Big magic arm

I made the first prototype, but it didn't work so well :(

The idea was to make something like this:

A central knob when turned presses the bottom and top pincer arms together, clamping the balls attached respectively to the ground and to a laptop. This should fix both the ends as well as the hinge.

Here's a video of my first prototype and some images of how i built one of the arms of the above mechanism.

But as you can see, it hardly holds. Thinking of another prototype with stronger gripping action.