Some More Heat Shrinking

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I like to put these up every once in a while as I'm doing them(and I do quite a few).  Good thing for new guys to see, if they haven't seen it before.Welding bein' about heat, creates heat related problems.  Mainly heat distortion.  Stuff shrinks as it cools, and pulls everything out of line.  You really can't fight it, and you have to learn how to live with it.Heat will undo the problem that heat caused.Now don't get yer undies in a bunch, and start talkin' about restraining the joints with gussets, clamps, strongbacks, or your grannie's clothespins  Preheat works to some extent, but not always.  All, and I mean all, of the time honored methods will not work under all conditions.This is the gooseneck hitch/pocket that I've gotten back around to working on.There are two distortion issues.....................The first is the strongbacks added to the underside of the pocket. There's two 3/8 x I" strongbacks added to the original design as cut from the truck.  The 3/8 plate by itself is simply too weak to support a 4-5000 tongue weight load.  And most importantly, it is not strong enough to support that kind of live load.  Hitting a pothole at 60 could very well magnify the load 4 fold.  It's called inertiaWhile I would have preferred a 3" strongback, it wasn't feasable due to interference from exhaust components just below the pocket/hitchThe heat input from the welds, on one side of the plate, not balanced by heat applied to the other side of the plate, caused the strongbacks, and the plate, to crown/bow.The mission(if you choose to accept it), is to return the plate to a nice flat state.The channel, and clamp, provide pressure opposing the bow.  Heat is then applied to the opposite side of the bow with a rosebud.  The metal should be heated to the near red color, then take a few seconds to let it cool a bit, then hit it with water.  I prefer to do it in short bursts.  Too much at once can cause another type of distortion.  The metal will dimple and deform (that's another discussion altogether, and related to tubing).Heated metal shrinks when it cools.  THAT'S WHAT CAUSED THE PROBLEM IN THE FIRST PLACE  You're simply fighting fire with fire.It turned out nicelyThe second issue is the distortion caused by welding the 2 connecting plates to the floor of the pocket.......... The jack is used to apply the opposing pressure, and you do the heat thing on the backside of the plateBUT AS IT TURNS OUT......MY ROSEBUD'S TOO SMALL FOR THE REQUIRED HEAT OVER A LONG JOINTThis will be handled by what I call "backbeading".  A bead is run on the backside of the plate in order to introduce heat, and to benifit from the shrinkage that occurs when the filler material cools, and contracts.It was getting late, and had other things to do.  Pics tomorrowBackbeading is a positive PITA.  Lay enough beads to get the required shrinkage, then grind them off  It's not for the faint of heart Attached Images"Any day above ground is a good day"http://www.farmersamm.com/
Reply:benefit  typing isn't my strong suit"Any day above ground is a good day"http://www.farmersamm.com/
Reply:I get all hot and steamy when I talk about heat shrinking Attached Images"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Hitting a pothole at 60 could very well magnify the load 4 fold. It's called inertia.
Reply:Samm, I've found that Granny's clothespins tend to burst into flames when I'm welding ..... Good information there, thanks.