Rock Crusher Feed The Beast Wiki
The Crusher is built out of 12 special blocks made from a Block of Steel, Pistons, and Diamonds. If broken down, it takes 3 Blocks of Steel, 12 Pistons, and 12 Diamonds to build one Rock Crusher. Rock Crushers cannot be built adjacent to each other—there must be at least one tile in between Rock Crushers.
Source Mod: Railcraft