Image Discuss: Experiment for what?
 

That looks like a poorly made model of a trebuchet. I like mangonels better. I made one once, but the tension on that torsion spring ripped my side beams in half. My next one will be bigger and better!

I doubt it is a trebuchet though. From the looks of the picture I think the rope serves some purpose. Maybee it is serves it's purpose as a spring which.

aha!
 

I got it! its a thing to make it so the mauseuring tape doesnt colapse when you pull it out really far caue your trying to poke someone :D