Mechanical harvesting of clingstone peaches

J. ogric. Engng Res. (1977) 22, 247-257

Mechanical

Harvesting

Peaches

of Clingstone

ANDREA ZOCCA* ; R. B. FRIDLEJ t A new self-propelled harvester for Clingstone peaches is descihed. Design features include a low profile, a single-unit construction, decelerator strips eve:* most of the catching area, a trunk-type shaker and independent front-wheel and rear-wheel steering for good manoeuverability. Field testing was conducted on 7 Clingstone peach varieties to evaluate machine performance, tree damage, fruit removal, fruit maturity, fruit damage and economics. Machine performance was judged to he very good. Fruit quality was nearly equivalent to that obtained by hand harvesting and the cost of machine harvesting was fourd to he competitive with that of hand harvesting.

1.

Introduction

Interest in the mechanical harvesting of Clingstone peaches has increased in Italy because of labour shortages in agriculture and continuing increases in labour costs without a higher product price (see Fig. I). A probable worsening of these conditions ied us to believe that mechanical harvest of Clingstone peaches will become a need in Italy.

1300-

Lobour cost ; (Lit/hour) /’ I

1250pryows

88 x

- 2100

/

Number of

- 1900

/I

- 1700

/’

1200/’

p 1150z’

,.-k

- 1500

.-

-.

1’

/’

- 1300

f

- 1100

A

-900

// __-’

- 2500 -2xX)

/’

- 700

.--

1100-

500 Fruit puce (Lv/kg) . .._........,,,.,.

. . . . . . .““.‘.‘..

. . . . .._...... ..‘.

“..’....

300 100

(ec tlmote)

Fig. I. Trends in number of agricultural workers, labour costs andprices of processing Clingstone peaches received by growers in Italy. Monetary values are expressed in ltalian live (Lit)

This paper reports on the development and testing of a shake-catch harvester designed for use for Clingstone peaches to be processed. The machine, developed for orchard conditions considered typical in Italy, includes several unique features intended to accommodate the significant differences between Italian and Californian conditions. In California, costs and fruit quality are generally about the same with machine harvesting as with hand harvesting. Since labour has been available to harvest most of the crop, the transition from hand to machine has been gradual, ‘Consiglio Nazionale delle Ricerche, Centro Studi di Tecnica Frutticola, 40126 Bologna, l’ia Filippo Re 6, Bologna, Italy tDepartment of Agricultural Engineering, University of California, Davis, California 95616, U.S.A. Received 10 September 1976; accepted in revised form 8 March 1977

247

Harvesting

mode

Fig. 2. Modes

of harvester

operator

250

MECHANICAL

HARVESTING

OF

CLINGSTONE

PEACHES

extending over the last decade. About 20% of the California Clingstone peach crop is currently harvested by machine. 2. Engineering aspects of harvester The catching frame used was designed by Baldini and Zocca’ and was successively improved for these research trials (Fig. 3) to include the following features: (1) a very low profile to permit use in orchards with rather low-hanging branches; (2) a single-unit construction (as opposed to a 2-unit machine with one unit on each side of the tree), to permit one-man operation and to handle tree rows that parallel a drainage ditch or other obstacles which prevent machines from moving down both sides of the tree row; (3) decelerator strips over a major portion of the catching area; (4) a trunk-type shaker; and (5) independent front-wheel and rear-wheel steering for the better manoeuverability that orchard operation requires.

Fig. 3. Side view of harvester

in position for shaking

The layout of the harvester is shown in Fig. 2. The machine was low, about one-half meter high at the tree row, to permit sealing around the tree trunk. A 45-horsepower engine powered all machine functions. The machine was self-propelled through a 4-speed gear box allowing for ground speeds of up to 12 km/h. The decelerator strips on the frame were flat rubberized fabric, 6 cm wide, spaced 2 cm apart. Each strip had a metal hook at each end so that the strip could be easily removed from the catcher for any maintenance needed. The collection wings which form the right-hand side of the catching surface are retracted to a position over the wide horizontal conveyor during transport and moving from tree to tree. After the frame is positioned beside a tree to be harvested, the shaker is moved toward the tree until the clamp is in contact with the trunk, at which time the clamp is closed. Then the wings are extended -one on each side of the tree-and elevated to an incline of 15”, by a cam arrangement on the frame extension cylinders (Fig. 2). For testing, the space between the wings was covered by handoperated flaps. Once the shaker and frame were in position for harvest, shaking was done in one to three short bursts of about four cycles each. A brief period between bursts allowed the removed fruits to get

ANDREA

ZOCCA;

R.

B.

251

FRIDLEY

beneath the decelerator strips and thus be protected against impact from fruits removed in subsequent bursts. Harvested fruits move by gravity onto the draper conveyor, which moves laterally, conveying the fruits onto a lengthwise conveyor whicr in turn transports them to the bin (Fig. 2). 2.1. Shaker design The shaker, constructed in 1975, is patterned after a unidirectional shaker developed for olives by Fridley et al.* and used as a trunk shaker on pears and appkzs by Fridley et al3 The shaker has a 75-horsepower hydraulic motor. Oil is supplied to the motoi. by an accumulator. Three unique features incorporated in the design are: (1) a dual connectin: rod with an eccentric crank pin, facilitating changes in stroke from 0 to 14 cm (Fig. 4); (2) a tvro-arm clamp configuration which,

J

Fig. 4. Slider-crank mechanism fbr tree shaker. The housing and all parts fired to the housing are the reactive mass of the inertia shaker

when open, permits the shaker to be moved longitudinally toward the tree trunk for easy attachment (Fig. 5); (3) a support linkage consisting of a single-acting hydraulic cylinder pivoted at each end to permit the shaker to swing freely during operation (bottom of Fig, 2). A small accumulator connected to the lower part of the cylinder attenuates shake in the vertical direction. Stroke change is accomplished by removal of Allen screws A (Fig. 4) and rotation of eccentric crank pin B. The frequency of the shaker is preset by a flow-control valve which can be adjusted to permit shaking in the range of 400 to 1100 Hz. When frequency and stroke were not experimental variables, they were adjusted to provide effective removal for a given orchard and then left fixed during further harvesting. 3. Horticultural aspects The orchard used for the harvest trials was relatively web suited to mechanical harvesting.

252

MECHANICAL

HARVESTING

OF

CLINGSTONE

PEACHES

Fig. 5. Shaker clamp mechanism

Even so, a few problems were encountered since the tree training and land preparation had been intended for hand picking. The trees were vigorous Syear-old trees pruned in the form of an open-centred vase with as much low fruiting wood as possible. The basic tree shape was very good for mechanical harvesting though some pruning would be necessary for best results. The low-hanging branches impaired operator vision and generally interfered with machine operation; some fruiting limbs were relatively long hanger-type branches, too flexible for effective removal because of poor transmission of vibration; and some trees had trunks so short that the shaker could not be attached. The trunk diameters had a range too great for the particular clamp used, but this problem can be resolved by relatively minor design changes. 3.1. Ground conditions The orchard floor, like the trees, had been prepared for hand harvest. The irrigation furrows interfered with manoeuvering of the harvester, and cultivation practices had resulted in a high ridge of soil along the tree row, especially around the trunks. The interference caused by the furrows was minimized by driving parallel to them. Still, it was not easy to operate with one side of the machine down in the furrow and the other side elevated between furrows; also, crossing the furrows to move toward and away from the tree was difficult. The ridge of soil around the tree interfered with extension of the wings of the catching frame and with attachment of the shaker. The problems are not serious, however, and can be remedied by dragging or planing the orchard just before harvest. Experience in California indicates that growers resist tree modifications or land preparation in established orchards until they actually begin mechanical harvesting for themselves. Then the disadvantages of inadequate orchard preparation become greater than the small cost of the required changes. New trees are being so pruned that the trunk and primary scaffold branches are right for good machine operation. 4.

Field testing

Tests were conducted on the varieties Babygold 6, Babygold 7, Andross, Vivian and Babygold 9. The evaluations made were on machine performance, removal, fruit maturity and fruit damage. Harvested fruit was transported cannery, where it was peeled, evaluated for quality and canned. The canned opened after 3 months and again evaluated for damage. 4.1.

Fortune, Carson, tree damage, fruit to a commercial fruit was then re-

Machine performance

Overall performance of the machine was judged good. The harvester could be manoeuvered

ANDREA

ZOCCA:

K.

B.

FRIDLEY

253

around the orchard and from tree to tree with relative ease. l‘he only significant difficulties were the interference of low branches with operator vision and the rough ground condition. Each tree was harvested in about 90 seconds. Average harvest rate was about 30 trees per hour, including turns at the end of the rows and routine minor maintenance. 4.2. Tree damage Damage to the bark was a major problem in preliminary tests. Careful observation and past experience indicated that the clamping force was not sufficient to withstand the shaking force. The clamp therefore loosened during shaking and tended to c,hatter, breaking the bark loose at the cambium. Increasing the clamping pressure was not practical since the control valves were a bank of valves having a single relief valve. The original 5cm diameter cylinder was therefore replaced with a 9-cm cylinder, and the operator adopted the practice of ensuring that the clamp was tight by applying pressure to the clamp cylinder just befor:: each shake. One disadvantage of the clamp design is that the leverage of the clamp arms is decreased by attachment to large trunks--that is, leverage is best on small trunks that require a relatively small shaking force. Even so, tests with the large cylinder showed that bark damage could be avoided. 4.3. Fruit removal Results of the tests are shown in Figs 6 and 7. Removal o fruit was very good except when

Removal (%I

3a.a

Ii3 25.5

Frequency (Hz)

Fig. 6. Eflect of frequency

and stroke on fruit removul.

Shaking time 0.95 s

the stroke was clearly too small or the shaking frequency too ow. When removal was around 95 %, the remaining fruit was that on willowy branches which dampened the shaking action. 4.4. Fruit quality The quality of mechanically harvested fruit was acceptable in terms of both fruit maturity and fruit damage (Tables I and II). It was not practical to shake trees lightly for selective removal of mature fruits (Fridley et aL4). Thus, all tests were a single-pick harvest. Since the trees were trained for hand harvest there was some small green fruit in the lower central portion of the trees. Such fruit could be reduced without significant reduction in yield by pruning out the low

254

MECHANICAL

HARVESTING

OF CLINGSTONE

PEACHES

Removal P/d

4

16 Number of cycles

Fig. 7. Effect of the number of cycles and stroke length on fruit removal. Shaking frequency

18 Hz

branches and keeping the top centre a little more open. As mentioned earlier, pruning out of the lower branches is advisable also to improve operator vision. The range of maturity among fruits on the same tree can be minimized by avoiding excessive nitrogen fertilization. Observations of fruit damage (Bazzocchi et ~1.~~ confirmed results in California. Cuts and abrasion are caused primarily by fruit impacting against tree branches. Bruising is related directly to fruit maturity, for fruit softening increases susceptibility to bruising. Therefore, it is important for harvesting to begin as soon as ripeness permits. In harvesting on a single-pick basis, the optimum day for harvest is when there are equal numbers of immature and overmature fruit. (In evaluating the number of overmature fruit, the good overmature fruit which has dropped to the ground must be considered.) Thus, if harvesting will extend for more than one day, the grower should initiate harvesting with the fruit somewhat on the green side. Judgment is essential, of course, since inadequate maturity will lower the quality of the canned fruit (Bazzocchi et a1.6: Zocca’). TABLE I

Fruit quality when harvested by hand. Results are expressed as a percentage I

I Fruit quality before processing

Fruit quality after processing

Varieties Injured ---

Uninjured

Injured

Green

Vivian Babygold 6 Babygold 7 Andross Babygold 9

81.3 84.0 87.9 85.4 87.0 87.1 88.1

16.2 12.4 10.3 13.2 10.5 9.8 10.5

2.5 3.6 1.8 1.4 2.5 3.1 1.4

96.1 96.5 97.8 97.2

6.9 4.1 3.5 3.9 3.5 2.2 2.8

Average

85.9

11.8

2.3

96.2

3.8

Fortuna Carson

93.1 95.9 96.5

I

ANDREA

ZOCCA;

255

R. B. FRIDLEY TABLE II

Fruit quality when harvested by mechanical harvester. Results are expressed as a percentage and concern only fruit which was canned. Omittedis fruit which fell to the ground before or during harvest, fruit not removed from the tree, and undersized fruit

-

Vurieties

-

I

Fruit quality before processing

_--___

._

Uninjured

_--

Injured

--

I

Green

1 kit quality after processing Uninjt red _-

Fortuna Carson Vivian Babygold 6 Babygold I Andross Babygold 9

52.6 60.5 66.3 64.6 65.9 14.2 69.6

34.0 27.0 22.2 20.1 19.6 15.3 16.9

13.4 12.5 11.5 15,s 14.5 10.5 13.5

82. j 89.1 93, I

Average

64.9

22.1

13.0

90.

-

90. I 91. ) 91.’ 92. i

Injured 17.2 8.8 5.9 8.3 8.1 6.3 7.4

4.5.

1.9 1.0 1,3 0.9 2.0 0

8.9

--

-

Green ____-.-

1.0

-

Overall fruit recover)

According to Table III we notice that the major loss of prb)ducts in mechanical harvest compared with hand harvest is caused by undersize fruit and by unharvested fruit (those that remained on the tree or fell before harvesting). Loss of product caused by/ fruit injury is very limited because most fruit that cannot be utilized for canned halves can be l:sed for making fruit salad with a modest increase of manpower in the cannery line. The large range in the percentage of undersize fruit and fruit fallen before harvesting is caused by variations in yield and weather conditions at harvest time. In particular, bad weather conditions and a high yield cause fruit size and maturity to be hiirhly variable and cause many fruit to fall before harvest. TABLE III

Product recovery and loss for mechanical and hand harvesting. Average of 7 varieties. All results are expressed as a percentage of the total fruit on the tree Mechanically Average

Fruit fallen before harvesting Fruit dropped during harvest Fruit remained on the trees Undersize fruit Overmature fruit Green fruit Injured fruit usable only for fruit salad Injured fruit not usable for canning

2.9 0.6 2.1 8.7 1.7 1.0 7.5 1.4

harvest.ad Rang z ____1.5-4. :

04Q. ’ 1.5-2.:: 4.5--14 0 1.0.-2. .’

o--2.1I 4.9--15 2 1.0.-2.r I

Hand harvested Average

1.8 07 4.1 0.6 3.8 -

-

Range

l%-3.0 0.2-1.0 1.8-8.2 O-1.0 2.2-6.9 -

4.6. Economics Figs 8, 9 and 10, respectively, show computed harvesting costs for different fruit prices, fruit losses and yields. The costs shown include the indirect cost associated with loss of saleable yield in addition to machine and labour costs. Fixed costs are assumed to be 2,775,OOOLit every year for machine costs depreciated in 8 years; 8% interest and operating costs are assumed to be 6900 Lit per hour for labour, fuel and repairs. It was assumed ?hat the machine could be used for 300 hours per year.

256

MECHANICAL

HARVESTING

OF

CLINGSTONE

PEACHES

25,000 i20,000 20 metric ton per hectare

1

I

\

25 metric ton per hectare

I

I

I

I

20

30

40

50

Hectares

I

I

60

70

harvested

Fig. 8. Effect of crop yield and harvested area on cost of harvesting including the indirect cost offruit loss. Mechanical harvest at 30 treesper hour with Lit 150,000 per metric ton fruit value and 10% fruit loss

35,000

30,000

-

25,000

Lit 250,000

,\--

per metric ton

y..:yL___-Lit 200,000

per metric ton

Lit 100,000

per nwtric ton

20,000

15,00( 1

I

I

I

20

30

40 Hectares

Fig. 9. E&t

I

I

I

50

60

70

_

harvested

of crop value and harvested area on cost of harvesting. Mechanical harvest at 30 trees per hour with 10 % fruit loss and 20 metric ton per hectare yield

Economic harvesting by machine depends on good management, including orchard preparation, besides management of the harvesting operation. It is important to keep the machine busy

ANDREA

ZOCCA;

R.

B.

257

FRIDLEY

throughout the harvesting season. To do so requires selection of varieties which will provide a long harvest season. Also, acreage must be matched to harvester capacity and the number of days during which a given variety can be harvested (about 3 to 5 ilays). It is essential that irrigation be planned so that wet conditions will not cause delays.

15,000

,

Ly

I

I

I

I

20

30

40

50

Hectares

60

70

horvested

Fig. IO. Effect of amount of crop loss associated with mechanical harvesting on cost of harvesting. Mechanical harvest at 30 trees per hour with Lit 150,000 per metric ton ,fruit vale and 20 metric ton per hectare yield 5.

Conclusions

Mechanical harvesting of Clingstone peaches has been shown to be feasible in Italy as it is in California. A harvester designed for Italian conditions was found to be very effective. Fruit quality was nearly equivalent to that with hand harvesting, and the costs of machine harvesting were found to be competitive with those of hand harvesting. The primary impediment to machine harvesting would appear to be failure to prepare the orchards to accommodate the machines. REFERENCES

Baldiui, E.; Zocca, A. Zndagini sulla raccolta meccanica dei frutti: caratteristiche di un nuovo tipo di “telaio raccoglitore”. Riv. Ortoflorofruttic. ital., 1972 3 31-99 ’ Fridley, R. B.; Mehlschau, J. J.; Hartma~, H. T.; Logan, S. H. Mechanical harvesting of olives. Trans. ASAE, 1973 16 (1) 58-61 ’ Fridley, R. B.; Claypuol, L. L.; Mehlschau, J. J. A new approach 10 tree fruit collection. Trans. ASAE, 1975 18 (5) 859-863 ’ Fridley, R. B.; Adrian, P. A.; Claypool, L. L.; Riii, A. D.; Leonard, S. J. Mechanical harvesting of Cling peaches. California Agricultural Experiment Station Bulletin 851, 1971 5 Bazzocchi, R.; Marangoni, B.; Zocca, A. Influenza de1 metodo di raccolta sulla qualita dellepesche sciroppate. Riv. Ortoflorofruttic. ital., 1975 3 204-209 6 Bazzucchi, R.; Laudi, P.; Maraugoui, B. L’epoca e il costo delltr raccolta meccanica delle percoche. ’

Italia agric., 1971 8 (108) 741-748 7 Zucca, A. Ulterioriprove di raccolta meccanica delle percoche. Attt S.O.I. “La raccolta meccanica ed i sistemi di allevamento per la frutticoltura da industria”. 1975, 53-61