I just finished building this today! It is 78" in length and the inner rectangle section is 16" by 16". I got the I-beams from a metal scrap yard and welded everything together. (sorry for the crappy images, it was done by phone)
Now all thats left is to paint
You're very likely going to have to put some vertical supports in the middle. Those are pretty tiny i-beams, you'll be surprised how much they'll deflect once it's pressurized!
Other than that, looks great!
What would you suggest for virtual support? I was thinking of running a cable from through the outer I-beams in the center area
consider some additional plate to cover the gaps. thick plate and perhaps a truss type system to minimize deflection.
It will deflect in teh middle.
More on top then bottom. for some reason.
You can do moveble center supports like some others have done but it will deflect and meet load on taht support so it and the pin you use better be beefy.
I agree on the center supports. I used 2x3 steel rectangular tube with 4 grade 8 bolts to handle the shear force. My center support in the back of the press is fixed, the front is removable.
My main frame is 6x6 5/16 inch steel. With the center support I get minimal deflection at 50-60 psi. There is some though as the the pins can not be pulled out once pressure is applied. I figure I'm generating 45,000-60,000 pounds of force at 55-60 psi in a layup that includes a pair of skis in the 175-185 cm range.
I'd stay away from a cable, if that snapped while you were nearby it would make for quite the story in the emergency room...
A few steel bars, with some big grade 8 bolts or shear pins should have you sorted, as Vinman said.
