Tipi Dome

Some years ago I happened onto a website owned by a French Architect whose name was Alain Lobel.  Alain had researched for many years structures generated by utilizing equilateral triangles.  His space frames were similar to geodesic domes but their strength not only came from following a curved surface but also from convex and concave bends in the structure.  For example when you crinkle an aluminum pop can the can's surface becomes much more rigid and resists added pressure making it much stronger to outside forces.  I emailed Alain otfen and he was very amiable, courteous and generous with information regarding his research.  A truly friendly fellow who expressed his solidarity with America during the 911 World Trade Center attack.  Unfortunately Alain died suddenly of an illness a few years back and many lament his passing.  Our hearts go out to the Lobel family and friends.  Thank you Alain for sharing your amazing work with us.  Alain's family have kept his site up which is quite fascinating with many representations of building designs and literally thousands of wire frame examples of his structures.  The web address is www.equilatere.net/

This Instructable is a demonstation using very meager materials to show one simple method of how these structures can be put together and I am also publishing some photos of the Tipi Dome, various other paper models which use Alain's methodology and with permission from his family some pics from Alain's site.

Step 1 Strut and Hub Placement

I went out and over purchased two bundles of 4' X 1 1/2" X 3/8" thick "quality" wood lath. which were 50 to a bundle and weeded out the unusable ones which had weak spots and unwanted knots. ( I wasn't sure how many good ones I would end up with)  I also purchased  50' of 1 1/4" steel strap and cut them into 4" long pieces. You only actually need about 27 feet of strap but I made extra for making additional struts for larger structures later on.

There are 39 wood struts in the small Tipi Dome so you will need 78) 4" steel strap pieces.  I also purchased 160) 5/8" X 1/8" slotted round head bolts with 1/8" Nylock nuts and 320) 1/8" washers to fasten the steel strap ends to the wood lath..  To assemble the Tipi Dome frame connect the struts together at the hub use 39)  1" X 1/4" slotted round head bolts, 39) flat washers, 39) 1/4" lock washers and 39) 1/4" wing nuts.  

After I cut the 4" pieces of steel strap to length by hand using quality sheet metal shears (piece of cake). I built a small wooden box where I could stack the 4" pieces of steel strap tightly inside and then screwed a wooden lid over the little box, clamped the box to a drill press and then drilled the holes using an 1/8" bit for the small holes and a 1/4" bit for the larger holes.  ( WARNING Do not try to drill these steel strap pieces one at a time by hand or the drill will cause the steel strap pieces to spin around and will slice your hand wide open.)  


As you can see in the photo I jogged the hole placement a bit which gave more strength and resisted splitting the wood.  The wood lath struts were exactly 48" in length and since some of the struts will be stacked at the hubs in sixes you have to allow a little length from the end of the strut for the steel straps to be able to bend over when the Tipi Dome is assembled.  Since the struts are 1 1/2" wide extend the steel strap out to 2 1/2" from the end of the strut.  See diagram "Drilling Pattern & Measurements".  I then built a jig out of a 5' length of a wooden 2" X 4: and  pounded long finishing nails exactly 51 1/2 " apart on the 2" X4" surface.  (See Strut Drilling Jig Diagram).  1) Place the 48" piece of wood lath dirctly in the center of the jig.  2) slide one 4" steel strap piece onto the finishing nail, hold steel piece in place firmly maintaining a straight position and with a hand drill, carefully drill through the wood lath with an 1/8" wood drill bit.  Now attach steel end piece with hardware, 5/8" X 1/8: slotted round head bolt, 2 washers and Nylock nut, tighten with 1/8" wrench and slotted screwdriver carefully (Do Not Overtighten) 3) Now place finished end onto the finishing nail and repeat the same procedure on the other end being careful to maintain 51 1/2"  You will need 30) 48" pieces, 6) 41 9/16" pieces and 3) 24" pieces of wood lath for this dome.  For making the shorter struts simply reposition the nail on the jig as needed.

Add for the steel strap end pieces and you will have

30) 51 1/2" wood lath struts
6) 45 1/16" wood lath struts
3) 27 1/2" wood lath struts

NOTE:  On the three shorter struts where they meet at ground level  where there is only three intersecting I made the steel strap ends shorter at 2".  I then drilled the hole only1/1/2 " away from the end of the strut so they would bunch together more tightly and makes a more stable connection when staked down to the ground.

The most tedious part is putting together these struts.  When I had put the frame together I was totally amazed at how strong the wood lath structure was! 

Comments

[solitary man]

Hello Ed,
Larger versions can be built using 2X2", even 2X4" lumber. Instead of the steel strapping I used you can use heavy gauge sheet metal strips cut to the width of the lumber. Using heavy steel gauge strips on top and below as shown in the picture when overlapped and bolted together increases the hub strength greatly. You will however will have to cut the lumber ends giving them at least 32 degrees yet being careful to maintain the 48" strut length. I hope this was helpful. :)

[edvannatta]

like information on how build this you get thing build this long you put this together want us it for want some live in one all us for G plant in all?