Jack Mounting Base Repair

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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

Smith Oxyacetylene TorchMiller Dynasty 200DXLincoln SP-250 MIG WelderClausing/Coldchester 15" Lathe16" DuAll Saw15" Drill Press7" x 9" Swivel Head Horizontal Band Saw20 Ton Arbor Press BridgeportLincoln LE  31 MP & Lincoln 210 MP
Reply: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

Smith Oxyacetylene TorchMiller Dynasty 200DXLincoln SP-250 MIG WelderClausing/Coldchester 15" Lathe16" DuAll Saw15" Drill Press7" x 9" Swivel Head Horizontal Band Saw20 Ton Arbor Press BridgeportLincoln LE  31 MP & Lincoln 210 MP
Reply: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

Smith Oxyacetylene TorchMiller Dynasty 200DXLincoln SP-250 MIG WelderClausing/Coldchester 15" Lathe16" DuAll Saw15" Drill Press7" x 9" Swivel Head Horizontal Band Saw20 Ton Arbor Press BridgeportLincoln LE  31 MP & Lincoln 210 MP
Reply:16. Right side painted

-DonSmith Oxyacetylene TorchMiller Dynasty 200DXLincoln SP-250 MIG WelderClausing/Coldchester 15" Lathe16" DuAll Saw15" Drill Press7" x 9" Swivel Head Horizontal Band Saw20 Ton Arbor Press BridgeportLincoln LE  31 MP & Lincoln 210 MP
Reply:Maybe pull the snap ring and get the jack out of the way and put even just a tie strap at the top and bottom where it would lock it in solid so i isn't able to tear it away by bending and flexing all the time.
Reply:

Originally Posted by danielplace

Maybe pull the snap ring and get the jack out of the way and put even just a tie strap at the top and bottom where it would lock it in solid so i isn't able to tear it away by bending and flexing all the time.
Reply:Would a bead along the top and bottom not help take some of the stress off the sides, or are you concerned that will just increase the HAZ?250 amp Miller DialArc AC/DC StickF-225 amp Forney AC Stick230 amp Sears AC StickLincoln 180C MIGVictor Medalist 350 O/ACut 50 PlasmaLes