Torsion Spring Rules & Formulas

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