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 Post subject: EndCap Failure...
 Post Posted: Mon Jul 28, 2003 1:00 am 
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Originaly posted by Bartman007,
No this hasen't happened to me, but I have a few questions about it.
I am building a pneumatic piston, quick-exhaust gun. The endcap is going to have over 1000 lbs of force on it when the gun is charged to 100 psi. I was planning to use a 1" sprinkler valve to exhaust the air behind the piston, this was going to be attached to the endcap by a 1"x1/2" threaded bushing and a 1/2" nipple. I don't want that endcap to fail so I may try reenforcing it. My questions are:
1) If I place a piece of sheet metal (1/8") inside the endcap, and thread it to the 1/2" nipple, then seal these threads with pipe dope, and then epoxy this to the endcap making sure I have a seal all the way around the sheet metal edge (to keep the pressure off of rear of the endcap.) Will this strengthen the endcap, or will it just be a big piece of shrapnel if the endcap fails on me.
2) If this won't work, what can I do to strengthen the cap?

Peace,
-Bartman007
P.S. I know that threading the piece of 1/8" sheet metaal won't give me more than half a thread, but hopefully it, combined with the pipe dope, will help make a seal then air can't get through.


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 Post Posted: Mon Jul 28, 2003 8:00 am 
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Originaly posted by mta,
I have 4" guns with endcaps that I have tested to 150 psi and routinely shoot at over 100 psi. I've never had endcap failure. I use Charlotte endplugs.

I bought a few different brands of plugs to test them, but I went with teh Charlotte because it's a lot thicker and heavier than other brands, most notably PTI. I weighed the things, and the Charlotte is 50% heavier than the PTI.

I'd get a Charlotte plug and not worry about reinforcing it with steel. I doubt that would be necessary. A 3/8" nipple in mine causes no problems. A 1/2" nipple likely would not either.


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 Post subject: rubber stops?
 Post Posted: Mon Jul 28, 2003 11:00 am 
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Originaly posted by pacogoatboy,
you could use rubber stops as a sort of bumper for the piston. it wouldn't change the force applied to the endcap, but it would help to spread the application of that force over a longer period of time, which seems like it might help things hold together a bit better. i'm not aware of any source for solid rubber cylinders that would be applicable here, but maybe some stiff rubber tubing, or something like screen door spline. you could also try your metal idea, but it seems to me that if your metal is getting slammed by the piston, it is going to transfer that jolt right into the pvc without helping out too much.


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 Post Posted: Mon Jul 28, 2003 5:00 pm 
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Originaly posted by Bartman007,
because I was planning to use rubber to cushion the blow anyway. I was originally going to use a 1" nipple to connect the sprinkler valve and that was why I was originally going post this.
To mta: those charlotte endcaps, are the the f*cking huge type with a hexagonal shaped back (I hate those endcaps, too bulky) or are they the ones with the square plug on the back?

Peace,
-Bartman007


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