While the invention is herein illustrated with generally axially aligned twig-breaker sweeps 238; other-shaped rigid twig-breaker impeller elements such as rods, studs, blocks, plates and other forms may be fastened to the surface of twig-breaker-rotor body 234, and other spacings and arrangements of impeller elements such as spirals, ???V??? shapes, etc. can be used as well, so long as a crenel f