×
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

"Set" height calculation
3

"Set" height calculation

"Set" height calculation

(OP)
I am very new to spring design and need some help with what I hope is a simple calculation. I have a spring that takes a shorter height “set” after application (I believe it is being bottomed to solid height and cannot prevent this from happening in the application) and need to be able to calculate this shorter height at the design stage (before I have samples). Can anyone help?



Thanks in advance.

RE: "Set" height calculation

You can find some formulation in the book Spring Design A Practical Treatment, W. R. Berry 1961. However, to my best knowledge and 30 years of personal experience the calculations of the spring length are not accurate because the parameters may change with every wire batch.

I real life the spring maker makes test samples longer than the desired spring and bottoms them to find the free length needed before bottoming that will give the desired spring properties after bottoming.

Anyway, designing for a spring bottoming during application is a bad idea. With each bottoming the spring enters the plastic zone and the spring will have a very!!! short life cycle. If the spring is designed to stay bottomed for long periods it will become even shorter due to relaxation.

Taking your words that you are new to spring design and my experience I am pretty sure that a spring that will not bottom can be found. However, more information regarding forces, deflections, maximum solid length, maximum outside diameter/minimum inside diameter, type of application (static/cyclic/impact), environment, etc., is needed.

http://israelkk.googlepages.com/home

RE: "Set" height calculation

Also, as some springs are scragged or "set" the diameter may increase - if the dimensions are critical to the application this increase must also have to be considered.

Jack

RE: "Set" height calculation

neophite,

It is common for a spring manufacturer to coil/wind the spring longer than the final intent, compress it (cold or hot) to remove the set, and the final result will be the spring that meets the length, force, etc. requirements.  Even springs that bottom out during impact loading can be successfully designed to achieve > 100,000 cycles before failure, but it requires high quality raw materials, shot peening, etc.

RE: "Set" height calculation

Have you considered installing a lift stop inside the spring to limit travel and prevent the spring being compressed to solid height?  

J. Alton Cox
www.delucatest.com

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