This is a support page for American Polywater's Duct Winding Factor Calculation Page. You can return to the calculation page by using the Return Link here or at page end.
Amplitude: The duct displacement from a straight line. The amplitude is limited by the way the innerduct is constrained, ie., the walls of exterior conduit, the diameter of a back-reamer hole, etc. The model treats this displacement as two dimensional. The most accurate amplitude is the displacement of the cable itself, assuming it rubs on the "inside" wall of the undulating duct. The higher the magnitude of the amplitude, the higher the Duct Factor and the higher the bend degrees in the in the duct per period. The amplitude must be greater than or equal to zero, but can be no larger than 1/3 of the period. An amplitude of zero (0) is "no bend."
Period: The repeating length including one "positive" and one "negative" amplitude displacement. The period is a measure of the frequency of the displacement. Period length is typically influenced by duct reel memory. Lengths representing the circumference of the duct reel are a good place to start. The shorter the period, the higher the Duct Factor and the greater the bend in any given length of duct. In this model, the period must be greater than zero and at least three times the amplitude. However, the period cannot be greater than half of the total run length.
Run Length: The start to end distance for the straight section. The run length must be greater than zero and at least twice the period length.
Cable Weight: The weight of the cable in lbs/ft (kg/M). The cable weight must be a number greater than zero. Cable weights higher than 2 lbs/ft (3 kg/M) are not accepted. Such heavy cable weights do not represent fiber optic cable pulling into innerduct as intended by this model.
Incoming Tension: The tension on the cable as it enters the conduit. This back tension is typically from reel or some other drag getting the cable to the conduit entrance. The incoming tension must be zero or greater. Incoming tensions above 100 lbs (400 Newtons) are not accepted.
COF (Coefficient of Friction): The coefficient of friction is always a critical factor in tension calculations. American Polywater's Polywater® F, an extremely efficient lubricant for PE jackets on HDPE conduits, typically shows COF's of 0.10 to 0.15 in laboratory testing. Unlubricated cable shows 0.35 to 0.50 in the same tests. The calculator allows a default entry for Polywater® F, or the manual entry of any COF greater than .05 and less than 2.00.