Rack and pinion makes the arm expand
Cableing makes it rotate and a pneumatic piston for extra support (its got some insane torque)
Note on arm: It owned 2 people in 2 seconds around midnight on sunday yes i was one of them and it was all on camera....
Two directions well you have 2 types of goal height..... so one end is only for the smaller of the 2.... and a higher res ver of that image can be found
Here