×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Jobs

Planetary gear efficiency

Planetary gear efficiency

Planetary gear efficiency

(OP)
I'm looking at a planetary gear transmission (no it ain't on a car), and I would like to know what would be a reasonable figure for its efficiency.  I have found in one reference that a spur gear can be counted upon to have 98% efficiency.  With that in mind, will 98%N work (where N is the number of stages)?
Seems I get a rather small result if I do so.

Also, can I count on bevel gears to be as efficient at transmitting power as straight spur gears?  My reference books don't give that information, either.

Any references would be helpful.  Thanks.

Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

RE: Planetary gear efficiency

If the pitch line velocity gets over some tiny value the lovely 9X% efficiency will get undermined and maybe even hornswoggled by the churning losses when the teeth squish the lube.  9HP to drive a 50 HP gearbox at full speed with zero torque output is not very good efficiency.

RE: Planetary gear efficiency

SparWeb,

   Are you designing this gear train, or ordering something from a catalogue?

   Dudley's Gear Handbook, Dennis P. Townsend, McGraw Hill has a whole section on Gears in Action.  This covers efficiency of all sorts of gears, including bevel and hypoids.  It covers planetary drives.

   I haven't read the section carefully or applied any of it, so you are on your own.  Probably, the book is on Amazon.

                        JHG

RE: Planetary gear efficiency

SparWeb, are you intending to use straight cut gears, or hypoids?

Cheers

Greg Locock

RE: Planetary gear efficiency

(OP)
All,

I'm doing some reverse-engineering, actually, so the configuration is quite fixed.  This is the transmission on a Bell helicopter.  The 1350hp engine drive is output horizontally to a bevel gear driving the planetary reduction gear which in turn drives the mast.

Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

RE: Planetary gear efficiency

(OP)
To continue... (was cut off yesterday) ... The point of the reverse engineering is to simply fine-tune a rotor performance model.  I'm realy only interested in the aerodynamics of the system so a simplified idea will suffice.  So far the feedback from various sources has indicated that only a few percent of the torque will be lost through this system.  Any nay-sayers?

Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

RE: Planetary gear efficiency

Not my specialty, but I would think from a plausibility perspective that the efficiency must be quite high, otherwise the power loss must be manifested as heat generation, which would be deleterious to the engine and the gear.

TTFN

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!


Resources