Semi-Truck Cross member Fish Plate Help

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I have a Hardee dump trailer with a cross member that is cracked and needs to have a fish plate.How do I figure the "correct" angles for the fish plate. Is there a formula ?Thanks for any help...
Reply:Got a picture?  I like the elongated diamond shape myself, though only as an admirer. Is the crack on a flat surface? Or is it in a corner next to a rivet, covered by a flange and through bolted to a bracket?  City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:The reason no response is nobody, but nobody welds HD truck frames.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:I can tell you that is definitely not true.  People do weld HD truck frames.Whether they should or not, and how they should do it if they do, might be an interesting topic!I have an International single axle tractor with a welded in gooseneck hitch.  Definitely not recommended, but it is there!  It was there when I got it.  No cracks at the welds so far!Dave
Reply:Originally Posted by tanglediverThe reason no response is nobody, but nobody welds HD truck frames.
Reply:Another "nobody" here.  I believe the original poster stated "dump trailer", not truck.  Most (but not all) truck frames are heat treated and if welding is not recommended by the manufacturer, it will be labeled as such (unless the label is removed).When I repair a cracked frame, I clean the entire area, "vee" the crack at least 80% of the thickness of the frame rail, weld the crack (vertical up) with 7018 or 11018 rod, grind flat with the surface of the frame rail then apply the plate.  I fab the plate according to what area I have to work with.  Could be square, rectangular, diamond shaped, or some weird shape to go around something.  Sometimes adding an additional plate on the reverse or another frame rail that will fit is in order.Haven't had one fail yet, and I've done many.  Good luck.
Reply:Just a quick note all the warnings that I have seen from the manufacturers say not to weld or drill the flanges of the frame. I know a lot of truck frames are welded, there is a right way to do this and the next one I get in I will post pics of. As far as the original question post a pic or at least tell us what shape the cross member is and the dimensions.Last edited by flatbustedbroke; 09-28-2008 at 11:55 AM.
Reply:I,ll second that nobody, cause i fall under that catagory also.
Reply:Another nobody here. Looks like there are a few nobodys that hang around this site being nobody.
Reply:Originally Posted by yoyo1003I have a Hardee dump trailer with a cross member that is cracked and needs to have a fish plate.How do I figure the "correct" angles for the fish plate. Is there a formula ?Thanks for any help...
Reply:I have been welding frames for the last two weeks on fire trucks. The process that we use is tig root with 70s filler rod. then I fill with smaw process using a 3/32 7018 rod. heat the frame  to 1000 deg wrap in blankets and cool. then grind flush and heat again and wrap and cool. We have bee doing this for some time with other trucks and have great sucess with no more craking. reinforcement will only be done if we see it happen more then once.  matt
Reply:google 'fletch' plates. Some good stuff there...
Reply:Told you.  My apologize for stirring the thread. Not calling anyone nobody by any means. Trucks wouldn't last long if they could never be mended. Thanks for adding your viewpoints! Attached ImagesCity of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Frank Marlow has a decent book out called "Welding Fabrication & Repair, Questions and answers" that covers repairs to truck frames, among other things. Might be worth picking up a copy.
Reply:thank you guys for your help.I have taken the advise of "fat bastard" I would find the ends of the crack and drill (1/4") then I would "V" out along the crack and weld.For reinforcement I would look at using an angle shape and weld it only in the long direction of the cross member.thanks...
Reply:I'd bet Tanglediver was just bumping the thread. 9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:if no sticker prohibiting then its pretty simple and has been done for years.my 50's GM truck manuals show proper weld technique depending on crack location.it appears in no instance is a new weld all the way around whatever patch/"fish plate" is used.I can provide copies of illustrations if you guys want.mark
Reply:Originally Posted by yoyo1003thank you guys for your help.I have taken the advise of "fat bastard" I would find the ends of the crack and drill (1/4") then I would "V" out along the crack and weld.For reinforcement I would look at using an angle shape and weld it only in the long direction of the cross member.thanks...