Rules and Formulas
Door Weight: (1) Divide the total spring(s) IPPT by the cable drum multiplier
(2) Multiply the spring IPPT by the number of turns, and then divide by the Hi Moment Arm
High Lift: Measure the distance from the top of the closed door to the bottom of the horizontal track
IPPT: Inch Pounds Per Turn. Force spring exerts per 1 turn of the spring
IPPT Required: Multiply the door weight by the Hi Moment Arm, and then divide by the number of turns
Spring ID: Measure the outside diameter, and then subtract twice the wire diameter
Spring Conversion: Always convert torsion springs to a spring of equal or greater wire diameter
Spring Growth-Torsion: Multiply the number of turns by the wire diameter to find spring growth
Spring Stretch-Extension: The stretch of an extension spring is always ½ the door height
Spring Length: Multiply the wire diameter by the total number of coils in the spring
Wire Size: Measure a length of the spring, then divide by the number of coils within that length
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