×
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

Designing a simple cantilever spring
2

Designing a simple cantilever spring

Designing a simple cantilever spring

(OP)
I am trying to design a simple cantilever spring that needs to bend through 90 degrees.  Do I use simple cantilever beam theory to determine the stress?

I am going to use 1055-1065 spring steel approximately 0.5mm thick.  The beam will be approx 50mm long and 4mm wide.


|                       force
------------------------
|


|
-----
|     \
        \
         |
         | force

Regards,


Ian.
 

eng-tips, by professional engineers for professional engineers

Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
 

RE: Designing a simple cantilever spring

No, because simple beam theory assumes, well, several things.

But E/R=s/y=M/I still holds true

so all you need to do is determine the bending moment at each point along the beam, then you can work out R, and then you can work out how much it bends. The problem is that the BM will depend on the results from the rest of the beam. It is unlikley to have a nice analytical solution.

However, in theory that isn't a problem, since your boundary conditions are straightforward, and a numerical solution will be good enough.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Designing a simple cantilever spring

Using a beam for 90 degrees deflection is impractical. If you need 90 degrees than you should use a torsion spring instead. Anyway, this is a large deflection case, therefore, the standatd formulations do not apply, see http://users.cybercity.dk/~bcc25154/Webpage/largedeflection.htm
 

RE: Designing a simple cantilever spring

See MECHANICAL SPRINGS, 1963 2nd Edition. McGraw-Hill Book Co. By A.M. Wahl. page 179, too.

RE: Designing a simple cantilever spring

(OP)
What I am designing is sort of like a automotive clutch pressure plate, where I want the fingers to bend through 90 degrees without yielding when a large shaft is inserted through it. The spring rate is not as critical as long as the fingers can spring back to their original position.  Hence I thought if I use thin enough spring steel, I just might be able to do it.  

I can get some pieces of light gauge spring steel and perform some bend tests to see if I am exceeding the yield strength, but am hoping to refine my design before hand (tapering the finger width).  

Thanks Greg & israelkk for your posts.  I will work through the large deflection attachment now and see if I can get my head around it.  Of course the solution is linked to fly fishing!

Ian.   
 

eng-tips, by professional engineers for professional engineers

Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
 

RE: Designing a simple cantilever spring

Sounds entirely feasible. Quite a neat little problem. Only thing is, I think 'F' in your drawing will have a strong leftwards component (governed by the coefficient of friction).



 

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Designing a simple cantilever spring

mu was 0.3, I assumed that the contact surface was //to the y axis, units are consistent.

 

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Designing a simple cantilever spring

Also check out Mechanical Spring Design, by Carlson

RE: Designing a simple cantilever spring

OHSpringGuy

To my best knowledge, Spring Designer Handbook by Carlson doesn't deal with the case of large deflection flat cantilever springs.

RE: Designing a simple cantilever spring

Incidentally the SAE handbook for leafspring design has many nomograms for this and similar problems.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

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