Dave: On a standard 6-string guitar the total "pull" for the 6 strings is on the order of 200 pounds -- about 30 to 35 pounds per string. Of course, the exact amount depends on the scale length, string gage, etc.
Roy is right. At Dekley we checked by hooking one end of a string to a spring scale. When we tested a few strings over the changer up to the normal pitch for their gauge, they all registered within a pound or two of 30 pounds. This was on a 24" scale guitar.
