A home made trigger to surprise someone

I made a contraption in which a frisbee can expand instantly when you let go of a string from far away. It can be used as a prank..., just a thought.
How did it trigger? :-) :-D #Istagood #happylife #contraption #trigger #geartrigger #gears #nowordsneeded #mcm #tbt #photooftheday #love #instaphoto #follow #likeforlikes #instacool #followme #藝 #homemade #machine #diy #arts #instayeah #instaright #wireart #wirecraft #unlimlikes #pretty #photogram #cool #howdidthisgetmade