Contact US

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!

*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

bearing materials for planet gears

bearing materials for planet gears

bearing materials for planet gears

Under high loads soft materials can distort enough to allow some missalinement, what are some good materials to use for bushings/bearings to support these gears? Also differential gears could be grouped into this too.

RE: bearing materials for planet gears

I have always used needle rollers with harden pins. I wish there was a way to make a pressured plain bearing work because of the loads and speed. I sometimes design high speed and high load PSRU's (power supply reduction unit) for aircraft.To make them last until the overhaul requirement I spray lubricant right on the spinning gear, even though the gears pick up some from the sump area..


I don't know anything but the people that do.

RE: bearing materials for planet gears

High performance, aircraft planetary gearset planet spur gears,  typically employ spherical roller bearings.  The spherical roller bearings allow for pin misalignment due to torsional wind-up in the planet carrier.  Otherwise, the gears will edge load.

If you're using a journal or plain bearing, as opposed to a rolling element bearing, and you have high radial loads, do everything you can to ensure the bearing operates in a hydrodynamic condition.  The bearing substrate should be a material that has adequate fatigue strength, and it should have a thin overlay of a softer material to provide embedability of debris.

If, as you say, there is excessive deflections of the journal, then the bearing will edge load and fail. Regardless of what bearing material you use.

RE: bearing materials for planet gears

For automotive use, use whatever is currently used, there is no need to re-invent the wheel. This means needle roller bearings in the planetary. The GM powerglide is the standard drag racing transmission. Many companies are supplying upgraded powerglides. They have stayed with needle rollers which seem to work well. Using currently mass produced part numbers will mean much lower cost. Same argument goes for a differential. Use proven and mass produced parts if at all possible.


RE: bearing materials for planet gears

The gears should be a high quality low carbon steel that is surface hardened to HRC58-62.  The bearing needles and pins are typcially SAE52100/100CR6 or equivalent through hardened steel brought up to HRC58-64.

All surfaces must be ground to size and super-finished beyond the quality that a normal machine shop could achieve.

Single digit microns make the difference between life and death in these parts.  Some manufacturers will even sort components to optimize fit.  Others size the loose rollers vs. the bore so that they will lock securely in the gear until the pin is inserted.  Still other choose to use needles mounted in a cage - reducing life but improving speed and friction performance.

What I mean by this is to support Matt51 - in a modern automatic transmission don't go messing with this stuff unless you REALLY know what you are doing.  Use OEM parts.

RE: bearing materials for planet gears

I reread your question and I remember a failure (not mine) of a PSRU. It was  the planet carrier for a Ford C6. It seems the (3) planet carrier is a cheap aluminum casting, and after reading tbuelna's post I wonder if that is what caused the failure in deforming under load to edge load the needle bearing.
I have used OEM from an Allison trans before as it was close to the load and speed requirements that I needed at the time.

Also a side note is the gear vendors will offer different grade of gears. I use between 7 and 10 as budget allows.


I don't know anything but the people that do.

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


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