts of combustion pressure by limiting the theoretical adiabatic temperature.
- Cold also caused reduced maximum fuel tank pressure below what is needed to use the fuel meter pipe correctly. Using oxygen greatly increases the amount of fuel that can be used. Ended up using a lower pressure but charging twice.
- Cold makes the heavy clear vinyl fresh air supply hose inflexible. Very difficult to keep it on the blower nipple.
- Plumbing configuration was making the MAPP tank point downhill when the gun was elevated for trajectory. This allowed liquid MAPP into the regulator which caused the regulator to freeze and freely vent raw MAPP gas. Not a nice odor.
- The pulley & counter weight used to support the 8' barrel is a pain in the ascii. It is very effective for supporting the barrel, but you end up constantly trying to reach through the wire. The wire hanging straight down at the back of the gun also interferes with the panning action of the gun mount.
- Starting to get minor spud shredding before exiting the barrel.
What's next: Extreme hybrid mode. Built, but not tested yet. I will fill you in as soon as the weather allows. This just may become the most powerful combustion spud gun on the planet. Sure wish I could find a competition in my area (Northeast US).
- Sealed off low-flow vent with solid hunk of aluminum
- Replaced fresh air check valve with ball valve for perfect seal
- Re-sealed ignition wire hole (was leaking at high chamber pressure)
- Added silicone gasket glop to chamber ends to make perfect seal
- Closing the breech on a piece of very heavy polyethylene makes a nice burst disc that easily holds 30PSI, and double layer should hold even more. Couldn't be simpler! Would like to find a non-hydrocarbon material because polyethylene becomes very flammable in pure oxygen.
- Built much longer remote trigger for added safety during extreme testing.
- Charging will be much different than the old meter pipe method. First fuel will pressurize the whole chamber to say 15PSI, reaching the setpoint of the regulator. Then oxygen will continue to raise the pressure to say 30PSI. This will take a lot of experimentation.
- I will test the anti-materiel destructive potential on various materials with various projectiles.
- Still trying to find a Shooting Chrony to borrow/rent.
- Built a jig for freezing 3" long ice slugs, very uniform in size and shape. Makes 7 at a time. Should be very destructive.
12/02/06 Update: new interior photos
Link to huge photo
All aluminum, breech loading, car ignition. Fuel with any combination of metered air, oxygen, acetylene, MAPP, or propane. Extremely destructive. Extremely loud with acetylene (and safer than you might think). Detailed web page here. Massive pan & tilt tripod is collapsible for transport. These photos are a bit out of date. The fuel system has evolved quite a bit over the past year and the gun is much cooler looking now. Built 8' barrel but have not tried it out yet.
My friend Jason demolishing a picnic table using air/MAPP.
Link to animated breech action
Last edited by Dumbascii on Wed Dec 13, 2006 5:37 pm, edited 4 times in total.
wow. some of the nicest, most quality work I've seen. try shooting through 1/8 inch aluninim, and steel. has it been chronographed? how fast was it?
also, what was the cost? I would like to hear more.
Last edited by schmanman on Wed Dec 13, 2006 4:02 pm, edited 1 time in total.
Persistence is a measure of faith in yourself
Amazing! That is a sweet gun!
I like how complicated it looks! Did you have many parts already or buy them all for the 700 dollar price?
nice gun, finally more people making powerful metal guns rather than plastic ones. i love the breech loading system you have made, however i think the car ignition is a bit over kill but thats just my opinion. man you have built one kick ass gun
What is that pipe rated to? If it's rated high enough you could throw a burst disk on and use it as a hybrid. That would be pretty sweet.
*Runs to room. Slaps self a few times. Comes back to computer. Images are still there.*
That is one awesome gun!!!! Looks like you really know your stuff! What mixes have you tried so far as far as compression goes? Have you only done atmospheric mixes so far?
Sorry to all that I have not measured the muzzle velocity. I also have not measured the range with the 8' barrel and acetylene and MAPP/oxygen fuel combos. These things will happen soon.
Every part was made by hand from raw stock.
I needed an extreme spark because of the series of four spark gaps. It also makes for a 100% reliable ignition - never misfires. (really!)
Scary, but possible! The ignition chamber pipe is rated at 300PSI minimum working pressure, 1200 PSI burst. The gas gun it's inspired by uses a burst disk to build very high pressure. I could theoretically safely raise the fuel/o2 pressure to say 4 atmospheres before ignition. The result would likely be a supersonic spud. I don't have a formula for calculating the chamber pressure for pre-pressurized fuels. I NEED a supersonic spud . . .
nice gun! very well built, does the scope even work that great with the big size ammo? What propellants have you all used with it and which ones were the most powerful?
I've used the following:
Air / Propane = boring and moisure laden
Air / MAPP = Excellent
Air / Acetylene = Freakin' loud
Oxygen / MAPP = Perfect
I won't try Oxygen/Acetylene unless distance tests with the new 8' barrel are a letdown. The theoretical pressures are fine, but acetylene's tendency to detonate could wreck the gun.
Dang you made this from raw stock?! You have some good skills there. I love it! This gun looks very professional and looks better than joels aluminium gun. Whats the chamber diameter?
SOO CUTE!! OMG!! I COULD JUST LICK YOU!!
The gun on Spudtech isn't wasn't really designed Joel and I don't think it was aluminum but don't take me up on that, it doesn't even say that on his site.
well I would be very proud of that cannon, that is one nice piece of work! This cannon has officialy stripped joel of the "most advanced spudgun" in my opinion!
Oh and bluetooth, Joel's cannon was not designed by joel, it was made by ed goldmann (sp?) and it is made of aluminum, it says so on his site
bravo dumbascii! this cannon is badass!
Where does it say aluminum i was just there on its page looking at it and thats what i said "The gun on Spudtech wasn't really designed Joel".
Holy Sweet Jesus!! That is one freakin HUGE cannon! Beautiful cratsmanship. I'll comment a bit more later when I settle down!
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