Liberate a stop sign knocked over by some drunk. Actually cities have piles of used "street furniture" like this, if you have a buddy who works for the city....
Recycling places get $2 per pound for Aluminum: 1/4 inch is best. I still have several tubes obtained from the University many years ago.


Dacarls:
A-class USA 196, USA 21, H18, H16
"Nothing that's any good works by itself. You got to make the damn thing work"- Thomas Edison