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mistakes in spud gunning

A place to ask general spud cannon related questions.
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Unread postAuthor: velocity3x » Tue Apr 27, 2010 12:00 pm

I made a bad design mistake which almost caused an accident. On my first cannon (pneumatic GB), I used a Scuba tank (size 80, one tank per shot). In a couple of past threads, JSR pointed out the the tank was much to big but, I didn't listen to him. A while back I loaded 700 psi (nitrogen) into it and a friend braced hard against the gun and pulled the trigger. The secondary recoil from the excessive tank volume was so severe, it launched my 250lb friend and 300+lb cannon w/dolly mount rearward about 6 feet. It damn near dislocated his shoulder. Afterward, we could see that it would be like trying to hold a Saturn V rocket under your arm, igniting it and trying to hang on.

Excessively big tanks = Bad mistake
Small tanks = Good
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Unread postAuthor: jackssmirkingrevenge » Tue Apr 27, 2010 12:13 pm

Gun Freak wrote:Wow jsr that's a lot of fails :shock:


To be expected when you're doing spudgun R&D on the cutting edge :roll:

In a couple of past threads, JSR pointed out the the tank was much to big but, I didn't listen to him


To be honest, it was because of efficiency concerns as opposed to safety worries :? glad no one was seriously hurt
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Unread postAuthor: deathbyDWV » Tue Apr 27, 2010 1:17 pm

Yep, I have failed...

I forgot newtons laws again.

I meant 3rd...

:(
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Unread postAuthor: velocity3x » Tue Apr 27, 2010 2:08 pm

jackssmirkingrevenge wrote:To be honest, it was because of efficiency concerns as opposed to safety worries :? glad no one was seriously hurt


Jack,
You were absolutely correct about the efficiency aspect. The tank was 6 times bigger than required to do the same job as a tank appropriately sized. The gun I cited isn't equipped with a muzzle brake. At 100psi, it was no big deal. I failed to consider excessive gas volume at 700psi through a barrel cross section of 2.29 in^2 would act like a rocket and generate heavy force. That tank was quickly exiled to the scrap pile.
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Unread postAuthor: clemsonguy1125 » Tue Apr 27, 2010 3:43 pm

Yeah, I forgot to put a bumper on my 2 inch piston valve, luckily I was just test firing it at 25 psi and nothing broke but since the piston was made from a coupler and washers im suprised I didnt crack the tee
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Unread postAuthor: Hubb » Tue Apr 27, 2010 4:12 pm

Wasn't there already a thread like this? I could have swore I posted some of my "mistakes" before...
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Unread postAuthor: clemsonguy1125 » Tue Apr 27, 2010 4:14 pm

Hubb wrote:Wasn't there already a thread like this? I could have swore I posted some of my "mistakes" before...

I think there was a topic about combustion mistakes
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Unread postAuthor: MrCrowley » Tue Apr 27, 2010 4:58 pm

Oh yeah I forgot that one time with my SGA golfball cannon, the handle exploded. Not sure why, I used pressure rated parts (rated for 260PSI). It just blew up. Other time I blew the back of the piston housing off when I assembled it and forgot the bumper haha.
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Unread postAuthor: maxa1 » Tue Apr 27, 2010 5:32 pm

forgot to glue my endcap on it went for a fly but hit no one
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Unread postAuthor: daberno123 » Tue Apr 27, 2010 5:41 pm

I was shooting a pneumatic bb gun at a a bulletin board hanging on a wall. I t wasn't until late that I found out that the bb was going through the bulletin board and then continuing through the wall behind it... :D
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Unread postAuthor: Lockednloaded » Tue Apr 27, 2010 5:47 pm

on my first pneumatic i put teflon tape in between some of the non-threaded joints :lol: needless to say it never made it over 10 psi. that was 3 years ago
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Unread postAuthor: Gun Freak » Tue Apr 27, 2010 5:52 pm

Lockednloaded wrote:on my first pneumatic i put teflon tape in between some of the non-threaded joints :lol: needless to say it never made it over 10 psi. that was 3 years ago



haha that's great :D
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Unread postAuthor: kjjohn » Tue Apr 27, 2010 5:53 pm

On my first spudgun, a BV pneumatic, I didn't glue in the chamber end cap well enough, and it flew across the garage and slammed into the workbench, before ricocheting. My uncle, who lives in the apartment below us, wanted to watch me shoot it, and he caught the end cap. :lol:
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Last edited by kjjohn on Tue Apr 27, 2010 5:56 pm, edited 1 time in total.
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Unread postAuthor: Gun Freak » Tue Apr 27, 2010 5:55 pm

One time i decided to pressurize my unglued co-ax! The barrel and front bushing blew off about 10 feet :D lol

that was actually funny
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Unread postAuthor: twizi » Tue Apr 27, 2010 8:23 pm

once my qev piston froze when using co2 and shatterd
on another note i was fishing made my own leader and we hooked a 700 pound black marlin but of course i forgot to crimp the leader :oops:


epic fail
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