Without the harsh light of reality, engineers trying to develop products for farmers can never get it right; something unexpected always jumps up and bites unproven gear in the bum under field conditions.
And so it was that Andrew and Jack – MEA’s two senior and most experienced engineers – made the run down the Murray Valley Highway to the vast almond fields of Victoria in the Spring of 2013. Here we set up our prototype 6m Plexus masts in a vast 1200 hectare property with undulations like the Mad Mouse at the Adelaide Showgrounds.
It immediately became apparent that these very sandy soils (the remnants of ancient sand dunes) just did not have the mechanical strength to support such a tall structure; we could literally push the supporting star-droppers into the sand with one hand.
A second problem sprang from the fact that all the surrounding almond trees were conspiring against us; one needed to choose a line between these trees to lay out the 6m mast before proceeding with the seemingly simple business of tilting it up.
Problem three was that, even though the mast was light-weight aluminium, without a hinged pivot point it needed three men to raise and lower this 6m+2m high structure safely. Our first attempts drifted all over the scenery.
The final problem was the first problem; couriers and carriers will not handle packages longer that 6m. We were exceeding that by the time we’d got end adaptors fitted and everything packed up sufficient to survive interstate travel.
So back to the drawing board in Adelaide…
The solution developed by Jack was to create a 2m-high sheet-metal C-channel that included a fixed pivot point near ground level, had wings below ground to stop it slumping around in gutless sands, that could be hammered into the ground using a customised dolly and would allow a single installer to raise and lower the pole safely while working alone. And yes, we shortened the main pole back from 6m to 5.8m to get them onto standard transport.
Humbled by Mother Nature and 6m poles, Jack took personal responsibility for Round 2 of the Plexus tall pole installation saga. This installation was in an almond grove in Griffith NSW. The new shipping arrangements worked out fine, Jack flew in and the on-site manager helped push the new base brackets into the soil using the bucket on a convenient backhoe, driving them gently into the soil.
All good now, but why all this fuss about tall Plexus poles?
Lots of perennial tree crops – almonds, olives, avocadoes, macadamias, pecans, citrus, bananas and lychees – all block solar and radio access for systems below canopy height, so we need to get the Plexus field stations as high as possible for maximum transmission distance and reliable power supply.
Are our troubles over?
Justin Clarke in our Queensland office came back and introduced us to the realities of pecan farming, where trees nudge 20m in height.
So then we sent gear up there and tested that in avocadoes and pecans, transmitting below canopy level and with partial shade.
Data flowed - we’ll keep up those field tests!
Dr. Andrew Skinner
on 07 August 2014