@wondercoolguy, just in case you're not already aware of these bits;
Blade Traps take a portion of the damage they deal to zeds themselves. Meaning, even when you protect the central hub/motor of a blade trap from being hit by angry zeds, they will still break after dealing x amount of damage.
That said, an awful lot of designs expose the blade traps middle to getting hit by zeds &/or cop puke, or cop/demo explosions. Or even being shot by the player.
While you can shoot through the _blade_ part without damaging the trap, if you shoot the center motor it will take damage.
Won't assist with your design but for a corridor kind of setup, using flat half-height blocks will effectively 'sort' which zeds a blade trap will hit in the head. With the half-height then only tall zeds like the cop, demo & wight will be hit, and I've never had this config set off a demolisher. While normal, full-height blocks lane that has blade traps set to hit all the zeds has been reported to set off demolishers.
Point of view in the pic is slightly elevated to clearly see the setup. Zeds enter from there. First hitting e-fence to stun lock them standing on a trigger plate over a dart trap. I'm on the far end shooting towards camera popping z-heads, heh. Then the first blade trap. Can see the two side lanes are half-height so BTs only skull crush tall zeds. Center lane is blocked, so zeds are very unlikely to swing at the BT motors. I have had cop puke damage the two BTs after the one you can see, when the cop was in the lane 'away' from where I was at the time.
With this setup I just had day 49 horde night, gs ~160? had 5 demolishers, only a few cops for some reason, fair mix of rads etc. I was actively shooting zeds as they came in and got their first zap; used ~200 9mm & ~250 AP 7.62, only a few spiders made it to the end of the lane. That first BT only took ~500 damage; I was making sure to focus on the big baddies of course. Those first dart traps burned ~1700 darts and their e-fences were almost broken. And they would have been but the horde rng kept sending vultures so the whole night was a bit slow, had to keep running upstairs to lure the vultures down, and then some of the other zeds would get confused where to come in. oh, and only 8 at a time, old potato comp.
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