This project was based around the discovery of small hour glass bulbs many woodworking shops have them and particularly wood turning shops, they are also on ebay in bright colours training out of HonKing. They were designed to be egg timers.

At keystage 3 I would look to this being either a laser or wood or even cardboard project. The nice part of hourglasses is the fact that the technology is very green after manufacture it costs nothing to run and their life span subject to not being broken is unlimited.

At keystage 4 their are larger versions one some 75mm tall and one some 25omm tall. that would allow this project to be extended into much larger versions.