×
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

blevins solution for centre pivot beam

blevins solution for centre pivot beam

blevins solution for centre pivot beam

(OP)
I have a rocker ohv shaft supported by 3 springs. The first is the pushrod stiffness, the third is the valve stem stiffness and the second is the rocker shaft reaction point.  The rocker pivots about this centre point.  When I try to calculate the natural of the assembly, I get an incorrect answer, I think I incorrectly omit the rigid body rotation effect.  Blevins (Book - Formulas for frequency and mode shape) I recollect has the solution for the natural frequency for this system.  Anybody got the book and tell me what the closed form solution is?

k1        k2             k3
=========================
|         |             |
|         |             |
|---a-----|------b------|

note a and b are distances  k1,k2,k3 are the spring stiffnesses with the rocker pivoting about k2 position. m1,m2,m3 not shown but go with k1,k2,k3.

RE: blevins solution for centre pivot beam

If the pivot is fixed, it is effectively infinitely stiff.

Then the rotational natural frequency about 2 is:

f = sqrt[(k1.L12^2 + k3.L23^2)/(m1.L12^2 +m3.L23^2)] /2/pi

where
L12 = distance from 1 to 2
L23 = distance from 2 to 3
m1 = mass at 1
m3 = mass at 3
f = frequency

masses in kg, lengths in metres, frequency in Hz (or use another coherent system of units - but I recommend metric SI).

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