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Old 12-26-2018, 08:26 PM
Spencer Spencer is offline
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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?
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Old 12-26-2018, 08:47 PM
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milomilo milomilo is offline
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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.

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Old 02-04-2019, 02:24 PM
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Big_Eddy Big_Eddy is offline
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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.
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Old 02-05-2019, 11:25 AM
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Walker Walker is offline
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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.
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Old 02-05-2019, 11:40 AM
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greywynd greywynd is offline
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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!

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Old 02-05-2019, 06:41 PM
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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.
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Old 02-08-2019, 12:11 PM
threepiece threepiece is offline
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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.
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Last edited by threepiece; 02-08-2019 at 02:53 PM. Reason: Change "force" to "stress"
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