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#1
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Triaxial polytunnels
Greetings, fellow urglers ;-)
I've made a page about triaxial polytunnels. In particular I've created the following pages: Triaxial index : http://hexdome.com/triaxial/ Weaving : http://hexdome.com/triaxial/weaving/ Polytunnel : http://hexdome.com/triaxial/polytunnel/ Sphere : http://hexdome.com/triaxial/sphere/ It's probably best to start on the first link. The material about polytunnels is what's likely to be of interest to the denizens that inhabit this group. Basically, I built a model of a triaxial weave polytunnel, photographed it, wrote some material about its significance - and then uploaded the results. To quote from the introductory paragraph: ``Farmers do not need the wide spans and high spaces domes offer - for them, polytunnels make much more sense. I looked at conventional polytunnel designs. As far as I can see they make little structural sense. Their structural elements often rise straight into the air with little sign of support. As a result the designs often have to rely on the use of excessively rigid (and expensive) materials - and braces. Polytunnels represent an /excellent/ case for using triaxial weaving. Triaxial weave is light, resiliant, strong in all directions, /very/ resistant to shearing forces - and yet still easy to construct.'' As I go on to argue: ``For a given strength, an intelligent structural design allows substantially lighter (and cheaper) materials to be used. In particular, polytunnels of reasonable size can be constructed along these lines using PVC conduit - which is an astonishingly inexpensive material. [...] Polytunnels facilitate growing sensitive, tropical fruiting plants in northern climes - where much of the planet's landmass and population reside.'' Thus, I consider polytunnels to have significant economic importance. It's my hope that I can contribute to making many of them cheaper. Enjoy, -- __________ |im |yler http://timtyler.org/ Remove lock to reply. |
#2
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Tim Tyler wrote:
Greetings, fellow urglers ;-) I've made a page about triaxial polytunnels. In particular I've created the following pages: Triaxial index : http://hexdome.com/triaxial/ Weaving : http://hexdome.com/triaxial/weaving/ Polytunnel : http://hexdome.com/triaxial/polytunnel/ Sphere : http://hexdome.com/triaxial/sphere/ It's probably best to start on the first link. The material about polytunnels is what's likely to be of interest to the denizens that inhabit this group. Basically, I built a model of a triaxial weave polytunnel, photographed it, wrote some material about its significance - and then uploaded the results. To quote from the introductory paragraph: ``Farmers do not need the wide spans and high spaces domes offer - for them, polytunnels make much more sense. I looked at conventional polytunnel designs. As far as I can see they make little structural sense. Their structural elements often rise straight into the air with little sign of support. As a result the designs often have to rely on the use of excessively rigid (and expensive) materials - and braces. Polytunnels represent an /excellent/ case for using triaxial weaving. Triaxial weave is light, resiliant, strong in all directions, /very/ resistant to shearing forces - and yet still easy to construct.'' As I go on to argue: ``For a given strength, an intelligent structural design allows substantially lighter (and cheaper) materials to be used. In particular, polytunnels of reasonable size can be constructed along these lines using PVC conduit - which is an astonishingly inexpensive material. [...] Polytunnels facilitate growing sensitive, tropical fruiting plants in northern climes - where much of the planet's landmass and population reside.'' Thus, I consider polytunnels to have significant economic importance. It's my hope that I can contribute to making many of them cheaper. OK: that makes structural sense, given cheap enough materials. But have you put _time_ into your calculations? Mike. |
#3
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Mike Lyle wrote or quoted:
Tim Tyler wrote: Greetings, fellow urglers ;-) I've made a page about triaxial polytunnels. In particular I've created the following pages: Triaxial index : http://hexdome.com/triaxial/ Weaving : http://hexdome.com/triaxial/weaving/ Polytunnel : http://hexdome.com/triaxial/polytunnel/ Sphere : http://hexdome.com/triaxial/sphere/ [...] Thus, I consider polytunnels to have significant economic importance. It's my hope that I can contribute to making many of them cheaper. OK: that makes structural sense, given cheap enough materials. But have you put _time_ into your calculations? My model took me an hour and forty minutes to construct - and twenty minutes to dismantle. Basically, triaxial weaving is simple - to the point of being trivial. The construction process is a bit different to the building of a conventional tunnel, though. The structure is typically constructed flat on the ground - and then gradually pushed/lifted into shape. If the structure is of any size, the lifting would be a progressive process - using a mixture of ropes from the outside, stakes to pin in the far edge - and perhaps props from the inside. I think it even makes sense put the polythene in place (and hold it there using pegs along the edges) while the structure is lying flat - only battoning it down after erection. This avoids any need to clamber up onto the top of the structure while positioning the polythene - i.e. these steps: http://www.murcrusto.eclipse.co.uk/p...2/page_02.html ....and makes adding an insulation layer in the process a more practical proposition. -- __________ |im |yler http://timtyler.org/ Remove lock to reply. |
#4
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"Tim Tyler" wrote in message ...
Greetings, fellow urglers ;-) I've made a page about triaxial polytunnels. It looks sensible for a permanent structure, but for a small garden polytunnel of the type that you use as a cloche, rather than walking into, you need some way of making it collapsable. The typical concertina type can be folded into a small package for storage but I think it would be more difficult with your design which looks ike it would be strong against compression in all directions, not just in the directions needed. a normal polytunnel with a guy rope at either end keeping it in tension would be more practical I think. Have you looked at the pop-up childrens play tents? They seem to be very cheap to make and a reasonably sized tent which will easily hold a child can be folded with a neat twist into a package not much larger than a dinner plate. maybe the same sort of approach could be used to make your tunnel collapsable. -- Martin & Anna Sykes ( Remove x's when replying ) http://www.users.globalnet.co.uk/~sykesm |
#5
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The message
from Tim Tyler contains these words: /snip/ If the structure is of any size, the lifting would be a progressive process - using a mixture of ropes from the outside, stakes to pin in the far edge - and perhaps props from the inside. I think it even makes sense put the polythene in place (and hold it there using pegs along the edges) while the structure is lying flat - only battoning it down after erection. /snip/ I haven't got round to looking at your pages yet - but I will. I mention this just in case you've suggested this... Have you thought of pegging (preferably burying the bottom of) one edge of the polythene and folding it away from where you are having the tunnel? Construct your lattice on the ground where the tunnel is to go, then erect it, and afterwards, pull the membrane over it? It wouldn't work in my garden, as it's far too narrow to lay it flat, sensibly, and is somewhat - er - mature. http://www.users.zetnet.co.uk/hi-fi/garden.htm It has been tidied up a bit, but things will keep growing, despite the best efforts of the resident molluscs. -- Rusty Open the creaking gate to make a horrid.squeak, then lower the foobar. http://www.users.zetnet.co.uk/hi-fi/ |
#6
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Martin Sykes wrote or quoted:
"Tim Tyler" wrote in message ... Greetings, fellow urglers ;-) I've made a page about triaxial polytunnels. [snip http://hexdome.com/triaxial/polytunnel/] It looks sensible for a permanent structure, but for a small garden polytunnel of the type that you use as a cloche, rather than walking into, you need some way of making it collapsable. The typical concertina type can be folded into a small package for storage but I think it would be more difficult with your design which looks ike it would be strong against compression in all directions, not just in the directions needed. a normal polytunnel with a guy rope at either end keeping it in tension would be more practical I think. Yes: the structure was intended for semi-permanent use. Making it collapsable was not a significant design consideration. If you wanted to take it down, you would indeed have to dismantle it. -- __________ |im |yler http://timtyler.org/ Remove lock to reply. |
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