by GJ Stoltz (Reg Eng Tech)
This month we discuss windrow screens and safety guards, guide wheels, tine arms, carriers and the operational features of the single rotor rake.
We thank the ARC Agricultural Engineering in South Africa for making their manual on rakes and tedders available to the readers of ProAgri Zambia.
Windrow screens and safety guards:
The windrow screen is mounted on the side of the rake and is kept in place with a bolt (see Figures 1 and 2). The width of the windrow is adjusted by removing the bolt and moving the screen inwards or outwards. The bolt must be replaced by using any suitable hole in the cross-member of the windrow screen when adjusting the width of the windrow. A sub-frame is mounted on each side of the main frame to serve as safety guards so that the tractor operator does not bump the tine arms and tines against trees or any other objects by accident (see Figure 2).
Guards, and also the windrow screen, can be folded upwards when transporting the rake, or storing it.
The rake is mounted on two centrally placed height-adjustable castor wheels (also called guide wheels). Four wheels are also sometimes used, in tandem, for adjusting the raking depth of the tines and to keep the machine as stable as possible during the raking process. Tandem wheels also allow maximum smoothness during operation at high land speeds (see Figures 3 and 4).
The tine height can, on some models, be set by adjusting the guide wheels hydraulically from the tractor so that the tines can match the length of the stubble and different ground conditions.
The pivoting guiding wheels are equipped with balloon tyres that perform very well on hay stubble and irregular terrain (see Figure 5). The guide wheels can also be adjusted up or down by turning a mechanical screw on top of the centre hub, also known as the central positioned hexagonal axle support (see Figure 6).
Tine arms carrier:
The tine arms are detachable and can be transported in a suitable carrier on the main frame of the rake (see Figures 7 and 8). This carrier consists of racks for securing the tine arms. The tine arms are detachable for reducing the transport and storage width of the rake.
Single and double rotor rakes are positive in their raking action, but due to their high peripheral tine-tip speed, excessive leaf loss and shattering may occur in leafy or dry crops.
Airy windrows, with little soil contamination, can be expected from this type of rake.
The land speed will be determined by the type of crop to be raked, and the power requirements differ between 11 and 15 kW. A single rotor rake can weigh up to 300 kg. With a rotor diameter of 3,6 meter, a single rotor rake can cover as much as 3,2 hectares per hour at a land speed of 10 km/h.
The three-point hitched, single rotor rake, can be raised up to a height of 50 cm from the driver’s seat (see Figure 9).
The following types of windrows can be formed with a single rotor rake:
- Single windrow (see Figure 10)
- Double windrow (see Figure 11)
- Multiple windrow (see Figure 12).
Front-mounted single rotor rakes can also be used to form windrows (see Figures 13a and 13b).
Next month we shall look at the double rotor rake. Published with acknowledgement to the ARC Agricultural Engineering for the use of their rakes and tedders manual. Visit www.arc.agric.za for more information.