I couldn't understand why my force draw machine gave a lovely big vertical deflection when calibrating it on the dial spring balance, but when I tested it with a bow the deflection wasn't the same!!?? In fact it was about half what it should be!
Had the bows mysteriously lost weight?
I investigated carefully by attaching the balance to a bow so I was pulling both at once, then the penny dropped.
I wasn't a factor of 2 out, it was more like 2.2
Have you twigged yet? Yes I was reading Killograms instead of pounds when testing with the dial balance.
I shall add another pulley to get more vertical deflection.
What an idiot!