I need to plate a crack in a pup trailer frame rail, actually one side of the tongue. It's a channel shape: Here's what I'm thinking about: The bottom drawing is how I've always plated things. Never had a problem. The top drawing is what I'd like to try. Can't really explain but one end will have to look something like this anyway because of how it's built. I've noticed this shape on just about all the thumb mount base plates I've seen. It looks like it pretty much eliminates stress risers and can be welded all the way around. And it looks like it would be fairly flexible when the frame twists. What do you guys think?
I would probably plate the crack inside and out, and grind the crack out really good and get 100% pentration thru the chracked channel. Ive always been told to avoid corners when plating, use circles and stuff care corners cause cracks so i think your on the right idea.
How about this..? It's very similar to what your idea but instead of welding right round the plate you weld it top and bottom then weld it inside the curved area at each end. The welds on top, bottom, & curves are all "tailed out" for a length of maybe 2" or so past the doubler plate and parallel to the edge of the existing structure. This means that nowhere in the high-stress areas close to the edge of the existing structure are you running a weld at 90-deg to it. In your drawing there will be 4 very short sections of weld (round the curved parts) that are actually at 90-deg that are in a high stress area.
Either plate will work just fine. I would want the one you are wanting to try. The curves will handle any stress real well and look nicer too. Cheers Lowbed Driver
That's exactly where I got the Idea Nige. So the curved edge (the 90) of the flange is the high stress area? Plating both sides is probably a good Ides Stumpjumper but it's not an option. Lowbed Driver- My boss saw the same make of trailer with the same crack. They scabbed a piece of channel over the crack. Like you said, probably doesn't matter which plate I use.
I like to add plug welds on plate repairs. Might not be necessary, but they make me fell like the repair is stronger.
Rob, If a channel like the one in your original sketch of the crack is loaded then the stress in it will vary from compression in the area of the top flange to tension in the area of the bottom flange, or vice versa depending which way the load comes on it. Either way, right along the centreline there will be zero stress. So you want to make sure any welding you do in those high(er) stress areas is parallel to the structure rather than being at 90-deg to it. What would worry me are those 4 "bulges" on your proposed doubler plate that for maybe a half inch or so are going to have welding on them that is at 90-deg to the structure and those welds are going to be really close to the high stress zone. That's what makes the other option a better bet in my opinion. The welds at 90-deg to the structure on that plate are right in the centre, a zone that has very little or even zero stress. I'm also a believer in plug welds in doubler plates, provided they aren't close to the original crack. Not sure what the actual size is of your plate but I would think that a couple of plugs of maybe 1-1/2" diameter or maybe a tad larger would be the way to go. The plugs should be right on the centreline, again to put them in an area of little or no stress.
Yair . . . I was told way back to taper the ends of plates at about sixty degrees if possible and terminate with a radius one third of the member being strengthened and weld all round . . . two or more two inch plug welds on centre line. Around salt water leaving unwelded sections to avoid stress risers are not an option although it may work for some. To me the longer taper and single radius on the centre-line is possibly a bettter and time proven system. There is less of an abrupt transition from 'hard' to 'soft' in the structure and only a single radius to weld around at the centre line, the least stressed section of the member. Hope that makes sense. Cheers.