decreasing opportunities

There is an old bicycle wheel rim sitting around in the back garden, which was once intended either as a sort of large drum head or possible garden/allotment decoration but which I'm thinking might be quite useful as a combination drum/decoration and rain warning indicator, by stretching some polythene across it and mounting it somewhere out of the way of trees in the hope that rain hitting it would be load enough to grab.my attention in time to dart out and save any outside washing.