Adigun and Oje (1993) reported that nuts whose
shells/pods cannot be easily broken by the roller cracker are
commonly cracked using a centrifugal cracker. Makanjuola
(1975) evaluated some centrifugal impaction devices for
shelling melon (egusi) seeds (Citrullus vulgaris) and found
that a centrifugal impact method is a good technique for
shelling melon seeds. He evaluated three types of impellers
(A, B and C) with four slots, eight slots, and two parallel
plates, respectively. He concluded that impeller type A was
the most effective of all the three types tested. Odigboh
(1979) developed and tested a prototype impact melon
(Citrullus vulgaris) shelling machine that gave about 96%
shelling efficiency and 100% winnowing efficiency. He also
evaluated three types of impellers at different vane
angulations with four vanes each. Impeller type A had
radially positioned vanes, type B vanes positioned at 45 to
the radius, while type C vanes at 90 to the radius of the
circle. He concluded that impeller type B gave the best
combination of higher shelling and low percentage of
damage.