I'm cleaning up my bloated schematic folder. I found the proto-type for my defense towers. Gave it a tune-up, refilled the arrow chests, double checked the hoppers. It has a centralized command room where you can operate the three levels of arrow cannons. On/Off Lava fire arrows from the middle cannons. Arrow auto-loaders. The 3 slab pads in front color coded for range finding with a hopper/elevator system to collect any drop into a chest in the command center. This is my plainest but most brutal defense tower. It faces West try to turn it and I won't help you realign all those hoppers. Included is a raw guts version that might help if you need to repair.
CREATIONS
MINECRAFT-SCHEMATICS.COM