A 5-Step Guide

Step 1: Prioritize Constant Velocity (CV) Design
This is the most important technical consideration for generators.

• The Problem: A single Cardan joint causes speed and torque fluctuation, leading to a non-uniform input to the generator. This can cause voltage frequency instability and undesirable stress.

• The Solution: You must use a double Cardan shaft (Constant Velocity Shaft). This assembly uses two joints connected by an intermediate shaft, phased correctly to cancel out speed fluctuations, ensuring a smooth, constant input to the generator.

Step 2: Determine Key Application Parameters
Gather these specifications with high accuracy:

Step 3: Analyze the Operating Angle & Joint Phasing

• Equal Angles are Ideal: For perfect constant velocity, the operating angles at the engine end and generator end must be identical. In practice, they should be as equal as possible (within 1-3°).

• Correct Phasing: The yokes on the intermediate shaft must be in the same plane (“in phase”) to cancel the velocity fluctuations. An improperly phased shaft will magnify the problem.

• Consult Charts: Use the manufacturer’s “angle vs. speed vs. torque” derating charts. Higher angles and speeds significantly reduce the permissible torque.

Step 4: Select Specifications for Reliability & Maintenance
Generators often run 24/7, so reliability is paramount.

• Torque Capacity: Select a shaft where the rated torque is significantly higher than your calculated continuous torque. A safety factor of 1.5x or more is common.

• Dynamic Balancing: The entire assembly must be high-precision balanced (e.g., to G2.5 or G6.3 per ISO 1940) for the operating speed to prevent destructive vibrations.

• Lubrication System:

  • Grease Nipples: Standard, require periodic manual lubrication.

  • Centralized Automatic Lubrication: Highly recommended for critical, hard-to-reach, or large-scale generator installations to ensure consistent lubrication and maximize service life.

Step 5: Finalize with a Specialized Manufacturer
Choose a partner with proven experience in power generation.

• Engineering Review: They should verify your calculations for torque, speed, and angles.

• Certified Quality: ISO 9001 certification is a baseline. Look for specific quality controls for balancing and heat treatment.

• Custom Flanges & Yokes: Ensure they can provide the correct flange (DIN, SAE, etc.) to match both your engine and generator.

Summary: Key Selection Criteria for Generator Cardan Shafts

Final Recommendation: The selection of a Cardan Shaft for a generator is not a place for compromise. Always provide the manufacturer with your power, speed, distance, and expected misalignment. Rely on their engineering team to specify a balanced, constant velocity assembly that guarantees the reliability and stability your power generation system requires.