I have an access hatch and diagonal leg braces could be in the way.
is there a formula for sizing a gusset? The leg is 45"
The size of triangulation required depends on rigidity of the supported beam and the vertical leg taking the transferred bending load, assuming the triangulation is sturdy itself. The gusset is in compression so that’s not usually an issue.
The real source of the problem is in the joint you need to support. An inserted gusset will be more effective than a tacked over gusset which depends on the fastening method for rigidity. Glued on gussets can work really well if you can’t insert the triangle into the 90 degrees. If you originally glued and screwed the beams to the legs then you don’t need much triangulation to preserve the integrity of the joint.
So there won’t be a formula for model railroad layout loads. Very low weight loading. A surprisingly small gusset adds a considerable amount of rigidity. If you use wood then a small plywood triangle inserted into the 90 degrees works well.
Length of each side of the gusset depends on the relative flexing of the leg or beam. Also, don’t discount use of an arced gusset if room is tight. A plywood triangle with an arc cut into the hypotenuse will be as strong as a full triangle for all practical purposes and intrude less into the space you are concerned about.
Henry, when i need to strengthen legs, but have clearance issue, I have used 90 degree metal brackets that Home Depot has near the gate hinges.
The do not sick out at all like gussets, and are very rigid.
-Kevin
Pressed metal shelf brackets with the moulded in tubular reinforcing sections should work well. Pretty much no intrusion into the space.
Not thin gauge shelf brackets. Those are not suitable for anything structural.
These are the 10 inch 1/8" thick steel angle brackets that are the correct thing to use. Two of them 90 degrees apart are good.
Ten inches might be overkill.
-Kevin
The shelf brackets will be stiffer. 1/8" steel isn’t very stiff.
It’s the stamped forming that stiffens the bracket.