I just cba to draw it, because it'd have to be in 3D to make sense and that's more drawing skills than i can muster without a lot of effort :lol:
I'm sure you get what I mean by a perimeter wire though. So if you imagine just 4 wires in the middle of a mesh lens replacement, like a noughts and crosses board, and each of their ends is wrapped around the perimeter wire. To force the crossed wires apart, so that the square-oid in the middle becomes wide enough for a BB to pass through, the whole system has to deform, because instead of being the straight line from the point of impact to the edge which it was, each wire becomes the hypotenuse of a triangle, where the right angle is at the point of impact, and that can't happen to the 4 wires only, yeah?
Either the perimeter wire bends, the wire stretches, or the the curls of wire around the perimeter wire uncurl. The weakest part of the system is the perimeter wire, so we might reasonably expect it to bend, but if it is pulled in by just those 4 wires then it can only deform in 2 ways -
1) a small amount over a wide area: the perimeter wire must also push the other wires which are also attached on either side of those under tension inwards also, unless the perimeter wire stretches, and since they are interwoven with other wires, that compression is acting against the shape of the whole system, trying to make it bulge out; or
2) the perimeter wire is pulled in sharply at those 4 points: again unless it stretches, the wires on either side act as pivots, and the wires further away are pulled out, again acting against the shape of the whole system, but in the opposite way, trying to compress the convex shape.
This plan depends on a few assumptions: 1) the tensile strength of the wire being well in excess of any force which could act on it, but I'm certain that even common or garden SS304L has more than enough, I mean it's measured in Kg's for each wire ffs and we're talking about forces measured in single figure Joules divided across many wires 2) that the temper is such that the coils around the perimeter wire can't uncoil - a more difficult proposition, but having managed to bend a £15 pair of jewellery makers pliers making such coils from SS316 in its 'as is' state, I'm confident that oil quenching would make sure them, and 3) that the steel isn't elastic enough to deform as much as necessary to allow a BB through and then spring back... I believe that this might be possible, although probably not under the forces we're concerned with, but the main reason why not is friction between all the wires in the system.
It probably hasn't escaped your engineer's nose that the 'either/or' 1) vs 2) scenario above is a false dichotomy. In reality the impact force would try to make both happen at the same time and whichever aspect of the system proved weakest would allow the greatest pattern of deformation in the end. But in the initial microseconds after impact, both of these patterns of deformation would be acting in opposition to each other. Add to this oil quench hardening and a layer of black Krylon, or even better an alkali black surface treatment (which would leave the wires thinner than paint and increase friction between surfaces) and I'm certain we'd have a winner...
