Trajectory

Trajectory is the path the top section of a sectional garage door traces as the door opens. As the door begins to rise, the top section travels straight up along the vertical track. When it reaches the curved radius at the top of the vertical track, the section begins to pivot around that curve and swing out toward the driveway before it levels off and travels horizontally into the garage. The arc it sweeps during that transition is the trajectory.

The outward swing during that transition extends in front of the plane of the door, with the amount depending on the track radius. On a standard 12-inch radius track, the top section projects forward during the transition; on a 15-inch radius track, that projection is larger. Installers treat this outward clearance as a required obstruction-free zone.

Trajectory matters during installation for two reasons. First, a car parked close to the garage door may be struck by the swinging top section if the driver does not pull far enough forward before operating the opener. Second, the opener rail and any hanging light fixtures near the header must be positioned so the top section clears them during the transition arc.

The double low headroom track changes the trajectory significantly because it uses a modified radius and dual-track layout to reduce the outward swing when headroom is very limited.

An installer checks the trajectory clearance during rough-in, before the door is hung, by measuring from the face of the closed door to any overhead obstruction along the path the top section will travel.