Abstract: A system for sensing, computing, and displaying the length and the speed of chain or cable payout or reel in. The system employs only a single sensor which measures cable drum movement. The calculation function is accomplished by a microprocessor or minicomputer which is programmed with the basic dimensions of the cable and cable drum and with the required calculation formulae. A display gives continuous readout to the operator of the cable payout and speed values from a predetermined cable reference point. The system is directly employable in drum payout and recovery systems regardless of their application. The cable references may be of steel, rope or even chain and the system may be incorporated in helicopter or aircraft cable systems, mine hoists or elevator systems wherever a precise control or readout of cable payout is required.

Abstract: A well drilling apparatus includes a first swing-up elevator platform on which the mast structure is pivotally mounted. After the mast structure has been raised to its erect position, the first elevator platform is elevated to carry the mast structure to a high operational level. A second swing-up elevator platform is provided to carry the drawworks to the same high level at which the two elevator platforms are coupled together to form the working floor. All of the raising and elevating operations can be accomplished with power supplied by the drawworks. The elevator platforms may be lowered after the drilling operation has been accomplished without interfering with any control valve structures that have been placed on the wellhead while the structure was at its raised operational level; the swing-up elevator platforms swing down in opposite directions over any such valve structure.