3 V Shallow Icosahedron Cap model and dome making
Ashok Mathur
Dear List
Shallow Cap Icosahedron domes - 3V truncated, leveled domes
I have been able to trace reference to above type of domes in the list from 2007 onwards.
I initiated a discussion on a 3 frequency shallow cap geodesic dome with flat base on 9th April 2012 .There were many participants in the discussion, but Gerry and I were particularly interested in the subject.
On 26th April 2012 Gerry calculated and produced in a spread sheet the calculations for a shallow cap 3 frequency flat base dome.
On 26th December 2018 Gerry produced a spread sheet that also covers 4 and 5 frequencies geodesic domes.This detailed spread sheet can be downloaded from this link.
https://drive.google.com/drive/folders/1MtdCmvNu-krskwRZJEy9Ry7Mn2-LfVwz?usp=sharing
I was invited to teach Geodesic domes over two day workshop to the students of architecture at the College of Architecture at MMA Pune.
One day of the workshop would be spent on theory coupled with model making, Next day we would assemble an actual dome.
Because the 3V truncated leveled version of the dome saves about 40% of all cost and is easy to build, I decided that this is what I would build with the students.
The dome would be 14 feet in radius and only 9 feet in height and would be made from struts fabricated from 33mm OD steel pipes flattened ends with holes for nut-bolt joining.
On the first day the students would build 3 models, a 3V truncated, leveled, shallow dome, another model of the same dome with 30 inch raiser walls and finally a standard 3V 5/8 dome. An idea of the first days working can be had from this You Tube presentation https://youtu.be/V0Y_9-uJnvI.
The second day the actual dome assembled in about 2 hours.Its presentation is here
Regards
Ashok
Meparth singh rajput
Second, how i perform fea analysis in a dome? I choose a 3V dome of 5/8. Can you help me out? And also, how do i prepare a dom model in CAD software? Please help me this.
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Ashok Mathur
Ashok
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Ashok Mathur
Ashok
Ashok Mathur
Ashok
Dx G
https://www.scribd.com/document/464894264/206668595-CADRE-Analysis-of-Geodesic-Dome-pdf
Casdre Geo Software, originally developed by Cadre Analytic (not sure if still in business)
https://www.ijert.org/research/parametric-study-and-optimization-of-steel-dome-structure-IJERTV11IS080017.pdf
https://sear.unisq.edu.au/31457/1/Peng_Z_Sourish.pdf
https://www.irjet.net/archives/V9/i6/IRJET-V9I6491.pdf
https://www.researchgate.net/publication/363697192_Parametrical_Analysis_of_Structural_Dome
Ashok Mathur
In addition, an Excel spreadsheet was developed using finite element analysis method to extract the forces for each element, then the results were compared against the outcomes from computational analysis method for validation purpose. The spreadsheet was aimed to standardize the design procedure and to reduce the time required for analysis and design in the future, and sensitivity analysis could also be conducted easily and quickly using the spreadsheet." Note that it does compare the computed results against any real tensegrity structures.
Page 40 of the report say the following "The model was analysed as a 3D space truss with its ground level nodes restrained for
lateral movement. Each member was treated as single element with two pinned end restraints, therefore, each member undergoes axial forces only"Ashok
To view this discussion visit https://groups.google.com/d/msgid/geodesichelp/5709ee6a-be09-4491-91b6-4fd1f2173183n%40googlegroups.com.
Gerry in Quebec
Ashok Mathur
Ashok
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Dx G
If you are going to be working with greenhouses in a hot climate, let me pass along a few thoughts in case they might be helpful.
1) Firstly, as rule, without active cooling, usually the best you can do is prevent the inside of the greenhouse from getting warmer than the ambient air. However, there are exceptions where passive methods can also.
a) Typically refrigerated air conditioning is not used for greenhouses, but of course is an option
b) A common cooling system used in greenhouse are "pads". Usually water is dripped through an air permeable paper, aluminum (or other material) "pad", which functions like a radiator. It can work well at low ambient humidities, less so at higher humidities, but less so or not at all at higher humidities.
There are also stand alone "swamp coolers" that substitute for refrigerated AC units and work really well at low humidity, although consume water.
c) Certain systems circulate water through the glazing to prevent heating with minimal loss in light intensity, but these are used more in greenhouse research and not often in more commercial settings.
Alternatives would be a fine droplet spraying system that applies water to the roof surface to prevent heating, or the use of "fog" systems inside the greenhouse (available commercially).
d) Geothermal cooling approaches could be a good option as a passive or powered system.
e) Some regions reliably have much cooler temperatures at night, and good use can be made of this to help prevent high temperatures during the day. Typically this is done using hollow masonry or stone passages as a heat exchanger, although water (typically a tank, pool, etc.) is much more effective than stone on a volume basis.
2) Passive methods - do not require energy input
a) Rather than using clear poly for the cover, white poly can help reduce temperature a great deal. Typically there will be some reduction in light intensity. However, the reduction in temperature can be far greater than light intensity loss, especially in regions with high sun light intensity.
Another commonly used method is spraying clear poly with a paint-like coating called shading compound. The applicator has some control over the level of shading desired by how much is applied. Usually this coating can be removed in a cooler season so that the poly does not have to be replaced.
b) Venting at the top of the greenhouse with air intakes lower down can help prevent hot air buildup. Vents are available which automatically close/open at a temperature setpoint without any power source at all (further info available on request).
We have had some discussions about the "chilling machine" on the list. I reviewed this some time ago and have some doubts about the veracity of explanations I have seen about why it works. However, clearly it does, and I think I see why. This leads me to suspect the system is highly dependent on the local weather, thus will work poorly or not at all under some conditions.
Blair was making a concerted attempt to deploy a chilling machine, so perhaps eventually we will hear more from him on the topic. The background work I did led me to suspect that in his climate, there would be some days it would work and others not at all.
I might think of a few more things, but wanted to pass these along in case they were not already on your radar screen. In addition, I thought it might be of interest to others on the list.
Dx G
Ashok Mathur
Dear Dx
I am thankful for your detailed guidelines. Because the work I want to do in North Africa may be outside the interest of most members of the group, I will keep my replies brief and embed them in your response in a blue font.
Ashok,
If you are going to be working with greenhouses in a hot climate, let me pass along a few thoughts in case they might be helpful.
1) Firstly, as rule, without active cooling, usually the best you can do is prevent the inside of the greenhouse from getting warmer than the ambient air. However, there are exceptions where passive methods can also.
a) Typically refrigerated air conditioning is not used for greenhouses, but of course is an option
b) A common cooling system used in greenhouse are "pads". Usually water is dripped through an air permeable paper, aluminum (or other material) "pad", which functions like a radiator. It can work well at low ambient humadities, less so at higher humidities, but less so or not at all at higher humidities.
There are also stand alone "swamp coolers" that substitute for refrigerated AC units and work really well at low humidity, although consume water.
c) Certain systems circulate water through the glazing to prevent heating with minimal loss in light intensity, but these are used more in greenhouse research and not often in more commercial settings.
Alternatives would be a fine droplet spraying system that applies water to the roof surface to prevent heating, or the use of "fog" systems inside the greenhouse (available commercially).
The above constitutes what is called passive evoprative cooling and is used on a massive scale in India and I am familiar with it from childhood.I doubt if I will incorporate this in my design . I would rather use canopy management and reduce leaves to the minimum.
d) Geothermal cooling approaches could be a good option as a passive or powered system.
Conditions in North Nigeria are like a hot dessert, which is next door and no Geothermal structures exist in the area.
e) Some regions reliably have much cooler temperatures at night, and good use can be made of this to help prevent high temperatures during the day. Typically this is done using hollow masonry or stone passages as a heat exchanger, although water (typically a tank, pool, etc.) is much more effective than stone on a volume basis.
North Nigeria always has cooler nights than day the difference is considerable.
2) Passive methods - do not require energy input
a) Rather than using clear poly for the cover, white poly can help reduce temperature a great deal. Typically there will be some reduction in light intensity. However, the reduction in temperature can be far greater than light intensity loss, especially in regions with high sun light intensity.
Another commonly used method is spraying clear poly with a paint-like coating called shading compound. The applicator has some control over the level of shading desired by how much is applied. Usually this coating can be removed in a cooler season so that the poly does not have to be replaced.
I will use a shading compound on poly. If the structure is made with bamboo and skills to make bamboo panels exist in the region, I will use bamboo panel as shades rather than poly.
b) Venting at the top of the greenhouse with air intakes lower down can help prevent hot air buildup. Vents are available which automatically close/open at a temperature set point without any power source at all (further info available on request).
I will use vents at top. For bigger green houses, there are wind driven vents which use no electricity.
We have had some discussions about the "chilling machine" on the list. I reviewed this some time ago and have some doubts about the veracity of explanations I have seen about why it works. However, clearly it does, and I think I see why. This leads me to suspect the system is highly dependent on the local weather, thus will work poorly or not at all under some conditions.
My approach is this: A geodesic dome or a tunnel, is not the most important part of the solution- teaching farmers good Agriculture practices will give far more income to the farmers.
Brief bullet point wise good agriculuture practices involve.
u Ensure non-expired VAM mycorrhiza is incorporate in the rooting soil.
u Ensure planting soil has vermicompost, biochar, and VAM.
u Use modified Root Feast methodology for underground wick irrigation.This system does not use a pulsating pressure pump, difficult to maintain filters etc but inserts terrycot material wicks in a drip pipe and feed the water and organic nutrients after sun set by gravity and capillary action.
u Select the crop from a limited set of crops that can be grown like a vine on a trellis.
u Leaves are your enemy; use canopy management to cut them away with disinfected sequencers
Blair was making a concerted attempt to deploy a chilling machine, so perhaps eventually we will hear more from him on the topic. The background work I did led me to suspect that in his climate, there would be some days it would work and others not at all.
I might think of a few more things, but wanted to pass these along in case they were not already on your radar screen. In addition, I thought it might be of interest to others on the list.
Dx G
Ashok
To view this discussion visit https://groups.google.com/d/msgid/geodesichelp/93cbffb0-471b-49a1-b88d-8246d24fda82n%40googlegroups.com.