Possibly the most compact, simple, cheapest and fastest iron farm.
Setup:
1. Waterlog the Mechanical Drill and the Andesite Funnel.
2. Apply rotational force to any point in the machine (64 RPM seems to be the sweetspot).
3. Watch the fan. If it sucks, reverse the source of the rotation. If you are unable to do so, change the 2 Cogwheels behind the fans to Encased Chain Drives or a Belt.
Instead of sorting flint, it is now left to despawn.
Previous version: http://createmod.com/schematics/simplest-compact-iron-farm
It has a cobble leaking issue. It's like 1/3 so pretty bad leak
Easily correctly by just doing a belt below it with a tripple fan setup for increased speed (yes makes it a bit bigger but more reliable