×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• 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.

# centre of gravity

## centre of gravity

(OP)
I am trying to moment weigh a set of turbine blades, I have a radius from the engine centre line to a gtiven point on the firtree roots, however, to produce a true moment weight for the blade I need to find out the exact centre of gravity. Is this a trial and error or can it be calculated (simple shapes can), if so where can I find a formula to calculate this.

### RE: centre of gravity

StrainGauge

The center of gravity for any arbitrary shape is computed independently in each of the x,y and z axes using integral calculus.

x.c.o.g. = integral (x * dm) / integral (dm)

where x.c.o.g is the x axis center of gravity, same for y and z.  x is the distance, and dm is the mass at a particular distance.

The integral(dm) is just the total mass (or weight).

For simple shapes, the integral can be evaluated.  For complex shapes, the integral usually does not have a definite solution, but the integral can still be approximated in a piecewise linear fashion or can be approximated as a bunch of small elements, which is the basis of FEA.

It can also be approximated using graph paper and counting squares.  The closer the approximation (more pieces or smaller squares)the less error there is.

Unless you have a mathematical formula, a cad design, or take careful 3d measurements, then computing the c.g. for the turbine blades is going to be difficult.  If you need an answer with 2 digits of precision, its pretty straightforward to approximate.  If you need more than that, then the computations and accumulated errors are easier resolved with a computer.

Good Luck

#### 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.

#### Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a partâ€™s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. 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:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!