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The high power availability and hence high fuel usage demand high productivity. This translates into
high machine pour rates. In addition, high parasitic losses (e.g. cooling losses, component no load
power consumption) reduce overall machine efficiency. Improved machine component-crop
interaction (e.g. improved feeding) and minimising weight can reduce the need for high power
requirements.
Mallee system
Energy inputs for chipping are high due to the high wood density (750 to 850 dry kg/m 3 ). The Claas
Xerion has an engine power output of 357 Hp at 1800 rpm (six-cylinder CAT C-9 8.8L). As the
chipping system requires high and constant speeds, the harvester attachment is driven by the rear
PTO and requires almost all the rated PTO power of 303 Hp at 1800 rpm.
The performance of the prototype mallee harvester is limited by available power. Increased power
will be required to provide economically viable pour rates, possibly in the vicinity of 500 kW, with
most of that power required by the chipper.
2.2.2.4 In field transport
Mallee system
Mallees are a dispersed resource, with harvest yields typically of about 1 -2 green tonnes per paddock
hectare (though yields will be about 60 green tonnes per belt hectare). This low harvest yield means
infield transport will be over relatively long distances, so haulout capacity will need to be large and
speeds will need to be as high as possible.
In addition, it appears unlikely that the biomass can be tipped from bin to bin, as is common in cane,
because the tipping action will reduce the bulk density of the loads, and trucks will be limited by
volume rather than weight. Considering the long road haul distances, this loss of bulk density is also
unacceptable.
Due to this combination of factors, it is probable that haulouts will need to be at least 25 tonne
capacity and about 70 cubic metres in volume, so that loads can be transferred from vehicle to vehicle
undisturbed within the containers that are filled by the harvester. Large haulouts could become
another driver for high pour rates from the harvester, as these large capital-intensive machines will
demand a high flow to dilute their costs. High harvester pour rates necessitate heavier mallee crops,
and increasingly push the harvester itself towards higher power and increasingly heavy robust design.
2.2.3 Discussion
The sugarcane industry does not have a uniform row spacing and standardised row-spacing
configuration. Furthermore current sugarcane harvesting equipment has a detrimental agronomic
impact on current 1.5 m row spacing systems. The industry is thus moving towards a controlled
traffic system which will also control the impact of harvesting equipment on soil compaction.
Sugarcane and the current prototype mallee harvesters have similar mass and engine power as
indicated in table 2.1 below. However future mallee harvesters will need about twice as much power
and if tracked, they will need two pairs of tracks, which will add to the weight of undercarraige
components. The pressure to increase harvester pour rate will also necessitate a more robust machine,
adding further weight.
Similar “systems-thinking” and integrated harvester/soil/crop solutions will be required for the mallee
harvester and infield machinery configurations. High harvester output is critical to reduce costs per
tonne of biomass while minimising impact on the mallee plant coppice and adjacent production areas.
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