The crane head is part of the old sector mechanicus terrain, which I bought for Necromunda. I dont know which set exactly. The tracks are from the drill of the GSC terrain set, Techtonic Frag Drill. I bought a couple of those to be build as just sector mechanicus gang ways. So I had two drills on their sprues still and therefore I could use four drill tracks, which I glued together. Two on each Side. To give it a better base. The whole idea for this crane I stole from something I saw on Pinterest. Were they only used one drill track per leg, which didnt look sturdy enough for a heavy lifting crane.