Saturday, August 16, 2014

How we make large hydroponics runs

For want of a better place to document the process, here's how we make our hydroponics runs. We make them in 2 sizes; this is the 150mm x 100mm version, using a 3m length of PVC rectangular downpipe. The ends must be cut off square and smooth so the endcaps fit.

The downpipe is marked off starting 70mm in from one end every 230mm with the seam (if there is one in the downpipe) uppermost. A mark is also made on the underside corresponding to the first 70mm mark. This is for the drainage hole underneath and an inspection hole on the top.
The drain hole is drilled out to suit whatever type of drainage bung you're using at the time (sometimes I drill these later), the inspection hole is drilled to 45mm, and the plant pot holes to 82mm. We find that is what we need to get a so-called 3 inch pot into. To do this we use a small drill press and hole saw.

Now, as a surprising amount of hot crap gets flung around by the drill at this point, even I can be persuaded of the benefits of wearing safety glasses and tying my hair back. Check the fit of a pot after drilling the first hole, just to make sure you're not about to wreck a fortune in downpipe.

Once the holes are drilled, take off any wiry edges with a de-burring tool, rasp or whatever so the pots fit in neatly and the gardener won't cut themselves. Then clean all the bits of crap out of the downpipe. A shop compressed air line is handy there!

The downpipe now looks like a real hydroponics trough. The endcaps and trough ends are then cleaned with isopropyl alcohol or meths, and a continuous fillet of silicone sealant is squirted into the inside edging of the endcap. The endcap is then thwacked on with a mallet and allowed to cure. I'm using shop-bought ones here, but we often 3D print our own .

When the troughs are mounted, I drill a hole at the high end to match the inlet pipe I'm using. This is left until later so the hole goes in the most convenient place :)  Then of course we need to plumb them in, but that's another story.

Saturday, April 12, 2014


I like to have a reliable way of lighting a fire on me at all times. The most durable firelighting system is a ferrocerium rod, but these tend to be a bit large and don't hide well from Australian airport insecurity staff. So I invented my micro-tinderbox, that is extremely lightweight, works after a thorough soaking and drying, and strikes on a TSA-approved blunt nailfile or the file on your multi-tool.

Take a 3mm ring crimp terminal and shave off the insulation. Widen the wire inlet with a spike until you can fit a lighter flint into the hole. Then crimp really, really tight. There's the world's smallest ferrocerium rod!

To catch the spark, make a wad of charcloth, which you hold next to the flint when striking. Put the whole lot in a little baggie - with a spare flint - and hide it away for a firelighting emergency.

Friday, January 31, 2014

Homemade Fogging Fumigator

Looper caterpillars invaded our tomatoes. This is an act of war, and so I needed a way to disperse toxic dust particles (Derris Dust) amongst the plants in a thorough and pervasive manner - though I should imagine the same technique could be used to fog with any dry powder. It certainly beats heck out of the little pepperpot holes on the end of the derris tub. Here's a shot of it being tested; it's more impressive when a lot of powder is used and great billowing clouds come out.

We have an air compressor system in the workshop, so I dragged an air hose outside to provide the puff at 80 psi. On the end of the hose went the air gun fitted with a ball inflator needle. That pokes into a piece of plastic tube on a 13mm (1/2 inch in old money) barbed T joiner from my hydroponics plumbing box. Into the upright of the T goes a piece of 6mm i/d stiff PVC pipe, wrapped with tape to fit. This only goes half way up the T. Blasting air through the needle causes entrapped air to be sucked up the 6mm tubing and blown out of the open end of the T, together with any dust it may have sucked up. Cool, eh?

Derris dust is organic, but so is hemlock so only use it when no cold-blooded things you want to see alive are around, mask up, and don't muck about with it. Testing of the fogger was done with plain flour.

Saturday, January 18, 2014

Recycled raised planter frame

Suz said she wanted a big planter, raised off the ground so she could tend it easily. We have no actual dirt except for a small strip under the factory security fence which we've already planted with hundreds of peas and beans. So she needed a large planter to grow crops that don't like hydroponics.
The planter, part-filled with tubs.

I scavenged 8 x 20l polythene cooking oil containers (couldn't find the lids, buggerit) and hacked the tops off with a skillsaw. A couple of 10mm holes 50mm up from the bottom provide drainage, and a load of river pebbles hold a reservoir of water at the bottom of the container below the drains. The rest gets filled with potting mix. Planting tub x 8; 150 litres of soil where none stood before.

OK, so now we have a large plantable area, but it's not raised up off the ground. So I dismantled a couple of palettes and with the 2x4 from them and a length of preserved 2x4 from a previous project, built basically a bed frame. Suz didn't like the yellow colour of the tubs, so the frame is enclosed with scavenged timber. The bottom is slats, allowing drainage, which would have been hard to arrange without using the tubs.

The tubs also allow herbs with wandering roots to be kept separated, and things to be moved around individually if needed. I'll try to score some more identical tubs as backups.

As you can see, it needs a bit of wood preservative, but otherwise looks fairly functional. Another recycled success story!