What's the largest torsion box that can be made? - Router Forums
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post #1 of 45 (permalink) Old 06-28-2015, 11:30 AM Thread Starter
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Default What's the largest torsion box that can be made?

I have a Kreg work bench frame that measures 44" x 64". I need to make a top for it but having such a large span I worry about sagging through the middle. I have come up with various designs using 2x4 and center legs to prevent this but this will also make it very heavy. So far I am at 17-20 2x4's in the design, plus the top, plus the metal frame itself. I will need to move this later to do other work to complete my shop so this seems too heavy in my mind. So I was considering a torsion box top to keep it flat and lighter weight. Maybe all made from plywood and pocket hole joinery?
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post #2 of 45 (permalink) Old 06-28-2015, 12:00 PM
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I would guess unlimited. However, there might have to be a proportional increase in material and construction thickness to prevent sag at some point.
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post #3 of 45 (permalink) Old 06-28-2015, 12:29 PM
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Quote:
Originally Posted by Duane Bledsoe View Post
I have a Kreg work bench frame that measures 44" x 64". I need to make a top for it but having such a large span I worry about sagging through the middle. I have come up with various designs using 2x4 and center legs to prevent this but this will also make it very heavy. So far I am at 17-20 2x4's in the design, plus the top, plus the metal frame itself. I will need to move this later to do other work to complete my shop so this seems too heavy in my mind. So I was considering a torsion box top to keep it flat and lighter weight. Maybe all made from plywood and pocket hole joinery?
hollow core doors are essentially torsion boxes and they can get pretty big...
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post #4 of 45 (permalink) Old 06-28-2015, 12:47 PM
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If you are concerned with the potential weight - 2x4s are probably over-kill. I probably shouldn't comment on this because I used 2x4s in mine - convenience/availability and it was only a 30" x 4' table. You just need something that won't compress (i.e. height) - I suspect an internal frame using 3" tall pieces of 3/4in pine or plywood would give you just as much structural support. I can't imagine 1/4" thick x 1.25" angle iron will be bending or sagging much either
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post #5 of 45 (permalink) Old 06-28-2015, 01:10 PM Thread Starter
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hollow core doors are essentially torsion boxes and they can get pretty big...
This is true, but they are vertical instead of horizontal, so I doubt they would have the same sag factor, but then again, they are only supported from one side by the hinges so maybe they actually have to be even stronger to resist sag. Hmm...
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post #6 of 45 (permalink) Old 06-28-2015, 01:51 PM
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I believe aircraft wings are basically torsion boxes and each wing on the Antonov AN-225 Mriya (one of the world's largest aircraft) is over 130 feet long and supports three engines. I think you'll be pretty safe with anything you build.

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post #7 of 45 (permalink) Old 06-28-2015, 02:09 PM
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For the weight problem, a set of casters that lift off the floor when in place would work. Rockler has a set that will take 400 pounds.
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post #8 of 45 (permalink) Old 06-28-2015, 02:26 PM
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hollow core doors are essentially torsion boxes and they can get pretty big...

I made my own for portable work benches that use saw horses.




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post #9 of 45 (permalink) Old 06-28-2015, 02:32 PM Thread Starter
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Well, I have a concrete garage floor that is not level and even. I have to use adjustible feet to level it out, and then when I move it any rollers I use woud be up and down from each other instead of on the same plane. So I figure I'll have to just lift it.
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post #10 of 45 (permalink) Old 06-28-2015, 02:40 PM
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Duane, unless you are planning on rebuilding engines on your bench it shouldn't have a sag problem over a 5' span.

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