Not two but only one 50 kg base unit will be used in my design.
Yes, the weight issue is there. However the prevalent design of the roof slab of our urban houses can easily withstand this kind of load. However it would certainly be prudent to install something like this over a beam or a column in an existing building. I have the option of installing it on ground as I have space available. For others particularly urban dwellers this option may not be available.
The Fanta is just for perspective so that the viewer can get an idea about the size from the photo. Incidently the bottle is filled with motor gasoline for cleaning a tough stain on a table cover that refuses to go away using conventional cleaning :-)
The height of the shaft will depend upon the size, particularly the width of the panel. I have looked at Yingli and Akhtar Solar panel sizes. Yingli is 990 mm wide while Akhtar is 550 mm. Therefore say if I decide to use Akhtar then the shaft height would be 2x550=1100 mm. Add another 50mm for clearance from the base, for rotation, and you have 1150mm. Add the height of the base rotation unit (440mm) and you have 1590mm. That makes it about 5 feet above the roof/ground level. This is a reasonable height resulting in a stable structure one which one can work easily while standing on the ground without using ghori or table.
The width would be equal to 2xlength of panel. Again taking Akhtar case it comes out to be 2x1560mm which is 3120mm or just over 3 meters. So the turning radius is about 1500mm.