<BLOCKQUOTE>quote:</font><HR>Originally posted by RMC:
....Wolfgang Fleischer Die deutschen Sturmgeschütze 1835-1945.
Comment: Before Lewis' posts on the subject I had never heard of this at all. Now I am finding references to it in odd sources. For me it still doesn't quite pass the common sense test. I figure that the fragments from the exploding round would still have forward velocity at detonation and therefore the fragments would form sort of a cone in the direction of travel. Getting the round to detonate in the right spot must have been a real trick. Getting the round to be in downward motion (aimed at the target) must have been a feat of rare skill.
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I am a motion control engineer and am wondering about your "common sense test" (No insult intended..just realize that there are pitfalls to non-scientific analysis).
As I see it, it is a case of related rates and vectors. The vectors of the fragments have a component that is "added" to them. Lets take the case of the "front piece of shrapnel" of the shell, the velocity of the moving shell and velocity imparted by the explosion would be additive. For the sides of the shell, the velocity of the moving shell puts a forward component on the shrapnel so that "flies forward".
Now, the question is then related rates. Is the shell rate (velocity of the shell) comparable to the frag rate (velocity of the fragments)? I would venture a guess it depends on fragment size because smaller fragments would have a higher escape velocity and the shells velocity would not matter much.
BTW, this is not peculiar to a shell bouncing, it would happen in the case of a point detonating shell also.
I have seen xray photos of shells exploding. The breakage of the body of the shell is mostly lenghtwise (the cylindrical nature causes the body to bulge as the ends hold strong) causing the fragment effect to almost be like a "ring" or toroidal in shape about the sides with large "chunks" heaved forward (additive) and to the rear (where they would have subtractive velocity effects if I am not completely wrong). The point being, that having the sides of the shell "facing" the enemy on the ground pays off nicely.
I can imagine that EXPERIENCED gunners would logically aim in front of a target, naturally, and guage the results. Shell seems to be tearing up the ground behind the target area (you WILL see the nastiness of shrapnel hitting the ground)? Decrease time setting or try ricocheting at a closer range.
Lastly I would like to remark that 1835 seems a bit early for StuGs. (I believe that you mean 1939-1945.. I have the same book).
Lewis
PS The spinning also has an effect it just occured to me. Again, it has to have a related rate.