We've installed a 'zip line' and are trying to figure the maximum load it can safely carry. To date, it has handled, without complaint, 210 lbs. This is fine except over time an overload will obviously weaken the cable - we don't want to do that! :surprised The line is a 3/8th inch aircraft cable (14,400 lbs test) attached to upright 16" x 10" x 1/4" steel i-beams which are embedded in 5' deep x 4' diamenter concrete plus the tops are anchored, via the same 3/8th inch cable, apx 8' to the rear in more concrete. The attachment point on one i-beam is 11' above the other i-beam. The trolly is a commercially mfg 14,400 lb test unit. The deflection is about 14-20" over the 275' span (a sight guess). Does anyone know of a formula to determine the maximum safe working load?