Browsing Wikipedia, I found myself going from the current events in the Gaza strip to the military of Israel (as you do with Wikipedia)
I came across the article on their Merkava tank and read about the chains installed around the turret to help defend against RPG or anti-tank rounds.
How do these help? Are the chains simply heavy enough to detonate the rounds before they strike? Or are they meant to deflect the path of the projectile somehow?
It looks like it’s a way to protect the junction between the body of the tank and the turret at the back from anything that might be thrown or fired in there (which would probably disable the tank).
Right, they’re there to defeat shaped charge warheads like you find on many RPGs. When an RPG hits it’s target the explosive charge detonates in such a way that it expels a jet like plume of molten copper, which is what actually penetrates the armor. If the charge explodes before contact with the armor the penetrating force of that jet of metal is severely hampered.
This is similar to the Schurzen, or armored skirts the germans put on their panzers in WWII. A shaped charge warhead really needs to go off at just the right distance from the armor to get the real penetration. Prematurely detonating the round destroys this. The chains are cheaper than “real” armor but still do this job very well.
It’s not because of cost. It’s because of weight and balance. To give similiar level of protection you’ll need to have put a lot of heavy sheet metal in the place of chains, which means too heavy to the rear turret. Things like chains or slat armor do the same work, but are much lighter.
So the chains are heavy enough to prematurely detonate a projectile then, I thought at first something moving fast enough would just slip right through them.
But RPG’s & other man portable anti tank weapons aren’t very fast. They depend on the shaped charge affect alluded to above to penetrate armor. From here, an RPG only moves at 140 meters/second. Those chains wouldn’t be much good against a nice depleted uranium shell like the M829, which moves at 1680 m/s and depends solely on kinetic energy to destroy the target.