Make two 6mm holes in the 1st cap (4). The distance between the holes should be enough for (6)

Connect (6) and (7) and insert into (4). If (6) is long enough you can use the nuts as on the 1st picture on the left. If (6) is short, do not use nuts on this side of (4), like on the 2nd photo.

Use silicone sealant and rubber washers inside (4). This is to prevent leakage. Do not overtighten the nuts. The rings should move freely.

Drill a 6mm hole in the 2nd cap (4)

Insert the rope into the hole you have drilled in the previous step. Tie a loop on the outer side of (4). You may want to use a steel "socket" (or whatever it's called) for the outer loop (shown on the photo).

Put the rubber tube (5) (just the tube without any metal bands) on the plastic fitting (1). The rubber tube is used as a thermal insulator here. Cut the excessive rubber off.

Glue both (3)'s into (1) with PVC glue. Use sand paper and/or file to scratch the corresponding surfaces first.
Here you can find an excellent tutorial on how to weld PVC pipes

When glued (several minutes) assemble the lock. Screw the cap (4) with the rings, insert the rope into the lock, pour water, screw the second cap (4) with the rope and freeze the lock.

This is the result. We have an ice based time-lock with the Special Ring Device on one end (unmovable part) and a run of rope on the other (movable part). No part of the lock is cold to the touch thanks to two layers of thick plastic with a layer of glue in between and one layer of even thicker rubber. I suggest you to warm up the rings with hot water before use. Almost no dripping happens when the lock is "closed" but not frozen.
When the ice allows, the rope will slide out of the cap hole and release you.