I'm working on a project for above ground water storage tanks for people in Burma who earn less than $1/day. Thick plastic sheeting is the most economically viable solution, but when sewn, springs leaks. So I thought origami would be a useful and elegant solution.
Here's the basic parameters of the shape I need in the end. In essence it's a low, large cup, with walls that slant ever so slightly inward (but definately not outward). It will be filled with many gallons of water and hence there is a lot of pressure on the walls outward. Is there a way to use this pressure to induce the walls to stiffen up? or put another way, is there a way of using hte outward forces to tighten the folds that hold the walls up? A starting point for an idea might be to think of a finger trap: as you pull your fingers outward, it tightens down.
I'm not very familiar with origami, so I'm counting on you guys!
Folding for poverty
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wolf
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I assume you're talking about using a no-sewing-required solution for your problem. If that's the case, unless there's some special requirements that you need, eg the storage tank needs to be collapsable and fitted into a small space when not in use, you're better off using conventional engineering solutions, aka glue or some other adhesive to hold things together.
For one, the materials properties of paper and plastic are very different. With paper, you can do tension folds that tighten under pressure (up to a certain extent); this however depends a lot on the surface friction, something that plastics generally don't have much of.
The next problem is one of scale - physical and material properties don't always scale up nicely, the simplest example being that of the volume/surface area ratio. A small tabletop sized model may work adequately to hold a litre of water, but if you attempt the same thing with a water tank a few meters across, you're likely to find that the whole thing may just fall apart, as the large size now means that the weight of the material used must now be considered, whereas it could be simply neglected in a smaller model.
Finally, folding large structures is a very inefficient use of time and material. A sturdy structure will require several support folds, which means that you're going to need an extremely large sheet of material to start with, if you want to get something of a decent size. Handling this material now becomes a multiperson effort, for example, one person to hold down one corner, another two to fold this edge to that corner, etc. It will probably turn out to be cheaper, in terms of cost and labour, to build a such tanks using conventional engineering techniques.
----------<origami purists, don't read any further - you have been warned!>----------
Now, you've stated that the main problem is with the stitching of the plastic, as it causes leaks. Which means there are two possibilities - get rid of the stitching altogether and use some other means of holding the material, or find out how to stitch the tank together such that the stitches do not end up in a place that causes water leaks. For example, if we consider the traditional folded paper cup (instructions are all over the net), we see that the raw edges of the paper all lie at the top of the cup. The two flaps that are normally folded down at the last step are external to the cup, so we can ignore them for now. Water leaks will only occur at the raw edges, so if you fill up the cup below that line, the cup will hold water indefinitely since there's no open edges of paper to leak from.
[img]http://img216.imageshack.us/img216/6659/cup11hk.gif[/img]
Now, a storage tank sized plastic origami cup is not going to be able to hold itself together from the strength of the folds alone (neither do you want it too, it's always good engineering practice to have redundancy), so all you need to do is to stitch around the top. Since the stitching occurs above the 'water leak' line, you can fill the cup almost to the brim and it will not leak.
Naturally, this is not the most efficient way of making a storage tank; we want to maximise the container volume for a given area of material. So here's another solution:
[img]http://img155.imageshack.us/img155/6584/cup24ay.gif[/img]
Again, as with the paper cup, all the raw edges are at the top of the tank, where they can then be stitched without causing leaks. This is a more efficient use of material compared to the paper cup, but as to whether it is the most efficient, I'll leave that as an exercise for the reader.
For one, the materials properties of paper and plastic are very different. With paper, you can do tension folds that tighten under pressure (up to a certain extent); this however depends a lot on the surface friction, something that plastics generally don't have much of.
The next problem is one of scale - physical and material properties don't always scale up nicely, the simplest example being that of the volume/surface area ratio. A small tabletop sized model may work adequately to hold a litre of water, but if you attempt the same thing with a water tank a few meters across, you're likely to find that the whole thing may just fall apart, as the large size now means that the weight of the material used must now be considered, whereas it could be simply neglected in a smaller model.
Finally, folding large structures is a very inefficient use of time and material. A sturdy structure will require several support folds, which means that you're going to need an extremely large sheet of material to start with, if you want to get something of a decent size. Handling this material now becomes a multiperson effort, for example, one person to hold down one corner, another two to fold this edge to that corner, etc. It will probably turn out to be cheaper, in terms of cost and labour, to build a such tanks using conventional engineering techniques.
----------<origami purists, don't read any further - you have been warned!>----------
Now, you've stated that the main problem is with the stitching of the plastic, as it causes leaks. Which means there are two possibilities - get rid of the stitching altogether and use some other means of holding the material, or find out how to stitch the tank together such that the stitches do not end up in a place that causes water leaks. For example, if we consider the traditional folded paper cup (instructions are all over the net), we see that the raw edges of the paper all lie at the top of the cup. The two flaps that are normally folded down at the last step are external to the cup, so we can ignore them for now. Water leaks will only occur at the raw edges, so if you fill up the cup below that line, the cup will hold water indefinitely since there's no open edges of paper to leak from.
[img]http://img216.imageshack.us/img216/6659/cup11hk.gif[/img]
Now, a storage tank sized plastic origami cup is not going to be able to hold itself together from the strength of the folds alone (neither do you want it too, it's always good engineering practice to have redundancy), so all you need to do is to stitch around the top. Since the stitching occurs above the 'water leak' line, you can fill the cup almost to the brim and it will not leak.
Naturally, this is not the most efficient way of making a storage tank; we want to maximise the container volume for a given area of material. So here's another solution:
[img]http://img155.imageshack.us/img155/6584/cup24ay.gif[/img]
Again, as with the paper cup, all the raw edges are at the top of the tank, where they can then be stitched without causing leaks. This is a more efficient use of material compared to the paper cup, but as to whether it is the most efficient, I'll leave that as an exercise for the reader.
Ok, no offense is intended with this post at all, this is NOT sarcastic. Thanx for pointing out the pro's and con's of the approach. Let's from here on post only constructive ideas and solutions to the above mentioned problems. Remember, this can save lives. I know there is some way in which the origami community can help in this cause. Ok?
There is a time for everything, that time has been pre-ordained be almighty God. Trust Him, and no harm shall come to you. He will keep you safely inside his loving hands.
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wolf
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Look over the posts again - a few solutions were already posted.Tjips wrote:Let's from here on post only constructive ideas and solutions to the above mentioned problems.
That's the point I'm trying to make - whatever solution that's finally employed needs to be extremely robust, if you want it to be worthwhile. Elegance, coolness, etc, needs to be ditched in favour of structural integrity. My experience from doing relief efforts is that we get a lot of stuff from well-meaning folk - but many of these are short term, stop gap solutions, which come apart when push comes to shove. A lot of quick solutions result from fixations on using only one particular method (or to promote one organisation's personal agenda) to solve a problem. That doesn't help the folk on the ground at all, and they're more likely to think you're an idiot for foisting ill-suited and unreliable stuff on them.Tjips wrote:Remember, this can save lives.
An inventor friend of mine, Bob Wulkowicz, designed something that's at least half a possible solution to your problem. When working for the Chicago Park District he wanted a cheap way to build plastic walls around trees so he could fill them with water that would seep in thru the bottom & prevent the trees from dying of drought.
What he came up with was this: you know those plastic bags you get at supermarkets for fruit? They basically consist of a long plastic tube that is heat-sealed every foot or so to form individual rip-away bags. So they are available from the manufacturer in the pre-heat-sealed state. He takes the long plastic tube, lays it in a big ring around the tree, attaches and turns on a fire hose in one end; the other end goes inside the ring. The tube first fills up and forms a stable wall; then the whole interior fills as a shallow pool. The water eventually seeps down into the ground through the open bottom over a period of days. --Simple, cheap and brilliant.
In short, the walls and water pressure side of the problem is perfectly SOLUBLE. I see no reason a solution that is hermetically sealed at the bottom too and uses origami should be ruled out in advance.
Possibly walls could be made using this sort of water filled plastic 'tubing', and a tarp laid over the top onto which the water was poured (it will sag into the cup shape and fill). More information on the height of the walls, the width of the pool, how long the container is supposed to last and under what conditions--heat, rain, hail etc.--is needed before really proposing an answer.
Anyway I love problems like these, and will think about it some--and maybe forward a copy to Bob too. Thanks for bringing it to our attention
Saadya
What he came up with was this: you know those plastic bags you get at supermarkets for fruit? They basically consist of a long plastic tube that is heat-sealed every foot or so to form individual rip-away bags. So they are available from the manufacturer in the pre-heat-sealed state. He takes the long plastic tube, lays it in a big ring around the tree, attaches and turns on a fire hose in one end; the other end goes inside the ring. The tube first fills up and forms a stable wall; then the whole interior fills as a shallow pool. The water eventually seeps down into the ground through the open bottom over a period of days. --Simple, cheap and brilliant.
In short, the walls and water pressure side of the problem is perfectly SOLUBLE. I see no reason a solution that is hermetically sealed at the bottom too and uses origami should be ruled out in advance.
Possibly walls could be made using this sort of water filled plastic 'tubing', and a tarp laid over the top onto which the water was poured (it will sag into the cup shape and fill). More information on the height of the walls, the width of the pool, how long the container is supposed to last and under what conditions--heat, rain, hail etc.--is needed before really proposing an answer.
Anyway I love problems like these, and will think about it some--and maybe forward a copy to Bob too. Thanks for bringing it to our attention
Saadya
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emmistanford
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clarification on problem
Thanks everyone for your great comments! It's helped point out the parameters of the problem. I want more!
i wanted to clarify a few point on the problem.
firstly, Myanmar (Burma) is a country that is almost complete cut off from outside manufactured goods because inport taxes are so high. As an example, a car, in US dollars, cost at least $50,000. So imported solutions seem like a dead end.
Secondly, in Myanmar, manufacturing is pretty basic. As an example, when welding metal, because they can't afford (or there aren't available) welding glasses and welding will blind you pretty fast, they simple shut their eyes i.e. they weld metal blind (think about that a second, can you imagine building a frame out of metal with your eyes shut?). While welding plasitc is a likely possibility, the low-tech manufacturing concerns me, hence if folding were possible it would be 100% feasable.
Thirdly, this will be used by people filling up metal watering cans at least 8 hours a day. Crops are water every free minute of the day. So it needs to be very durable. Stitching or welding creates an obvious stress point, again a reason to consider folding.
And now a few detalis concerning the material itself. It's a woven together plastic material (i.e. it has a wharf and a weave). Two layers of this stuff is stuck together somehow in the manufacturing process, which makes it water proof. This may be beneficial for folding, because there are obvious crease lines.
I would really like to hear what more you guys have to say about the topic, because it could make delivery and set up so easy and cheap. As another though i had on how it may work, I was thinking of making a basket, where there is a strap that goes from one wall to the opposite wall. as the water pushes the walls outward, the strap would hold it back together. I know this means you have to cut the paper - a no no for oragami purists - it might get your imagination going.
i wanted to clarify a few point on the problem.
firstly, Myanmar (Burma) is a country that is almost complete cut off from outside manufactured goods because inport taxes are so high. As an example, a car, in US dollars, cost at least $50,000. So imported solutions seem like a dead end.
Secondly, in Myanmar, manufacturing is pretty basic. As an example, when welding metal, because they can't afford (or there aren't available) welding glasses and welding will blind you pretty fast, they simple shut their eyes i.e. they weld metal blind (think about that a second, can you imagine building a frame out of metal with your eyes shut?). While welding plasitc is a likely possibility, the low-tech manufacturing concerns me, hence if folding were possible it would be 100% feasable.
Thirdly, this will be used by people filling up metal watering cans at least 8 hours a day. Crops are water every free minute of the day. So it needs to be very durable. Stitching or welding creates an obvious stress point, again a reason to consider folding.
And now a few detalis concerning the material itself. It's a woven together plastic material (i.e. it has a wharf and a weave). Two layers of this stuff is stuck together somehow in the manufacturing process, which makes it water proof. This may be beneficial for folding, because there are obvious crease lines.
I would really like to hear what more you guys have to say about the topic, because it could make delivery and set up so easy and cheap. As another though i had on how it may work, I was thinking of making a basket, where there is a strap that goes from one wall to the opposite wall. as the water pushes the walls outward, the strap would hold it back together. I know this means you have to cut the paper - a no no for oragami purists - it might get your imagination going.
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wolf
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Re: clarification on problem
I think I know the kind of material you're talking about, and unfortunately, it doesn't really hold a crease well - soft plastics just don't hold a crease, while for harder plastics, creases are extremely stressed points where a crack will spring up fairly easily (just try creasing a plastic transparency sheet - it'll snap in two after a while).emmistanford wrote:It's a woven together plastic material (i.e. it has a wharf and a weave). Two layers of this stuff is stuck together somehow in the manufacturing process, which makes it water proof. This may be beneficial for folding, because there are obvious crease lines.
'Welding' this plastic is in a sense possible - just melt it over a flame and let it harden again! An adjustable blowtorch would work nicely for this, perhaps even an impulse sealer, if it can go hot enough. All you need to do is to work out the optimum temperature to do this at - too low and it will just split apart, too hot and it will cause certain parts of the plastic to neck and break off.