×
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

Center of Gravity Height Question....
2

Center of Gravity Height Question....

Center of Gravity Height Question....

(OP)
Is 22" reasonable estimate for a center of gravity height on a 4 door sedan (like a 1995 Nissan Maxima)

I understand if I jack up my car a few feet, I can calculate my actual cgh, but I don't have wheel scales, or a jack that can lift that high?

I thought I read in the Bosch Handbook that you can take 1/3 of the vehicle height as a close estimation.
(in my example 55.7" * .333 = 18.54")

Any realword examples someone can share?

Thanks.

RE: Center of Gravity Height Question....

2
The CG height on a sedan is typically around 20-21 inches.  A rule of thumb is the bumper height.
As for jacking the car to get the CG, you have to do it more than a few feet because of the cos error at small angles.
There is also a paper on measured vehicles.  It contains a table about 1/4 of the way thru it.  Link:
http://www-nrd.nhtsa.dot.gov/vrtc/ca/capubs%5Csae1999-01-1336.pdf
Hope this helps
Kevin

RE: Center of Gravity Height Question....

(OP)
Thank you! That is a great document.

RE: Center of Gravity Height Question....

I seem to remember reading somewhere that the height of the camshafts on OHC cars is also a good approximation of the CG height.

RE: Center of Gravity Height Question....

In a tube frame race car, the camshaft height of a pushrod engine is commonly used, but that's a very rough estimate. If you differentiate the equations used in the "jacking" method, you'll find that a very, very small measurement error will result in a significant CG height error.

For a tube frame race car, I prefer to use the "tabulation" method, where heights, weights, and height-weight products are tabulated for as many components and structural pieces as possible. If this is carried far enough, the height of the remaining weight becomes inconsequential (i.e., you can use a very rough estimate for its height) and the calculated CG height will be sufficiently accurate. Unfortunately, for a passenger car, it's much more difficult to identify significant structural components.

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