A prototype betel nut husking machine was designed, constructed, tested and evaluated.
The design concept was to tear-off the husk of the dry betel nut by exerting differing
dynamic friction forces on opposite sides of the nut via normal pressure. The prototype
featured a hopper into which dry betel nuts were fed, a husking mechanism, and a power
drive. The husking mechanism was composed of two identical husking wheels mounted in
series. Each husking wheel consisted of a rubber tyre and a concave sieve constructed from
steel rods. The dry betel nut was fed into the space between the running tyre surface and
the sieve surface of the husking mechanism. When the nut passed through the first wheel,
the combined compression and friction force crushed the nut husk and loosened the nut.
The husk and nut were further separated by repeating the operation with a second tyre.
Results showed that (a) the optimum machine settings, identified by the greatest
production score (PS), were characterised by a tyre pressure of 138 kPa, a tyre speed of
440 rpm, and a 15mm spacing between the surfaces of the tyre and the sieve; (b) the
optimal betel nut fruit moisture content was 6.31% w.b. Performance testing of the
prototype based on the optimum settings produced the following results: optimally husked
full nuts (64.4%); broken nuts (15.2%); unhusked nuts (20.5%). Thus, the PS was 76.9%.