Jack Mounting Base Repair

[Don52]

This welding project was to repair the cracked welds, which attached jack mounting base to the tubular frame of a boat trailer.

1. Steve's 27' boat


2. Welding site


I used garbage cans and a portable shade to block the wind.

3. Garbage cans and shade for wind block


The crack on the bottom was due to the moment loading due to the offset jack post. At first, I thought that the crack on the top was due to cold lap, but I should have known better. Rarely do cold lap joints occur on the end of a weld once everything heats up. It turns out the crack was a combination of shrinkage stress around the end of the weld combined with the moment load due to the offset jack post. As the crack propagated on the bottom of the weld, the length of weld supporting the load diminished so the stress due to the moment load increased on the top. It turns out that the crack goes all the way through the tube.

4. Left side of jack pad


5. Right side of jack pad

[Don52]

6. Weld ground off


I made several weld passes on the left side because the bracket plate itself had a small crack in it. I noticed it when I was welding it because one side was bright red and the other side was black.

7. Left side welded


8. Right side welded


After welding I primed the welded area. This brought out the crack almost like dye penetrant.

9. Left side crack after priming


10. Right side crack after priming

[Don52]

I grooved out the crack but I avoided grinding all the way through the tube, because I was concerned with drawing rust from the inside of the tube into the weld and contaminating it.

11. Left side grooved


12. Right side grooved


13. Groove weld left side


14. Groove weld right side


15. Left side painted

[Don52]

16. Right side painted



-Don

[Sberry]

Looks wonderful. Some post finish blending along the edges does help some for future cracks but I bet with the bigger footprint it be dandy. Don,,,, I have about a day wire feeding to do,,, feel free to swing by and weld it out.