tips on geodome v3

Navigation

Geo-Dome Home

Forum Home

View All Threads

New thread

Member login

Title:	tips on geodome v3
Posted on:	2/7/2010 7:36:00 AM
Category	Construction Techniques and Tips
Author	scrdcow
Status	Open
Views	9823
Replies	(17)


Hi! i''m thinking of building a panalised 5/8 v3 geodome with a diameter of 4.25. I''m going to live in it during the cold winter here (up to maixmum -30 celcius). I have some questions about how stable it could get if I also want to be able to take down triangles and shift them while the rest of the structure stands? could this be doable or would it break the structure and make it fall? i''m not planning to shift the lowest triangles. this is so that I can change the windows during different seasons. and it should also be mobile. any suggestions on how to do this without wearing the wood to much by screwing unscrewing? i''m also thinking of what would be preferrable, to level it by adding wood underneath or leveling it by changing strut length of the lowest triangles? I wonder if it would get cold if I use wood leveling instead of changing the struts so the isolation can go further down. I also wonder if a door entry that is made of one of the hexagons on the sides and sticking out a little bit to make a straight door entry would destabilise the structure alot? Will I need extra thick wood for those parts? I also have a question about heat, does the warm air by itself transcend to the top and then cicrle downwards a bit, is there any such effect in the dome structure? or does it just stay flat on the top? even if i''m trying to be very precise will it be hard to make the dome fit excatly without serious gaps that would draw alot of air inside? and how do I in the easiest way calculate the angel I need to saw the struts so as they will when connected together make no gap between themselfs on the outside of the dome? I was thinking about maybe setting some metal plate on the sides as to be able to overlap them so as no rain will come in. do you have any other solutions for rain comming through gaps? I was thinking about putting some rubber on the sides of the triangles so it would seal the gaps, will rubber be durable, any other solution? any tips on very very good isolation in the triangles? maybe styrofoam, it''s light enough. Do you think that the bottom triangles made with great thermal mass would only be cold during winter and won''t work as planned? I was thinking about just having som extra thermal mass triangels on the inside to put on the north wall that way I would have isolation on the outside and I can have my stove in the middle and triangles on the sides. I want to try to figure out how to keep the floor as warm as possible even thou the warm air goes upwards. I was thinking if a solar panel powered fan could help to transfer hot air down to the floor, would it be worth the effort? how thick does the wood struts have to be to be durable? were is the pressure targeted, will they need to be very very hardly bolted to eachother or can it be doable with 4 screws on eachside with tvo hinges in total? there will come alot of snow, and I would like to keep it on the dome as insulation, but the structure has to hold. very many questions... but I would be helpfull for any info I can get. i''m constantly looking up these things but just wanted to send them out to people already exerienced because it can take some time to get answers back :-) do you have any other tips on on building a dome like I planned please let me know. thanks a bunch! also this site is very good :-)

[ Comments 17 ]

posted by scrdcow	07/02/2010 08:05:26
I just realised that my plan is a bit the same as p12 wrote about in the thread "dome without hub connectors". And maybe I need to explain a bit more exctaly what I want. I'm going to make all triangles indoors during the winter and then put it all together. I don't want any gaps, and I want the wood struts from the different triangles to fit nicely together without making any gap on the outside that I need to insulate. I'm not sure what the dihedral angel is, if it's not the angle between the triangles to make the dome concave. I also as p12 think it's important to make it correct so as the structure will be as strong as possible since it's very snowy here during winter and I would like to keep the snow on the dome as insulation. thank you! :-)

posted by Gerry

07/02/2010 18:36:49

Dear Scrdcow,
Lots of questions! Since the conventional 3v icosa dome does not sit flat at the 5/8ths mark (also sometimes called 5/9ths), consider using another geometry.

The Fuller-Kruschke version of the 3v icosa has 4 strut lengths instead of 3, and 3 kinds of isosceles triangles instead of 2. But it has the major advantage of sitting flat, without the need to adjust the bottom row of triangles.

Here are the chord factors, namely the edge lengths when the dome's spherical radius i 1 unit:

A = 0.329706
B = 0.382290
C = 0.421489
D = 0.441056

I will now attempt to insert a jpg line drawing to show which strut goes where. The floor radius of this dome is 0.982247 times the spherical radius. The height of the 5/8ths version (what I call 5/9ths) is 1.187592 times the spherical radius.

This dome is used by many dome-home manufacturers to avoid the problem you mention, the need to level the dome if you use the conventional geometry (alternate division, also called class I, method 1).

Gerry

posted by Gerry	07/02/2010 18:41:26
Scrdcow: I tried to upload a line drawing but it didn't work. Maybe the website adminstrator can help. Gerry in Canada

posted by scrdcow	08/02/2010 04:06:58
thanks alot! but I would prefer to do the conventional 3v dome if it can be leveled without to much problem. what is the main problem, will it not stand stable enough, it wan't tilt? no? it's also ok to change the strutlengths so that it will level. that is preferrable, that way the insulation can go all the way down. and it looks neater. but I also count that as a sort of leveling without change the whole geometry, which I don't like. I need the rest of the dome except the lowest triangels to be interchangeable. and therefore no more sizes than two. that was my whole idea originally anyways. if it's doable without the structure falling or wearing out the screwholes etc. i'm only doing this two times a year, late autumn before winter, and in the early summer when it's gets warmer, so I could practically tear down a larger part of the house and rebuild it if it won't be able to just switch triangels when it's all set up. I want to use solar thermal warming of triangle blocks inside at the north side of the dome, with the normal insulated triangles in the normal structure. the stove will be placed there in the middle. so as the stove will warm them during winter also. they can be moved to the second floor/sleeping quarters of the dome if they won't get warm at all, or just be put outside. since yesterday I also have this question, that I don't think I have mentioned. How is the airflow in a geodome? if I have a ventilation gap at the top of the dome. will all the hot air from the stove just travel to the top and then flow out of the building or will there be some kind of automatic air circulation in the dome? how will the air travel? how about the other side of the dome furthest away from the stove? I was thinkig of having an heat exchange ssytem with a conduit sucking in air from the lower side of the dome then, twitching around the hot air conduit going up from the stove, and release the somewhat warmer air closer to the top, how will that change the airflow? You have to consider that the dome won't be completly insulated without any gaps at all but the air will still be sucked into the building because the air gets warmer in the conduit but the stove might suck are from small gaps on the floor sides of the dome instead of sucking down the air from the conduit. I will include a picture...

posted by scrdcow	08/02/2010 04:20:39
Couldn't upload picture either. Anyways, the picture was only of a dome with two conduits spiraling around each other exchanging heat and som arrows showing how my friend thought the airflow would travel, to picture it think of a dome with a stove on one side with the conduits going straight up from the stove halfway up, letting midly warm air flowing in (preferrably ;-D). It sucks air from the lower side of the dome. It could also suck air from underneath the dome if that is preferrable but I think it would make it drafty underneath. i'm going to seal that off so as no winds are blowing in cold air underneath when it's not enough snow to cover it. thanks for all the help I can get :-)

posted by scrdcow	11/02/2010 23:27:08
Sorry about my lousy posts, I was very up in arms about this project. I have gotten most of the things sorted out except two important ones. How to protect it from rain, and how to connect the triangles so as to easly take them apart. I was thinking about maybe some hinge with a splint that kan be picked off. But the rain issue is harder to solve. I still want to level the dome by changing strut length in the lover triangles. If any of you have calculations for that I would be glad. Else I will find it or calculate it myself. Thanks! :-)

posted by Gerry	13/02/2010 23:47:41
Scrdcow: The new diagram includes the chord factors for leveling the base of your dome. Good luck. Gerry

posted by Gerry	14/02/2010 00:15:25
Scrdcow: Maybe a 10-sided dome is an option. See the diagram. Gerry

posted by p12	20/02/2010 10:42:02
have never heard of The Fuller-Kruschke version. but it gives me lots of new ideas. I wanted to build av 2v or 4v dome because it will be flat on the ground. this tread gives some innovative ideas ,thank you!

posted by Jorge	16/05/2010 07:09:10
I am planning to use Used Steel Crossarms [Angle steel bar, used to connect insulator string to the poles] to build up a 8 meter diameter eV dome in a Mountain property in El Salvador [Central America. I got the drawings and I am planning to put together all the materials in two months. Frankly, I am not sure wich material is the best for covering the dome, since I live in a tropical place which is humid and warm. Moreover, the place is not the best for delinquency issues. So I need a safe and secure place and good looking as well. Does anyone knows wich material is the best for my project? and the method to covering the dome. I look forward to hear from you guys. Jorge

posted by Jorge	16/05/2010 07:15:07
There is the steel crossarm picture to have a better idea.

posted by Jan	13/09/2010 19:00:36
Hi Gerry Your two posts above have very different cord factors ? Anyway I want to build an aprox 40 ft diameter dome with the most important length being a longest strut of 8 ft plus I think 3 inches for the hubs (SIMPSON GT6Z and a STARPLATE kit available at building supply stores) I Want to build a 4/9 (3/8) 3v alternate dome. What cord factors should I use to get it to sit flat. Do I need a 4th cord. From Desertdomes.com I have A = .34862 B = .40355 C = .41241 Where do you get accurate info for this stuff?

posted by Gerry	17/10/2010 01:19:41
Hi Jan.... It's been more than a month since you posted your message. Not sure if you're still around... Yes, the two main sets of chord factors I posted are different. Although both are for so-called class 1 icosahedral domes, the layouts are slightly different. By using the 4-chord factor Kruschke version, you don't have the problem of the non-planar dome base. (Back in the 1970s, David Kruschke, a math teacher in the USA, showed the geometric derivation of some of the dome layouts used by Buckminster Fuller.) But you can also fiddle with the chord factors in the bottom row of triangles to get the dome sit flat. I posted that solution too, above, which includes a fourth chord factor. Or you can just make a 10-sided dome, which also adds a fourth chord factor (which is twice the length of the 0.403548 edges. If you're looking for books on dome math and construction, post a reply. Cheers, Gerry in Quebec

posted by rui	24/12/2010 00:10:30
Hello Gerry I have the same difficulty to make a dome of 3m in 3v because the base is not flat to the ground. desertdomes the site does not give me that option, or should I be wrong? how can I fix it? where can I calculate this? thanks in advance

posted by Gerry1	31/01/2011 16:24:53
Hi Rui: Earlier in this same thread, you'll find three suggestions for flattening the base of a 3v icosa dome. For each diagram & solution, chord lengths are given. (1) Use the Fuller-Kruschke layout. (2) Adjust some of the strut lengths in the bottom row of 15 triangles. (3) Convert five clusters of three CCB triangles in the bottom row of triangles into five trapezoids; this reduces the number of edges in the footprint from 15 to 10. The Desert Domes calculator uses the so-called class I, method 1 layout. When such domes have odd frequencies (3, 5, 7 & so on), they are either more or less than a hemisphere and the dome base "oscillates". In other words, not all 15 vertices defining the dome footprint lie in the same plane. I hope this helps. Gerry in Quebec

posted by David Kruschke	30/10/2012 02:30:42
I'm adding a clarification here. I've seen Buckminster Fuller's chord factors for two and four frequency domes but I've never ever saw any 3 frequency chord factors he might have had. I independently derived the 3 frequency chord factors myself during the Fall of 1968 and later published my domebook that included these. I published the derivation because I didn't want people to use a geometry that they couldn't independently check before cutting materials. To this day, I've never seen the derivation of a three frequency dome geometry elsewhere that has a flat cut off plane at ground level...

posted by Logan	16/11/2012 17:11:14
Hoe many 1, 2, 3 frequency triangles are there in a 5/8 3v dome