Abstract: Disclosed is a mechanical force generator for use in a drillstring that provides a sinusoidal or near sinusoidal oscillating output, comprising: a rotatable cam plate connected to a mass, the cam plate having two opposed oblique bearing surfaces rotatable through a bearing, wherein upon rotation, the two opposed oblique bearing surfaces cam against the bearing to oscillate the mass longitudinally, wherein the bearing comprises opposing bearings for bearing against the opposed oblique bearing surfaces and wherein at least one bearing adjusts to follow the respective opposed bearing surface and maintain engagement.

Abstract: Disclosed is a mechanical force generator for use in a drillstring that provides a sinusoidal or near sinusoidal oscillating output, comprising: a rotatable cam plate connected to a mass, the cam plate having two opposed oblique bearing surfaces rotatable through a bearing, wherein upon rotation, the two opposed oblique bearing surfaces cam against the bearing to oscillate the mass longitudinally, wherein the bearing comprises opposing bearings for bearing against the opposed oblique bearing surfaces and wherein at least one bearing adjusts to follow the respective opposed bearing surface and maintain engagement.

Abstract: A downhole assembly able to generate a vibrational output reliant upon a fluid feed drive to cause relative rotation extending magnetic arrays and thereby a relative longitudinal vibration causing reciprocation.

Abstract: A boring tool having downhole hammered impact elements that present to the bore face from platforms or plateaux of the work face of the tool, such work face having shear cutters able to benefit over the bore face from disruption caused by the impact elements.

Abstract: A downhole assembly able to generate a vibrational output reliant upon a fluid feed drive to cause relative rotation extending magnetic arrays and thereby a relative longitudinal vibration causing reciprocation.

Abstract: Vibrational apparatus to direct stress waves (eg. to a bit 2 or other downhole tool) by generating vibrations as a consequence of shuttling responsive to relative rotational movement between magnetic arrays and wherein there is, or can be, a use of a system (whether rebound, recoil, spring, pneumatic, magnetic or not) able at least in part to return acquired potential energy in addition to any acquired at the same time by the interacting magnetic arrays. A free travel distance can be provided for one of said components prior to the onset of any substantial collection of energy from the movement (relative) of that component in a direction (eg, uphole) for use in return travel (eg, downhole) preferably synchronized, or synchronizable, to enhance the return travel causing forces of any repulsive and/or attractive forces generated otherwise than by the said magnetic arrays.