The working drawing of the shelling plate showing the plate 4 and plate 5 which make up the  V shelling device  note that the plate appears twice so that melon that was not shelled during the first contact of melon with plate 4 an5 will definitely re make contact with the second shelling plates 4 and 5 for efficiency
It is very very important that the gap between plate 4 and 5 is not too wide , size of the thickness of a flat metal bar of 2-4mm  is okay  , otherwise the melon will not bend into c shape of shell seed