Problem with rope torsion spring for make catapult

[Terminatueur]

Hello everybody, i need help for make catapult, in first i have try to make trebuchet but cant because rope dont destroy so i try to make a catapult.

So i have see lots of videos for tutorial and i am blocked with the torsion spring because in video players can bring rope horizontally but im cant after a moment of turned pulley rope get blocked at vertically and i cant pull more the rope.....

Rope get blocked in this position:

http://image.noelshack.com/fichiers/2015/08/1424461631-sans-titre.png

(i have try to turned pulley in the other way rope go at the begining position)

So if anybody would help me I would be grateful.

Sorry for my bad english