Contact US

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

A-arm question

A-arm question

A-arm question

Hey everybody!

Could anyone shed some light on this phenomenon?
I've been taking accelerometer measurements of the A-arms on my minivan (front suspension). Why is it that at higher speeds (65mph) the peak frequency of vibration does not increase with speed, but instead the nearby frequencies will increase. Is this mainly the result of the A arm structural design, or response of the spring and dampers at higher speed?

Any insight would be appreciated.

RE: A-arm question

Yes you are correct, one big peak around 12 that distinguishes it from the rest.
I've read literature that automotive suspensions are designed with frequencies under 20 Hz for ride comfort.
Is there another reason that driving on the freeway would increase the 10, 15, 18 Hz peaks and keep the 12 Hz peak the same or lower?


RE: A-arm question

The 12 Hz mode is almost certainly wheelhop. Its excitation on a well balanced wheel is from bumps in the road, and its frequency is more or less constant. However there are other excitations that occur at multiples of wheel rotational speed, so the frequency of those peaks changes with speed.

You'll probably need to read up on campbell's diagrams, waterfalls, and rotating machinery analysis.  


Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies  http://eng-tips.com/market.cfm?

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


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
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’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:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close