How does an articulated gate arm work?

Question

How does it pivot at the elbow, and the front part stays level to the ground while the back half pivots up?

In: 2

Answer 1

You’re talking about the gate arms in parking garages?

I’ve worked in the industry but have barely touched that variety. But I’ve been told about them by colleagues.

There’s gearing hidden in… let’s call it the “shoulder” joint of the arm, which attaches to a rod which moves the “elbow” joint.

The gear ratio is effectively 1:1 but reversed, so that for every degree the shoulder joint turns, the elbow joint turns a degree in the opposite direction, keeping it level.