Gusset Design

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In the pic you'll see the two 45* cutouts (in the corners) where the tube facing the camera sits on the horizonal tube, the cutout is to allow space for the weld that will be there.My question is should I weld the gusset to the existing welds or leave room there?I printed it out to scale and the paper wasn't long enough to includethe full length, I know it looks funny

RichardWest coast of Florida
Reply:I'm not an engineer, but I feel like I want more info, especially about where the loads will be. I guess there will be a load that wants to twist/torque the upper piece of tubing?Also, will the gusset be welded to the edge of the bottom piece of tubing so that it's flush with the edge toward the camera? Or will it be welded to the web?A 3-view drawing and explanation of where the stresses/loads will be would sure help me. (Not that I could necessarily answer your question even with that, but...)  

I'm wondering whether you could accomplish the same thing simply by welding a cap on the end of the upper piece of tubing...to keep it from racking into a rhombus. Or simply weld a couple of 45-45-90 triangles on each side of the upper piece.My gut says not to weld the gusset to the fillet on the lower weldment. Not sure why, except that it seems like it's gonna make a gigantic weld nugget with internal stresses going every which way that are likely to distort things if not crack. But like I said, I'm not an engineer and probably know just enough to be dangerous.I'm curious to hear what more knowledgeable folks will say.Last edited by Kelvin; 3 Days Ago at 08:43 PM.
Reply:Don't know whether it will answer your question, but a good book for trying to figure out stuff like this is "Design of Welded Structures" by Omer Blodgett, printed by the Lincoln Welding Foundation. It's got lots of good info and is fairly old, so you might be able to find it online.
Reply:If it's going outside, I would want it fully welded to avoid water traps and the resultant corrosion and freeze damage that can occur.Looking at it without any other info, I'd say you'll get away with stitching the bottom, the sides and the top, no need to fully weld it for strength purposes anyway.Murphy's Golden Rule: Whoever has the gold, makes the rules.
Reply:Gussets are a funny thing.You always see them at a moment connection.............but, all things considered, they just move the moment further away from the corner.I don't like a gusset that falls in the center of the tubing wall.  The wall has a tendency to collapse.  I prefer a gusset to fall on the shoulder.It all depends on the force you're trying to resist.  Not knowing, it's hard to tell what you're trying to accomplish.
Reply:Is anything going inside the tubes ? If its just a gusset, not a mount for something else, a few stitch welds are all that is needed for some added strength, but....If its part of equipment  in an area that is washdown, outside, or in a position that requires an aesthetically pleasing weld, then fully welded is maybe a better choice.If you are tig welding you can alway do a partial and then stand back and look at it. If you don't like it that way you can always go back and finish.Are you going MIG , or TIG, or maybe even stick ???Let us know what you decide.RegardsAirco 250 ac/dc Heliwelder Square waveMiller Synchrowave 180 sdMiller Econo Twin HFLincoln 210 MPDayton 225 ac/dcVictor torchesSnap-On YA-212Lotos Cut60D
Reply:

Originally Posted by LtBadd

In the pic you'll see the two 45* cutouts (in the corners) where the tube facing the camera sits on the horizonal tube, the cutout is to allow space for the weld that will be there.My question is should I weld the gusset to the existing welds or leave room there?I printed it out to scale and the paper wasn't long enough to includethe full length, I know it looks funny


Reply:The material is 4" square 1/4" wall aluminum so I'll be TIG welding, this is a boat lift and the customer estimates the boats weighs about ~600-700 lbsThis is in Florida so no freezing temps

Last edited by LtBadd; 2 Days Ago at 06:34 PM.RichardWest coast of Florida
Reply:This, or something else????????????


Reply:If you figure a force is stronger than your joint/connection, you analyze which direction the force is being exerted.  Then you make the gusset.

  This is an oldie but a goodie............  About a 25yr old build.  We're taking it out of mothballs to make the new crane.The gusset at the base is made to resist tearout when a load is on the beam.

  Don't laugh, I was just learning to weld back then

  But, the important thing........the gusset falls on the web, not anywhere on the flange of the tubing.  No problems with the tubing wall collapsing under load.

  Same here.............the load ties into both webs,, not the flange.You can do reinfocements to resist tearout, a directional moment, or rotational force.  It just depends on the lines of force.
Reply:Picture only shows what I am doing, there is another structural that this will fit into/onto

RichardWest coast of Florida
Reply:I would suggest that your gusset covers top and bottom then extends to the right. ……even further than shown as I ran out of picture.  To make it even more robust, sandwhich it with a gusset on each side of the horizontal beam. Additionally, the vertical beam will need right/left support to the horizontal beam as well.

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Reply:

Originally Posted by LtBadd

Picture only shows what I am doing, there is another structural that this will fit into/onto


Reply:Bill had the right idea for what you're doing.I'd modify it a bit, if your setup allows you to run the gusset slightly above the end of the tube.

The end cap on the left prevents the tubing from collapsing, or twisting, when you close it in.The end cap/gusset on the horizontal piece, prevents the same thing.  It prevents rotation.  If your design allows, extending the gusset above the tube gives you something to weld to besides just doing a corner weld.  It allows you to place a bead there without fear of burn through.Bill has you welding to the corner of the tube on the main gusset.  This is fine.  It will transfer stress to the shoulder.  I tend to extend clear down to the middle of the web.  It's just something I do, and it's not absolutely necessary, but I feel it's stronger.
Reply:I don't really like the weld across the top flange on the tube.  It's a fatigue break waiting to happen.  Aluminum is known for this.You could completely do away with this, and the gusset, if you simply tee the assembly.  Drop the top tube down, and weld it to the side wall of the other piece.
Reply:just appears to me that there is going to be quite a bit of "leverage" on the horizontals.  And the boat is 600#?  That is todays boat, now add the gear and the motor that he forgot about.  I think I'd try to figure out how to strengthen the outbound horizontal and incorporate that into the gusset.  Seems that there was a previous post in here (somewhere) where a member was to repair a tower (along the water) that was having issues with splitting aluminum tubes.  Keep us posted, Richard.
Reply:

Originally Posted by BillE.Dee

just appears to me that there is going to be quite a bit of "leverage" on the horizontals.  And the boat is 600#?  That is todays boat, now add the gear and the motor that he forgot about.  I think I'd try to figure out how to strengthen the outbound horizontal and incorporate that into the gusset.  Seems that there was a previous post in here (somewhere) where a member was to repair a tower (along the water) that was having issues with splitting aluminum tubes.  Keep us posted, Richard.
Reply:Don't know whether it will answer your question, but a good book for trying to figure out stuff like this is "Design of Welded Structures" by Omer Blodgett, printed by the Lincoln Welding Foundation. It's got lots of good info and is fairly old, so you might be able to find it online.just looked this up and there is a free download.  I didn't follow thru, but saw that anyway.