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Tech Note August 1997

Technical Notes from Dr. Mel Giberson, P.E. – TRI President

Extension Shaft Vibration

Large turbine and generator rotors are frequently designed with large bearings and small extension shaft. Many extension shafts have high amplitude vibrations causing damage to the steady rest bearings.
TRI can answer questions and provide solutions. Using computer models, TRI analyzes bearing performance and vibration characteristics for turbine-generator-extension shafts

Bearings, Shafts & Pedestals

Contact TRI for a source with proven design and fabrication experience.


  • Should the design incorporate steady rest bearings?
  • How much “lift” is appropriate for a steady bearing?
  • How much “lift” will cause fatigue and failure?
  • How will the critical speed be affected?
  • If required, what is the best type of coupling?

Variable Speed Drives

Look to fluid drive technology for increased reliability, efficiency and noise reduction.

Variable speed power above 400 HP is delivered most reliable with fluid drive technology. With TRI’s latest advances, fluid drives can be designed more efficiently than either electronic variable frequency drives or mechanical drive steam turbines. By introducing a second element in a surprisingly simple package, the new TRI design has dramatically increased efficiency at lower speeds.

For Fans, Pumps and Compressors

TRI provides variable speed power systems up to 40,000 HP for horizontal or vertical applications, new or retro-fit, and direct or geared systems.

Over 15,000 MW of Electrical Generation Depend Upon TRI Bearings

Tel: 610-363-8570 or 800-363-8571 Fax: 610-524-6326 EMail:

TRI Answers phone calls, returns e-mails and responds to fax inquiries

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