The most dangerous mechanical component hiding in every home — and the physics of why you should never touch one.
A torsion spring is a tightly wound coil of hardened steel wire wrapped around a metal shaft mounted horizontally above your garage door opening. When the door closes, the spring is wound tighter by cables attached to drums at each end. This winding stores enormous rotational energy — energy that is released to lift the door back up.
These numbers might look dry on paper — but each one represents a force capable of serious destruction.
To understand just how much energy is in a wound torsion spring, compare it to things that move fast and hit hard.
A wound garage door spring stores more energy than a professional pitcher's fastball or a rolling bowling ball. The difference is that all of this energy can be released in a fraction of a second.
Drag the slider to wind the spring and watch the forces build. Notice how stress accelerates non-linearly as you approach maximum wind.
Garage door spring injuries send thousands of people to the emergency room every year. Here's exactly what happens when things go wrong.
Every one of these has caused real injuries — many of them life-altering.
When a spring breaks, the stored energy releases instantly. Broken wire ends whip outward at 100+ mph — fast enough to embed in drywall, shatter car windshields, or crack skulls. The bang is as loud as a gunshot.
Professionals use steel winding bars inserted into the spring cone. If a bar slips during winding, it becomes a high-speed projectile powered by 30+ turns of stored energy — commonly causing shattered wrists and forearms.
A broken spring means nothing is counterbalancing the door's weight. A 300+ lb door in free fall generates enough force to crush bone, pin a person to the ground, or total a car underneath it.
The shaft spins at ~300 RPM the instant a spring breaks. Anything in contact — fingers, clothing, hair — gets caught and wound in before you can react. Degloving injuries and amputations are documented outcomes.