Here not experienced with traps, but i recently saw a perfect contraption device. A large, round container as usually used to collect/store water. Over it, a rod that is fasted on both ends to the bin. A couple of large coke bottles through which the rod leads through the middle, making them spin. Some bait on top of bottles. Rat goes on bottle to reach bait, bottle spins, animal falls into container.
RE: Oh Rats - They Are At It Again