Abstract: A drill string sub is disclosed for measuring the torque and axial compression in the drill string. The drill string sub includes an outer tubular housing and an inner sleeve type apparatus mounted thereto for amplifying the strain the sensors measure. The sub further includes a section for compensating for the axial stresses due to the local pressure differential between the drill string bore and the well bore annulus and for the thermal gradients occurring during operation. This section includes a balance tube for isolating the internal bore pressure from acting on the strain amplifier and for creating an upward axial force on the tubular housing and strain amplifier which is responsive to this pressure differential to counter the axial stresses mentioned above. The sensors are encapsulated in oil to avoid the effects of the corrosion and electrical shorting which are promoted by drilling fluids.

Abstract: A double acting damper for use in rotary drilling includes a splined tubular telescopic joint and employs plural paralleled stacks of double acting series stacked roller Belleville spring washers in an annular pocket between the inner and outer tubular members of the joint. The springs, spline and telescopic bearings are in an oil filled volume sealed from the outside by a pressure seal at the lower end of the damper and a floating seal at the upper end. Electric and magnetic means are provided to check on the condition and quantity of the lubricant.