3 ms·

Fwiw 40lbs in motion produces more force than at rest. The area it is applied to (among other things) also changes how the beam handles the load. Lack tables ha

Fwiw 40lbs in motion produces more force than at rest. The area it is applied to (among other things) also changes how the beam handles the load. Lack tables have such simple construction that they may handle higher than usual loads without deformation; four large posts supporting a single beam pinned at the ends can handle a decent load, if the beam and posts are big enough. They might also use cheap hacks, like strengthening the bottom of the beam to account for increased tension. Walmart has some pretty decent mdf tables for about the same price as similar ikea tables. Sometimes their construction is really good, too, such as this table[1]. It brings the posts in closer to center which distributes load better and increases load rating for the beam, and the post supports both the beam and the strut, and the strut helps reinforce the beam. Everything is brought in farther from the edge to make the effective load-bearing part of the beam smaller, which makes it stronger. Their dressers are total shit, though, unless you pay a pretty penny for real wood. [1] https://www.walmart.com/ip/17767350?wmlspartner=wlpa&adid=22222222227014448734&wl0=&wl1=g&wl2=c&wl3=40845383552&wl4=pla-78658557992&wl5=9004012&wl6=&wl7=9004027&wl8=&wl9=pla&wl10=8175035&wl11=online&wl12=17767350&wl13=&veh=sem#about-item https://www.walmart.com/ip/17767350?wmlspartner=wlpa&adid=22...

semi-extrinsic 10y ago
I'm not a structural engineer, but I've sawn off the legs of a Lack table a few months ago, and they are hollow (I think fibre board) with wood blocks inside at both ends. Seems like a sturdy construction.
- rhizome 10y ago
  Ikea uses torsion boxes with cardboard a lot: http://www.core77.com/posts/26334/A-Look-at-Torsion-Boxes http://www.core77.com/posts/26334/A-Look-at-Torsion-Boxes
  - peterwwillis 10y ago
    Yep. It has the effect of making the top layer in compression, the top of the webbing in compression, the bottom of the webbing in tension, and the bottom layer in tension. The webbing distributes force as shear along a large area (and along the entire beam), so it can handle a great force with a pretty thin member. It's like building a really wide, really short I-beam. But better. Because the top skin only has to resist compression and the bottom only tension, you can choose materials that will perform each of these best. The top can be really thin, while the bottom can be thicker, and the result will be a slightly stronger table than if both skins were a thickness in between. The length of the web will also directly affect the strength (part of why those table tops are so thick... to have longer webs) In fact, you can build "torsion beams" that work like long torsion boxes, but instead as beams. A 6-foot long beam might weigh only 20lbs. Sit them on sawhorses and you now have a stowable assembly table. Another benefit to torsion beams is they are easier to construct straight because finding small members that are straight is easier than finding big thick straight members. (Uh.... let's ignore the obvious jokes here) The downside to all this strength-hackery is, if one of the webs fail, structural integrity is gone. So don't land anything too heavy on a single spot.

semi-extrinsic 10y ago

I'm not a structural engineer, but I've sawn off the legs of a Lack table a few months ago, and they are hollow (I think fibre board) with wood blocks inside at both ends. Seems like a sturdy construction.

rhizome 10y ago
Ikea uses torsion boxes with cardboard a lot: http://www.core77.com/posts/26334/A-Look-at-Torsion-Boxes http://www.core77.com/posts/26334/A-Look-at-Torsion-Boxes
- peterwwillis 10y ago
  Yep. It has the effect of making the top layer in compression, the top of the webbing in compression, the bottom of the webbing in tension, and the bottom layer in tension. The webbing distributes force as shear along a large area (and along the entire beam), so it can handle a great force with a pretty thin member. It's like building a really wide, really short I-beam. But better. Because the top skin only has to resist compression and the bottom only tension, you can choose materials that will perform each of these best. The top can be really thin, while the bottom can be thicker, and the result will be a slightly stronger table than if both skins were a thickness in between. The length of the web will also directly affect the strength (part of why those table tops are so thick... to have longer webs) In fact, you can build "torsion beams" that work like long torsion boxes, but instead as beams. A 6-foot long beam might weigh only 20lbs. Sit them on sawhorses and you now have a stowable assembly table. Another benefit to torsion beams is they are easier to construct straight because finding small members that are straight is easier than finding big thick straight members. (Uh.... let's ignore the obvious jokes here) The downside to all this strength-hackery is, if one of the webs fail, structural integrity is gone. So don't land anything too heavy on a single spot.