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Building with 2x4's, no glue, nails, fasteners, or cutting of the wood allowed.

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Bridge.jpg
Have a pile of 2x4's, and a while before you use them?

Well, if you don't cut them, or use fasteners or glue, they will still be usable in a new project after trying these projects.



The dome was more than 30 feet across. Note that the dome is NOT a geodesic dome, it is actually a lofted tiling.  (Which is why it is so flat.)

The bridge supported two adults of my weight, and that of several children, at the same time.
If I were to do this for something permanent, I'd want to bolt the pieces in place at the places that they cross.

8bit3 years ago
Ha! Do you think that hexagonal tiling would hold even if it was upside down? Maybe you could do a sphere.
nahaj (author)  8bit3 years ago
I'm afraid not. Gravity is what is ultimately holding the pieces together.
One could inverse the junctions to make a bowl shape, but there is not (to the best of my knowledge) any way to do the vertical sides needed to join the dome and the bowel without needing something more than gravity to hold it together.

But, now that you mention it, a "flying saucer" shape would be possible, but I've not done an engineering analysis of it. The lower section would have twice the strain, and therefore would hit the size limits much earlier, but I don't know the limits would be. (Nor can I see an immediate way around some assembly issues.)

The current dome by adding cells to the edges of an original cell. So it was always a dome during construction, and I had freedom to put the legs anywhere. I can't, right off, see what the partly constructed version of the saucer would look like. [I think I'd have to prop parts up during construction to make it work right.]
If I had to mate it to a lower half I'd have less freedom of where to put each leg, and I have my doubts of whether or not I could be accurate enough to pull it off.
if you turned the chinese/leonardo bridge on its side and just continued it until the ends met, wouldn't the tension hold it together? I guess you could make a fence like that if you did not need to get in or out...
nahaj (author)  macrumpton2 years ago
I've seen such a fence done that looked like that in animal pens in pictures of nomadic peoples somewhere.
But those all had at least somewhat elastic materials. I'll have to think about how it would work with something as non-flexible as 2"x4"'s.
macrumpton2 years ago
I have seen a similar kind of circular building with a roof made with the rafters all lying on each other in a sort of spiral pattern. I can't remember where I saw it though.
nahaj (author)  macrumpton2 years ago
I can see several ways that could be done, I'd be curious to see it if you find it again.
jag2173 years ago
This reminds me of the popsicle stick bomb:
http://en.wikipedia.org/wiki/Stick_bomb

Can you make 2x4 bomb?
skimmo3 years ago
ha the de vinci bridge is the first thing i thought off when i saw this, its great
i seen a full sides one at his exhibit, maybe your his reincarnation
leonardo-da-vinci-machines-arched-bridge1.jpg
nahaj (author)  skimmo3 years ago
You all are right, that is exactly the same basic idea.
Do you have a pointer you could share to where this was found?

And no, I'm definitely not his reincarnation.
nahaj (author)  nahaj3 years ago
The design predates DeVinci by a bit.

Here is the PBS program documenting the design from a 900 year old painting.

http://www.pbs.org/wgbh/nova/lostempires/china/builds.html
nahaj (author) 3 years ago
crestind (below) included a link to the Chinese "Rainbow Bridge", which clearly predates both Da Vinci and me. Thank you for the link... I knew I'd seen it before but couldn't find it anywhere.


I recommend the link. And it also shows how they put a deck on it, which is something I'd not tried.

Note that because 2x4's are proportionately skinnier than the logs that are used in the Nova program that the link points to, my bridge that holds our weight is a lot flatter than what they constructed. (Although the first picture below has an arch closer to what they used... but if weight is applied it drops down to the same as the other)
foobear3 years ago
I think that Da Vinci invented the bridge design. It's neat to see it can actually hold a person up like that. Very cool.
nahaj (author)  foobear3 years ago
I had not seen it in Da Vinci's stuff, if you have a pointer to it I'd appreciate it.

The same basic bridge design exists in 2000 year old bridges in China also.

Here is a picture of starting another bridge we did that afternoon.
It may make it clearer how it works.
bridge2.jpg
foobear nahaj3 years ago
Here's a link to the davinci bridge.  I couldn't find the original sketch though... 
nahaj (author)  foobear3 years ago
Nice! (Although they cut their pieces.) (Thank you for tracking down a link.)
What they get my cutting it is that they can have much steeper ends.)

It is clearly the same arch.

I've seen this as a 1000's of year old Chinese or Japanese bridge also,
but I've not been able to find it on the net. (But
crestind nahaj3 years ago
This may be the bridge you are referring to, the rainbow bridge.
http://www.pbs.org/wgbh/nova/lostempires/china/builds.html
canida3 years ago
Whoa, that's awesome!
Was this just an exercise in making something without fasteners, or do you have a use for this kind of lofted tiling?
nahaj (author)  canida3 years ago
If you bolted the bridge (or epoxied it, or both) it should be a practical bridge.

I have used the square cell version of the dome for a grape trellis, but not for anything else practical.
Here is a photo of the square celled dome.
Note that all the supporting legs are on a rectangle... So if you build a raised rectangular frame over a picnic area, and build the dome on that, you can cover it nicely. (I never actually bolted the one I used... and after a year the grape vine itself started to hold it steady.
sdome.jpg
nahaj (author)  nahaj3 years ago
This is possibly a better view of the square celled dome.
The important thing to notice here is that, unlike the hex dome, none of the 2x4s are anywhere near their engineering limits.
Therefore this design is a MUCH better choice than the hex dome if you plan to put weight on it. (Such as I did when using essentially the same design for a grape trellis)
dome2.jpg
You could build a den for kids in it if you raised it up on some more 2x4's bolted onto it with some tarp secured to the top and sides of it :)
nahaj (author)  Callum Snowden3 years ago
Maybe.
*BUT*
But you'd want a lot more overlap on the joints if you were to have people under it.
And I've not undertaken an engineering analysis of the weight of the water pooled in the middle of each cell... How tight you you put it on would make a difference.
Kryptonite3 years ago
That's incredible! Did you design each of these yourself? They look brilliant!
nahaj (author)  Kryptonite3 years ago
Forgot to answer your actual question... Yes, these are my own design.

But any tiling with equal length edges, and edges meeting at intersections of three or more edges, with no angle greater then about 60 degrees, can be turned into one of these domes. The four sided cell dome below shows how to join four edges at a junction. I assume that how to join more is reasonably obvious. But joining more than about 6 at a junction poses practical issues.

Note that these don't have to be what are called "regular tilings". Turning children with stir sticks to the task of design usually gets me some nice irregular tilings.
Ha ha, I'm sure it would.

Certainly makes for a bit of fun, I'll have to have a fiddle next time I get my hands on some.
nahaj (author)  Kryptonite3 years ago
If you get the long skinny coffee stirring sticks, you can practice these on a table top. Since the sticks are fussier than 2x4's, once you have mastered them with the sticks you can pretty much just go out and make them with 2x4's without any problem.

The sticks are fussier because they don't have as much friction (compaired to weight) as 2x4s, which will mostly just stay where they are put.

I've started eight year old kids with sticks in the house, and then a few hours later they've been able to build the same structures, full sized, outside.

Just remember that stir sticks bend better than 2x4's, so limit yourself to structures that don't involve bending.


But, if you just get into making small structures WITH bending, but without fasteners or glue, there is a lot you can do also.
Otherbridge.jpg
deziderro3 years ago
BRAVO !
okff23 years ago
could you have closer pictures?
nahaj (author)  okff23 years ago
I'm sorry, but I don't understand.
What features are you having trouble seeing? Are you talking bridge or dome?
KottonKandy3 years ago
AMAZING! I sooo wanna do this! It would be awesome if you put up a vid with step by step instructions. But yah, this is pretty much what instructables is all about...awesome creative ideas!