07-12-2015, 08:58 AM
The twisting adds strength to the shaft. Plumbata seem to have been made from assorted scrap iron, an thin band of metal can be made stronger (resist bending) by twisting it into a spiral. What you are basicly doing is making a cylinder from a strip. The flat strip is easy to bend/fold, once twisted, it will resist bending, as the whole thing will act as a cylinder the size of the widest part of the strip. So a strip of metal 1 mm thick and 10 mm wide will act like a cylinder about 8 mm across. You can do that test in any woodfire, using a strip of iron, two pliers and a pair of thick gloves for safety.