3. Results
3.1. The mechanical device: design and construction
A bespoke rotary system for use in circular tanks was constructed.
The device (Fig. 1) which comprised of a novel bearing unit rotating
arounda 350 mmhigh×40 mmdiameter standpipe in an anti-clockwise
movement powered by an Airpax 12 V stepmotorwith a 7.5° step angle
geared down through a McLennan G11L82 25:1 gearbox and finally
geared down again through a 5.5:1 internal gear housed within the
Fig. 1. A cross section diagram of a circular tank showing the bespoke cleaner unit in situ that consists of a bearing shell operating around a central standpipe. A controllable step
motor, gearbox, and driveshaft connected to the basal bearing moves the modular wiper arm round a tank at pre-determined speeds. A key part of the cleaning device is the bearing.
The bearing consists of four main components, a base that has inlets to allow water and detritus to flow through, a middle section to which the wiper arm attaches, an inner gear that
connects to the driveshaft via a spur gear, which allows the unit to turn, and finally a top section to cover and protect the gears and bearings from detritus. A modular wiper arm,
which can be extended by the addition of extra brush units to fit the exact diameter of the tank to be cleaned, dislodges debris, which is moved towards the centre where the
standpipe creates suction drawing the material in and away. The step motor and gearbox are readily interchangeable to provide variable speeds of wiper arm rotation to meet the
needs of specifically sized tanks and husbandry requirements of different tank water inflow rates, stocking densities and rates of cleaning.
A.S. McRobbie, A.P. Shinn / Aquaculture 317 (2011) 16–19 17
device (Fig. 1).