Farm Machinery and Equipment-II

LESSON 15. ROOT CROP HARVESTERS FOR POTATO, GROUNDNUT-DESIGN CONSIDERATIONS

A.  According to the source of power:

i) Manual operated, viz. hand tools and digging aids such as spade, khurpa, digging and picking fork etc.

ii) Animal-drawn equipment such as potato-plough, animal drawn groundnut digger etc.

iii) Tractor operated equipment such as spinner-digger, elevator-digger, groundnut-digger-shaker-windrower, sugarbeet-harvester, carrot-harvester, radish-harvester etc.

iv) Self-propelled machine such as potato-harvester/combine, groundnut combine, sugarbeet harvester etc.

B. According to the mode of hitching:

i) Trailed type

ii) Mounted type

iii) Semi-mounted type

iv) Self-propelled type

C. According to the unit operations performed:

a) Simple digger

b) Digger-shaker

c) Digger-elevator-windrower

d) Digger-shaker-conveyor/digger-shaker-windrower.

D. According to completion of operation:

i) Direct harvesting equipment, i.e. equipment which accomplishes the complete operation of digging and separating to the soil as well as of collecting the recoverable products in one 'go'.

ii) Indirect harvesting equipment, i.e. equipment which accomplish the complete operation in more than one passes. For instance, a groundnut digger shaker windrower digs the vines and deposits them in a windrow after shaking out the soil. The vines are sun-dried for a few days and thereafter a groundnut combine with a pick-up attachment is used to pick the vines and separate the nuts.

Considerations for proper field operation of root crop harvesting equipment: Following are some of the general considerations for efficient utilization of the root harvesting equipment:

(i) Proper field layout

(ii) Proper planting method

(iii) Proper moisture content at the harvest time

(iv) Pre-harvest treatment such as haulm-cutting, vine-killing etc.

(v) Proper adjustment of the depth of the digging.

(vi) Proper hitching of the machine.

(vii) Proper adjustment of the speeds of the picking, conveying and shaking system

(viii) Selection of desired forward speed in keeping with the field and crop conditions.

(ix) Number of workers in the crew to pick and collect the material simultaneously.

(x) Matching of the transport and handling equipment to the capacity of the digger/harvester.

(xi) Proper harvesting, maintenance and repairs of the equipment.

General design considerations for root crop harvesting equipment: For designing a root crop harvesting equipment, the following points should be kept in view:

a) Variety of the crop and its cultural practices: In case the existing varieties and cultural practices pose some problems in mechanical harvesting, attempt should be made to make necessary modifications.

b) Soil Type: The soil type and moisture content at the time of harvesting are important factors influencing the machine performance. Suitable soil-amending substances may help to develop the proper soil-texture to eliminate problem of excessive blade clogging and clod-formation. The soil for root crops should be friable for easy separation.

c) Method of Irrigation: One must carefully consider the method of irrigation being followed. Depending upon where the crop is sown on ridges/beds/flat surface, proper method of irrigation should be selected. The availability of right moisture content at the time of harvesting is very essential for proper penetration of blade and efficient soil-fragmentation.

d) Machine design considerations:

(i) Type of the digging shovel, shape and size.

(ii) Conveying and separation system. It must be efficient to handle and separate the loose material with minimum injuries.

e) The height of fall: Avoid excessive height of fall of the roots/tubers to lesson injuries. If required use inside rubber padding at the components to minimize external/internal injuries.

f) Proper speeds: The speeds of the components used for the translocation and separation of the material should be such that these do not lead to excessive agitation, damage and loss of the products.

g) Controls: The various controls for raising and lowering of the blade, varying speeds, etc should be carefully designed. Provision should be made for adjusting the speed of the components in accordance with the field conditions.

(h) Use of Multi-speed gear box and vary-speed drives is desirable on root crop harvesting machines.

Operational design considerations: Design requirements of the root crop harvesting equipment should be as follows:

(i) The digger should cut the vines below the tuber zone, say at a depth of 7 to 10 cm, lift all vines, shake off the soil and put them in a windrow in single operation.

ii) Desired penetration of the blade should be possible at the working moisture contents of the soil.

iii) The digger should work with a seasonable overall efficiency for both erect and spreading varieties.

iv) Pod detachment losses for the existing varieties should be reasonably low.

v) It should be possible with a tractor of 30 hp or more.

vi) It should be mounted type for easy transport and better operational manoeuvrability.      

Types of Blades used: Three types of blades are usually used in the diggers. Half sweep types blades are sometimes not used as the flow of material is not smooth and some undug plants are also left. The single piece curved blade is commonly used in the diggers.

Adjustments & method of working: Before working the machine, necessary adjustments should be made. The depth of penetration of the blade is adjusted with the help of the gauge wheels and by lengthening or shortening the top link of the tractor. Normally, a depth of working of 7.5 to 12.5 cm or about 4 cm below the pod zone is adequate.

The front end of the shaker conveyor should be adjusted with the help of a hand lever, so that the spikes on the cross bars do not go too deep in the soil. These should comb the top about 3 cm of the soil. Precautions should be taken not to run the teeth deeper than necessary as it increases the load on the shaker conveyor and makes separation of the soil from the vines more difficult. Forward speed of the tractor should be kept between 2.5 to 3 kmph. Speed of the shaker conveyor should be about 10% more than the forward speed of the tractor to clear the harvesting stuff quickly without accumulation. After making necessary adjustments, the machine should be operated in the field. For better efficiency and output, it is necessary that the machine should be operated along the length of the field, which should also be the direction of the rows. The size of the fields should be kept as big as possible.