other problem was deciding how political I dared make it - there's so
much fuss about nurse's pay and productivity, and private financing of
parts of the NHS. In the end, I left it subtle, but the idea of the
insatiable patient and the bottomless pit of NHS funding are there for
anyone that likes analysing stuff.
the main challenge was handling the coins. Coins have sharp edges and
tend to dent things they fall on. I soon abandoned my original idea –
which would have involved many coins missing the patient’s mouth and
landing on his face. In its final form, the nurse stops in a precise
position and every coin goes into the mouth.
then, it took ages to get the coins to flow reliably, without the
occasional one bouncing out of the mouth, or off the side of the cup.
It’s a bit like making contraptions involving water – you really
have to double the amount of time you think it will take to make. With
coins, the key thing seems to be to remove energy – the slower they
are moving, the less far they can bounce. But there are other less
obvious factors. Towards the end of the testing period, coins started
bouncing out of the mouth because the nurse’s polythene cup was
becoming scratched, so coins were being tipped from unexpected angles.
Replacing the cup with a stainless steel one solved the problem.