ABSTRACT

 In order to eliminate the drudgery involved in cracking of periwinkle, this project embarked on a research on the development of a motorized periwinkle cracking machine. A motorized periwinkle cracking machine was designed, fabricated, assembled and evaluated. Cracking is done by a serrated-rolls crusher which carries out size reduction by compression, impact and shear force. The machine was tested at three different cracking speeds of 251rpm, 539rpm and 656rpm. Based on these speeds, the percentage shell lost, throughput capacity, mechanical damage, cracking efficiency and material efficiency of the developed motorized periwinkle machine was evaluated. The discharge unit was also evaluated on the effects of cylinder speeds of 13rpm, 15rpm, 27rpm, 39rpm, 70rpm and 86rpm on axial discharge displacement at inclination angles of 1.51°, 2.72°, 3.92°, 5.13° and 6.35°. Testometric compressive strength test and linear size analysis of periwinkle were established and used for machine shear force validation. The study on both cracking and discharge units were at three replications. Data for the performance evaluation were subjected to analysis of variance for test of significance of the experimental factors and their interactions using a one factor and factorial design (CRD) for the cracking and discharge units respectively. The mean cracking efficiency increased from 99.0 1% - 99.66%, mechanical damage from 17.20% - 37.10% and throughput capacity from 32.67kg/h — 40.76kg/h with increase in cracking shaft speed of 25 1rpm — 656rpm. The material efficiency decreased from 82.80% - 65.20% with an increase in cracking shaft speed of 25 1rpm- 656rpm while the percentage shell lost increased from 1.50% - 1.59 with an increase in cracking shaft speed from 25 1rpm- 539rpm and decreased to 1.58% with additional increase in shaft speed at 656rpm. Highest discharge displacement of 23.63cm was obtained at cylinder speed of 251rpm and at 3.90° inclination angle. The discharge displacement decreased with an increase in cylinder speed from 13rpm - 86rpm, increased with an initial increase in inclination angle from 1.51°- 3.90° and then decreased with further increase in inclination angle from 3.90°- 6.35°. The highest and lowest discharge displacements were obtained at the cylinder speeds of 13rpm and 86rpm respectively with inclination angles of 3.90° and 6.35° respectively. ANOVA results showed no significant effect of mean percentage shell lost and cracking efficiency at P

<0.05, a significant effects of mean material throughput at P><0.05, a highly significant effects of mean mechanical damage and material efficiency at P><0.05 and a highly significant effects of mean cylinder speeds, inclination angles and their interactions at P><0.01 level. The average compressive strength test of Tympanotonousfuscatus var radula using Testometric machine showed 759.90N and 1287.00N at the longitudinal and neutral (lateral) positions respectively while the machine shear force was calculated as 1178.89N. The linear size analysis of periwinkle showed the major and intermediate diameter as 48.90mm and 18.10mm respectively. The periwinkle cracking machine at a shearing force of 1189N, cracking shaft speed of 251rpm, discharge speed and inclination angle of 13rpm and 3.90° respectively is recommended for cracking and discharge of Tympanotonousfuscatus var radula. >