Economics of Tracking
As outlined in Why Tracking?, the attitional energy harvested through tracking is 20-40%, depending on the geographic location. If tracking is used, it's cost has to be less than the cost of just adding 20-40% more panels/inverters.
On smaller arrays, this is a challenge. For example: Assume a 1 kWatt array, with hardware (panels and microinverter) valued at $1,000. Assume 30% gain by tracking. 30% of $1000 is $300.
So, the costs of tracking have to be less than $300. The costs consist of 1). the structure 2). actuators 3). microcontroller. A great source of motors is Ebay.
1. For the structure, the design is controlled by the need to withstand wind loads, and maybe snow loads. I am using square and round tube, welded and bolted.
2. On a linear actuator, the relationship between extension of the actuator and rotation of the panels is heavy on trigonometry. Linkage geometry here.