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Need Air Mover Options for a Couple of Projects

11/03/2017 11:46 AM

I'm working on two things, and could use some ideas for something that will pump air, which I can get off the shelf, or otherwise easily source.

First thing I'm prototyping is aircrete, in order to rapidly and cheaply construct shelters for refugee camps. I've tried doing this chemically, but not quite been happy with the results. Other main way is by making soap foam and mixing it with normal concrete.
For the foam generator I need an air mover which will do about 15-90 psi at about 1-5 litres per second.

The second thing is dry quicksand, made by blowing air through fine sand so that it effectively liquefies.
For this I need about 2-5 psi at about 10 litres per second.

Both things can be the same pump if it'll do all those ranges, or two separate solutions. They can be mains powered and will only be run about ten to twenty minutes at a stretch, so can be manually re-oiled if necessary.

Must be super cheap and easily got in Germany.

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#1

Re: Need air mover options for a couple of projects.

11/03/2017 11:54 AM

Maybe a leaf blower, gas or electric?

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#2
In reply to #1

Re: Need air mover options for a couple of projects.

11/03/2017 12:38 PM

Good flow, really low pressure.

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#13
In reply to #2

Re: Need air mover options for a couple of projects.

11/03/2017 10:06 PM

Yeah, you're right. He wants good flow, moderate pressure, and cheap. An impeller gives good flow but low pressure, but you need a pump for more pressure. So you need a big pump for more volume, I guess, but there goes cheap.

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#3

Re: Need Air Mover Options for a Couple of Projects

11/03/2017 1:31 PM

Good luck with foaming concrete with air, forget soap bubbles. Styrofoam beads (or some other low density solid) is your best bet.

Secondly, you want a fluidizer bed for the dry ? quicksand.

Look here ⇓ for ideas.

Fluidized bed - Wikipedia

You'll need an air compressor also.

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#4
In reply to #3

Re: Need Air Mover Options for a Couple of Projects

11/03/2017 1:47 PM

Styrofoam etc would work well but I'd need to line up a reliable source of potentially thousands of litres of the stuff, which would be tricky.

Fluidiser bed I'd be making, and shouldn't be much of a problem, just need the capacity to put enough air through the thing.

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#5
In reply to #4

Re: Need Air Mover Options for a Couple of Projects

11/03/2017 2:35 PM

Look for a solid, "something" that will decompose and give off gas at the curing temperature of concrete,when it almost solid.

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#6
In reply to #5

Re: Need Air Mover Options for a Couple of Projects

11/03/2017 2:48 PM

I tried aluminium powder, which releases hydrogen and does foam the concrete to an extent, bu requires too much Al for not enough volume. Other options, like acetic acid, soften the cement.

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#7
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Re: Need Air Mover Options for a Couple of Projects

11/03/2017 3:50 PM

I thought that commercial air travel has installed strips of aircrete out past the runway ends to stop airliners that are too hot on the runway.

new construction material is strong, lightweight

https://en.wikipedia.org/wiki/Autoclaved_aerated_concrete

Apparently, this is not made by pumping air into Portland cement or concrete, but is made a completely different way through the use of aluminum powder with lime and fine quartz sand to eventually make calcium aluminosilicate material with many voids initially containing hydrogen, that diffuses out and air diffuses in during autoclaving procedure.

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#8

Re: Need Air Mover Options for a Couple of Projects

11/03/2017 3:53 PM

What about converting a V8 engine. Four cylinders could still be used as an ICE to drive the other four cylinders. Intake and exhaust manifolds would have to be modified to isolate pure air from air/fuel mixture and compressed air from exhaust. The compressor side would need a new, custom cam configuration to open the the exhaust valve shortly after TDC. The compressor half can also be a two stroke instead of a four stroke operation.

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#9
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Re: Need Air Mover Options for a Couple of Projects

11/03/2017 3:57 PM

Or just hook up the V8 to a large compressor, and get after it.

Still going to need something that makes a stable foam with his mix, or it is all a waste of pants.

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#10
In reply to #9

Re: Need Air Mover Options for a Couple of Projects

11/03/2017 4:07 PM

Where's the engineering fun in just connecting two reliable, robust devices together.

Also, I'm assuming the OP already has a method to make a stable foam since they had some plausable attribute requests.

I wonder if sawdust could be used as an acceptable consumable spacer before firing in a furnace.

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#11
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Re: Need Air Mover Options for a Couple of Projects

11/03/2017 4:21 PM

Not sure if that one has ever been tried, I think it ends up in spall hell.

You need a reaction that generates gas that diffuses out after curing, and then is replaced by other gas (air for example).

Could do styrofoam, and then pyrolyze carefully, or just heat cure slightly above the melt temperature of the styrofoam I suppose. Or, maybe avoid heat cure altogether.

engineered foam filled concrete instructions

http://www.drn.com.my/

I see they do not have an outlet in Germany, talk to the folks in England, and convince them you need this.

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#14
In reply to #11

Re: Need Air Mover Options for a Couple of Projects

11/04/2017 8:35 AM

Various ICE mods would be theoretically workable but a bit more involved and bulky than I'm wanting. Also would be nice to keep the setup electric.
I've been playing with Alu powder, which does work but only gives about a 1:1 gas to
solid and I'm looking for about 3 or 4:1 if possible.
High temp curing etc not really an option where it's going.

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#12

Re: Need Air Mover Options for a Couple of Projects

11/03/2017 4:27 PM

I am presuming the Aircrete you are thinking about is not Autoclaved Aerated Concrete, but instead Foamed Concrete.

I also presume that you are thinking of the Little Dragon, or something along that line, for production.

I did a search for air compressor super cheap and easily got in Germany and I got 542,000 results. I looked at every single one of these (well, okay, I looked at three) and saw nothing promising.

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#15
In reply to #12

Re: Need Air Mover Options for a Couple of Projects

11/04/2017 8:37 AM

Autoclaving not an option, non autoclaved aerated concrete works but not enough volume.

The Little Dragon unit is pretty much what I'm trying to reverse engineer and not spend five hundred bucks on.

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#16

Re: Need Air Mover Options for a Couple of Projects

11/04/2017 12:40 PM

Texas Caterpillar morphed into Inexpensive Refugee Encampment

Note: a tipi or teepee is a very efficient shape(read clever) and this post is intended to be only complementary to my brother(a small DNA fraction in my case) Native Americans and hybrids(like me), so all you PC trolls, go elsewhere. As far as refugees, this might contribute to a better(possibly even educational, productive, and dignified) living experience while in a camp with any luck.

Maybe you could use a bigger bubble in your concrete. This caterpillar near Dallas,TX uses rebar/polyurethane form with sprayed-on concrete. For the quicksand, you could build one of these domes, then pump it up with a low flow(cheap) 100% duty-cycle blower to buffer your low duty-cycle high-flow application. I would buy a used HVAC squirrel cage commercial/industrial air circulator to either run the quicksand device directly or via the concrete air tank. Now, back to refugee camp construction(using Peace Corps like) methods:

To do the concrete bubble really cheaply(albeit oddly shaped for a bubble), you could have refugees or a skid steer (eg. Bobcat) build squat concrete teepees. Use rebar and styrofoam(maybe Bluecore) buried in a very large mound of dry sand to make forms for short(eg. 4ft) horizontal slices of teepees. Progressively add sand externally at roughly the same level as you have added dry cement ingredients internally. Yes, the Bobcat driver has to be skilled enough not to damage or move the styrofoam too much. You can put poultry netting against the styrofoam to reinforce it if your Bobcat driver is not skilled enough without it. As one layer of foam becomes close to full, wrap it with another layer of foam a bit farther up but with all layers tilting in so that when your teepee gets taller it takes less material. Attach brackets for a large, lightweight traditional roof vent when the center hole gets small enough. Alternatively, you could also construct smaller concrete vent teepees and install them with a crane on the top of incomplete but larger teepees. More than one layer of nested teepees could implement larger diameter structures. Plan ahead and place large rigging eye bolts embedded inside the narrow teepee hole (even the very top teepee should have a vent hole) so crane lifting is efficient. Leave these bolts inside the finished teepee for adding suspended upper floor levels inside the structure for the primary residents. These techniques build a well-insulated building without concrete sprayers unlike the caterpillar domes in the link. Cheaper, weaker insulation than the polyurethane(used for the caterpillar for build strength) can be employed if it can stand water immersion.

Oh. I omitted a couple of details. All construction is completely dry until it lies embedded beneath the large mound of sand. A large amount of dry sand is placed on top of the mound, then soaker hoses on the surface provide the curing water. Do not make any streams or you will make a big expensive mess. You need to protect the site from even small amounts of water until the mound is complete. The mound will take a lot of sand but the sand (after removal and drying) can be reused for the next project. Locate your refugee camp where sand is available free or very cheap. Just to be clear, there are no voids in the mound. All voids should be filled with dry sand until the curing process is complete. Insulation floats so enough sand must trap the insulation to keep it from moving or exiting the pile. Capillary action will carry water to cement materials if they are not shaded too severely by insulation but some provisions should be made to insure that water quickly saturates the entire mound when the curing process begins. Some combination of total mound flooding, many small holes in the insulation, using progressively removed non-insulation form materials, and/or buried piping could be used to insure complete wetting. Remember that concrete continues to harden the longer it stays wet so avoid extracting your structures as long as you can and maybe even keep them wet for a good long time(eg. >2 months) after extraction if you can. The Bobcat, flowing water, and the crane can all be used to expedite extraction. The truncated cones are an inherently strong shape but the teepees will be heavy. The truncated cones should be shells(meeting whatever building codes apply in terms of thickness and reinforcement) with dry sand forming the center void. A layer of polyethylene sheeting on the ground to keep groundwater from wicking up before the curing step is likely necessary and a foot or two of plain dry sand(no insulation or concrete) is appropriate to allow cure water to also soak in from the bottom once you turn on the soaker hoses. The hoses apply water at the top but getting the entire mound wet is important so enough water must be applied. Some care must be taken to wet it quickly without causing actual flowing water, then as the mound saturates, the water flow can be slowed to a much lower rate, just enough to keep the mound wet for the period of time you have decided to allow for cure.

Larger torus teepees can be construted of two large diameter teepee slices concentrically arranged(one smaller and inside the other but upside down) if a single floor larger structure is desired. This forms a kind of triangular cross-section doughnut with a very nice courtyard.

A teepee can be used as a low pressure tank if the bottom edge is buried and some kind of pressure holding hatch (use a bicycle tire as an O-ring) is used at the top.

This post is intended as just a conceptual guide. Many subtopics come to mind like techniques for doors and windows but I already have a long post, so good luck. Remember, you may not have ANY voids, low-density, large-volume objects that might float, or substantial volume-crushable objects under the mound. Sand and water are heavy. Realize that some (esp. thick) insulation might become significantly compressed or move due to excessive displacement against only the clamping provided by the wetted sand.

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#19
In reply to #16

Re: Need Air Mover Options for a Couple of Projects

11/05/2017 4:01 PM

In high production situations, with some logistical planning, one can form many concentric teepee sections (and/or yurt cylinder walls) in a mound. A thin layer of plain sand in between each concrete ring will allow final extraction from the outside inward. This configuration will yield a far greater proportion of structure volume to mound volume thus requiring far less sand be moved for a given amount of structures produced. The down side is that more care must be exercised in progressive form construction and filling. Your more experienced refugee builders can probably handle this and benefit from the better time-motion numbers. Some innovations will be required to implement concentric forms if you want to fill them using a skid-steer. Notice that a large number of graduated size concentric teepees is nearly the shape of a natural circular mound especially if you start building on a plain dry sand circular mound with the smallest diameter teepee on the center top of the mound and allow the bottom edges of larger diameter teepee slices to fall as they will on the lower edges of the initial mound. Some planning to allow adequate room for the crane-rigging eye-bolts should occur before committing to a specific configuration since this will position each successive outer ring lower on the initial mound than the remaining rings within. Renting a big crane to extract all the cured teepee sections from the wet mound will very likely be necessary. A pressure washer might prove very useful for blasting out the plain sand between the outermost ring and the next to the outermost ring after attaching the crane rigging to the outermost ring and applying a tension with the crane matching the calculated weight of the outermost ring less a small swag. The goal is to have as little movement of the outer ring as possible the instant it detaches from the mound. Planning the route and means of transportation of the extracted rings to their final site will prevent expensive extension of crane rental time.

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#17

Re: Need Air Mover Options for a Couple of Projects

11/04/2017 12:55 PM

A small curiosity on the previous (#16) post. A two layer teepee with a non-tilted lower level is familiar to a lot of people around the world as a yurt, another clever building style. Of course, I have chosen reinforced concrete as a not-very-traditional building material.

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#18

Re: Need Air Mover Options for a Couple of Projects

11/04/2017 4:12 PM

For your liquefied sand high volume low pressure application you could look at a side channel blower. 350mbar@36m³/hr (5psi@10l/sec) is about the output of a 1.1Kw single stage blower that would cost approx £250 (€280, $325) There are lots of German manufacturers but it is worth spending a bit extra to get high quality. Nothing worse than getting to a disaster zone only to find that your blower has failed. Try contacting the manufacturers direct rather than their sales agents as your project could generate enough PR value to warrant them supplying at a hefty discount or with luck giving you a sample in return for credits in any published accounts of the project.

The foam generation high pressure low volume application is pulling up to 6 bar. The higher end is only possible with a compressor and that means high cost. Screw compressors are generally more expensive that reciprocating compressors but if you have to produce 18m³/hour that is very a big recip. and a screw of that size may well be cheaper.

Your turn down ratios seem high and I suppose that they reflect that your are still experimenting with foaming agents. But bear in mind that a side channel blower that will deliver 36m³/hr@350mBar (5psi.) will produce 120m³/hr@120mBar (2psi.) so work towards reducing the pressure rather than the flow. Equally there is no price difference between a compressors with equal flow rates producing 90psi. or 60psi. but a compressor delivering 1litre/sec is ¼ the price of one delivering 5 litre/sec so work towards reducing the flow in that application.

A tip based on experience. Consider spending as much on air intake filtration as you spend on the compressors. These machines will be working in an atmosphere loaded with fine blown sand particulates. Try to compress that air without first removing those particulates and you can count the life of your compressors in weeks rather than years.

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#20

Re: Need Air Mover Options for a Couple of Projects

11/05/2017 9:57 PM

What about using the foam concentrate used by firefighters? If workable, I have seen it available in 5-G containers.

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#21

Re: Need Air Mover Options for a Couple of Projects

11/06/2017 5:48 AM

Cheers yall for options, I'll be checking them out.

If I end up with something like a car A/C compressor, can I get suck the air/water/detergent mix in and through it without issue, and will that keep it lubed enough to avoid damage?

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#23
In reply to #21

Re: Need Air Mover Options for a Couple of Projects

11/06/2017 8:50 AM

God no, don't do that, use an eductor. It sucks the other (mixed) ingredients into the air stream.

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#22

Re: Need Air Mover Options for a Couple of Projects

11/06/2017 8:49 AM

The consensus seems to be moving toward large piston compressor, or a screw compressor. How about you lease one of the standard screw compressors available through construction equipment outlets? You might find you production rate of air-foamed concrete is less, but this should be a fairly attractive cost level.

What would be the harm in mixing styrofoam beads with concrete, and letting it cure in a domed mold? That could lower the panel/dome weight sufficiently to allow human power utilization for putting the finished work in place.

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#24
In reply to #22

Re: Need Air Mover Options for a Couple of Projects

11/06/2017 8:53 AM

Styrofoam would probably work fine, but I'd need a local source of potentially thousands of liters of it, which can't be relied on.

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#25
In reply to #24

Re: Need Air Mover Options for a Couple of Projects

11/06/2017 10:03 AM

Walk in the woods and see if there is something else, like a wood or cereal grain that can be expanded to make a rigid foam to simply add. Puffed wheat?

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