Entirely mechanical model :

-Manually-lit slow fuse

-Charge lowered by gravity

-60m spool of cord

-Spool holder with a brake to control the descent

-Slow fuse comb-shaped holder with a 1m diameter circumference to simplify calculation for slow fuse length. Up to 15 turns for a maximum time delay of 30 mins

-A tube to hold the charge during transportation time

Ref : DG70