Here's an iron farm designed by Mysticat. https://youtu.be/_ECjjeS-prY I really like Mysticat's tutorials because they are short and to the point as well as very effective. This is one of two iron farms designed by Mysticat. I haven't personally used this one, but I have used his other design, and it did not disappoint!
Specifically, the question is whether or no they work on emc. Please comment on the one that does work?
I assume that the design in the video will work fine on emc because it is based on the same principal as cubefragment's iron farm on smp7. Mysticat's larger design (the one that I have used elsewhere) should work on emc as well since it too is based on the same principal as cubefragment's design: namely, having a zombie scare villagers into spawning an iron golem. I know there are rate limits on how frequently villagers can spawn an iron golem on emc, but won't that only reduce the yield of the iron farm, not prevent it from working altogether?
Getting zombies to not despawn has been problematic. Not sure if it has stabilized or not recently. (EMC)
There's an iron farm on /smp1 at /frontier northwest with zombies still in it. It's been there for a while, so it looks like that might have been stabilized.
