How a Cantilever Carries Its Weight
Weight on a cantilever never touches the ground at the opening, which is the whole point and the source of every design constraint that follows. The load explanation kept at Mount Pleasant Sliding Gates Narcoculture starts from that fact, because a sliding leaf in Mount Pleasant that appears to float across a driveway is in fact balanced on two roller assemblies behind it.
The Lever Arrangement
The gate rides on two truck assemblies mounted to posts on the receiving side. Everything forward of the leading truck is overhung, and the counterbalance tail behind the rear truck holds it down. It is a seesaw with an uneven fulcrum, so the rear truck carries an upward force while the front one carries downward load plus the weight.
Why the Tail Has to Be Long Enough
The usual rule is a counterbalance of at least half the clear opening, which is why a cantilever needs roughly one and a half times the opening in side room. Shorten the tail and the forces at both trucks rise sharply, the front of the gate droops, and the rear truck starts trying to lift off its rollers.
What the Posts See
Those two vertical forces, one down and one up, only a few feet apart, produce a substantial couple at the footing. That is why a cantilever installation has larger posts and deeper footings than a swing gate of the same size. On sandy coastal ground it is also why an undersized footing shows as a gate that gradually noses down.
Why the Frame Is Different
A cantilever leaf carries bending along its whole length, so it is built with a deep truss rail rather than a simple rectangle. That rail is structural, not decorative, and cutting into it or hanging a heavy sign from the overhung end changes the numbers the gate was designed around.
The Failure Modes
Nosing down at the leading edge means the rear truck, the tail length or the footing has moved. A gate that lifts at the tail means the rear truck bracket is failing. Neither is fixed by adjusting the rollers, and both get worse quickly once they start, because each cycle works the same joint.