Abstract: There is disclosed a multiple output belt driving geared transmission wherein control of the speed and power delivered to the belt means and subsequent prime user is provided.

Abstract: There is disclosed herein a mobile well drilling rig apparatus adapted for rapid assembly and disassembly thereof. The drilling rigs of the invention comprise a trailerable telescoping mast assembly and a separate sectionable substructure assembly therefor comprising a rig base, a working floor mounted in spaced relation above the base and a rig base extension extending outwardly from the drawworks side of the rig base. In a preferred embodiment, rail means defining a mastway are provided between the erected working floor and the rig base extension. The base mast section of the telescoping mast assembly is provided with cooperative mast roller means whereby the base of the mast structure is readily conveyed to the working floor and whereby the drawworks side mast legs are engaged into a trunnion arrangement therefor. Means are also provided for raising of the mast structure to the vertical from the drawworks side of the rig.