Release mechanism.

I have made a mechanism, which will hold on to a ring, until the string is pulled.

This is a schematic diagram, which I'll explain below.

You'll need:

• a suitable piece of wood (preferably hardwood), app. 7 x 10 cm (3" x 4")
• a cone drill, which can deliver a hole with a 4 cm diameter (1 3/4")
• a saw
• a 4 mm wood drill
• a drill, which can make a suitable hole for the head of a screw
• a 8,5mm wood drill, so long, that you can drill through the wood 'the long way through'
• an 8mm bolt, or something equal, to lock the ring in place
• sanding paper

What to do:

• Mark the center of the 4 cm hole (blue, number 2)
• Mark the circunfrence of the 4 cm hole
• Mark, at the end of the wood, where the hole for the bolt is going to be, (green, number 1) centered app 1 cm lower than than the center of the 4 cm hole
• Mark the cutting-line, (red, number 3) parallel to the hole marked for the bolt, but app 1 cm lower
• Drill the hole for the bolt, (green, number 1) all the way through the wood
• Drill the 4 cm hole, (blue, number 2)  
• Mark 2 cutting lines,  (red, number 4 & 5) in such a way, that the result will be an opening which is wider at the bottom
• Cut the wood,  (red, number 3) to 'open' the 4 cm hole
• Cut the 'inward edges' off,  (red, number 4 & 5) to make the 4 cm hole 'open up' downwards
• Drill a 4mm hole at the top of the 4 cm hole, (pink, number 6) for a mounting screw (if you want to screw the mechanism into place from this side)
• Drill the groove, which will hold the head of the mounting screw
• Sand all edges and cutting-faces, to a nice and gentle surface

Mount the mechanism where you want it to be, but notice that yu'll need to be able to either pull the ring out of the mechanism, or turn the mechanism 'top side up', in order to let the ring 'drop down/out' of the mechanism, to achieve the desired effect..!

Here you see the mechanism mounted underneath a chair.

Here you see the mechanism 'in use', meaning that the images show (1) how the ring is 'locked into place' as long as the bolt is, next you see (2) an intermediate picture, where the bolt is 'moving out of' the hole, and (3) how the bolt finally release the ring (which by now has dropped to the floor).

A possible set-up would be to tie the rope holding your hands over your head to the ring, and leave it to a weight, hanging from an ice-lock to pull the bolt from the mechanism, once the ice has melted.

You'll need to be aware of 2 things: 1/ it IS possible, to pull so hard on the ring, that the mechanism will fail, and 2/ if you (as I do) use a threaded bolt, it is NOT a good idea, to let the bolt hold a rope (loop), as the threading might 'grab hold of' the rope - which in short terms will stop the bolt from sliding out - leaving you with a serious problem.

Here you can see a video clip, showing how the mechanism works