Hello Moneer,
Weight really isnt an issue on a pv tracker if you have everything balanced and well built. There are 2 ways to do tracking,
1. is to use use 2 green led's to sense the strongest light and redrock.com has some good schematics for this.
2. Is hammer a long nail say 4" into a square board say 6" square, then point it at the sun and use an angle guage to find the azmuith. Once you know that build a simple frame with a centre mount rod and put 2 dead stops an each end of the frame. Then put a very low speed motor via gearing say bike sprockets to get the required reduction, so from the morning until night it will make 1 path between the stops. For example as we just had the winter soltice so I checked the angle for our place and it was 65 degrees. I need to do the same thing in summer and the azmuith can be simply adjusted for each season.
See it aint that hard to make a tracker which will give upto 30% more output from a roof mounted static panel.
Now if you choose to go this route draw up what you think and I can give you some advise on WHAT you show.
As this IS your school project I'll help where I can but only from the advise point of veiw.
Regards Bryan