I'm confident that I made a new type of  solar tracker.  It uses compressed air generated by a low pressure aquarium air pump to both rotate the tracker and control the speed of rotation.  One airline brings air with gradually increasing pressure to stop and start its movement and  a separate line brings air to  run the air lift pump that primes the waterwheel to rotate the reflector.  I have changed it a little bit since the video but it is essentially the same.  The waterwheel replaces a slow motor in a normal tracking solar cooker or normal tracking solar panel.  I would love to find a smaller controller for the thing.  The controller consists of 2 roughly 20 cm tall 10 cm diameter pieces of drainage pipe. They are connected and one has a float in it.  It works well but it is bulky.  An electronic on off air valve could do the job and be much smaller.