WeedSwiper - Frequently Asked Questions
Posted Aug 27, 2019
How does the control system (the Hydrostat) work?
The Hydrostat is powered by the tractor battery and works in a manner similar to a thermostat. A thermostat regulates room temperature by switching a heater on and off in response to temperature changes in the room. The Hydrostat regulates the supply of herbicide to the pad in response to the changes in the amount of herbicide in the pad. As a consequence, the pad is always saturated to a level just below the drip threshold no matter how dense the targets are or how fast or slow the WeedSwiper travels. There is a good transfer of herbicide for a good kill, but the pad does not drip. Valuable crops or pasture are not put at risk from drips.
What if a different herbicide is used? Does the system have to be recalibrated?
The Hydrostat never has to be "calibrated" in the sense that a boom spray is calibrated. Every time the Hydrostat is switched on, the operator "recalibrates" it. This is done by setting the knob to the balance point appropriate for the particular concentration and type of herbicide being used. Even with a new mix it takes only a minute or so for the true concentration to reach the sensors, after which it is only a matter of seconds for the controller to settle. Operators soon learn the approximate range of a mix and fine tune as they go. The Hydrostat can operate on a range of herbicides from dilute Lontrel™ to 33% glyphosate.
If the sensors are only 300mm apart in the centre of the boom, how does the Hydrostat know what is happening along the rest of the boom?
In practice, it is not necessary to monitor the total length of the boom. Theoretically it is possible for one part of the boom to be saturated and another part very dry. This could happen if a very long line of dense targets were wiped so that the herbicide was removed from only one section of pad outside the sensors. In practice, targets are usually positioned randomly, and the problem does not arise.
What are the pads made of?
The pads are made from industrial quality synthetic felt, which has a central core of woven nylon mesh (for strength) through which is tufted synthetic fibre.
How long do they last?
That depends on the targets being wiped. When used on thorny or hard plants such as blackberries or cape broom, the bottom leading edge of the pad shows considerable fraying after 100 hours or so. Conversely when wiping grasses for pasture topping, the pad will last for many years provided it is stored out of sunlight. The pads are not expensive to replace.
What are the outrigger springs made of?
The springs are rubber storm water pipe rings.
Are they strong enough?
For most work, yes. There is a trade-off between having a strong spring to hold the outriggers straight in dense brush and a soft spring which will allow the outriggers to swing back and still return to the work position without stressing the machine. The current design incorporates rubber buffers in the outriggers, allowing two springs to be fitted. If the targets being wiped are so dense that the outriggers are frequently or continually forced back, we recommend that they be folded back, and the delivery hose disconnected or removed. It takes only a few seconds to remove each outrigger.
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