Introduction
The repair and restoration of a 1930’s Chicago Flexible Shaft Company Sunbeam Eternatime Clock offers a fascinating look into the early era of American electric timekeeping. These clocks were produced during a period of rapid technological innovation, when manufacturers were transitioning from traditional spring‑driven mechanisms to synchronous electric motors designed for continuous, low‑maintenance operation. The Sunbeam Eternatime line represents one of the earliest and most successful attempts to bring reliable electric clocks into American homes, combining simple engineering with dependable performance.
This comprehensive guide explores the history of the Chicago Flexible Shaft Company, the development of early synchronous electric clocks, the mechanical and electrical design of the Sunbeam Eternatime movement, and the most common issues encountered during restoration. It also provides a detailed overview of servicing procedures, case restoration, long‑term maintenance, and collector considerations. For restorers seeking authentic replacement parts, VintageClockParts.com remains a trusted resource for gears, wiring components, lubricants, and specialized tools for both electric and mechanical clocks.
Early American Electric Clockmaking Tradition
The shift from mechanical to electric timekeeping
By the early 20th century, American households were rapidly adopting electric appliances. Clock manufacturers recognized the opportunity to create timepieces that required no winding, offered consistent accuracy, and could operate continuously as long as they remained plugged in. This shift marked the beginning of synchronous electric clock production, where the motor’s speed was regulated by the frequency of the electrical grid.
The appeal of synchronous electric clocks
Synchronous electric clocks offered several advantages over mechanical clocks:
- No winding required
- Consistent timekeeping tied to the 60 Hz power grid
- Fewer moving parts
- Lower maintenance requirements
- Quiet operation
These benefits made electric clocks highly desirable for modern households of the 1930s.
Acknowledgement: Video demonstration provided by Mark, the clock repair guy
Development of Early Synchronous Electric Clocks
The rise of AC‑powered timekeeping
As AC power became standardized across the United States, manufacturers began designing motors that operated in perfect synchronization with the electrical grid. This allowed clocks to maintain accurate time without the need for pendulums, balance wheels, or escapements.
The synchronous motor breakthrough
The synchronous motor was the key innovation that made electric clocks practical. Its rotor spins at a fixed speed determined by the frequency of the electrical supply. This eliminated many of the mechanical variables that affected accuracy in spring‑driven clocks.
Early challenges
Despite their advantages, early electric clocks faced several challenges:
- Motor startup reliability
- Gear wear due to constant operation
- Heat buildup in enclosed cases
- Power cord deterioration
- Rotor lubrication issues
These challenges are still relevant for restorers working on 1930s electric clocks today.
Chicago Flexible Shaft Company and Sunbeam Eternatime Clocks
From industrial equipment to household appliances
The Chicago Flexible Shaft Company began as a manufacturer of flexible drive shafts for agricultural and industrial machinery. Their engineering expertise eventually led them into the production of household appliances under the Sunbeam brand.
Expansion into electric clocks
By the 1930s, the company introduced the Sunbeam Eternatime line of electric clocks. These clocks were designed to be affordable, reliable, and easy to maintain. Their simple synchronous motor design made them ideal for mass production.
Characteristics of Sunbeam Eternatime clocks
Sunbeam Eternatime clocks typically feature:
- A synchronous AC motor
- A reduction gear train
- A worm gear or pinion drive
- A metal or Bakelite case
- A simple hand‑setting mechanism
- A cloth‑covered power cord
- Minimal internal wiring
Their simplicity is one of the reasons they remain popular among collectors and restorers.
Identifying Authentic Sunbeam Eternatime Clocks
Maker’s marks and labels
Authentic Sunbeam Eternatime clocks often include:
- A Sunbeam logo on the dial
- A stamped or printed model number
- A motor housing with manufacturer markings
- A rear label with electrical specifications
Case materials
Most 1930s models were produced in:
- Bakelite
- Painted metal
- Early plastic composites
These materials help date the clock and confirm authenticity.
Movement identification
The synchronous motor and gear train design are distinctive. Many models include a small red or orange gear that is known to deteriorate over time.
Understanding Synchronous Electric Movement Design
The rotor and stator system
The synchronous motor consists of:
- A rotor that spins when energized
- A stator that creates a rotating magnetic field
The rotor must spin freely and maintain proper alignment with the stator for the clock to operate correctly.
Gear reduction
Because the motor spins at a high speed, a reduction gear train slows the rotation to drive the minute and hour hands. This gear train must be clean, lubricated, and free of wear.
Hand‑setting mechanism
A simple friction‑based mechanism allows the user to adjust the time manually. If worn, it may slip or bind.
Multi‑Train Movement Configuration
Timekeeping train
The primary gear train drives the hands and must operate smoothly for accurate timekeeping.
Auxiliary components
Some models include:
- A startup mechanism
- A manual spin‑start feature
- A secondary gear for alarm functions (in certain models)
Understanding these components is essential for proper restoration.
The Rotor, Stator, and Gear Train System
Rotor operation
The rotor is the heart of the movement. It must:
- Spin freely
- Maintain proper lubrication
- Avoid binding or wobbling
A worn rotor will cause noise, vibration, or failure to start.
Stator performance
The stator must produce a strong, consistent magnetic field. Corrosion or damaged windings can weaken performance.
Gear train wear
Constant operation can cause:
- Worn gear teeth
- Cracked plastic gears
- Excessive play in pinions
These issues must be addressed during restoration.
Common Problems in Sunbeam Eternatime Clocks
Hardened lubrication
Old oil becomes sticky and prevents the rotor and gears from turning freely.
Deteriorated gears
The small red/orange gear is notorious for crumbling with age.
Power cord deterioration
Cloth‑covered cords from the 1930s often become brittle and unsafe.
Internal wiring fatigue
Insulation may crack or crumble, creating electrical hazards.
Rotor alignment issues
Misalignment can cause humming without rotation.
Dirt and debris
Dust inside the motor housing can interfere with rotor movement.
Comprehensive Movement Servicing and Cleaning
Systematic disassembly and documentation
Each component should be removed, photographed, and labeled to ensure proper reassembly.
Cleaning techniques
Cleaning typically includes:
- Removing old oil
- Cleaning the rotor and stator
- Cleaning the gear train
- Removing dust from the motor housing
Rotor servicing
The rotor must be cleaned, polished, and lubricated with appropriate oil.
Gear Train and Mechanism Service
Gear replacement
Worn or damaged gears must be replaced with high‑quality reproductions.
Pinion inspection
Pinions must be checked for wear and proper engagement.
Hand‑setting mechanism service
The setting mechanism must be cleaned and adjusted to prevent slipping.
Case Restoration for Sunbeam Eternatime Clocks
Structural repairs
Bakelite and metal cases may require:
- Crack repair
- Surface polishing
- Paint restoration
Electrical safety
Power cords and internal wiring must be replaced with modern, safe equivalents.
Final Assembly and Operational Testing
Movement installation
The movement must be reinstalled with proper alignment.
Initial setup
The clock should be tested for:
- Smooth rotor operation
- Accurate timekeeping
- Quiet running
- Proper hand movement
Performance optimization
Fine adjustments ensure long‑term reliability.
Long‑Term Care and Maintenance
Operating environment
Electric clocks should be kept in:
- Stable temperatures
- Low‑humidity environments
- Dust‑free locations
Maintenance schedule
Periodic cleaning and lubrication extend the life of the movement.
Collector Value and Historical Significance
Market considerations
Sunbeam Eternatime clocks are valued for their:
- Early electric motor design
- Simple engineering
- Historical significance
Documentation and preservation
Proper documentation enhances collector value.
Parts and Restoration Resources
Visit VintageClockParts.com to browse our extensively photographed inventory and find the exact components your project requires. Every part is individually photographed from multiple angles, ensuring you can make informed decisions for your valuable work on vintage electric clocks and all other American and European timepieces.
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