A modular foundation support system includes modular foundation support components including shafts provided with integrally formed coupler features on their respective distal ends. The coupler features are configured with a non-uniform wall thickness defining a plurality of sections of respectively different diameter to matingly couple the shafts to one another in a torque transmitting relationship. The coupler features may be integrally formed and fabricated on the distal end of each respective shaft.

A spline connection having a hub with a toothing profile on the inner circumference, an axle journal having a toothing profile on an outer circumferential portion, a shoulder for axial support and/or abutment against the hub, and a tensioning device for axially bracing the axle journal with the hub. The hub has a constant toothing profile and the axle journal has a first portion and a second portion with different toothing profiles. The first portion is arranged on the insertion side to be further away from the shoulder than the second portion and has a constant toothing profile with play with respect to the toothing profile of the hub. The second portion is arranged on the shoulder side and has a toothing profile which has reduced tooth spaces compared with the first portion and which is play-free with respect to the toothing profile of the hub.

A power transmission shaft includes: a bearing including a cylindrical portion, an internal spline portion, and an internal spline side annular groove including a bottom surface, and a first side wall and a second side wall, the first side wall which includes a first inclination surface inclined with respect to the rotation axis of the shaft portion, and on which the circlip is abutted in a state where a radius of the circlip is decreased within the internal spline side annular groove, and the second side wall on which the circlip is abutted in the state where the radius of the circlip is decreased within the internal spline side annular groove.

A low surface-roughness part is formed at a first tapered part, and, as a result, the roughness of an opening-edge of a groove part of an internal spline part that opens at the first tapered part is reduced, and surface pressure applied by the opening edge to a tooth of an external spline part can be reduced. As a result, the opening edge of the groove part of the internal spline part can be kept from digging into the tooth, and variation, between products, in the insertion load of a second shaft part can be suppressed.

A connector system facilitates the connection of a first tree trunk to a second tree trunk of an artificial tree system. The connector system can prohibit rotation of the first tree trunk relative to the second tree trunk.

A modular foundation support system includes modular foundation support components including self-aligning and torque transmitting coupler features wherein a plurality of axially elongated ribs are aligned with a plurality of axially elongated ribs to rotationally interlocke the modular foundation support components to one another.

A force-transmitting assembly includes a metal shaft having at least two longitudinally-extending grooves defined in an outer surface, and a metal hub having at least two longitudinally-extending grooves defined in an inner surface that surrounds the outer surface of the shaft. A plurality of discrete parts is disposed in the at least two longitudinally-extending grooves of the shaft and the hub in an interference-fit manner so as to transmit a torque from the shaft to the hub. Each of the discrete parts is composed of at least 50 mass % of technical ceramic selected from Si.sub.3N.sub.4, SiAlON, Al.sub.2O.sub.3, ZrO.sub.2, or a mixture of two or more of Si.sub.3N.sub.4, SiAlON, Al.sub.2O.sub.3, and ZrO.sub.2.

A connector system facilitates the connection of a first tree trunk to a second tree trunk of an artificial tree system. The connector system can prohibit rotation of the first tree trunk relative to the second tree trunk.

A connector system facilitates the connection of a first tree trunk to a second tree trunk of an artificial tree system. The connector system can prohibit rotation of the first tree trunk relative to the second tree trunk.

A drive shaft is formed by welding two spline shaft heads to a hollow middle section of tubing. The spline shaft head includes teeth which are crowned to permit an angular offset of the drive shaft relative to cylindrical splines of connectors, such that the end faces of the teeth define a barrel shape. The teeth of the spline shaft head include a side face curvature, defining a football-shaped tooth cross-section. Torque is rotationally transmitted across a permitted angular offset of the drive shaft relative to cylindrically arranged linear splines of drive and driven connectors (i.e., relative to the engine output axis of rotation and the differential input axis of rotation), thereby avoiding the use of prior art universal joints.