Dome design

MikeVDS · Post by **MikeVDS** » Sat Feb 24, 2007 10:32 am

I'm wondering if anyone has constructed a 2 frequency dome out of a single length strut. Basically you'd use the longer of the two strut sizes and just leave the smaller size completely out. So a v2 would be made out of 6 pentagons. I know it can be done but is it very sturdy when made out of the typical smashed end tubing design?

Lassen Forge · Post by **Lassen Forge** » Sat Feb 24, 2007 11:42 am

In other words a modified bucky ball? Sure, you can do it, but why??

It's OK until you get to the ground. Then what's your support? You need to tie the bottom together.

Also you lose way too much internal room. Ergo the 3-5 freq. domes - increases your usable area. a monodome is pretty scrunchy. And you lose the sides.

I dunno - try one in scale and see if you can live with it and how strong it is...

bb

thisisthatwhichis · Post by **thisisthatwhichis** » Sat Feb 24, 2007 12:07 pm

Yes, the dust devil "tornados" last year would have made spaghetti out of something like that......

MikeVDS · Post by **MikeVDS** » Sat Feb 24, 2007 12:55 pm

Sorry, I'd complete the bottom ring of the dome as well, which are still the same size struts.

Have you tried something like that This is? Any insight to what size tubing would have made yours strong enough? Also what size are you thinking?

I'm considering using something like this for the roof of a structure and trying to hash out some ideas.

Looking at it I do not think it would support any significant vertical weight where the pentagons meet. I am considering welding pentagons out of angle iron but I'd have to make the joints support most of the weight at those points.

Toolmaker · Post by **Toolmaker** » Sat Feb 24, 2007 1:58 pm

I made the 6 pentagon version out of thick wall aluminum.. a little stronger than commercial EMT but more expensive. Cost was about 350 instead of the 200 for EMT ordering from material supply house. If memory serves the angles were about 8 degrees on the ends and I used some eyebolts in places to have rigging points inside. I used a torch to heat the ends to aid in bending since i didn't have a press brake handy. The hammock inside was able to support 2x250lbs. I also hung up 200 lbs on the other side to simulate gear. I used the plans from space lounge which look like the first pic you posted, 6 pentagons and extra pieces connecting the bottoms. If you use PVC it may not supprt any weight since it flexes so much. I wound up selling my dome to my father for outdoor storage after my injury.. if I make another one I would probably go with the "star plate" method using 2x4s to get the increased strength and ability to have a second floor safely. Another possibility is the larger one from alt. eng. using a stronger material than PVC.
http://www.alternativeengineering.com/D ... mePVC.html

timburly · Post by **timburly** » Sat Feb 24, 2007 3:17 pm

Need 135 sticks of 1inch EMT. So far the cheapest i've come up with is $6.95 a stick. Anyone have a hookup with an electrical supply house or other means to get it at discount? Its all for a dome for Mallard camp :)

MikeVDS · Post by **MikeVDS** » Sat Feb 24, 2007 6:10 pm

I assume a stick is 10"?

robotland · Post by **robotland** » Mon Feb 26, 2007 6:41 am

MikeVDS wrote:I assume a stick is 10"?

For the model, maybe....

Seven bucks per for a ten foot stick of 1" EMT is pretty good. Try checking the local scrapyards for bits. I've made several small domes from bits snagged out of dumpsters at downtown construction sites, since they routinely chuck pieces plenty long enough for dome struts. Is there a Habitat For Humanity "Re-Store" in your vicinity?

Toolmaker · Post by **Toolmaker** » Mon Feb 26, 2007 9:13 am

The supply house I deal with has 12 foot and 20 foot lengths in stock standard, than again I used shedule 40 pipe not EMT for the last dome. I don't know what EMT standard sizes are but the next one I am going to do out of solid bar stainless for an even stronger dome to support a second story. This will also allow for protection from the elements. I am also planning on have the 3way and 4way connectors out of solid bar stock "scrap" ends. My final decision is going to use the alternative engineering freq. 4 dome since it has 2 "standardized" lengths of 66 1/2 inchs and 79inchs. I am just going to use 20 foot standard lengths for my material. I can get 3 lengths per so I will be using 22 bars for struts and use leftovers for making the connecting rods. I have leftover stainless pipe from another job that can handle my "sleeve" needs. These are so much fun to build and make I may wind up changing careers in the near future.

Dome design

Dome design

!