Shop Floor Talk  

Go Back   Shop Floor Talk > Welding and Metalworking Forums > Fabrication

SFT Search:   
Reply
 
Thread Tools Display Modes
  #1  
Old 12-26-2018, 08:26 PM
Spencer Spencer is offline
Senior Member
 
Join Date: Nov 2005
Location: Western Michigan
Posts: 361
Default Examples Of Areas Where Welds Make It Weaker

I remember years ago there was a post where someone pointed out that one of the welds someone added to their project potentially made it weaker, not stronger. It may have been one of my projects, but I honestly don't remember.

Can you guys post some examples of situations where adding an extra weld somewhere will do more harm than good?
Reply With Quote
  #2  
Old 12-26-2018, 08:47 PM
milomilo's Avatar
milomilo milomilo is offline
Auction Addict
 
Join Date: May 2010
Location: Wheatland, Wyoming
Posts: 14,410
Default

There are many examples for this question.

1. Adding welds vertically on a track frame.

2. Increasing weld sizes in excess of the base metal thickness.

Just a couple examples. Both create stress points where the welds inhibit flex of the structure.
__________________
Chris

You want a friend in Washington? Get a dog.
Harry S. Truman
Reply With Quote
  #3  
Old 02-04-2019, 02:24 PM
Big_Eddy's Avatar
Big_Eddy Big_Eddy is offline
Senior Member
 
Join Date: Sep 2007
Location: Ontario
Posts: 287
Default

Where a trailer A Frame crosses under the front cross member of the trailer box, everyone wants to weld across the top of the A frame along the front and back edges of the cross member.

Instead - weld along the sides of the A frame tubing to the underside of the cross member and avoid adding a stress riser to the top surface of the A frame tubing.
Reply With Quote
  #4  
Old 02-05-2019, 11:25 AM
Walker's Avatar
Walker Walker is offline
Standard of Excellence
 
Join Date: Aug 2004
Location: Cave Creek AZ
Posts: 4,313
Default

Just imagine taking a cut off wheel and scoring the area you are thinking of welding. If the score turned it into a place where it will crack through quicker then the weld will do the same.
__________________
Walker
Chief slag chipper and floor sweeper, Ironwood Artistic
Reply With Quote
  #5  
Old 02-05-2019, 11:40 AM
greywynd's Avatar
greywynd greywynd is online now
I can dig it
 
Join Date: Dec 2005
Location: Wainwright, Alberta
Posts: 4,533
Default

Quote:
Originally Posted by Walker View Post
Just imagine taking a cut off wheel and scoring the area you are thinking of welding. If the score turned it into a place where it will crack through quicker then the weld will do the same.


A good, simple explanation. Makes it very easy to picture weak points and stress points. Thanks for that example!


Sent from my iPhone using ShopFloorTalk mobile app
Reply With Quote
  #6  
Old 02-05-2019, 06:41 PM
digr's Avatar
digr digr is offline
The Real Deal
 
Join Date: Apr 2005
Location: Duluth MN
Posts: 7,794
Default

I once tacked a piece of of key stock onto a 2 1/2"OD 4140 shaft to stop a conveyor belt head pulley from walking to the side. Two days later the shaft snapped off right at the end of the key stock, needless to say I wasn't the top hand on the ranch that day, shut the blacktop plant down for the day because I was to much of a hurry and didn't take the time to warm up the shaft before hand.
__________________
Drawing by Smartdraw
Reply With Quote
  #7  
Old 02-08-2019, 12:11 PM
threepiece threepiece is offline
Elite Member
 
Join Date: Jul 2011
Location: Suburban Detroit Mi
Posts: 1,191
Default

Not exactly in reference to the original question but within context I think.

Picture a horizontal beam that is supported on the ends. Now imagine a load placed on top of the beam near the center.

If you consider what is happening to the beam in this condition you may see that the bottom portion of the beam is being stretched (in tension). Conversely, the top of the beam is being squeezed together (in compression). So through the cross section from top to bottom you have stress going in opposite directions. You may see now that at some point in between there is no stress (neutral zone) and that the stress increases in one direction or the other as you look farther away from the neutral zone.

This is why truck manufactures recommend (or not) drilling or welding near the center of the web of their frames and why it is good practice to drill passage holes for pluming or wires near the center of floor joists.

I wish someone would have explained this simple but important concept to me when I was young. It would have saved me a fair amount of effort and grief.
__________________
A technologically advanced society would teach their children how to start a fire by rubbing two sticks together before teaching them how to use a lighter.

Aren't energy consumption and computers supposed to make life less stressful?

If you are not having fun then you are doing it wrong.

Last edited by threepiece; 02-08-2019 at 02:53 PM. Reason: Change "force" to "stress"
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Web Search:

All times are GMT -5. The time now is 09:28 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.