Blow Out "Plug" for jammed gun
Blow Out "Plug" for jammed gun
(OP)
I'm trying to design a blow-out plug for a gun to relieve chamber pressure if the projectile jams the gun barrel. I have thoroughly read the Machinery Handbook as well as other various materials and can't find a set of consistent equations for thread shear. This problem seems relatively simple, and I feel like I've confused myself by reading too much into it. I need a bolt whose threads shear (assume bolt much weaker material than chamber, ie brass vs hardened 4340 steel) @ 100,000psi chamber pressure. Most of the equations in the literature are for "safe design", not for purposeful destruction. I'm also concerned with load sharing in the threads; its been my experience that the 1st thread bears the most load and failure subsequently engages the next thread. Additionally, how would initial torquing of the bolt affect its ultimate failure? Any assistance with this problem would be greatly appreciated. The plug diameter can be as large as 1" and the length of thread engagement as long as 1.25".





RE: Blow Out "Plug" for jammed gun
RE: Blow Out "Plug" for jammed gun
RE: Blow Out "Plug" for jammed gun
How about a spring loaded pop-off valve? This might be easier to design and probably more accurate than shearing threads.
As stated by ornerynorsk; be careful.
RE: Blow Out "Plug" for jammed gun
Pressure reactors that I used to use had small diameter blow out discs in them. They were only about 3/8" diameter. They were domed and seated against a large step. They were replaced every time we had an 'event'.
In your case that might mean every shot.
A spring loaded relief sounds good, but I don't think that it will work. If the pressure loaded area is 0.250" diameter then you only need a spring with about 5,000 lb of load. That is a tall order.
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Blow Out "Plug" for jammed gun
I will put some thought into the idea of a blow out disc and bounce it off the other guys I work with. It obviously has a mass advantage over a threaded plug in the sense of ballistic ejection. I think I'll throw it into an FEA run and see what pops out the other side.
RE: Blow Out "Plug" for jammed gun
RE: Blow Out "Plug" for jammed gun
This system must have a very quick acting valve.
http://www.tempresstech.com/watercannon.htm
RE: Blow Out "Plug" for jammed gun
I don't have a copy with me right now, I think that this was covered in a previous thread. Try searching for thread shear calculation.
Dick
RE: Blow Out "Plug" for jammed gun
http://www.highpressure.com
RE: Blow Out "Plug" for jammed gun
http://www.spiralock.com/
Also you may want to look at the thread arrangement on my previous post.
Here is some good information on thread stripping.
http://www.hexagon.de/dose/dose1e.ht
Look at lesson 28
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RE: Blow Out "Plug" for jammed gun
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RE: Blow Out "Plug" for jammed gun
RE: Blow Out "Plug" for jammed gun