Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

high speed gears

high speed gears

high speed gears

I am in the idea generating phase of my gear design.  Does anyone see a problem with lubricating high speed gears (at 20000 rpm) with an oil bath?  I know oil injectors are the norm but I am just curious why thats so.  

    Thanks in advance for any advice

RE: high speed gears

Aireation possibly, just a guess....Mike

RE: high speed gears

Foaming is very likely, as already mentioned.  Also, if you can cure the foaming then windage losses (fluid drag) may become a big factor and cause overheating and low efficiency.

RE: high speed gears

You don't mention the diameters but at that speed I would guess centrifugal force would throw off any oil before it got to the mesh. Anything over 4000 ft/min should ideally be force fed.

RE: high speed gears

It is my understanding that one problem with an oil bath on a high-speed gearbox has to do with the fluid dynamics of the oil.  As the gear tooth reaches full engagement with it’s mating space, the only place for the oil to exit is out the sides at the root.  What may amount to an urban engineering legend has it that if the gear is turning fast enough and the face of the gear is wide enough, the exit velocity of the oil becomes supersonic.  I suspect that before you get close to that situation, the fluid dynamics will overcome the mechanics of the transmission and instead of a transmission, you end up with a self-contained oil pump.

RE: high speed gears

We usually look at the rubbing velocity at the pitch line. Anything over 20,000 fpm is considered high speed. covert your 20k rpm to see how fast the teeth are coming into and out of mesh. Churning loses become a problem along with dynamic affects in the load zone. I suspect the biggest problem will be in the support bearings. They die a quick death at that speed if the design isn't just right. (ask the turbine bunch)

RE: high speed gears

Thanks for all the responses!  You all are too kind.


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


eBook - Integrating the Engineering Ecosystem
Aras Innovator provides multiple options for integrating data between systems, depending on the scenario. Utilizing the right approach to meet specific business requirements is vital. These needs range from authoring tools, federating data from various and dissimilar databases, and triggering processes and workflows. Download Now
Research Report - Simulation-Driven Design for SOLIDWORKS Users
In this engineering.com research report, we discuss the rising role of simulation and the paradigm shift commonly called the democratization of simulation. In particular, we focus on how SOLIDWORKS users can take advantage of simulation-driven design through two analysis tools: SOLIDWORKS Simulation and 3DEXPERIENCE WORKS. Download Now
White Paper - Industry 4.0 and the Future of Engineering Education
With industries becoming more automated, more tech-driven and more complex, engineers need to keep their skills and knowledge up to date in order to stay on top of this wave—and to be prepared for the Industry 4.0 future. The University of Cincinnati offers two online Master of Engineering degree programs designed specifically for practicing engineers. Download Now
eBook - The Design Gridlock Manifesto
In this eBook, you’ll learn 6 ways old CAD technology slows your company down and hear how design teams have put those problems to rest. “The Design Gridlock Manifesto” shares first-hand modern CAD experiences from 15 companies around the world. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close