Torsion box table

[Julio Navarro]

Has any one built one of these?

I read on DIY about jointing 2x4 and leveling them on saw horses to make a level work surface for the torsion box.

Are there any other ways to ensure a level work surface?

[Al Willits]

I made one off the DIY website, tried the saw horses, but they were the plastic style and started to flex when I laid the sheets of MDF on them, gave up on that and used a heavy table, then shimmed to get flat.

Also used the three cut board to make sure it was flat that they reccomended, not so sure that a good straight edge might work as well though.
If your following the DIY one, they use short pieces to connect the the 6 or 7 long pieces that make up the inside grid, next time I think I might just notch each of the boards and use longer pieces, that way they would interlock instead of trying to nail each of the short pieces in, if that made any sense.

Al

[Julio Navarro]

Thanks Al, I was thinking the same thing. Makes more sense in my humble opinion.

I think the table technique would work better than the saw horses.

[Al Willits]

Especially plastic saw horses....:D

Let us know how it turns out, I'm thinking of making a smaller one to.

Al

[Jamie Buxton]

Julio --
Use the Search function to find lots of threads about how to make torsion boxes.

[Cliff Rohrabacher]

jointing 2x4 and leveling them on saw horses to make a level work surface for the torsion box.

2X4s sounds like over kill and starting out with a crummy stick of wood to boot.


Are there any other ways to ensure a level work surface?

Oh yeah baby. Use you saw and jointer to lay out a pile of 4 to 6 inch wide boards of 3/4 or 1" thick and use 'em to construct the inside framewosk which you'll attach to a piece of sheet goods like baltic birch or MDF (top and bottom is sturdier than one side).

The geometry of the inside bracing you use is , I think, less important than the fact of having plenty of bracing in various directions (at least 2 directions). Laminating the sheet stock on both sides of the bracing makes it brutally strong.

I prefer a Torres style bracing pattern: a big X from corner to corner and smaller braces in between.

[Julio Navarro]

I understand what you mean Cliff, it sounds like an X pattern would be inherently stronger, truss pattern and all.

What I meant about making a level work surface with 2x4's is the initial work surface to set the MDF or plywood skin.

In the DIY web site they call for jointing 2x4's and laying them out on saw horses to create the initial level work surface. You need a level surface to begin with so the torsion box will be level as well. But this system doesnt seem reliable. I was just wondering if there was any other method to assuring the torsion box will be level.

[Al Willits]

Did you also see where he uses two different boards to check for level?

Works pretty well, but I still used a straight edge to check, here's an excert from the article
Hope it helps

Al


The steps thus far provide a work surface that is ostensibly flat and level. To be absolutely certain of a dead-flat surface, a traditional technique is used by employing winding sticks.
Our two winding sticks were made from mahogany and walnut. Contrasting woods were used to make them more easy to differentiate in this visual check. It is essential that the winding sticks be jointed and planed so that they are truly flat and parallel.
Set the winding sticks on each end of the work surface, making certain that they are parallel to each other (figure H).
Once they are in position, sight down the edge of the winding sticks. If the plane of the two sticks are uneven with each other, the difference will be visible because of the contrasting color of the woods (figure I).

[Julio Navarro]

That's the article, Al.

To be honest with you , though, I didnt understand this part of the instructions at all. It just didnt make any sense to me. And the pics are not very helpfull. It's probably my denseness.

I dont know what a winding stick is and it is not clear to me what he means by this ".. Once they are in position, sight down the edge of the winding sticks If the plane of the two sticks are uneven with each other, the difference will be visible because of the contrasting color of the woods .."
I wish the pictures were clearer.

But of course I would wager that someone here knows what a winding stick is.:D

[tod evans]

julio, winding sticks are used to set a surface in plane. if you set two identical sticks at either end of a board and squat down where you can look over one at the other, kinda like sighting a gun, you`ll be able to see any twist. you can accomplish the same thing using strings streched corner to corner, raise or lower a corner `till the strings just kiss eachother and you`re good to go...02 tod

[Julio Navarro]

Thanks Tod.

That makes sense now.

[Stu Ablett in Tokyo Japan]

The best Winding sticks I've ever had are two 3' lengths of aluminum angle iron.

I painted one black, and I put the black one at the back this way I can really see if the surface is flat.

I used these to set up my workbench, and it is still dead level.

I recently built a small torsion box for the old C-man lathe, I think a buddy might buy it from me, but his ww skills are fairly low, so I'm making the lathe a stand of sorts, which he can then put on something, a table etc.

I've been really impressed at how strong that torsion box is.

Cheers!

[Chris Barton]

If you want to make a truely easy torsion box table take a hollow core door and sandwich it between two sheets of 1/2"-3/4" MDF (just glue with cauls) and edge trim with the wood of your choice. The resulting table top will be flat and you can attach it to the support base of your choice and level the entire structure at the point you plan to place the table.

[Al Willits]

Julio, it helps if you can watch the DIY channel when they run the episode where he builds it, his instructions are a bit vague at times and out of sync, pays to read them though a couple of times, least for slow learners like me...:)

A X frame possibly could be stronger, but I built the squared version and its strong enough for me to stand on and I run over 250, so I'm not sure the dealing with angles would be worth it.

Also he mentions waxing one of the MDF surfaces after you have it all set up, make sure you do it before, much easier.
The waxing is so glue doesn't stick to it btw

I also used Pine as an edging, it works just fine and is cheaper.
I also set this thing on a 3.5'x3.5' aluminum table I had from enging building and installed casters on it, being able to move this is a plus for me, also lets you turn the project for better lighting if need be.
He builds a wooden support under it for legs, but it got to heavy for this old guy to move easily.

Al

[Cliff Rohrabacher]

I dont know what a winding stick is
Tis really very, very simple don't let the name throw you.

All a winding stick amounts to is two (or more) fairly good sticks (parallel and the same width) that you lay on the board with the questionable geomerty. The sticks are laid at a right angle to the subject board.

They merely amplify the unevenness in the subject board by the length the winding stick projects. So if the stick is 24" long and you place the center at a right angle on the subject board it'll have multiplied the error in the subject board twelve times.

Do this on a few places and you will have a very good map of the subject board.

PICTURES available below Woo Hoo:

Go here:
http://www.shavings.net/WINDING.HTM

and here:
http://en.wikipedia.org/wiki/Winding_sticks

and here:
http://www.woodcentral.com/cgi-bin/readarticle.pl?dir=handtools&file=articles_340.shtml

and here
http://www.diynetwork.com/diy/ww_materials_products/article/0,2049,DIY_14442_2278181,00.html

and here:
http://www.taunton.com/finewoodworking/ToolGuide/ToolGuidePDF.aspx?id=24145

[Alan Schaffter]

I recently made a beam box/torsion box assembly table with adjustable legs. You might be interested in some of the things I did. I started with the David Marks DIY design but cut the grid differently and designed and built some adjustable legs. Sorry about following two links, but could not do a cut and paste:

http://www.ncwoodworker.net/forums/woodworking/general.woodworking/2980-assembly.table.w.pics.html

http://www.ncwoodworker.net/forums/woodworking/general.woodworking/3063-assembly.table.done.w.pics.html

[Al Willits]

We had talked about making the grid out of innerlocking pieces, instead of nailing the short ones in, nice to see it does work.
Thanks Alan

Al

[Frank Chaffee]

Al,
The strength of the interlocking joints is less important than that the two planer surfaces are securely glued to those separating members.

Frank

[Michael Adelong]

I think I might just notch each of the boards and use longer pieces, that way they would interlock instead of trying to nail each of the short pieces in, if that made any sense.

Al

This is exactly how I made my DIY torsion box. It took 2 attempts. On the first attempt, I used my dado blade to cut the notches (I stacked all 6 ribs together and cut the 7 dados, then stacked the 7 stretchers and cut 6 dados in them). It did not work because I used exactly 1/2" for the dado stack. Dry, the parts slid together perfectly. When I tried to glue it up, the MDF expanded, and I could not get the pieces together. On the second attempt, I added the thickest shim that my dado stack came with. Seemed too loose during dry fit, but when glued up everything came out fine.

Mine came out dead flat (as far as I can measure). I used the 2x4s on the sawhorses, but I didn't rely on them to build the box flat. I used the method described in the Sketchup drawing of the DIY torsion box that I posted in the design forum.

Edit: The SU drawing is too large to post. Attaching pics instead.

Michael

[glenn bradley]

I think the 2x4 on sawhorse method gets some stability from the 2 sheets of MDF that are used for the flattening step.

[Michael Adelong]

Pic #6 attached

M-

[Al Willits]

True, but making them interlocking would seem to be easier that trying to nail all them little boards in straight.

Al