A wheeled support tower for a travelling irrigation machine is provided. A tower frame includes at least two legs and a base beam interconnecting lower ends thereof and at least two wheels located towards two extremities of the base beam. The base beam that houses at least two drive shafts therein, and preferably the legs, are of a tubular construction. One or more center drives for rotating the drive shafts are also located within a housing forming part the base beam. The two legs and base beam may be arranged to form a generally triangular support tower. The drive shafts may be coupled to wheel boxes each of which houses a driving gear arrangement for an associated wheel hub. The wheel boxes are in a lower vertical position than the lower ends of the legs and fall at least partially within the width of the legs in plan view in the normal operative position thereof.