George Harris
Engineer
The whole point of constant tension is to eliminate the effect of temperature on sag. That is, at intervals there are weights attached to the contact wire to develop the desired tension. These weights move up and down with temperature change so as to maintain the desired tension. The issue is to provide sufficient distance for travel of the weight. This could (is?) the limiting factor on spacing of these weights. To keep the weight reasonable, there is a set of pulley wheels to provide a multiplier factor. Simply put, if the tension desired is ten times the weight, then the vertical travel of the weight must be ten times the change in length of wire segment with temperature variation.It would appear that the amount of tension might to be higher for each increment of higher speed, As well hanger spacing from the traveler to contact wire may need to be closer? Another is the expected wire temperature extremes causing wire expansion from low to high + a fudge factor. All this to reduce sag of the contact wire with train PANs.