×
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!

*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

Bevel drive efficiencies

Bevel drive efficiencies

Bevel drive efficiencies

(OP)
I'm looking to do some analysis for transmission options that include both transverse and longitudinal configurations. I.e. with and without a 90deg bevel gear set. At this stage there is plenty of design flexibility in the longitudinal case, such as performing the main reduction at a set of bevels with a ratio of 3:1 (like a conventional final drive) or running them at lower torque closer to 1:1 and performing the final reduction as a helical gear pair.

Can anyone help with rough efficiencies for the two options? Or ideally a reference to a calculation method so I can map efficiencies from 0 to 100% of rated torque?

The idea has been inspired by a number of motorsport transmission schemes that I've seen where the 90deg drives are all configured as high-speed / low-torque with ratios close to 1:1. I'm assuming that the reason was efficiency?

Thanks in advance, Ian
Replies continue below

Recommended for you

RE: Bevel drive efficiencies

murpia,

If your engine is transverse, then you'll want a parallel shaft gearbox (ie. all helicals or spurs).  If your engine is longitudinal, then you'll need at least one orthogonal gear axis.

Spiral or hypoid bevel gearsets tend to be heavier and bulkier than helicals or spurs simply due to their geometries.  If weight or package size is an issue, you'll want to do the bevel drive at the point in the drive train with the highest shaft speed possible, since that will be the point of lowest torque and will thus require the least amount of gear and bearing mass.  

Theoretically, spur gears supported by ball bearings would  have the best efficiency.  But even a spiral bevel gear mesh can be very efficient if designed properly.  The difference in mechanical loss between a spiral bevel or helical mesh of similar ratio is probably only a few tenths of a percent.  

Things like oil windage or churning can cause very significant losses if you don't pay attention to them.  Adverse changes in gear contact geometries can also be an issue, due to inadequate housing structural stiffness or material CTE mismatches between the gears and housings.

Regards,
Terry

RE: Bevel drive efficiencies

Ian, I don't think there will be much in it efficiency wise if it is all properly designed.

But that is a big if. Typically production diffs are very inefficient (85% would not be unusual) because you can't make the case stiff enough to hold the hypoid gears in their correct relationship, except at one torque and temperature. I think you will face similar problems.

Having waded through two boxes of textbooks and manuals, and 15 feet of bookcases, that is the best I can offer. Sorry.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Bevel drive efficiencies

For a given torque capacity, hypoid gears are more compact, but less efficient (significantly), than spiral bevel gears.

Running a long shaft at high speed can be problematic - you can get into natural frequencies, etc.

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



News


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