The self-propelled sprinkler has spray arms (15) fixed to a mast and held horizontal by guy wires (16). The mast is mounted on a plate (12) at the top of a chassis (1) formed with two side plates (2,3) made by bending sheet steel. A metal box (4) joins the two sides fo the chassis, and provides a rigid structure to support the mast and spray arms. The chassis also carries an electric motor (9) that drives a central wheel (6) at one end of the chassis. A belt couples the electric motor and the driven wheel. The other end of the chassis is supported by a second wheel (7). The wheels have a central groove (20) which fits over a raised ridge (22) formed along the centre of a track (21) that is laid on the ground.
