I use stone half steps at the end so that if a short mob refuses to jump, the next one will bump it. I expect spiders may not fit if you use ladders; if so simply replace with signs and know that occasionally a pig may sit there for a while. Note you need to avoid blocks of waterfall with air or glass next to them, they push down too hard for mobs to swim up.
Also, dig the knowing nod from the pig near the end of the vid!
Wow, that's an interesting mechanic... I built a base far above a skeleton spawner, but it's so inconvenient to travel down there that I never collect the arrows from my trap. Going to see if I can make this work in my base.
I've been thinking about how you could possibly utilise this as a simple mob trap. If you add a layer of lava above like so (sticks = ladders)
then mobs should jump up out of the water and hit the lava untill they die, dropping their items into the water. Though I'm not sure how, you could make a water delivery system to collect the items from. Maybe the bottom would be like this
(water flows in some direction)
though I'm not sure if having flowing water at the bottom of the elevator would interfere with moving mobs up in the first place.
You don't need lava. I made an unintentional mob killer by making the water elevator too high. The intention was to kill them by fall damage from the top, but most died on the way up. I got the same results with a shorter tower by capping just above the water source with stone. I'm still working on the water currents to get the drops out. And how to deal with chickens.
I was playing around with this today and was surprised at how well it works for hostile mobs in addition to animals. I had to make each lift 10 blocks as anything greater than 11 or so would cause them to start drowning and the survival rate wasn't very good after 4 lifts.
I'm still having a problem with the mobs getting stuck in the transitions though. I've tried various combinations of ladders and signs, but it almost seems as if they are getting stuck in the wall itself. I'm going to try different wall materials to see it that helps.
I'm still having a problem with the mobs getting stuck in the transitions though.
Have you included half steps next to the back wall? A player standing on them will drown, so I assumed any mob taller than a pig would start swimming up as soon as it was pushed onto the half steps.
Come to think of it...why not use STEPS-steps...time to test this with a proper game!
Update: this works very well. All of the tall mobs (creepers, skeletons, zombies) get sucked up pretty much instantaneously. I spent two minecraft nights without seeing any spiders or finding any in the mornings, so I went back to my spider spawner to try it there. Seems to work well with spiders as well but then they are trying to attack me, and I expect they are every bit as likely as pigs and chickens to sit on the steps for a while and think about things.
Speaking of chickens, THEY DIE!!! BWAHAHAHAHA!!!
They just hover at the very bottom of the water and drown! They are ironically the only creature you can't get to go upwards.
This thread gave me some ideas. While I have yet to work out a really good general mob trap, I did happen to put together a pretty good skeleton drowner about the time I found a convenient dungeon.
Here's a side view. As skeletons are two blocks tall and try to walk on top of the water, their heads hit the water held up by the signs. Silly skeletons then try to swim to the top and drown even though only their heads are in the water. I originally had the water above the signs filled in two or three blocks higher, but experimentation showed this worked just fine. And it leaves their legs dangling down where I can watch them twitch as they drown. (This game is a bad influence on me.)