Another incident with the QDV

Cannons powered by pneumatic pressure (compressed gas) using a valve or other release.
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Ranger
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I made another piston today with smaller O ring grooves so that it would seal better. It worked! It was filling up and it got to about 50 psi, then I heard a loud BANG ! And saw a piece of piston land next to me, I had no idea where the other pieces went. I looked in the barrel and found 2 out of 5 pieces in there so that makes 3 pieces. I kept looking and looking.... and looking! Finally I looked up :roll: There was a hole in the ceiling :lol:

These things are not toys, they are extremley powerful.
Here is where the gun was when I shot it
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Parts of the piston flew out of the barrel and hit this concrete ledge
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This is the ceiling tile...
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Thats where the ceiling tile was.
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All the parts of the piston, (minus 1 Oring)
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I make these pistons by cutting 2" circular holes with a holesaw in a cutting board and then heat them up and press them together. Then turn them down on a drill press. I guess when I heated and pressed them together, I didnt do it good enough. This happened on my first piston but I was able to break it with my hand, this piston took about 50 psi to seperate it.

Well, fourth times a charm... going to make another piston.
Last edited by Ranger on Thu Jun 24, 2010 8:43 pm, edited 1 time in total.
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jackssmirkingrevenge
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Haha! Welcome to the ceiling piston club :D

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Seriously though, spudder's luck eventually runs out, some more care is needed in your experimentation...
hectmarr wrote:You have to make many weapons, because this field is long and short life
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SpudBlaster15
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Last edited by SpudBlaster15 on Wed Jul 14, 2021 8:02 pm, edited 1 time in total.
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jackssmirkingrevenge
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SpudBlaster15 wrote:This just made my day.
You can thank clide for the comedy gold :)
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Technician1002
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I worried about that exact failure mode when I made my first laminated piston. To prevent that failure, I decided to laminate it the long way. It held up nicely. I really liquefied the faces of the plastic as my early attempts to make the laminations thin failed. A deep melt so it behaves like a grilled cheese sandwich did the trick.
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A good lamination squished out lots of liquid plastic in the process. HDPE turns clear when melted.
A good lamination squished out lots of liquid plastic in the process. HDPE turns clear when melted.
Looking at the side of the core after most of the laminations are added.
Looking at the side of the core after most of the laminations are added.
WMHWPE and many other plastics do not heat laminate. I tried some. It simply doesn't melt to a squishable liquid and comes apart. If it doesn't turn clear and become like melted cheese, you have the wrong stuff.
WMHWPE and many other plastics do not heat laminate. I tried some. It simply doesn't melt to a squishable liquid and comes apart. If it doesn't turn clear and become like melted cheese, you have the wrong stuff.
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Ranger
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I knew you must have had similar problems Technician...

I do have HDPE, it turns clear when heated. On this next piston (which I'm making ATM) I am really heating up the plastic, I'm taking no chances this time.
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kydavies
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jackssmirkingrevenge, is that your piston in the ceiling?
mikemurph wrote:yea, the ammo has been changed to a more aero dynamic projectile. it consists of the back half of a dart, and a hot glue ball
AHahahahah!!
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POLAND_SPUD
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This just made my day
lol same here :D
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deathbyDWV
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POLAND_SPUD wrote:
This just made my day
lol same here :D
Same here too... I'm fairly sure that made everyone's day that looked at it... :lol:
Life's too short to mark off the items on your wish list...
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Technician1002
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50 PSI indoors with a projectile on the loose and the roof falling in, I gotta ask, did you soil your shorts? :D

Indoors I bet it was loud. I have dumped mine at 50 PSI (no projectile) indoors and the noise is very impressive.

I try to think what could possibly go wrong and try to plan so it can't happen. Just in case it does anyway, I make sure down range is clear.
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Ranger
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Technician1002 wrote:50 PSI indoors with a projectile on the loose and the roof falling in, I gotta ask, did you soil your shorts? :D
No, I just sat there for a minute wondering what the f*** happened and then started laughing.

From now on, I'm going to do all of my tests outdoors and be prepared for anything to go wrong.
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Technician1002
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I looked for a good photo of my finished piston to show the laminations, but couldn't find one. I pulled the piston to get this close up shot.

Note, the o ring groove is narrow. The ring has little side play, but still loose in the groove, Note the top floating ring is hanging out on the left side. It is free to move in the groove.
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QDV Piston. Various amounts of squish makes a weird pattern. I don't worry about a bad lamination causing a part of the piston to launch. Chamber pressure squeezes it together, not pull it apart.
QDV Piston. Various amounts of squish makes a weird pattern. I don't worry about a bad lamination causing a part of the piston to launch. Chamber pressure squeezes it together, not pull it apart.
Last edited by Technician1002 on Thu Jun 24, 2010 10:56 pm, edited 1 time in total.
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jackssmirkingrevenge
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kydavies wrote:jackssmirkingrevenge, is that your piston in the ceiling?
Can't be, no epoxy on it ;P

It's from clide's golf ball launcher, letting you know the importance of a good bumper ;)

If I did have a false ceiliing in my room though it would have at least 3 major perforations, so I won't judge :roll:
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Technician1002
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I mix epoxy on HDPE. It doesn't stick. I wait for it to harden and peel it off. I doubt epoxy would have prevented the failure of the HDPE piston. :shock:
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jackssmirkingrevenge
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Technician1002 wrote:I mix epoxy on HDPE. It doesn't stick. I wait for it to harden and peel it off. I doubt epoxy would have prevented the failure of the HDPE piston. :shock:
Have you tried roughening the surface properly?
hectmarr wrote:You have to make many weapons, because this field is long and short life
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