Dianna
I think it's a bit more complicated than just using a Pan Brake: the square guards require cutting the blank, punch the mounting holes, press the ribs in the top (using a die in a press), notch the fold points, fold and flatten raw edges, fold edges at right angles, fold guards and weld, most of which are manual operations. For 1000 plus guards (for 500 trailers plus spares/replacement parts) that's a lot of time/labour. I don't doubt that the set-up costs of large blanking, forming and trimming dies for a double-acting press are something to consider, but I'm just not sure that it is the main driving force behind the square versus round design in this case. Same for the thousands of Aust jeep trailers: I think the main driving force in all these cases was access/mud clearance, rather than the economics of pressed versus folded guards. The Aust Army already had considerable experience with the Bantam trailer before the Aust No.3 & 4 were designed, and it is probably the reason why the No.4 trailer guard was mounted even higher on the body than the No.3: to provide maximum clearance.
Mike C
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