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This is a genuine Sellita SW220-255 H4 hour wheel, an original Swiss-made component for the Sellita SW220 automatic movement. As part of the motion work system, the hour wheel transmits power from the cannon pinion to drive the hour hand, ensuring accurate time display .
This brand new original part is essential for watchmakers restoring proper timekeeping function when the original wheel becomes worn or damaged.
The hour wheel is a dial-side component located under the dial. Proper engagement with the cannon pinion and minute wheel is critical for accurate time display.
Signs of Hour Wheel Wear:
Hour hand does not move when the crown is turned
Hour and minute hands do not maintain correct positional relationship
Hands move erratically or bind
Visible wear on the hour wheel teeth
Proper Handling Tips:
The hour wheel works in conjunction with the cannon pinion and minute wheel
Always inspect the cannon pinion for wear when replacing the hour wheel
Ensure the hour wheel is properly seated on the main plate before installing the dial
Tools Required:
Non-metallic tweezers
Hand removal tools
Dial protector film
Movement holder
Loupe or magnification
Rodico cleaning putty
Step-by-Step Installation:
Step 1: Movement Preparation
Remove the movement from the watch case
Remove the hands using hand removal tools (protect the dial with film)
Remove the dial
The hour wheel is located on the dial side of the movement
Step 2: Remove the Old Hour Wheel
Locate the hour wheel on the main plate (typically near the center)
Using non-metallic tweezers, carefully lift the old hour wheel from its pivot
Note the orientation for reinstallation
Step 3: Inspect and Clean
Inspect the cannon pinion and minute wheel for wear
Clean the pivot area using Rodico to remove old oil and debris
Ensure the new hour wheel’s teeth are intact
Step 4: Install the New Hour Wheel
Position the new genuine Sellita SW220-255 H4 hour wheel onto its pivot
Ensure the wheel sits flush and engages properly with the cannon pinion
The wheel should rotate freely but with minimal play
Step 5: Lubrication
Apply a small amount of Moebius 9010 to the pivot point
Avoid over-lubrication, which can attract dust
Step 6: Reassembly and Testing
Reinstall the dial and hands
Test time setting: pull crown to time-setting position – hands should move smoothly
Ensure the hour and minute hands maintain correct positional relationship
Verify that the hour hand points correctly at each hour position
Important Notes:
The H4 height variant must match your original movement‘s configuration
The hour wheel works in conjunction with the cannon pinion – inspect both when replacing
Professional installation is strongly recommended for those without movement service experience
Common Symptoms of Hour Wheel Issues:
| Symptom | Possible Cause |
|---|---|
| Hour hand does not move | Worn hour wheel teeth or damaged cannon pinion |
| Hour and minute hands misaligned | Incorrect hour wheel seating or worn teeth |
| Time setting feels rough | Debris in motion work or worn components |
| Hour hand jumps or binds | Damaged hour wheel teeth or bent pivot |
Diagnostic Process:
Visual Inspection: Under magnification, examine the hour wheel teeth for wear, chipping, or deformation. Compare with the cannon pinion teeth.
Height Verification: Confirm that the H4 height matches your original hour wheel. Using the wrong height variant can cause hand clearance issues.
Cannon Pinion Check: Inspect the cannon pinion for wear – worn cannon pinion teeth can cause hour wheel failure.
When Replacement is Necessary:
Visible wear or damage to hour wheel teeth
The hour wheel no longer engages properly with the cannon pinion
The movement has been in service for 5+ years and time setting feels loose
Preventive Maintenance:
Service the movement every 3-5 years
During service, inspect all motion work components for wear
Replace the hour wheel if any signs of wear are present
Always replace the cannon pinion simultaneously if worn
When to Seek Professional Help:
You lack experience with dial-side movement disassembly
Multiple components show signs of wear
The movement has other issues affecting timekeeping
You are uncertain about proper height variant selection
Q1: What does the H4 designation mean?
A: The “H” stands for height. The H4 designation indicates a specific hour wheel height within the SW220 family. Different height variants (H1, H2, H3, H4, H5) accommodate different hand stacking heights and dial thicknesses. The H4 is the tallest variant, designed for specific case configurations . Always verify that the H4 height matches your original movement‘s configuration before purchasing.
Q2: Which movement is this part compatible with?
A: This hour wheel is specifically designed for the Sellita SW220 automatic movement. It is not compatible with SW200 or other calibers without verification. The SW220 features a day-date display (full day at 12 o‘clock, date at 3 o‘clock).
Q3: What is the difference between the hour wheel and the cannon pinion?
A: The cannon pinion is mounted on the center wheel and drives the minute hand. The hour wheel is driven by the cannon pinion and drives the hour hand. Both work together in the motion work system. When the crown is turned to set the time, the setting mechanism turns the cannon pinion, which turns the hour wheel, moving both hands simultaneously .
Q4: Can I install this part myself?
A: If you have experience with movement disassembly and the proper tools (hand removers, non-metallic tweezers, etc.), installation is possible. However, the hour wheel is located on the dial side and requires removing the hands and dial. Professional installation is recommended if you lack experience. Also, ensure you select the correct H4 height variant for your movement.
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