Register for free
453,276 reg. members
453,276 reg. members
Results 1 to 8 of 8
  1. #1
    Join Date
    Feb 2006

    Angle Iron Deflection ?

    Hi working on new gantry router design and intended to use 3"x3"x10'
    1/4" angle iron spanning 8-10ft between support legs and predict a load
    of approx 100lbs. I am concerned with deflection or twist. if secured
    to supports diff and or where my load rides on the angle iron would change
    the amount of deflection. If I uploaded pic properly it might give an idea of
    what I am trying to do.

    Thanks Gads
    Attached Thumbnails Attached Thumbnails router4a.bmp  

  2. #2
    Join Date
    Jan 2008
    What accuracy are you looking for. 100 lb on a pair of 10ft L beams is enough to induce noticeable flex. The math for these is simple if you know what you are doing. If not there are some good tables for moment of inertia as well as cantilever beam calculators online. Accurate prediction of deflection is possible, the hard part is determining what is allowable.

  3. #3
    Join Date
    Aug 2007
    Hey Gads,

    A 3x3x0.25 has a moment of inertia of 1.24 inch^4 in both directions (Ix and Iy).

    E = modulus of elasticity for steel = 30,000,000 psi

    To calculate the max deflection over 10 feet (force concetrated at the center)
    = W * length³ / (192 E*I)
    = 100lbs * (120 in)³ / (192 * 30,000,000 * 1.24)
    = 0.0242"

    If the 100 lbs of force is distributed over two pieces of angle, moment of inertia I is doubled and the deflection is cut in half. Still quite a bit deflection at around 0.012".

  4. #4
    Join Date
    Nov 2007
    I was thinking about this same thing the other day - any good websites on how to learn these calculations?

    Gads, Hope you don't mind that i ask a question in your thread:

    How does the cross section of the design effect the inputs?

    for example I'm looking to use something like the following

    2.6" legs, 8" wide. 1/2" thick - 60" long

  5. #5
    Join Date
    May 2005
    Quote Originally Posted by multiplex View Post
    for example I'm looking to use something like the following

    2.6" legs, 8" wide. 1/2" thick - 60" long
    For these google UPN beam or UPN steel channel, and go from what you find there, Im sure you will get good info.


  6. #6
    Join Date
    Feb 2007
    Try these links for calculations... the sites also provide material properties and explanations in varying details for those with less experience with the equations.



  7. #7
    Join Date
    Sep 2006
    Try the freeware "BeamBoy" program. It's great for quickly doing this type of analysis.

  8. #8
    Join Date
    May 2006
    Unless your angle is loaded through the 'Shear Centre', it will twist as well as deflect vertically. The amount will depend on how the ends of the angle are supported at the ends - 'simple' or 'encastre', or something in between! You really need to have a chat to an engineer friend, if you have one!

Similar Threads

  1. angle iron & flat bar comb tool
    By anil in forum Metal Working Tooling
    Replies: 0
    Last Post: 09-29-2007, 07:13 AM
  2. machining angle iron
    By stymye in forum General Metalwork Discussion
    Replies: 14
    Last Post: 09-04-2006, 06:43 AM
  3. Cleaning up angle iron edge
    By Mark Van in forum General Metalwork Discussion
    Replies: 2
    Last Post: 11-16-2005, 10:20 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts