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This is a genuine second wheel designed for the MIYOTA 8N24 automatic mechanical movement, made in Japan and brand new. The 8N24 is a skeleton automatic movement measuring 11½‴, 5.55mm in height, featuring 21 jewels and approximately 42 hours of power reserve . As an original factory part, it is the ideal choice for service or repair.
MIYOTA 8N24 Technical Specifications :
| Parameter | Value |
|---|---|
| Movement Type | Automatic mechanical (skeleton) |
| Size | 11½‴ (approx. 26.0 mm) |
| Height | 5.55 mm |
| Jewels | 21 |
| Power Reserve | Approx. 42 hours |
| Frequency | 21,600 vph (3 Hz) |
| Accuracy | -20 ~ +40 sec/day |
| Functions | Hours, minutes, seconds (skeleton); automatic + hand winding; stop-seconds |
| Instruction | Details |
|---|---|
| Primary Use | As an intermediate gear train component, transmits power to the escapement while driving the seconds hand |
| Normal Function | The second wheel drives the center seconds hand for continuous smooth operation, enabling seconds time display |
| Failure Symptoms | Worn second wheel causes: seconds hand stuttering, stoppage, poor power transmission, unstable movement operation |
| Maintenance Advice | Professional movement service every 3-5 years is recommended to inspect second wheel gear wear |
1. Remove Automatic Module Remove the automatic winding module to access the gear train
2. Remove Train Wheel Bridge Loosen and remove the screws securing the train wheel bridge
3. Remove Wheels in Sequence Remove wheels in correct order: great wheel → center wheel → third wheel → second wheel → escape wheel
4. Cleaning Clean the train wheel bridge and mounting area – remove old oil and debris
5. Install New Second Wheel Place the new second wheel in position, ensuring proper gear meshing
6. Install Train Wheel Bridge Reinstall the train wheel bridge and tighten screws in a diagonal sequence
7. Lubrication Apply a microscopic amount of specialized watch oil to the second wheel pivots
8. Testing Manually wind and observe smooth gear train operation without unusual noise
Important Note: Proper installation sequence and gear meshing are critical. Ensure the second wheel teeth fully align with adjacent gears. Professional installation by a watchmaker is recommended.
| Note | Details |
|---|---|
| Movement Confirmation | This second wheel is specifically for MIYOTA 8N24 movement – verify movement model before purchase |
| 8N24 Features | The 8N24 is a skeleton automatic movement with 5.55mm height and stop-seconds function – precise gear train alignment is critical for proper operation |
| Installation Sequence | Gear train installation must follow the correct sequence – do not reverse |
| Simultaneous Inspection | If the second wheel is severely worn, inspect and replace the third wheel and escape wheel at the same time |
| Lubrication Requirement | Apply specialized watch oil (e.g., Moebius) to second wheel pivots – microscopic amount only, no overflow |
| Cleanliness Requirement | Thorough cleaning of the train wheel bridge and gears is essential before installation |
| Professional Advice | Gear train disassembly requires expertise – professional installation by a watchmaker is recommended |
| Aspect | Guidance |
|---|---|
| Inspection Period | Inspect second wheel teeth for wear or deformation during each movement service |
| Wear Indicators | Signs of wear include: unstable movement operation, unusually low amplitude, increased time deviation, seconds hand stuttering or stoppage |
| Cleaning Method | Use specialized cleaning solution and ultrasonic equipment; avoid corrosive cleaners |
| Lubrication | Apply specialized watch oil to second wheel pivots – microscopic amount only; gear teeth typically require no lubrication |
| Replacement Interval | Replace immediately if teeth are worn, missing, or deformed |
| Service Advice | MIYOTA 8N24 movements should be professionally serviced every 3-5 years |
Q1: What are the symptoms of a worn second wheel?
A: Symptoms include: the seconds hand stutters or stops intermittently, the movement runs inconsistently, power reserve may be reduced, unusually low amplitude, or the watch stops completely due to power transmission failure in the gear train.
Q2: Can I install this second wheel myself?
A: This repair requires complete movement disassembly, specialized tools (screwdrivers, tweezers, oilers), and experience with automatic movement gear trains. Professional installation by a qualified watchmaker is strongly recommended.
Q3: What other parts should be inspected when replacing the second wheel?
A: When replacing the second wheel, inspect the third wheel, escape wheel, and the train wheel bridge jewels for wear. Gear train wear is often synchronized across multiple components.
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