A timber-working head comprises a first motor, a second motor, a feed wheel, and an adaptor plate. The first motor comprises a first rotary output element. The second motor comprises a second rotary output element. The feed wheel is fixed to the first rotary output element for rotation therewith. The adaptor plate fixed to the second rotary output element for rotation therewith. The adaptor plate comprises radial projections arranged about the periphery of the adaptor plate and received respectively within corresponding axially recessed portions of the feed wheel so as to provide an operational interface between the adaptor plate and the feed wheel.