Gusset Design

[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 include
the full length, I know it looks funny

[Kelvin]

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.

[Kelvin]

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.

[Munkul]

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.

[farmersammm]

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.

[albrightree]

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.

Regards

[William McCormick]

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 include
the full length, I know it looks funny

I would make it an end cap that you can weld on and grind if needed before you lay it on the bottom piece of box tubing and weld it on. I would not go higher than the box tubing. This way you would be connecting to the solid wall of the lower box tubing and giving the upper tube a structure. Without that structure of the end cap, the tube may create some odd forces that tear welds. I would make the gusset portion of the end cap arched. So when it starts to be destroyed there will be an increased amount of time that the structure will hold together rather than just hold until it violently destructs. And I would put an end cap on the bottom piece as well. Just cut that end cap to the inside dimensions of the tube and weld it on. Without that endcap, it would be a point that would start to deform the tube prematurely.


Sincerely,

William McCormick

[LtBadd]

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 lbs

This is in Florida so no freezing temps

[farmersammm]

This, or something else????????????

[farmersammm]

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.

[LtBadd]

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

[mcspeed]

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.




Sent from my iPhone using Tapatalk

[Kelvin]

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

Assuming (from your first pic) that you're using something with 1/8" or 3/16" wall aluminum for this, and the boat weighs 600-700 lb., that looks awful flimsy to me...

Is there no way to get some triangles/braces into the design? Just seems to me that you're gonna have torque moments all over the place and will be asking the welds to do an AWFUL lot. Not sure I'd even want to stand on that, and I weigh a lot less than 600#...

If using aluminum, remember also that aluminum doesn't have anywhere near the fatigue resistance of steel, and once it gets work-hardened and starts fatigue cracking, it's gonna fall to pieces fast.

What size is the tubing in your first pic? Maybe I'm just looking at it funny...

[farmersammm]

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.

[farmersammm]

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.

[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.

[LtBadd]

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.

That is his estimated weight with the motor

[BillE.Dee]

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.

[LtBadd]

Thanks Bill, I told the customer I would weld this but didn't want to be involved in the design, this is made after 1 he has from steel and it's time
for that to be replaced. I was curious to know what others thought about the gusset idea...

[albrightree]

Something like this ?



Most single post lifts for jet ski's seem to be made from galvanized steel. Its all about the moment, how far out is the center of the load. Most seem to be 24"-36" out. It doesnt seem as bad after looking at some pix. The reason " it looks funny "( the gusset I'm assuming) is it doesn't really add much strength to the joint. When I look around at all the equipment around me, nothing is made like that. I'm sure its done somewhere, when its the only possible way to reinforce, or safety a design.

Its an interesting design challenge, I wonder if 2"x 4" x 1/4" wouldn't be a better choice . I almost think the extra 2" of horizontal weight is actually working against itself.

Well, best off letting the customer give you the design, and build it. When you're done, just put a few "No Riders", and "Not a Personnel lift" labels on. Just like the ones that are plastered all over forktrucks. LOL

Hope you get the work.

Regards

[Welder Dave]

I don't think you really need gussets where your original plan shows. I think braces going on a wider stance and extended out going up the vertical piece would give much better support. The original gusset placement wouldn't help any if the upright was to twist down at the edge of the tube it's welded too. I also wouldn't weld the upright on the back where it extends up. Welded along the sides should be sufficient. Also curious why the tubes are all sitting on top of each other? Looks more professional to have them fit inside each other, and especially the tube the upright is welded to, would be stronger welded all the way around. I'm thinking the gusset idea was to give more strength in this area but putting the tube between the outer tubes wouldn't require the gussets. The tube on top has more potential to twist at the ends where it's welded to the outer 2 tubes because it's only welded on the bottom. You don't want to have to add multiple gussets to beef every connection up. 700lbs isn't too much so shouldn't really need to get engineers involved. Just put on your thinking cap and come up with idea's. Sometimes better idea's come up once you get the basic design figured out. I ran into this designing some wheel adapters. It was an exercise in frustration finding the required fasteners and such and cost was a major factor. I've got the design finalized and it turned out to be the lowest cost option. I found an awesome machine shop too that is going to try and save me some money getting the pieces cut. In a former life I might have cut and drilled them myself but with CNC plasma tables that can cut all the outside holes (60) at the same time, I don't think I'd save any money doing it myself.

[LtBadd]

Something like this ?

Yes, that's what the customer wants

[BillE.Dee]

boy golly gee ... using the what looks like aluminum to support the boat isn't a real problem. I am looking at supporting the 700# at least 3 feet from the "fulcrum". I've looked at some of the specs for the pwc's (IF that is what he is lifting out of the water) and they are for the most part 4 feet wide. I "think" that I would build it pretty much like William stated and stretch the gusset out further to the end of the horizontal as a one piece unit on both (horizontals) and weld them to the horizontals just about where the corners are. I would probably over build it rather than have the boat have a splash down when no one is looking. Sorry I don't know how to draw on this electronic gizmo and my grandkids are not available.