Okay, let's go!
Maybe someone will find it useful, but it's a simple design.. ))
That what we need for modeling - 2 "i-beams" and "angle-beam"
Measure distance between planes of i-beams
and between holes of angle-beam
The distance of the hole welded lug you choose 75 mm, let's do so
Look at mates
The distances I made the way I liked, you can make like yours, because it not my project
2 lines 75 mm Along Z-axle
Point situated on plane surface of i-beam
2nd line point - on surface of i-beam #2
The distance of 150 mm got from my mind to the circle line =)
Now we must make PLANE for new sketch
Choose 75 mm lines for that
Make sketch on this PLANE
I made 2 lines of 200 mm
Mates look at screenshot
Now you must edit i-beam, and using Convert Entities - convert the 200 mm line to plane of i-beam
Extrude thin and make hole
Make the same with the 2nd 200 mm line
But by the reasons you make patterns wrong way and not made configurations, you'll have the lug at all beams
Not problem, but can be done more perfect...
And now we are ready to do the mates
And this is how it looks now