1. A pivot assembly comprising a pair of hollow beam sections relatively swingable to include an angle of less than 180* between them in one position thereof and axially aligned in another position thereof; a shaft extending through said beam sections and axially subdivided into a pair of interconnectable shaft sections disengaged from one another in said one position and mutually interconnected in said other position of said beam sections; and pivot means interconnecting said beam sections for relative pivotal movement thereof between said positions about a first axis laterally offset from said shaft in said other position and perpendicular to the axis thereof, and a second axis generally parallel to one of said shaft sections in one of said positions, said second axis intersecting said first axis, said hollow beam sections forming part of an articulated beam for a haymaking machine towable by an agricultural tractor, said shaft being driven from said tractor, said beam being provided with a plurality of rotary rakes operatively connected to said shaft and spaced along said beam for raking a ground crop upon advance of the beam and said rakes thereover, said first axis being generally upright and said second axis being generally horizontal.

5. A haymaking machine comprising a pair of hollow beam sections relatively swingable to include an angle of less than 180* between them in one position thereof and Axially aligned in another position thereof; a shaft extending through said beam sections and axially subdivided into a pair of interconnectable shaft sections disengaged from one another in said one position and mutually interconnected in said other position of said beam sections; and pivot means interconnecting said beam sections for relative pivotal movement thereof between said positions about a first axis laterally offset from said shaft in said other position and perpendicular to the axis thereof, and a second axis generally parallel to one of said shaft sections in one of said positions, said second axis intersecting said first axis, said pivot means including a ball member mounted on one of said beam sections at a location laterally offset from said shaft, and a socket member formed on the other of said beam sections and receiving said ball member, said members forming a ball joint permitting at least limited pivotal movement of said beam sections in all relative angular positions thereof about a horizontal axis parallel to at least one of said beam sections; and a plurality of rotary rakes mounted on and driven by said shaft sections, wherein said other of said beam sections is formed with a lateral projection generally coplanar with the respective shaft section and formed with said socket member and with an outwardly extending sleeve having an axis coplanar with the respective shaft section and with said second axis of said socket member while extending radially therefrom, said one of said beam sections having a lateral flange lying generally in a horizontal plane and provided with an arcuate transverse rim having a pair of generally radial bores separated by an angle of approximately 90* about said first axis, one of said bores having an axis parallel to the shaft section of said one of said beam sections, the other of said bores having an axis parallel to said shaft section of said other of said beam sections, said other of said beam sections being further provided with a radially slidable cylindrical bolt received in said sleeve and fittable in said bores, and with a compression spring in said sleeve resiliently urging said bolt into the respective bore in the respective positions of said beam sections.