Abstract: A motor or pump assembly (1) comprises a cylinder block (4) with a plurality of radially positioned cylinders (3), a piston (2) arranged slidably reciprocable in each of the cylinders, a cam ring (7) cooperating with the pistons and being rotatably journalled on the cylinder block, and a distributor valve (9) arranged centrally in the cylinder block to control a flow of fluid to and from the cylinders in operation. The cam ring (7) is journalled on the cylinder block (4) with at least one ball bearing with balls (25) arranged on each side of the cylinder block. These balls run in grooves which are positioned close to the sides and periphery of the disc-shaped cylinder block. This provides a structure which has a very small axial length and which is simultaneously capable of absorbing great loads both radially and laterally.

Abstract: A borehole (2) serves to produce e.g. hydrocarbons in a preferably soft or relatively soft underground formation (1), such as chalk or sandstone. The borehole (2) is surrounded by a substantially tubular reinforcement shell (9), which consists of formation material so compressed that the solid components of the material are substantially crushed to particles, and these are bonded together by the fluid or viscous components of the material and/or drilling mud. The borehole (2) if formed by first predrilling a small hole and then rolling said hole up to final borehole diameter by compressing the formation so that a reinforcement shell (9) of the desired thickness is formed. A self-propelling drive assembly (5) with a plurality of driven, elastic rollers (6) is used for this process, said rollers successively rolling down the borehole wall (7) and transferring the pressure force and moment from the drill bit (3) to the wall (7).