The two solar panels generate enough power, even on overcast days and right up to sunset on sunny days, to turn the chilli grower using a small motor and a 3-stage worm reduction gear. There's a small DC-DC converter to regulate the solar cells' output to 5V, at which voltage it draws about 25mA.
The main bearing and its aluminium cradle came out of an old water bath circulator. All the weight is supported by the bearing cradle and two steel bolts, the plastic parts don't have to carry it.
The plastic parts were designed using Open SCAD and 3d-printed. On the right here, we have the main parts, showing the cut-outs and supports for the gear train, motor and bearing cradle. The upper piece holds a second bearing to steady the main spindle. The main spindle itself was machined on a small lathe, drilled & tapped for the fixing bolt which holds a metal wire loop to hang the grower from.
Below that is a model of the geartrain, also modelled in Open SCAD. The motor cut-out and the holes for the gear shafts were generated by subtracting this from the main part above - the gear shafts were deliberately modelled longer than they needed to be to ensure that they would produce complete through-holes in the model above. The reductions are 1:52 for the motor to 1st gear shaft, followed by 1:30 and 1:60. That gives a nice easy way to measure the rotation rate - just time the intermediate gear for one revolution: however many seconds that takes, the chilli grower will complete one turn in the same number of minutes (22 with enough sunlight for the regulator to work).
Here's a couple of pics of the completed crop rotator, with and without the top cover fitted.
And finally, a short video of it running. It's not quite at full speed because the greenhouse is, as you can see, in the shade of a tree at the moment.
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