Tamping Test

[Axt]

Heres a test I tried after the use of dilatant tamping came up in the free posting period. It was an attempt to compare cornflour/water with other pourable, low shrapnel tamping agents.

Det-cord was run under 3 icecream containers containing equal volumes of the indicated tamping, with a 6mm Al plate as the target in the hope that the cord will cut into the plate at varying depths.

But as it happened - it didnt cut but just bent at close to the same angle throughout.

The Al plate should have been layed flat on top of a steel plate with three lengths of det-cord placed laterally so that the bend from one tamped area wouldnt influence the other areas and the steel plate would help it to cut rather then bend, but as it was done, the test doesnt really prove anything.

I would expect that the dilatant fluids would be best used in a bore hole rather that in the manner tested.

[nbk2000]

The link works fine.

[Stoic]

axt, did you record the angel to which each tamping bent the Al too? If you did could you please share them.

Edit: Sorry didn't realise!

<small>[ February 02, 2003, 02:08 PM: Message edited by: Stoic ]</small>

[Mr Cool]

I don't think he did record the angles, since he didn't do the test :rolleyes: .
Axt, do you know the angles? And have you tried it with three different Al sheets, one per tamping mass?

[Axt]

The distance between the edges is such -

cornflour/water - 257mm
sand - 259mm
water - 260mm

Not a whole lot of difference. The width of the plate was 276mm if you wish to work out the angles.

I havnt tried 3 seperate charges and I wont, as Al is expensive and I dont think a whole lot of difference will be seen if tested again in that manner.

I was trying to think up a way of testing it via a bore hole, this is all I could think of to give comparitive results.

<img src="http://ww1.ft100.com/~45653/guns.ft100.com/banners/tester.jpg" alt=" - " />

Im not going to do it, but It might be a god contraption to have, as it could test the strength of low explosives and oddities such as the dilatant tamping.

Why is it refered to as "dilatant" anyway, does anything "dilate"?

[Axt]

For what its worth -

The charge was a .222 case full of blackpowder, at the botom of a 15mm (1/2") PVC pipe with a safe working pressure of 18bar (260psi).

<img src="http://ww1.ft100.com/~45653/guns.ft100.com/images/tamping2.jpg" alt=" - " />

It was taped upright to a cane, and ignited - heres a crappy <a href="http://miss.fnpsites.com/tamps2.avi" target="_blank">movie</a>.

The Results -

<img src="http://ww1.ft100.com/~45653/guns.ft100.com/images/tamptest2.jpg" alt=" - " />

The sand didnt damage the pipe.
The water blew the bottom of the endcap off, pipe wasnt damaged.
The cornflour took away the bottom half of he pipe.

[0EZ0]

Very nice results Axt.

It does not surprise me at all that the cornflour/water combination performed the best. It being dilatant. The sand would have absorbed the explosion, as shown here. The water did a little better job, but still seems to absorb too much of the released energy.

Dilatant: : increasing in viscosity and setting to a solid as a result of deformation by expansion, pressure, or agitation.

A few more interesting tests could be done with sand/water, soil/water against the cornflour/water. You might be surpised with how well other water/granule or powder combinations perform.

Happy testing :) .

<small>[ February 05, 2003, 08:12 PM: Message edited by: 0EZ0 ]</small>

[nbk2000]

My theory

Sand: Inert, crushable, granular solid that would be easily ejected.

Water: Liquid that would, in the immediate vicinity of the explosive, be turned into steam, that wouldn't be able to escape out the pipe before rupture because of the inertia and viscosity of the liquid water mass.

Flour/Water: Solid that would not only get harder, but also be compressed in the pipe (hence expanding and locking in place), while the inertia of the sticky solid effectively plugs the pipe like plaster.

In the aluminum test, you should have cut the plate into 3 sections, each section being seperated from the other by an inch or so, but having the entire width of the det-cord covering the strip being itself completely covered by the box of dilantant.

This way, when the explosion is done, each strip will have bent without the influence of the other tampers twisting the sheetmetal, thus altering the results.

[Axt]

I wasnt suprised that the cornflour/water burst the pipe either, considering you cant even push the mix through a pipe with a pole, but as soon as you release the pressue it flows out the end, funny stuff.

A good test would be to compare "cornflour/water" with "wheaten cornflour/water" as they both have the same consistancy, yet the former shows far stronger dilatant properties so the only thing being compared is dilatancy against non dilatancy.

Judging by just the water results one would need far stronger pipe to test other material/water mixes as i'd expect they would all bust the pipe. Sand/water is itself dilatant but not to the extent cornflour is.

Note that I made sure the cornflour/water slurry was of a low concentration, therefor viscosity, so it could be easily poured into the pipe.

[CyclonitePyro]

I'm not sure that the corn flour you speak of is the same as corn starch, but if it isn't then I bet a corn starch and water mixture would produce some interesting results, which you may remember a teacher in elementry or middle school showing you.
Go in your kitchen and grab some corn starch and mix with a little water then experiment and add more. This mixture behaves funny, normally it's runny, however if you apply instant pressure like smacking it or squeezing it quickly, it resists and gets hard.
The shock from an explosive would probably make the cornstarch/water mix act like a dense solid for the duration of the explosive and work as a tamping material excellently.
Just a guess.

[Axt]

Cornflour & corn starch is the same thing.

[Da Boom Doctor]

Corn starch is probly a little more exact, considering the "jamming" of the corn starch/water mix is due to the static build up between starch molecules when they are agitated or "smashed" together.

How strange we were playing around with this stuff (the corn starch and water not HE) in my physics lesson last monday, now when I see my teacher on tuesday i'll tell her about this, perhaps arrange a class demonstration. :rolleyes: