Geodesic Dome Kit

Intro: Geodesic Dome Kit

This was a kit I created for visiting school children to assemble at The National Building Museum. It's meant to be easy to understand, collaborative, easy to tear down and clean up. If you are interested in having your school group build this geodesic dome at the National Building Museum, please visit their website for information about how you can sign up to participate.

This Instructible will show how to fabricate the parts to make a 6 1/2 foot tall dome that is rigid enough to support approximately 50lbs from the apex.

STEP 1: Tools and Materials

Tools:
chop saw
table saw
drill press
belt sander
3/8" drill bit
1/4" drill bit
machinists vice
olfa snap off knife and extra blades
2 disposable paint brushes

Materials
3/4" square, 1/16" thick wall extruded aluminum
3/8" thick rubber sheet (8568K536 - $51.07/ linear foot x 36" wide)
26x 2 1/2" long 1/4" lag bolts
260x 1 1/2" long 1/4" lag bolts
26x wide 1/4" washers
26x 1/4" wing-nuts
red and blue paint

STEP 2: Dimensions and Templates

We will need to make:
- 35x struts 47" long (red)
- 30x struts 41 1/2" long (blue)
- 20x 6way hubs blanks
- 12x 5way hub blanks
- 20x 4way hub blanks
- 130 wooden pegs 3-4" long

- The aluminum for the red and blue struts can be obtained online at McMaser Carr, or at an aluminum wholesaler at about half the cost. Look for places that sell "extruded aluminum" and also check to see if they'll cut it to length for you. If not, you can cut them on the chop saw.

- Rip wood for the inserts so they slip into the struts easily, and then cut them about 3 inches long. Paint and sand them before assembly so they will appear cleaner, like a plastic insert, not just a painted end of a stick. When you do glue in the inserts, use 5 minute epoxy, and just dab a bit on each side of the insert before sticking it in the strut. If they are tight, you can push them in against a wall, or if very tight, just throw the strut at the floor, like a spear to jam the insert in. I tried to avoid hammering them in because the struts seemed like they were bending.

- Drill the holes in the struts on the drill press using a good machinists vice clamped down to the table. I just put some tape with a mark on it to show me where to put the first hole, and then slid the strut to the edge of the vice for the other one. Make sure the far end of the strut is supported so the holes don't start getting more and more angled. Be very careful when drilling the holes, they are a bit bigger than the bolts, but if they are too far apart it won't fit, and will be garbage, or if they are not centered correctly, they look really bad.

- Sand and de-burr all the metal parts to get rid of anything that might hurt the kids.

- The rubber sheet material for the hubs and caps can be obtained at McMaster Carr. It is "shore A 80 neoprene" (shore A 80 refers to the hardness, and neoprene is the kind of rubber) Cut the rubber only with a utility knife, or snap off OLFA blade - If you cut too much rubber with the power tools, It Will Set Off The Fire Alarm. Cutting with a knife works best if you bend open the cut as you go so there is less blade friction. Have plenty of extra blades handy.

- Make templates for drilling the hub and cap holes out of at least 1/2 inch plywood and use a clamp to hold the template down,. Make sure you use a sacrificial board underneath, because the rubber really pulls the drill down when it's through.

- It's much easier and nicer looking to paint the bolts for the hubs before they are assembled.

- Getting the bolts into the rubber is the most arduous part of the process. Sometime you will need to get them started by twisting them in with a pair of vice-grips. You can also simply push them in with your thumbs, but that really starts to hurt after about 5. I've had some success with positioning the hole over a gap in the table and hammering the bolts in that way. Without the gap, the rubber bounces too much, and never goes in. You can also experiment with the size of the holes, as drilling a 1/4 inch hole through rubber never produces a 1/4 inch hole.

STEP 3: Assembly Instructions

To assemble the dome, lay out the 10x 4way pieces in a circle, making sure to alternate left and right handed versions. Next attach 10x red struts along the bottom, making a ring.

Now begin working on the first row of 10x red and 10x blue struts. Once all the bolts on a given hub have been used, you can secure them by attaching the appropriate hub cover with a washer and wingnut. Make sure you have plenty of spares on hand as they get lost very easily and make a very attractive souvenir :P

Connect their tips with 5 and 6way hubs and add 10 blue struts, making a ring to top off the first row. Now add the 10x red and 5x blue struts to fill up the remaining bolts. Add the caps to secure this level and now you should have 15x struts poking/ dangling in the air.

At this point you can either assemble the top of the dome in place or raise it into position already assembled. You may need a short step ladder to get to the top - I'm 6'3" and had my head poking through the dome when I constructed it.

Once it's all up, double check the hubs and caps. Give it a few sturdy shakes around the perimeter to make sure it's not going to fall apart before you try hanging anything from the center.

I never did any destructive testing, but I have a feeling the rubber will deform and invert areas of the dome before anything else comes loose or breaks. I'd recommend a maximum weight of 50 pounds, but you can experiment and if you feel it's safe, ask one of the kids to hang from the center. You could even consider replacing the center bolt of one of the 5way hubs with an eye-bolt to make hanging a test load or small child easier.

Tear down can be pretty fast once you've gotten a little practice. Just start at the top and start pulling apart hubs. chuck the hubs into a pile and lay the struts out according to length. The aluminum can be loud if you bang it against one another, so just drop them lightly onto a carpeted floor.

The whole kit should be able to be packed into a couple of 5 gallon buckets, but you will probably need a cart to push the whole thing around the aluminum weighs more than 50 pounds.


The dome kit PDF I've included at the end is an overall manual of how to reproduce this kit.

Comments

[Haihiru]

I luv this. How many feet of the Neoprene rubber do you need? I can't find it mentioned.

[mydian_nightshade]

Good catch: It's a lot - 26 hubs x 2 shapes per hub = 52 shapes which are about 6" square each. That's a minimum of 13 square feet, but you'll need to see what width rubber you can get & then do a full layout of the pieces before you order. Cutting the rubber is very unfun, but necessary for it to be durable, reusable, & safe for school children.

[rapidprototyping]

I made one these using 2 X 2's and 3/4 plywood scrape from construction site I had a jig saw a drill press and couple wrenches is all it took. I had just the old fashion miter box and hand saw then (1980) the 2X2 where better off being bought in batches I cut all the pieces by hand a chop saw would make fast work of this as all the pieces you just replicate the cuts over and agin till there all cut out drill them all out on drill press with positioning jig can't go wrong except for saw dust keep it out of the jigs. I used wing nuts and bolts the wing nuts were un-nessary by the way. I sold mine and painted it after erection it was sold as greenhousew for $150 we had good party firt time it went up we got it wrong thats embarassing but did go up second time no mistakes. These might make neat tent in the back yard or green house possibly. good job on being inventive with materials. Aluminum is always superior to wood with routers these days all the corners could be rounded over and sanded to make them smooth. I think a geodesic tent ought have sewn gesodesic cover same principle patterns pieces a tipi always gets attention a dome that can have a couple cots inside now the saving on motel rooms would pay for that in short order grandpa really doesnt mind camping out in the back yard does he if not him the kids will volenteer too for sure geodesic fort could be great adventure in the out back

[geraldvirieux]

Hi everyone this is a great instructable, does any one know of any company that sells hubs for geostatic domes I have looking on the net but can not see any firm selling them maybe the are to specialized as the hub is very complicated to fabricate as I was thinking about building a green house and would like to use glass in the design as the panels. most of the designs you see cover the dome with plastic

[rapidprototyping]

there are several one cast them as a hub thats the shape of a soda can with squares missing every so often in these openings a knuckle fits and inside the casting a pin like a bolt is added to hold things together. the struts are cut to length and bored with hole through a plate that fits on either side of dimensional lumber. bolts hold the flage to the strut on its ends a loop is formed that accepts the bolt there by holding the strut to the hub. did you try using hub and strut as your search term.

[Seth Black]

"what would happen if you replaced all the red struts with rope?"

I'm reasonably certain that you'd never be able to erect the dome, if you replaced all of the red struts with rope.

It might be interesting to swap out a select few of the red struts with rope.  Too many though, and it would simply not be able to support itself.

[nnygamer]

Looks like my house :) Great instructable

[dregawd]

If anyone is interested in building one, you can do it very cheap and easy. I was gonna do an instructable but I am a bit of a procrastinator. all you need is a hot glue gun, scizzors and bamboo scewers and go to desertdomes.com and check out the dome calculator. And you dont have to contact anyone :)

[mydian_nightshade]

yup - desert domes has a really good calculator for figuring out strut length.

I only mean for people to contact the museum if they want to us it in a school program. I don't want to feel like I'm taking patrons (and money) away from a place that I care about. Just reinforcing the non-commercial aspect of the license :)

[theRIAA]

awesome writeup. I might make one one day. don't they usually have all the tubes the same length?

[theRIAA]

what would happen if you replaced all the red struts with rope?

[dregawd]

no, the length of struts vary slightly, by design, but the connectors can take up a bit of that slack.

[theRIAA]

!!!

http://www.desertdomes.com/graphics/dome/6vdiagram.gif

[shooby]

Slick