Physico-mechanical characteristics of rose petals dealing with the pneumatic harvest of Rosa damascena

For the design of harvesting machines is important the study of characteristics dealing with the harvest of crops. This study focused on some physico-mechanical characteristics of rose petals, which are important for pneumatic harvest mechanization of Rosa damascena Mill. These characteristics are terminal velocity, picking force, mass, projection area, density, and drag coefficient of rose petals. The petals were handpicked at 06:30 a.m. (S1), 08:30 a.m. (S2), 10:30 a.m. (S3), and 12:30 p.m. (S4) at four different dates in 2009, June 5 (HI), June 11 (H2), June 17 (H3), and June 23 (H4), covering the potential flowering period. Terminal velocity of rose petals varied between 1.572 and 1.257 m s(-1); the picking force from 0.501 to 1.005 N; the mass measured from 0.049 to 0.122 g; projection area from 13.830 cm(2) for H1S4 to 7.071 cm(2) for H4S1; drag coefficient from 0.790 for H2S1 to 0.287 for H1S4. The results of the study indicate that as far as terminal velocity of rose petals is concerned the harvest of R. damascena should be executed towards the end of H4 and S4. On the other hand, the magnitude of the picking force, the density, and the drag coefficient of rose petals decrease when the harvesting hour increases from HI to H4 and the harvesting date increases from S1 to S4, which makes necessary to increase aspiration pressure.