Springs, Cables and Drums

The Half That Actually Lifts

Stand under an open garage door and look up. The steel bar running across the wall above the opening, wrapped in a tight coil, is the torsion spring. That is the part doing the work.

A residential sectional door weighs somewhere between a hundred and three hundred pounds depending on whether it is single or double, steel or insulated, glazed or solid. The spring is wound to store almost exactly that much energy. When it is set correctly, the door and the spring cancel each other out, and a grown adult can raise the whole thing with two fingers.

Everything else on this page exists to move that stored energy from the spring into the door.

Cable, Drum and Bottom Bracket

At each end of the torsion shaft sits a grooved aluminium drum. A stranded steel lift cable is anchored in that drum, runs down the side of the opening, and terminates at the bottom bracket, the L shaped fitting bolted to the lower corner of the bottom section.

Turn the shaft and the cable winds onto the drum, shortening, and the corner of the door rises. Two sides, two cables, two drums, and they have to wind in step or the door goes up crooked.

The bottom bracket deserves its own sentence. Whenever the door is closed, that bracket is holding the full pull of the counterweight. It is the one fitting on a garage door that a homeowner should never unbolt, and we say so on every visit, because it is where the injuries in this trade come from.

How Springs Fail

Springs are rated in cycles. One cycle is one open and one close. A standard spring is built for around 10,000 cycles, a high cycle spring for two or four times that. A household that comes and goes four times a day burns through a standard spring in roughly seven years. A household with teenagers and two cars gets there sooner.

The failure itself is unmistakable once you know it. A gap appears in the coil, usually an inch or two, as though somebody cut a slice out of the middle. There is a bang, often mistaken for something falling over. After that the door is dead weight, and if you press the wall button, the opener will strain against a load it cannot move.

Springs are replaced in pairs on a two spring door, always. The second one has done identical work in identical air and it is not far behind, and mismatched springs pull the door out of balance.

How Cables Fail Near the Coast

Salt gets into stranded cable and corrodes it from between the strands, which means the outside of the cable can look serviceable while the core is going. In Huntington Beach that is not a theoretical concern. It shortens cable life noticeably compared with an inland garage.

What to look for is fraying where the cable meets the drum, a single strand standing proud of its neighbours, flattening, or rust bleeding out from between the strands. If one cable parts, that corner stops lifting, the door goes up at an angle and jams hard in the track. Stop operating it at that point. Every further press adds damage to track and sections.

What a Visit Looks Like

We measure the existing spring for wire gauge, inside diameter and wound length, because a spring sized by eye is a spring that will not balance the door. We wind the new set to the door, not to a chart. Cables get replaced as a pair and the drums get set so both sides wind together.

Then the balance test, with the opener disconnected, at three heights. If the door holds at all three, the job is right. If it does not, we are not finished.

Call (657) 434-7519 and describe what the door did. If you heard a bang, we will bring springs.