Jamb Extension Spring Counterbalance
By Huu Khanh Nguyen · Updated October 28, 2026 · sectional-door, counterbalance, extension-spring, jamb, hormann, novoferm, normstahl, wisniowski
Extension springs on the sides of a sectional door, beside the vertical track, with a cable over a pulley on each side.
Parameters
| Name | Default | Unit |
|---|---|---|
| Door width | 2438 | mm |
| Door height | 2133.6 | mm |
| Shaft or track height above the door top | 330 | mm |
| Shaft position | front | |
| Backroom beyond the door height | 457 | mm |
| Track depth behind the door plane | Math.min(doorHeight + backroom, 3813) | mm |
| Springs per jamb | 1 | |
| Spring length | 869 | mm |
| Spring windings | Math.round(springLength / 3) - 1 | |
| Depth | 3 + 65 | mm |
| Height | doorHeight + 65 | mm |