The Midway

A simple but viable whole stalk harvester for operating under local field conditions, which is compatible with existing manual and mechanical loading and hauling systems, is described. The efficiency and output of the cutter which has been tested over a number of harvesting seasons, and the operating costs are estimated. Various systems of handling both green and burnt cane by the Midway are compared. Introduction The design of the Midway cutter was the result of experiences gained in operating the Sasex (Pilcher & van der Merwe3) and Edgecombe (van der Merwe et a14) cane cutters. It was felt that an improved cutter could be developed by retaining the simplicity of the Sasex and eliminating the problems caused by mounting it on the side of a tractor or by rear mounting an Edgecombe cutter. The location of the base cutter and the operator's poor visibility made it difficult to maintain proper base cutting height with both the Sasex and Edgecombe cutters. An advantage of the Midway cutter is that the cane tops are collected which makes it possible to load cane mechanically directly after it has been cut. The machine was tested and developed at the Experiment Station's La Mercy farm from 1978 to 1982. Description The Midway cutter is able to top and base cut a single row of burnt or green cane. The cane stalks are left in a single 'sausage' windrow parallel to and between two cane rows. The tops may be collected in a bin if so required. The prime mover is a Ford 5000 tractor which is fitted with a County reduction gearbox to give a wider range of forward speeds. Power steering and 305 mm rear wheel spacers are used. The wheels are spaced for maximum stability and to assist the operator in controlling the cutting height of the mid-mounted base cutter. Wheel spacing is such that the cut cane lying on the ground is not trampled. The only other modification to the tractor is that the cooling fan is reversed but none of the tractor controls are altered. FIGURE 1 General view of first prototype of the Midway cane cutter. CANE CUTTER Meyer .iment Station, Mount Edgecombe, Natal The topper, base cutter and hydraulic controls are attached to a 100 mm square tubular frame bolted to the tractor. The 800 mm diameter base cutter is bolted onto the main frame directly in line and ahead of the right-hand rear wheel of the tractor. It is hydraulically powered by a Bignozzi DS 150 radial piston motor and the height adjustment is controlled by a double-acting hydraulic ram. The topper boom is hinged onto the main frame from a point above the base cutter and locates the topper slightly ahead of and parallel to the tractor's bonnet cowling. The topper is hydraulically powered by a single S Series Charlynn motor (part NO. 1031028-007). A collecting bin for cane tops is mounted in front of the tractor (Figure 2); when it is full, the cane tops are discharged by means of a hydraulic ram. A 100 litre hydraulic oil tank and filters are mounted on a toolbar attached to the tractor's three point linkage. Hydraulic power is provided by a Melinda GPPl 40/30 double pump driven by a Hubcity 3,318:l ratio pto mounted gearbox. The 40 section of the pump operates the base cutter only and the 30 section powers the topper motor and all the hydraulic rams. All hydraulic controls are mounted on the left-hand side, in front of the operator. Operation The operator's visibility is good and this has resulted in the required control of base cutting height. The location of the hydraulic controls and the general positioning of the operator in relation to the base cutter and topper result in minimum driver fatigue. The general manoeuverability of the machine is excellent. The limited overhang at each end of the tractor means that a relatively narrow headland is required for turning. Power steering and independent brakes give the machine a tight turning circle. Cutting takes place on one side of the machine and on one face only so, to maximize the cutter's output, two faces should be worked. Breaks can be opened in a field by the Midway but at least one or two rows of standing cane are trampled in the process. These trampled rows are usually cut later with the Midway travelling in the same direction as it did when opening the break. The La Mercy farm's standard row spacing of 1,5 m is ideally suited to the machine although spacings down to 1,2 m are acceptable. The cutter is able to work on slopes from 0 to 32% and on the steeper slopes it performs best when the base cutter is on the uphill side of the tractor. When the base cutter is on the downhill side on these steeper slopes, the tractor crabs badly and knocks down and tramples the cane before it is cut. The width of the machine between the centres of the rear wheels is 2,45 m which makes it extremely stable on slopes. The cutter handles burnt cane yielding up to 120 tons per hectare and green cane yielding 100 tons per hectare provided it is not badly lodged. Cane lodged in the direction of travel causes no problems but twisted cane or cane lodged across the rows or against the direction of travel make conditions difficult for the machine. Badly lodged cane can be cut but cane quality is affected by broken stalks and poor topping efficiency and losses are high. During the 1982 season the Midway cutter was completely rebuilt to simplify its construction and to improve operator comfort while cutting bun t cane. A modified Mormat allweather cab was fitted and an additional ventilation fan was 224 Proceedings of The South Afican Sugar Technologists' Association June 1984 installed to cool the interior of the cab. The persistent problem in either light or heavy soils. The eight-bladed disc generally of overheating was finally solved by mounting the standard gave the cleailest cut when the blades were new and operating radiator at the rear of the tractor to reduce the amount of at ground level. Too high a forward speed, badly worn blades extraneous matter which was previoiusly sucked onto the raor cutting too high above the ground increased losses. The base diator fins. An hydraulically powered fan provides the air flow. cutter is set at an angle of 2l/2" to the horizontal. TO reduce even further the amount of trash which accumulated Because only two-thirds of the base cutter disc is used effecon the radiator, a large rotating screen has been positioned on tively, stool pruning should be practised on older ratoons to the air intake of the fanA separate small electric fan keeps restrict their lateral development. The life of the base cutter the surface of the screen clean (see Figure 2). blade depends on field conditions and can be expected to cut A more modem, dual purpose topper has been developed from 500 to 3 000 tons. and the lifting height of the base cutter has been increased by The neatness of the 'sausage' windrows is determined p i 140 mm. marily by the condition and yield of the cane. Short and lodged cane generally produces an untidy 'sausage' while the best results are obtained from tall, erect cane. The steepness of the terrain and the cutting speed also influence the neatness of the 'sausage'. Green cane 'sausage' windrows are always very neat and this facilitates subsequent operations by hand or machine. The topper performs well in burnt cane and the tops are cut into pieces approximately 150 mm long so that the holding capacity of the bin for tops is increased. The risk of loading and sending tops to the mill is reduced when they have been cut into smaller pieces. The amount of cane top delivered to the mill depends on the quality of the burn, the erectness of the cane, and the evenness of its height. The tops dumped in the field are easily avoided by the mechanical loader or manual labour when the cane is loaded. These tops should be spread evenly over the field later. More power is required to top green cane so the knives and anvils on the upper rings of the topper can be removed to reduce the load on the motor. This results in whole tops being thrown into the bin which remains in the tipping position and so directs the tops to the ground between two rows of cut cane. Topping efficiency is poor with only 36% of the stalks being topped correctly, ie at the natural breaking point of the cane. FIGURE 2 Latest model of the Midway cane cutter. Considerably more than 36% of stalks are topped when those which are topped slightly higher or slightly lower than the optimum height are included. Quality of Work The best base cutting was obtained in flat fields and under Performance and 0.utput flat culture conditions. Where cane was grown on a slight ridge, The performance of the Midway is determined largely by its there were no problems provided the cane was erect and the prime mover, in this case a 1971 model tractor producing 42 height of the ridge was uniform along the length of the row. pto kW. The performance data of the cutter during the 1981/ There was more damage to cane stalks where they had lodged 82 season are given in Table 1. These figures include time lost and were growing on ridges. The base cutter was not able to in travelling to and from the fields. The cutter's performance lift the cane stalks lying in the interrow over the base cutter is increased substantially in well prepared fields; row length, disc and tended to cut them into pieces. Mechanical loading yield and recumbency of cane are the most important factors was difficult in fields where the cane rows were hilled-up and affecting output. According to the tractor's hour meter, the avwhere cane was grown in a hollow, losses were high and the erage output of burnt cane was 17,6 tons per tractor hour or stubble was ragged. The high peripheral speed of the blades of 25,l tons per clock hour, a ratio of 1,43:1. The Midway con1 350 m per minute (477 rev/min) did not disturb the stools sumed 0,32 P of fuel per ton of cane that was cut. TABLE 1 Cutter performance during 1981/82 season Time studies were conducted at La Mercy while burnt cane was being cut. The results shown in Table 2 include data for TABLE 2 varying row lengths and degrees of slope and an average yield Field efficiency of cutter in burnt cane of 80 tons per hectare. A good field efficiency of 85% was obTotal area (ha)