The sheep farming series comes to an end. In our last edition, we discuss a few odd topics like slatted floors, gates and wool tables, bins and presses.
We thank the ARC Agricultural Engineering in South Africa for making their manual on sheep production and facilities available to the readers of ProAgri Zambia.
Slatted floors are usually from hardwood with typical cuts of 50 x 25 mm or 50 x 38 mm. One of the sides is usually bevelled so that the opening is larger on the bottom than on the top. The bevelling decreases the chance that the slits will become blocked. See Figure 1.
The slats are usually placed diagonally to the direction of movement so that the sheep cannot see through the floors. It is especially important where direct sunlight falls on the floor, such as at the entrance and along the northern and western walls. The direction in which the slats are laid in the centre of the building is not that important, because the underfloor part is dark anyway and will not influence movement negatively.
Other materials that can be used include concrete, steel mesh, expanded metal and aluminium, plastic or glass fibre sections. These materials are usually more expensive, but the installation time is much shorter. The steel mesh, concrete or expanded metal floors can be built in loose panels that can be taken apart easily. Sheep will initially be wary to walk on these, mainly because of the noise and the fact that the floor is more transparent, but they get used to it, without a negative influence on the flow tempo. Very little corrosion is experienced with the steel floors, because the waste is not in direct contact with the steel for long.
Incorrect placing of gates can hamper handling. It is important that joining bolts are cut off short and wire ends are fully bent back to prevent possible injuries. Typical placement of gates is illustrated in Figure 2.
Many forms and types of gates are commercially available or can be home made.
Gates must be wide enough (0,6 to 2 m) to let the sheep through. Camp gates can be up to 3 m wide to allow tractors as well. The height of the gates is usually the same as that of the fence. Gates can be either of the swinging type or the lift-up type. At handling facilities, the lift-up type usually has the benefit of closing quicker and easier than the swing-type.
The most commonly used wool table is the rectangular type measuring 3,0 x 1,5 m and 0,85 m high (Figure 4). The table-top consists of 32 x 32 mm planed wooden slats, spaced at intervals of 32 mm.
The table-top surface is made this way so that double cuttings and small pieces of wool can fall through onto the floor. The fleece thrower throws the fleece with a distinctive technique onto the skirting table, so that it lays spread out on the table. The classifier and the skirter then skirt the fleece and carry on with the separation of the fleece and the classing of the different fleece parts. Skirting is usually done by two persons.
It is important that there should be good, practical lighting above the sorting table. It may, however, not be direct sunlight, because it results in inaccurate grading and also stressed eyes. It is important that there should be unobstructed space for movement around the wool table. At least one metre of space is proposed.
In an endeavour to increase productivity, round rotating wool sorting tables were later introduced, on which the wool is moved to the grader and not vice versa (see Figure 5). Especially in smaller shearing sheds round tables are more practical. Skirting can easily be done by one person. In larger shearing sheds, where more handlers are available, the benefit is not that great. Round wool tables are however only recommended for experienced graders.
Movement space and the light situation for round wool tables is the same as for rectangular tables. The construction of the tables must be as light as possible, so that the tables can turn by merely handling the wool with the fingers. The grader must get used to the idea of not walking around the table, as with fixed tables, but to turn the wool towards him. In shearing sheds of three to six shearing points, two round tables next to each other are used. The grader stands between the two tables and works on them alternatively.
In larger shearing sheds, L-shaped tables are also used. The grader stands in the V of the table and works the fleece on one leg while the fleece thrower throws the next fleece on the other leg of the L. The disadvantage is, as with rectangular tables, that the grader must walk around the table.
The wool bins serve as temporary storage space for graded wool until there is enough wool for baling. It is important that the manner of storage is such that the wool can be transported to the wool press easily and with the minimum effort. In the past, fixed wool bins were used. This meant that large quantities of wool had to be reloaded and carted to the baling press. In order to do away with this unnecessary handling process, mobile wool bins, with sufficient capacity to fill a bale, were introduced. When the bin is full, the entire bin is taken to the baling press. An example of a movable wool bin is shown in Figure 7.
Different materials can be used to construct movable wool bins, but material to which the wool might cling should be avoided. Wooden planks, plywood or chipboard can only be used if it is finished very smoothly and painted or varnished.
Steel is also a useful, but expensive material. Wire netting and expanded metal has sharp corners on which wool gets hooked and must be avoided. It seems that wire mesh with a mesh hole of 50 x 50 mm is a good material to use. The wire mesh is welded onto the framework.
A cheaper and possibly easier way of temporary storage is by means of baling bags affixed in a bale container. The bale container (Figure 8) is a square steel framework with four legs. The baling bag fits into the square and is hooked onto the corners. The wool is placed into the bag and stamped down from time to time. When the bag is full, it is unhooked, the bag is pulled out of the container and taken to the wool press.
A method for making the collection of wool pieces on the shearing floor easier, is by having openings in the floor, under which baling bags can be suspended. The openings are safeguarded by steel grids. This method is limited to shearing floors which have an overhang for easy use. If there is no overhang, the method may be used, but then the baling bag must be installed from the top and pulled through the opening when it is full. This can be difficult to do when the bag is full. The usefulness of these “locks openings” is, however, questioned by some experts.
Mechanical presses were initially in general use, but hydraulic and electrical presses are more popular now. Presses can also be automated, but at a high cost. Presses are available in the trade and specifications depend on the brand. These specifications are therefore not discussed.
It is important that sufficient free space is provided around the press for movement and standing room for wool bins. A movement space of 1 m around the press is sufficient for movement. A strip of 1,5 m around the wool bins at the sorting space and the pressing space will be sufficient for pushing full wool bins to the wool press.
Next month we shall start with a new series on dairy farming.
Published with acknowledgement to the ARC Agricultural Engineering for the use of their Sheep Facilities Manual. Visit www.arc.agric.za for more information.