Household springs more commonly available than spring steel, with this modification you can replicate the results to produce a number of variable spring powered devices.
materlials - mild steel (various), spring (size approximately from trampoline)
method - some complications winding the spring mainly, as a novice at working with springs it is *very dangerous during construction*, i wound it as tight as it would go (variable - less winds, less force), clamped and welded in place. one thing to bear in mind, is scratches from tools and/or heat/welding spatter can really damage spring steel causing dangerous failure.
our habitat supports our life, do not abuse it. excerise caution, harmonize with nature and tread lightly.
please understand that this was a last resort, i now mean to construct a cage trap.
all differences aside the knowledge/ pratical benifits of this exercise were invaluable, springs have many practical applications that would not be possible without the aquisition of this knowledge.
summary - an alarm or signal system could be used to notify trap closure, that would be a considerable improvement, over having to check all the time.