A drive assembly for use with a mechanical flying or walking device comprises an articulated member (7) having first and second portions (7a, 7b) arranged such that the portions move relative to each other, and a drive mechanism (9) for imparting motion to the articulated member. The drive mechanism (9) comprises: a drive member for imparting a cyclic motion on the articulated member, and a control member for controlling, in a predetermined manner, the relative position of the first and second portions during each cycle of the cyclic motion of the articulated member. In the case of a mechanical flying device, two such drive assemblies may be provided, the articulated member of each assembly forming a wing.