Best use a worm gear drive for holding power and torque.
My experimentation with using a linear motor to position a 14Kw solar array is the motor goes bad and the motor parts rust out after a winter. What I found that worked better was to upsize the solar array and save on annual motor replacements.
I found that to set elevation at solar transit is to use an Amp meter to determine the proper elevation angle over some generalized angle.
With the motor costing $62 by itself and then the additional mounting complexity, I'm inclined to agree with you.
Do you have them set at a permanent angle?
I'm in the Northern Hemisphere and point my solar array's due south.
The panel weighs 2.8kg and the whole upper part that requires azimuth rotation weighs 7.5kg. The linear actuator I intend to use has a maximum stroke of 200mm.
So, right now, after everyone's input, I shall use a stepper motor with worm drive gearbox, and the ratio of 5:1 is all right, for real-time tracking and hourly tracking. The only open question would then be how to identify a quality stepper motor with worm drive gearbox.
Maybe an experienced "motorist" can briefly explain why a brushed DC motor with worm drive gearbox is not the best idea?
It is a fine idea, if you also have an encoder. You don't need an encoder with a stepper.
The motor type and gearbox are two separate questions and issues. Because you don't want the torque translating back to the motor, the worm gear drive is most appropriate for that. As far as best motor type, It comes down to positioning, speed, efficiency, etc. JR and I both discussed some of those points so no reason not to if it fits your needs.
I see.
It's quite perplexing that stepper motors with worm drive gearbox seem to either cost €70 or €1000, if one can find pricing information at all.
We order a decent amount of stuff from https://www.automationdirect.com/. No affiliation or anything. Even if you can't order from them, you can do some easy price comparisons.
The Chinese stepper/gearbox linked in post #13 would probably be adequate to the task. The maximum radial output shaft load is 0.57 kN, which is probably enough to handle significant wind shear on a .65 m^2 solar panel.
You will need a beefy current limiting stepper driver to handle the full 2.8 Amperes/winding. Hobby modules like the DRV8825 are generally limited to 1.5A/winding or less (which would work fine with that motor, but produce half the torque).
Gearboxes are generally custom items, not mass produced except for specific, large volume manufacturing (vehicles and the like), so prices vary a lot.
Right, thanks; those DC gearmotors are quite pricey, but probably quite good quality compared to unknown Alibaba Express items. I try to find similar vendors in Europe.
I see, 570N offers quite some load holding capacity indeed. I found two high current stepper motor driver PCBs from Pololu over 2A. There might be others from other vendors, so I will look around.
Okay. That is just a concern with PV and solar cookers.
Turn a large wheel or drum/etc with a small friction wheel on a worm gear motor for brake strength The same no-gear transmission spins up massive potters wheels with 1/4 horse motors without slipping.
Hi, @Lagom
Remember if you used steppers and want them to hold in position, you will be consuming energy from your power storage system.
The stepper cannot hold position in a inactive state unless you use a worm drive type gearbox or a brake arrangement. (more complexity in a hostile environment.)
Tom.. 
See above, in any case, a worm drive gearbox will be used for the azimuth rotation. There are two cases I will test - real-time tracking versus hourly tracking.
You can use a belt with a pulley, like a micro-V belt on a dryer drum. You can use it like an old-time flat belt to drive a narrow disk if you put a crown on the edge of the disk. I use a treadmill motor with its ~25mm microgroove pulley to drive a 5/8"x12" dia. crowned plywood disk for a wooden lathe. It works like magic.
Pulleys are more than a simple wheel against wheel friction drive for when you need more torque or a wider friction contact. When you have sensors pointing at the sun, counting steps to calculate exact turn is not necessary and open to error.
It takes the Earth 4 minutes to turn 1 degree. In 1 hour, 15 degrees.
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The worm gear drive solution is self-locking, to a certain degree, an important feature for solar trackers. A dual worm gear drive, a slew drive, would be optimal, but they are hellishly expensive and don't seem to be sold at the relatively small size I need. If I end up tracking only every hour, or something like that, I could use a solenoid as a secondary locking feature in addition to the worm gear drive.
Car power window motors use a worm gear. Wiper motors too. No feedback though...
Hi,
If you track using solar energy sensors, you don't need to know position feedback from the motors, just two limit switches for safety.
Tom..
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