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Munroe effect cone testing.

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  • #16
    Originally posted by Evan
    Fun stuff. I did quite a bit if unofficial experimenting when I was young.
    When I was young enough to still have a sand box in the back yard I used to build bridges etc. out of sand and then make demo charges out of firecrackers and blow them up.
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at

    Southwestern Ontario. Canada


    • #17
      I did try to do the spinning of the proto type cone shapes. I couldn’t get the hang of it in the short time we had to do testing. I ended up finding a calculator on the net that would unwrap the cone and print in on a sheet of paper. I then used spray adhesive to attach it the aluminum plate and cut it out on the band saw. Then rolled it to a cone and tiged it together. We had a shop in Florida do the spinning of the production cone. The cones are only .065 wall thickness. A copper cone would do a lot deeper hole. It has more mass. But one of the criteria of this job was to be able to see inside the hole for inspection. Aluminum will burn out of the hole where copper will stay behind possibly blocking the hole.

      The cone starts like this and after 25 million g acceleration looks like this. About ½” diameter and nice rounded back


      • #18
        Duffy this is the targets we talked about before.

        They think this one was hit with a cratering charge at one time.


        • #19
          I'd say your shape charge has some issues. here are my observations
          explosive wise-
          First i don't know if you calculated the collapse angle or if you have calculated the detonation velocity of the binary but it these would help your charge. Also the detonation velocity of binaries are typically slow (5-6mm/us) and tend to make poor shape charges in general (tamp some c-4 and try that, or a hot rdx based emulsion). Also if the binary is a non-homogenous mix you'll have poor results. i think you need more head height to plane out your wave (or use a waveshaper...). As a example, crappy old soviet stamped cone rpg's penetrate at least 12 inches, and the explosive is less than 2 lbs, and the bottom of a wine bottle can do 4 inches with less than a pound.
          i don't know the AL your using, or how you came about your shape (copy of a cu shape?) but i can suggest some things to try.
          test wise-
          A baseine at 0 cd standoff for a shape charge is kinda pointless, almost all need 4-6 CD's, spend the shots zeroing that in. Also some breakscreens may give you an idea of the jet velocity. i'd need a better look to verify but from the look of your crater you didnt get a jet, but you did get a nice efp, break screens would confirm this.

          If this is for giggles, then i think it's fun and have at, if it is for a client, i'd make sure they don't contact any places that do testing.


          • #20
            Wear still on tract got the pipe back from the CNC band saw. Man that saw is nice even if you only need one cut.


            • #21
              Shot over the weekend. Probably going with this standoff of only 2” with our modified cone. Still went just over 5 ½” deep in hardened steel at 2” wide down to 5”deep. Meats the clients specs for the job.


              • #22
                Do-it-yourself shaped charge

                Jeremy, That hole in the shell reminded me of a demo example.
                Among the GI-issued forms was a series of empty containers with stand-off legs, in the form of stiff wire with notches at one-inch intervals. The largest of these was about a 28 oz tomato can, (probably was ,) with a cone formed in the bottom. I filled one of these with C3, (TERRIBLE sticky stuff,) and we placed it about at the driving band on a 16 inch AP shell. I forget the stand-off but it worked! The shell shattered into several large pieces and the bulk of the explosive, (ammonium picrate-Explosive D,) scattered about. The shell was perhaps 4" thick where we placed the charge. That is a guesstimate, but the NEC was only 40 lbs, so the cavity was pretty small.
                The "experts" opined that, in a case like this, the jet JUST penetrated into the cavity causing a SMALL portion of the contents to detonate, bursting the shell and scattering the rest of the explosive. It seemed a good theory, since we did similar shots MANY times on both shells and bombs, and were always successful. This was training and we were told that the success rate dropped as the weather got hotter and the explosive sensitivity increased. We were working in April at Eglin AFB.
                IIRC, GP shells had an NEC of about 150 lbs, so the cavity is much larger, and the wall thickness should be correspondingly thinner.
                Duffy, Gatineau, Quebec