Please help me to create my flexible arms, almost there but struggling with finer details

To put this issue into context, I'm trying to create a small shaded area for a hot climate. It will create shade for a single person, and automatically turn away from the sun.

I am trying to create a pair of rising arms that can be raised or lowered with a single slider. I have created the pairs of arms, one of which operates ok but not the other. I've included a quick mock up .jpg of what I'm trying to achieve. They will eventually rise up to tension some material to create a small shaded area. 

The next task will be to make the whole system rotate around a vertical axis depending on sun path. But this isn't too important at the moment. I've had a stab at trying to rotate them around a notional vertical axis but this didn't go well.

As you'll be able to tell, the whole script is a little untidy as I'm quite new. There are some test versions underneath as well.

Thank you in advance for any help.