How a Mechanical Watch Normally Operates
A mechanical watch movement gets its power from the mainspring, a long metal coil hidden inside a small round box called the barrel. You wind the watch to tighten this spring. But when the spring slowly unwinds, it pushes the power through the gear train. The train includes the center wheel, third wheel, and fourth wheel.
Then, the energy reaches the escapement, which is the brain of the watch. It uses a small part called a pallet fork and a balance wheel to release the stored energy bit by bit. Thus, this action causes the ticking sound. Watchmakers design the entire system in a way that pushes energy in one exact direction.
Read: Mechanical Watch Myths
Can the Gear Train Actually Reverse
Watch gears are just flat metal wheels with tiny teeth. These are plain gears, which can spin in any direction. However, a normal watch can’t run backwards while keeping time. The reason is the very end of the gear train. The pallet fork locks the escape wheel teeth and holds the power back and only lets the wheel move forward when the balance wheel swings.
You can’t just wind the watch backward or force the wheel to swing backward to reverse time. The physical geometry of the escape wheel teeth and the pallet jewels blocks the gear train from moving in reverse under standard conditions.
Situations that Cause Backward Running
Although the layout blocks reverse movement, mechanical failures can cause a watch to run backwards. Most watchmakers, including our expert Aiman Moner, call this “recoil” or “unwinding.” The hands spin counterclockwise at high speed when this happens, says Aiman.
- Broken Click or Click Spring: The click is a tiny metal latch that sits against the ratchet wheel on top of the mainspring barrel. It acts like a doorstop and lets you wind the mainspring but stops the spring from immediately unwinding backwards. The mainspring releases its stored power at once and spins the gears in rapid reverse if this small click snaps.
- A Snapped Mainspring: Sometimes, the mainspring breaks inside the barrel due to metal fatigue. The sudden snapping force creates a sharp backward shock through the arbors and pinions.
- Damaged Pallet Jewels: The synthetic ruby stones on the pallet fork stop the escape wheel. The lock mechanism fails if these stones crack or fall out of alignment. A slight bump could then cause the gear train to slip backwards.
Watches Deliberately Designed to Run Backwards
Sometimes, people want a watch that runs counterclockwise on purpose. Watch brands have created specific reverse models, often called “anti-clockwise” or “backward” watches. For example:
- Russian Code: The Russian brand Raketa made a model called the Russian Code where the hands turn backward over a reversed dial.
- Azimuth Back in Time: This is another famous example. The Azimuth Back in Time is a Swiss watch that uses a modified ETA movement to run in the reverse direction.
Besides, small brands like Svalbard make single-hand backward watches for a fun and confusing way to read time. How do these work? The mainspring still unwinds forward, and the internal brain of the watch ticks in a normal manner. However, the watchmaker adds an extra gear into the motion works under the dial, which flips the direction of the hand movement. Thus, the hands display time backwards.
The Risks of a Reversing Movement
The movement faces heavy damage if an accidental reverse spin happens to a standard watch. The gear train releases a tiny amount of energy over 40 to 70 hours. However, it dumps all that stored energy in a few short seconds when a click spring breaks and causes the watch to run backward.
The intense speed causes massive friction. Watch gears have very thin metal pivots that hold them in place. The violent reverse torque can snap these delicate pivots and make the tiny metal teeth off the center wheel or bend the hairspring. If it suddenly spins backward, bring it to a professional watch repair service center.
Setting the Hands Backwards vs. The Movement Running Backwards
Turning the crown counterclockwise to move the hand back does not make the inside movement run backwards. Watches have a clever connection called the cannon pinion, which connects the hands to the inner gears using a friction fit.
The cannon pinion can slip when you twist the crown backwards. Thus, it lets the hands move backward while the internal gears stay still or continue running forward. However, you should be careful with vintage mechanical watches that have date features. Setting the time backwards around midnight can break the small date jumper spring, because that specific calendar part only likes to move forward.
Also Read: Causes of Rattling Sound Inside an Automatic Watch
Why the Swiss Lever is a One-Way System
The main reason a standard mechanical watch refuses to tick backwards is the Swiss lever escapement. Remember, this system is heavily asymmetrical. Look closely at an escape wheel under a microscope, and you will see that its teeth look like small boots pointing forward. The pallet fork has two ruby stones, named the entry and exit pallets.
When the balance wheel swings, the escape wheel pushes against the specific angle of these stones to give a forward impulse. The angles, the drop distance, and the locking faces are calculated for one-way traffic only. If you try to run it in reverse, the boot shapes of the teeth will jam against the flat side of the ruby stones. The whole system locks up solid.
