Lowering of Arms

[bayside]

Hi guys i need advice on lowering one of my arm in a slow motion without the use of any motor or gear(if possible),cause my PCB doesn't have anymore port for motor.i am thinkin of spring or other means,which can lower the arm in a slow motion,because for now,the moment when the string hanging onto the arm is being let loose it just roll,so now i was hoping to come up with an idea that it can slow up the speed of lowering the arm and let it drop in a gracefully manner.