Building torsion boxes

[chuckknigh]

Torsion boxes are miracles of engineering. It's a "honeycomb" structure on the inside...and 2 thin skins on the outside, which make a VERY strong composite structure.

They're perfect to use on these machines, too.

So, when I saw a TV show on the making of hollow core doors (just a big cheap torsion box) I perked up. They make them with a rectangular wooden frame, a large expandble cardboard honeycomb for the core, and 2 extremely thin panels for the skin. A little glue to hold it all together, and it's done.

Other than just cutting the cardboard, manually...is there anywhere to buy that cardboard honeycomb? It's simple...but it'd take forever to cut out. Seems like it'd be pretty cheap, too, which is always a good thing.

-- Chuck Knight

[ger21]

How about this? http://www.vacupress.com/accessories.htm#honeycomb

[chuckknigh]

That's more for fiberglass/epoxy composites...it's resin impregnated, too. Good stuff...too good for a "cheap" torsion box. And a 2x4 foot sheet is $15? Yeesh.

I wonder if the basic, untreated, cheap cardboard lattice is available for sale? Seems like it'd be super-cheap to manufacture, and have a ton of uses...

This site popped up on google...but no prices. I wonder how much their stuff sells for? And, I've seen it used as pallets, but don't remember where. Anyone else seen the 4" thick cardboard honeycomb pallets? Looks pretty sturdy!

http://www.kraftcomb.com/index.htm

-- Chuck Knight

[ger21]

I thought $15 was very reasonable.

[ger21]

Originally Posted by chuckknigh That's more for fiberglass/epoxy composites...it's resin impregnated, too. -- Chuck Knight

Actually, it's sold for woodworking, usually for making table tops, and/ or doors. It can be glued with regular wood glue.

[NEATman]

Why not just use foam insulation? It's cheap, light, and would probbably have about the same properties as inexpensive homeycomb core material.

Neatman

[joecnc2006]

I would be sceptical on using any of the cardboard honeycomb because of any moisture build up that could happen, thats why alot of people also primer and paint their MDF machines.

[chuckknigh]

Foam insulation is a good idea.

As to the moisture issue...this would be used as a core material. It would be completely encased within the skin.

I wonder what kinds of glue would work to join foam to wood?

-- Chuck Knight

[fyffe555]

Whats the intent of the torsion box? The torsion box strength comes carrying the stress loads in the outside panels and seperating the panels further increases the effective strength much like an I beam. But in the same way as an I beam the core carries *significant* compression loads. You don't get something for nothing. Note the torsion box is strongest in torsion, that is in twisting motion, hence the name. A door with cardboard filler carries no compresion load since the door carrys no twisting load to speak of. Composite cored panels such as fiberglass boats and aircraft derive thier strength from the curvature of the panel skin as much as the fact they're a torsion structure but even so they still carry large loads as a compression of the core. A torsion box beam as a simple load carrying member carries a major proportion of the load as a compression of the core. A Flat panel torsion box using cardboard would not be particularly strong, its strength being a direct function of the compression strength of the core material. take your favorite cardboard core off the hinges and supporting both ends stand on it. It will bend more than you think..