×
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.

# Torsional Constant For A Ladder Chassis

## Torsional Constant For A Ladder Chassis

(OP)
Hey guys! I'm currently designing a ladder chassis for a vehicle design assignment. I'm having troubles finding the torsional constant, J of a ladder chassis which is needed to find the torsional stiffness.

The ladder chassis will consist of 2 side members and 3 cross-members spaced equally along its length.
All the members are C-sections.

Am I suppose to sum up all the area moment of inertias, e.g. J = 2*I(side member) + 3*I(crossmember)
OR
Is this analysis only possible using a software?

### RE: Torsional Constant For A Ladder Chassis

It's not going to be that simple, and it's going to depend on how the crossmembers are connected to the main beams. If they're tacked on with a couple of rivets, they're not going to do much. A proper solid (welded-all-around) connection will do more. It is certainly not going to be as simple as the total of all three.

### RE: Torsional Constant For A Ladder Chassis

(OP)
Wow that was a quick reply, thanks alot! Okay, lets assume that the connections are properly welded.
How about if I simplify the model by using a frame with only 2 cross-members located at both ends (essentially making it a square when viewed from top). Is it possible to find the torsional stiffness by hand now?

### RE: Torsional Constant For A Ladder Chassis

C sections/channels like andy "open' section will have mighty low torsional stiffness.
C and I sections are used when Low torsional stiffness is sometimes desirable.
http://www.vanpeltsales.com/FH_web/FH_images/FH_ch...

Omer Blodgett says open section lateral Crossmembers don't add much.

http://weldingdesign.com/archive/no-twisters-or-sw...

More detailed info in Lincoln Electric's bargain Design of Weldments.
http://www.jflfoundation.com/ProductDetails.asp?Pr...

As I recall simply "boxing" the channels increased torsional stiffness

#### 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

Research Report - How Engineers are Using Remote Access
Remote access enables engineers to work from anywhere provided they have an internet connection. We surveyed our audience of engineers, designers and product managers to learn how they use remote access within their organizations. We wanted to know which industries have adopted remote access, which software they are using, and what features matter most. Download Now
eBook - Managing the Context of Product Complexity Using the Digital Twin
Keeping track of changes to complex products is difficultâ€”think Aerospace & Defense equipment, new generations of commercial aircraft, and software-based automobiles. A new way to managing the digital context of the physical product is required and the answer is the Digital Twin. This ebook explores the opportunity available for Operations and Maintenance for the Digital Twin. Download Now
White Paper - Trends in Industrial Filtration
Substantial progress has been made in filtration technologies in recent years. New filter media materials, designs and processes have led to filters that are more efficient, reliable, compact and longer lasting. This white paper will discuss the various trends that are impacting operational responsibilities of MROs today and the resources that are available for staying up-to-date on the latest filtration solutions. 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!