Of mice and men

Dave Wilson performs a design for assembly analysis on two painfree mice capture and removal devices and finds that simplicity is key to keeping costs down.

Just the other week, I discovered that a mouse had been visiting my mum’s kitchen without permission. Rather than extend it a permanent lease, I decided to visit the local hardware store to purchase a pain-free mousetrap so that I could capture it and release it into the wild.

After shelling out the phenomenal sum of £5, I arrived back home for product deployment. First though, I decided to closely examine the operation of my new toy with my son so that he could gain some insight into the engineering principles behind the design.

It was quite a cunning invention. Attracted by the smell from a piece of cheese, a mouse would enter the device only to find itself travelling down a metal see saw. Once at the end of the see saw, the see saw would tip back, closing off the only way out of the trap.

To my delight, the device did inter the intruder who, to the delight of my son – a practising Buddhist – was then escorted from the premises.

Next weekend, with one success under our belt, the trap was re-deployed with nourishment nouveau. This time, however, to our astonishment, the mouse was eating the cheese and then leaving the trap.

Rather than explain how this could possibly have happened, the steel see-saw trap was quietly deposited in the trash and we hit town in the hope of finding a better solution. And we did.

The new pain-free solution was a lot simpler than the first. It comprised just three parts: an L-shaped hollow tube, a cap at one end to which the cheese was affixed, and a swinging gate at the other. Once the mouse entered the trap and ran for the cheese, the trap tilted and the gate at the end swung shut, closing off its exit.

Three parts, rather than ten. Made from plastic, rather than steel. Cost me £3.50, rather than £5. Cost to manufacture: £0.25p (guesstimate).

I could tell my son was intrigued by the Design For Assembly Analysis technique that I performed on both the traps. So I set him a challenge – to design a larger trap – this time for a squirrel – that would use just one part and would cost less than £0.20 to manufacture in volume.

He hasn’t done it yet – but I hope he does soon. And so does Dan King the Publisher of e4engineering. Because I understand that a host of cheeky squirrels have just infested Dan’s loft and are still in residence despite eating lots of poison.

Got an idea for a better mousetrap? Why not drop me a line at: <a href=’mailto:david.wilson@centaur.co.uk’>david.wilson@centaur.co.uk</a>.