Production Practices and Quality Assessment of Food Crops. Vol. 1

– fingers or spikes;
– oscillatory motion, which apply a shaking effect on the fruiting structures.
They work on plants trellised in different systems: ‘T’, ‘V’ or ‘Y’ (Figure 8)
(Salamon, 1992; Peterson et al., 1989). The trellis system to be used and the shaking
functional parameters depend on the fruit species and the conditions of fruiting.
Drums are 50–100 cm in diameter, and the shaking is created by inertia shaking (see
below, fruit shakers). The frequencies depend on the fruit species: 5–10 Hz for
raspberries (Rubus) and much higher for currant (Ribes): 10–25 Hz, with amplitudes
40–75 mm. Travel speed is 1–1.7 km/h (lower speeds for lower shaking frequencies).
The quality that one may expect for the mechanically harvested small fruits
is highly dependent on fruit species and variety, yield, maturity, trellis system and
the functional control capabilities of the harvester units.
3.2.2. Grape harvesters
Fruit and Vegetables Harvesting Systems 271
Mechanical grape harvesters were designed in the USA during the late 50s. The fruit
detachment system consists of a series of vibrating horizontal rods, that are free
to move on their rear end and mechanically driven with an oscillatory motion on
their front end (Figure 9). The number of rods depends on the height of the plants:
8–16 rods, for wines which are 1.2–1.8 m high. The effect of the rods on the wines
Figure 8. Blackberry harvester. Side (a) and front (b) view of ‘T’ trellis, (c) ‘V’ trellis, ‘Y’ trellis.