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| Title: | 3V Dome construction | |
| Posted on: | 3/27/2008 4:52:11 PM | |
| Category | Construction Techniques and Tips | |
| Author | Mick | |
| Status | Open | |
| Views | 6319 | |
| Replies | (11) | |
| I would appreciate any help anyone can give in the construction of a 3V dome for use as a greenhouse. I have used the calculations given and laid the struts out to form the base of my 2meter radius dome but the dimensions given do not leave any room for a joining hub, have I done something wrong? | |
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| [ Comments 11 ] |
| posted by Colin | 28/03/2008 20:34:41 |
| Hi Can you give us a bit more information as i don`t quite understand your question. It can certainly be fixed though :) When you calculate the struts you need to take the hub size into account or the dome will be somewhat larger than you planned. Most of the time this wouldn`t be a problem unless it has to fit in with rigid sheet sizes (minimizing waste)or when you`ve sized the dome to fit the yard width down to the very last millimetre :) | |
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| posted by Mick | 31/03/2008 16:08:56 |
| thanks for your reply and I will try to explain better the problem I seem to be having. I would like to build a strut and hub construction dome greenhouse I have taken the strut lengths from the 3V calculation model for a 2 meter radius dome and, using a drawing package, laid them out around the diameter of my proposed dome and they do not leave much room for a joining hub. Can you help with any details of a joining hub? and therefore what allowances I need to make on the lenght of the struts. Also with comments from other area of this site in mind, are the strut ends just cut at one angle or a compound angle, or does the hub create the other necessary angle. I know to many questions but I would appreciate your help. | |
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| posted by Colin | 01/04/2008 00:29:57 |
| Hi Mick The calculator doesn`t take the hubs into account so it will calculate the strut lengths to the outside center of each vertex. The other thing to take into account is the base radius will be fractionally smaller than the calculated radius due to the 3v dome not being an exact hemisphere. Always use millimetres (not metres) in all calculations for better accuracy :) Regarding the hubs, the size will depend on the timber you plan to use (there has to be room for upto 6 struts to fit around it at the correct angles).If you are using timber of say 94mm x 38mm you will need around a 90mm diameter hub, for 94 x 44mm you`d probably have to go for 100-110mm hubs. Hub details are located on the "Make your own 3v dome Hubs" thread on the website :) You are correct about the strut end angles, they are simple 10 and 12 deg miters. With a greenhouse dome it pays to plan ahead about how you will fix the covering and make it waterproof..especially at the hubs. The same applies to opening vents and the door, try to plan everything to the last detail and work to the plan..designing around problems "on-the-fly" can be a pain so try to leave nothing to chance :) | |
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| posted by Mick | 01/04/2008 11:33:33 |
| Thanks for the info' | |
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| posted by nicki | 13/04/2008 21:13:13 |
| 2m radius is huge guess you need it that large for the height. I'm in process of building a 1.2m radius dome which is too low for green house,of hub struts. intended use as a large cold frame, with lift up lid so it can be walked into to water and pick vegetables. my hubs are constructed from new soil pipe with hole drilled into and small holes in struts with wire twisted to secure. Have you suggestion for making the same radius so it would be tall enough to walk into. | |
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| posted by Colin | 14/04/2008 03:35:15 |
Hi Nicki
A dome cold frame is a good idea. To gain extra height you could add a riser wall which could also double as a raised bed. The other way is to create a more of a sphere to gain height. The only downside is the floor area gets smaller. Here`s a a pic of a small 9.5ft dia x 7.5ft high (3/4 sphere) 3v dome, the bottom ring was about 8ft in diameter.
It doesn`t matter what size dome you build..as long as you build one :)
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| posted by Colin | 14/04/2008 03:48:46 |
Just for comparison, here`s the same dome but with an extra row of straight triangles added to the bottom. Its around 8ft tall but doesn`t look quite right :)
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| posted by Nicki | 16/04/2008 20:37:47 |
| Thank you for such wonderful feed back this is such a great site used the calculation tool to build. Many thanks | |
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| posted by colin | 18/04/2008 14:35:43 |
| Hi Nicki I think it`ll be quite a heavy lid to lift :) The base might deform too. If you can find an old 8ft diameter tubular trampoline frame you could use the ring for your base circle. They are usually made from 1.5" dia galvanized steel tube. Don`t forget the pics when you`ve got it done ;) | |
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| posted by nicki | 01/05/2008 20:57:50 |
| Ok so it has turned into a chicken run, as we decided that to put it up the allotment it may not be safe. It has been covered with net and One of the Hexagons has a net flap which also covers one triangle at the bottom for the chicken to get out. would love to add photos,can I add photos? unless I start a new thread. PS chicken love it!! | |
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| posted by Colin | 02/05/2008 03:52:27 |
| Hi Nicki, Always keen to see new pictures. Just click on the (upload image),browse to the file on your pc. Copy and paste the resulting link into your message. | |
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