I had had this idea in my head for a while, and just never did it. The nice thing about these is they can be rearranged in any way you need because of all of the pin connections (If you look closely, the red and yellow arms aren't layed out the same way).

Supplies

Small: lots of technic connectors

Big: Any pin-connecting joints you have on you

Step 1: Building the Arm

This took em a while to figure out, and uses an inordinate amount of technic pieces. You don't necessarily need this many joints, but they help with flexibility.

Step 2: Making It Bigger

This arm uses similar ideas to the smaller one, just with different pieces taking the place of the smaller technic ones, or even just spacers between the pieces to make the arm longer.