×
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.

Coil Spring Force Application Area on Rubber Insulator/Isolator

Coil Spring Force Application Area on Rubber Insulator/Isolator

(OP)
Okay, this is probably just a geometry problem, but I can't wrap my head around it.

If I have a coil spring sitting on an isolator pad the surface of the spring which makes contact with the isolator pad will increase as the force on the spring is increased and the rubber compresses and deforms around the spring end. I would like to predict how much the isolator will bulge out radially, based on the force applied, but I am hung up on the first statement. How can I determine the deformation/deflection of the rubber isolator given a certain spring (and spring force) and applied load to the spring?

Thanks,
Jeff

RE: Coil Spring Force Application Area on Rubber Insulator/Isolator

Is this a real problem? This seems odd. Why not use a steel washer between the spring and the rubber to avoid direct contact between the spring coil and the rubber? This should be the correct way to go. To your question, the only way to solve the actual problem is using a large deflection (of the rubber) non linear FEA analysis.

RE: Coil Spring Force Application Area on Rubber Insulator/Isolator

If you go your way, the force on the spring may not align along the spring axis which will force you to use the FEA and bucking analysis on the spring too. The direction of the force on the spring will vary from system to system depends on the rotational/circumferential direction of the spring assembly with respect to his axis.

RE: Coil Spring Force Application Area on Rubber Insulator/Isolator

This is a big real world issue since the road springs on a car use (shaped) rubber pads between the spring and the cap. Among other things the take up between the coil and the pad affects spring durability (if you get it completely wrong) and the effective point of application and direction of the spring load, which is of great interest in some suspensions. The shaped isolators also help to prevent the spring from rotating, which is important.

To be honest I've never worked on the isolator side of this arrangement, we typically modify the spring profile, a non linear FEA seems like a modern approach. We did it on a rig.

Cheers

Greg Locock

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

RE: Coil Spring Force Application Area on Rubber Insulator/Isolator

(OP)
Ok, so I guess the consensus is to use FEA to determine the amount the isolator will bulge. I guess that puts me in the usual iterative design loop...start with an assumed thickness, diameter and shape and apply the spring geometry and force and see how much it bulges, then revise as necessary and re-analyze.

What did we do before FEA? Oh yeah...build, test and break, build, test and break...sigh...

Jeff

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!