Mechanized green building techniques

     I hope to use this thread to explore many methods of utilizing machinery in order to reduce the amount of manual labor required with various green building techniques. I believe that the mechanization of laborious processes is absolutely essential if we are ever to bring green building techniques into the mainstream of North America home construction.

   I am 100% committed to doing this on my own projects and will probably use or rent out equipment for projects belonging to others. I haven't fallen in love with one particular material or technique as this would not serve me well in my endeavors.

     So I hope this doesn't turn into some sort of ideological debate as to whether or not machines should be used. Instead please accept that I'm going to use them and thousands of other people are going to, so therefore we should obtain the right machines and use them in the most safe and efficient manner possible.

  I have no interest at all in preserving any traditional techniques unless they prove to be better and faster. Rather, I would like to find ways to update those techniques using any and every mechanical device which is practical.

  There are  huge opportunities for improvements in labor efficiency in cob construction, cordwood cob, woodchip clay, earthen floors, green roofing and probably in other fields which I haven't mentioned here.

    I think just about every building system could be improved with mechanization with a possible exception for igloos.

  I'm not going to dump all of my own ideas here at once since that would produce several hours of reading . Instead let's post each labor saving technique or machine as a separate post so that this thread may be quickly referred to should one of us want to review something. Sometimes there are good YouTube videos which could be referred to. And there may be many techniques which some of us have developed but not shared. I'm taking a break now and will go first if nothing has appeared by the time I return.    Thank you: Dale

First a question. Has anyone used a hammer drill to compact the surface of cob walls?

   I am thinking that if a flat steel foot could be attached which would allow the drill to spin without spinning the foot, this could make a lightweight power tamper. For my purposes this would be used to tamp materials into formwork similar to what is used in rammed earth construction. I'll be using cordwood cob built within a form work with two or 3 inches of space at each log end filled with compacted cob. I could also see a device like this being used against the formwork in order to compact the finished face of the material before the forms are removed.

   Another method of achieving this same goal might be to use a pneumatic hammer with a flat plate attached. This same tool could be used as an edger when tamping earthen floors. Plate tampers work well for large floor areas.

   They make pneumatic hammers for the rammed earth industry but they are far too powerful for the type of formwork I'll be using as I only require enough compaction to make the materials stay in place whereas with rammed earth the materials must be compacted like stone since they are structural. My structure will be held up with post-and beam so the cordwood cob is simply infill.

        I've seen numerous methods of mixing cob demonstrated on YouTube. My computer skills are such that I have no idea how to bring those over to here. I like the idea of mixing it with the front-end loader of a farm tractor or bobcat. Driving over it continually with a truck might also work. On another thread I described how I envision mixing it with farm animals tied to a horse walker. That led to an unfortunate battle of wits with an unarmed man who believed that machines should never be used . It ended with deletions and one of those play nice notes from Paul.

    I watched a really good YouTube video which showed a highly mechanized method of mixing woodchip clay. It was done on a native reserve which I believe was in Michigan.

    I'd like to try something as simple as mixing woodchip clay with a Rototiller. Any information you may have on mixing cob with a Rototiller would be appreciated.

    I was thinking of doing some sort of clay slip over the course sawdust since there is a Cedar Mill 1 mile from me and I can have sawdust delivered in huge bins. Has anyone used clay slip sawdust?

   And finally a huge adaptation of the tarp method of mixing cob. My crane reaches 32 feet high. If I were to use a giant tarp that is strong enough to contain one or 2 tons of material it might be possible to roll it back and forth with a swing of the arm. Then rather than stomping on it as is usually done it could be driven over with an ATV or other light vehicle. I won't try this unless I stumble into some free canvas or other tarp type material since this could end in a badly damaged tarp.

   A few years ago I did some materials testing where I mixed cob with wood chips. The cob was mixed with a Rototiller and wood chips where worked into it by stomping. The resulting blocks dried quickly and were able to hold nails.I've also done some testing on used gypsum.

   I think we should also use this to post material testing and adaptations which are of a mechanical nature.

Mechanization to reduce labor costs for green building techniques? To me that means SIPS. Not a perfectly green product but arguably just as green as anything else. Its super energy efficient because its easy to make airtight and continuously insulated. They are largely built in a factory close to the labor force and dont require quality, older growth timber. Most importantly, they erect on site by the same set of skills used by traditional framers.

Most objections are due to the foam understandably. However, foam is mostly air and considering the permanence of the building envelope its a great use of this precious resource.

I'm facinated by insulated concrete form construction, by using foam molds and leaving them in place you get the strength and thermal mass of concrete with total insulation coverage

Personally I think thermal mass makes *much* more sense than super-insulation. Being bulletproof is kinda handy though...

I disagree that thermal mass is more important than super insulation but I guess it depends on what your definition of "super" is. There is a diminishing point of return but much more so with Thermal mass.

Unfortunately, most of the thermal mass in ICFs is not completely inside the conditioned space which means there is very little benefit from it. The thermal mass of uncarpeted concrete slabs is much more effective.

My biggest issue with ICF is the very high labor costs. Concrete is strong and durable but for the same reasons its difficult to work with and change. Concrete and steel have some pretty high embodied energy too. My favorite thing about ICFs is just what you mentiond Brice, "total insulation coverage". Pre-cast concrete panels is a great substitute for ICFs plus you get the decreased costs through the factory mechanization.

  Any debate regarding the merits of thermal mass versus super insulation must be taken with geography in mind. If I were building in Alaska north of the Brooks Range I would only consider super insulation and these panels would be invaluable.

    If I were building in Arizona where there is a large di-urinal temperature swing then thermal mass would be very important.

  Where I live on Vancouver Island I get plenty of sun and at most times of the year there is plenty of daytime heat which may be stored for nighttime use so I'm including plenty of thermal mass. Someone on this same island, closer to the coast and shaded by a mountain would not benefit nearly as much from big solar windows and massive thermal storage.

  So for me thermal mass is very important. I'm building my rocket mass heater into a Trombe wall and using earthen plasters and heavy flooring materials. Since the climate is relatively mild I don't need super insulation. But I would certainly go that route if I live 1000 miles north of here or if I was in a hot humid area. Hot dry areas tend to cool down or at night and thus benefit greatly from thermal mass.

    If I had to point out one major deficiency in North American home-building it would be lack of thermal mass but I believe number two would be inadequate insulation. I guess after that I'd have to say forced air heating and carpeting which are two of the worst ideas ever to come along.

I agree with Dale in that geography plays the key role in determining mass vs. insulation. In most places though, houses benefit from having an insulated exterior shell, with mass storage on the inside using mass floors and/or mass half walls or interior walls.

I fail to see the high labor costs of ICF's, in fact I would say the opposite is true. ICF forms are generally very light and lock together in a pretty straightforward manner, as opposed to SIPS or factory cast concrete panels (who uses those?).

Thanks for the link Dale! Rocket mass stoves are brand new to me so I appreciate the enlightenment. Combining them with trombe walls is very inventive and hope you will keep us posted on the results.

Iam sure you can understand my skepticism. Perhaps there is a better topic in this forum to ask questions about it? My main concerns with it initially is indoor air quality. Steam might be beneficial to some but generally for those of us east of the Mississippi its a problem. Any smoke inside a home should be a major concern to everybody.

Oak Ridge National Labs has done the most research on thermal mass benefits and from what I recall, Bakersfield CA and Phoenix are the only two areas of the US that thermal mass only walls can make sense. Both of which are high desert areas with consistent wide dirurnal swings. You certainly dont need to go as far as the Brooks range for insulation to make more sense than thermal mass.

I would say the major deficiency of NA home building is air infiltration followed by insulation. Thermal Mass is way down the list after the likes of attached garages, ducts in unconditioned spaces, and ventilated crawls and attics.

I agree with carpeting being a bad idea but forced air is one of the greatest things most homes can have.

  I always thought those panels were big labor savers. How is that they consume so much labor?


    I didn't realize I was creating a link. This site does that automatically when we use certain phrases.

    I'm assuming you've watched a video where there is lots of steam coming out of the exhaust. A certain amount of this will happen in any cold environment as water vapor condenses upon contacting cold air outside. With the video in question I believe this is the first firing, so they are purging the system of water.

                            The stove does not add humidity to the building.

      When the cob is curing it will lose plenty of moisture to the home, but once it is cured it would be no different than having bricks or a chunk of concrete sculpture within the home. I started a thread called ," building rocket mass heater long before the house is finished". I think that may be where I explained how I'll turn my rocket stove into a dehumidifier. Other than boiling a pot of water on the heat riser, I can't think of any way that this type of stove would add to humidity. Clay is naturally hygroscopic, it wants to absorb moisture. During periods of disuse it's more likely that your rocket stove would absorb some humidity. This moisture would be cooked out when the stove is fired next.

    I've given rocket stove design many hours of study and I fully expect to be a leader in this field at some point but most of my efforts to this point have been mental and I've only mucked with a small amount of clay. But this doesn't worry me since I've invented other things completely within my head and seen them work later. With some design changes a rocket stove can become a Trombe wall, an air-conditioner/dehumidifier, an exhaust fan, a water heater, a dehydrator, a light source, a cooking device, a smelter, a clothes dryer, and a power source for refrigeration and electrical generation .... And who knows what else. From the videos and photos I've seen most people are content to form there thermal mass into a bench. I like this but I intend to form cob into any shape I require for my indoor spa swimming area.

      The idea of me developing multiple new uses for thermal mass heaters is rather presumptuous of me and I realize that, but I like the idea of pushing the limits of otherwise simple technologies. It makes sense for me to do this since I intend to house many people and therefore I won't personally bear the cost of all the tinkering. Besides that I like to experiment. Better that I do this than fiddle with cars or other things which have been done to death. We have a member named "donkey" who leads a rocket stove development forum which discusses and exhibits many experimental designs. He generously invited me to join and I'm sure to learn plenty and I'll contribute things which I learn on my own.

     As for smoke in the house, this would only occur if there where some sort of malfunction. Smoke in the house is much more common with regular woodstoves which can suffer innumerable draft and airflow problems. Overall, having a rocket mass heater should increase indoor air quality.

     And back to my unpopular opinion concerning forced air heat. Forced air heat exists as an expensive, dirty, and wasteful means of coping with poorly built housing. I've lived in several homes heated with hot water and other radiant means. They are more comfortable, temperature swings are smaller with far less temperature stratification and these systems don't blow dirt around and become home to cockroaches, dust mites and years of accumulated pet hair. Often when I demolish buildings I'm appalled by all the horrible crap which accumulates within the ductwork. In most cases these system exists in order to maintain comfort within homes that were never designed properly. Thus they are a Band-Aid solution covering up a total system failure. This is more true in my climate than where you are. In areas requiring air conditioning, some ducting is often necessary. I have installed forced air heating in the past but I will never again use this antiquated technology.  This is probably not one we're going to agree on immediately and that's okay.

    Everything I intend to build will be designed to allow for plenty of airflow between different zones of the house and I hope to always be able to take full advantage of solar orientation. My parents live in a house which I can't see heating by any other means other than the forced air system it contains. It could be done but at great expense But their house is a poorly constructed 1970s model with too many rooms and too much separation. A large percentage of North American housing is built this way but the fact that it's commonplace has no bearing on whether or not it's crap.

Thanks for the extra insight. One of the things that makes this stuff so interesting is there are so many situations with so many different solutions.

In defense of ducts: Forced Air with ductwork is usually less expensive than radiant systems. As for Indoor Air Quality, good designs should include filters at the return grills and good construction practices keeps the debris out. Iam happy to say my ductwork installed in the 20s is working great and dust free (its an oil furnace with no AC through it). It was pretty easy to clean out when I bought the place. ERVs and HRVs are probably the best way to achieve the best Indoor Air Quality IAQ and they almost always rely on ductwork.

I would say most of the homes Ive seen on this site are too small to require ductwork. Any homes that have two levels and three bedrooms usually make sense to have ducting depending on the system, especially for homes with AC as you implied.

I have a few more questions about the rocket mass heaters. From the link that was created about them: "exhaust is nearly pure steam and CO2 (a little smoke at the beginning)" All the designs Ive seen so far have the intake going sideways or downward. I cant imagine not having smoke in the beginning without a fan involved. How in the world would they increase IAQ? Should I start a new thread with these questions?

Search for the rocket mass heater thread in the alt energy sub forum. There is a ton of good info there. Or buy the book.

   I believe a youtube search specific to lighting rocket stoves will lead to best methods. The initial fire is usually started by jamming paper deep into the chamber.                 

    On the ductwork  – I plan to build as large as they will let me, possibly 5000 ft.² with no intention of including ductwork. I may put an occasional in wall fan to move air from one zone to another.


    Now back to the original point of this thread. Does anyone have any insight as to how we can utilize machinery to make various green building techniques more efficient?

SpringtimeHomes wrote:
I would say the major deficiency of NA home building is air infiltration followed by insulation. Thermal Mass is way down the list after the likes of attached garages, ducts in unconditioned spaces, and ventilated crawls and attics.

high insulation with no mass = air infiltration problems... or to put it another way... stuffy houses where I can't open the window without all the heated air exiting. Mass with outside insulation means heating the mass. The insulation keeps the mass from cooling and the mass warms the body directly. because the mass is the main store of heat instead of just the air... I can have fresh air come in without all my heat going out... a much healthier home to live in. The air may be cooler than 72F. but feels comfortable anyway because of the warm radiation coming from the mass.

I agree with carpeting being a bad idea but forced air is one of the greatest things most homes can have.

Nix on the forced air. Heating the whole house to use one room with a gas furnace that calculates 85% eff. as 100% (15% of the heat from the gas just to make sure the flue works isn't counted... we won't even start on gas water heaters which are worse) I am not that rich. Forced air heating is wasteful, unhealthy and inefficient. I got rid of gas... heating and water... and now pay about $200/month less to heat for the last two years. thats using E-heat which costs more per energy unit than gas... But we only heat the bedrooms at night (2 out of 3 because one is unoccupied) and the dining room in the morning and evening. The kitchen gets enough heat from cooking... the living room is cool, but gets enough from the other rooms that it is only a few degrees less.... If we had forced air we would have to wear sweaters every where all the time... this way we have a few rooms that are comfortable... for less money.

To each his own....

One way to mechanize would be to use a cement mixer for the initial mixing for cob.  Most of us won't have access to the big ones on a truck, so that leaves the portable ones, from which a single batch probably won't be enough to complete a project of any size.  One idea may be to create a frame for the thermal mass stucture, then pour each batch into it, so there is a combination of creating the structure, while it does a primary cure - in place.   I'm thinking of how I can create a rocket/thermal mass stove in the basement that will be portable.  I live in one of those 1970's ranchers, and will be putting it up for sale in the future - I seriously doubt that one of these heaters would be a welcome sight to a prospective buyer.  I get that a stove can be portable, but the accompanying thermal mass of any length would be problematic.  I'm thinking of salvaged industrial ductwork to dump cob into, over stove pipe buried in the middle.  I'm wondering how heavy, & what kind of wheeled platform it could be installed upon. 

I saw a youtube video where a guy was mixing cob with a garden tiller. He said old dull tiller blades worked better than sharp blades.

Here's a description of making cob using a front end loader and tractor:

http://www.grisb.org/publications/pub22.htm

I also love technology, from low-tech to high-tech to app-tech, and I worked as a bike mechanic for eight years, so this machine rocks, literally:

A roofing tile machine at Maya Pedal - Microconcrete Vibrator for Roofing Tiles - http://www.mayapedal.org/machines.html

This machine produces the vibrations required to force air bubbles out of concrete. This produces long-lasting, impermeable concrete that is moulded into roofing tiles. The roofing tiles are attractive, durable, and create better insulation than the ubiquitous corrugated metal roofs.

I've seen these tiles in place and they work well, withstanding the absurdly heavy rains we get here sometimes (i.e. hurricanes) without a drop. They made the tiles on site.

I don't expect it'd take much to design a mobile tamper or a concrete vibrator, erm.

And there's a rather more hi-tech project going on here: http://opensourceecology.org/wiki/Main_Page

They have a bunch of stuff including open-source plans.

I would love to find some plans for the roof tile machine.  That would have a huge impact on my village in Northern Mexico.

velacreations wrote:
I would love to find some plans for the roof tile machine.  That would have a huge impact on my village in Northern Mexico.

They're very friendly at Maya Pedal and would probably send you a free copy, even though that specific one is not available on their site.

I'll check it out.  I have done a lot of ferrocement and laminated ferrocement, and I could see something like this being very useful for making panels for roofs or water tanks.

Yeah, If you find anything about home made tiles I'd like to see it too. I think about it now and then, but haven't gotten too far with it.

Here's ECO Sense's description of using rototiller to make cob:

http://www.islandnet.com/~anngord/builders.html#slic

It seems they take the wheels off the tiller.

    I've seen quite a few good YouTube videos and the consensus seems to be that cement mixers are ineffective because they gum up and just rotate the material round and round. I'm definitely leaning towards using a farm tractor since it can mix material and hoist it on to scaffolding.

    The pneumatic hammers used in rammed earth construction would be useful for my purposes if a scaled down version is available. I don't want to blow my forms a part with unnecessary pressure and I don't want to lift the machine which is too heavy for but job.

   I'm wondering if there is any sort of power troweling device meant for walls. I've used the big ones for concrete slabs. Or some vibrating plate machine in the 20 pound range might be suitable.

ronie wrote:
Yeah, If you find anything about home made tiles I'd like to see it too

I spoke with MayaPedal and their bicycle-operated cement tile machine costs $160 here in Guatemala, including the tile mould. CargoExpress would be the company to approach for transport. They don't have CAD plans yet but they're working on them.

I spoke with MayaPedal and their bicycle-operated cement tile machine costs $160 here in Guatemala, including the tile mould. CargoExpress would be the company to approach for transport. They don't have CAD plans yet but they're working on them.

How many molds come with the machine?  Do you have a contact that I can speak with via email (PM me, I speak Spanish).  The tile machine doesn't seem to be the hard part to build, but the molds could prove to be difficult to make 100 or so for a day's production.

I've done some research into the microconcrete tiles, and they are indeed very interesting, and probably very practical in an area like mine where cement and labor are cheap, but roofing metal is somewhat expensive. I could see them being a very beneficial local business around here.

I haven't really seen any open source designs for building the vibrating table or tile molds.  You can by the "kit" from several places in India, China, and Latin America, but I don't think it would be difficult to build the machine.  The molds will require precise manufacture, so either pay for some sort of plastic mold or possibly use an existing shape, like the profile from a metal roof sheet.

A DIY/open source design could really make a difference.  If I get anything going, I'll be sure to make plans and a how-to for others to follow.

If an owner/builder was able to source a decent mold, I think it would be very practical for producing the tiles on the home site, maybe 100 or so a day (100 square feet a day), without much effort or labor.

I'll continue to source machines, molds, and designs, and see if there is anything that is practical on the DIY/backyard level.

velacreations wrote:

I haven't really seen any open source designs for building the vibrating table or tile molds.

Heres a video on making a vibrating table:

http://www.youtube.com/watch?v=GWImU7CCU8g

We have vibrators at work for lining paper up. The vibrator is just a motor with a bolt stuck sideways into the shaft. This unbalances things and it vibrates like crazy. The motor is mounted on the bottom of the table top and the table top is mounted to the frame with thin nylon strips to act sort of like springs. I think ours had a speed control too so it could be turned down so that the papers didn't bounce off onto the floor

The moulds shouldn't be that hard... Though I could see some serious time getting them just right. I guess both the top and bottom have to be moulded. Once one is figured out though, the rest would be easy. Start with minimum slope and minimum thickness of tile for strength. Double that thickness for overlap and figure out length of tile up or down the slope for no leaks... maybe make it bigger for faster install/fewer moulds... but also not too big heavy/fragile. Width can be one pattern or a multiple... one is probably best. Is there a separate mould for the top (or other) ridge?

I can think of two ways to make a mould.

- take a tile I like cover with plastic and make a mould from it (with the same cement even)

- use various wood pieces glued or fastened together to make the shape.

The second is legally safer

I would think a heavy duty hammer drill would do the trick for a handheld vibrator. It has a hammer type mode so it basically operates like a mini jack hammer, to chip concrete. Have a fabrication shop modify a bit with a metal foot on the end instead of a chisel and i would think that would work for a mini tamper that could fit in a form.

Also, what about just using human weight in the form?

Mecahanized green building technique: Energy Recovery Ventilators ERVs or Heat Recovery Ventilators HRVs are mechanical ventilation providing fresh outdoor air to homes in a balanced and energy efficient manner. They usually require ducts which could also be considered forced air.

I helped install some of these when I lived in the cold winter climate of Ontario 20 years ago. There were plenty of problems with mold in homes which were built much too tightly. They called them air to air heat exchangers at that time.

I believe these things are best utilized in homes which contain plenty of toxic building materials. Homes which contain lots of glue together strand board, vinyl flooring, polypropylene carpeting and other horrible stuff require much more ventilation than those built of natural materials. So although these venting systems work, they don't exist just to save energy. In many ways they serve to make sick buildings habitable.

In the relatively mild winter climate of southern Vancouver Island these would make no sense for me. A south facing sun room provides an excellent pre-heater for air which may be drawn through the home simply by opening an upper window.

I remember when I was helping market heat exchangers they told us that all of the air in a home needed to be changed every half-hour. And I could see that making sense if you're swimming in chemical stew. But in a home constructed of safe, non-toxic materials I just can't see the need for that much ventilation especially if there are plenty of plants and other air purifiers within the home.
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I really like the idea of converting a hammer drill to a tamper. That's why I described it in detail at the beginning of this thread.

Good point Dale. I absolutely agree that the more VOC laden materials used the more important ERVs and HRVs become. I think whether or not they are needed in natural homes is it depends...

In mild climates that do not have lots of cooling and heating needs then I would agree but this is not something that applies to most North American housing. Opening windows or doors is not the best strategy when its cold outside or you spent money and energy cooling and de-humidifying the indoor air.

Even homes with all natural materials should be built as airtight as possible as this is the most cost effective approach to saving money and energy when heating and cooling. Airtight homes need fresh air introduction even ones built with all natural materials.

Outdoor air is always healthier than indoor air no matter how much trouble one goes through to make interior materials VOC free and all natural.

Carbon Dioxide, humidity, soil gases, are all things that contribute to indoor air pollution in all natural homes. Furniture, appliances, electronics contain harmful chemicals that off gas much longer and more potently than many common building products. We could live without such things but how would we participate in the great discussions as found on this site!?

POWER SCREENER------------I've invented a dead simple power screener. I'm sure this has been invented before but it worked so well I'm going to tell you about it anyway.----------- I needed to screen rocks out of some reasonably dry dirt. I had a big screen about 4 ft. in all dimensions. I found that it worked reasonably well when used on a slope with only gravity powering it but I wanted to make it process material quickly and to break up lumps.

I mounted an electric drill to the top of the screen. I used duct tape to attach a bolt to the side of a drill bit so that it was seriously out of balance. With the trigger locked in the "on" position, the drill vibrated wildly and transferred that energy to the screen.

No doubt this is hard on electrical equipment. But there are plenty of old drills and skill saws which have no value. Any of these items may be altered so that they shake a great deal. They could be used for processing earthen plasters, for soil sifting, etc.

I wanted to remind everyone about the difference between cement mixers and mortar mixers, which are generally more useful for mixing cob/clay/slip type stuff. Cement Mixers have a barrel that rotates and has fins on the sides. Mortar Mixers have a similar barrel but it has a rotating paddle suspended in the middle that spins, so its better at mixing chunky things.

Mortar mixers are much better at dealing with gooey substances that stick to the sides of cement mixers. The paddles keep things moving along. Quite often with a cement mixer, material gets stuck to the sides, and just goes round and round.

They aren't good at dealing with big rocks or other large aggregate. ---The following was gleaned from a posting I made concerning making clay slurry to seal ponds.

These are all adapted from the various ways I'm considering to create earthen plasters.

1. A large cement mixer could be used with a few big rocks included. These rocks would bash around and break up the clay. Each time a new batch of slurry is dumped into the pond, the last little bit could be saved since it will contain all the pebbles.

2. Another means of mixing lots of slurry would be to mount an old outboard motor in a slurry box and have it thoroughly mix the ingredients. The freshwater intake(for cooling the engine) would need to run off a separate source since a thick slurry would clog the intake or cause other harm. I suspect this would be very hard on the propeller but I know it would work since boats which run aground stir up massive amounts of mud when the propeller is engaged.

3. Mixing with a Rototiller would ease both processes but the tiller would not be useful once material is thinned out hugely. It would serve to break up lumps.

4. A small power tamper similar to those used for packing rammed earth could be used to pound the material and the brisk motion should create plenty of convective currents. I could see this working in a large pail. The operator would straddle the pail and use the machine jackhammer style. This process should produce percussive shockwaves which help emulsify small chunks.

5. Any number of contraptions could be spun with the power takeoff from a tractor in order to mix up a good slurry. The simplest would probably be to use a tractor mounted Rototiller inside a big slurry box.

6. And finally one that would work for me but not for most people. I could attach a large paddle to the end of my crane arm and mix up the whole pond bottom simply by swinging the arm in a big arc.

Does anyone have other mechanical means which they used to create large amounts of clay slurry?

ROCK SCREENER

I've been searching out the most efficient way to gather rocks for my building purposes. I require some large attractive rocks for building walls and foundations. In other places I'm just looking for small rocks for rubble trench foundations.

The Internet is filled with hundreds of expensive machines which automatically clean rock from soil. But I like the low tech ones. There are two types of rock fork that look promising. One is just like the bucket on a front end loader except that the entire bottom is made of rebar with 3 inch spaces to allow soil to filter through.

Another type of rock fork is towed behind a tractor. The simplest type requires manual removal of rocks. More expensive types have hydraulics. The operator pulls a lever when ever the fork fills and the hydraulic arm dumps the rocks into a storage bin which holds a couple tons of rock. Caution must be used when driving along with one of these since an extremely large rock can bring the fork and tractor to an abrupt halt, causing damage in the process. With the front end loader type of fork there is less chance of catastrophic damage since they are used at low speed and individual adjustments are made when large rocks are to be lifted.

I'm leaning toward the front end loader type because it will have a multitude of uses depending on which screen I install in the bottom. A fine mesh could be used if I'm looking to produce fine soil for seedlings or if I'm looking to sort materials for natural plasters .And since I need a tractor with a loader for other purposes, my only cost will be that of an additional bucket.

I could see screening a large section of field and getting a jumble of all sizes and description of rock. The larger specimens would be set aside for wall building and other landscaping purposes. All of the grapefruit to wallnut sized stuff would be used for rubble trench foundations and for adding to concrete.

I've looked at every mixing machine known to man in trying to determine the best cob mixer. Just missed a giant paddle mixer soil blender that went for $175 .Super robust. It was at an auction for a closed down facility. The most promising manufactured mixers are verticle auger feed mixers which are used to mix and distribute cattle feed. There are also obsolete commercial mixers meant for dough and other food items. Horribly expensive new so it's a matter of intercepting them on the way to the scrapyard. --------- Tractor boneyards have hundreds of machines containing augers and paddles including feed mixers, combines, manure spreaders, grain and manure augers and plain old post hole augers. ------- Clay pugging equipment would also work but hugely expensive new. So the best value is going to be the boneyards. -------------- There are garbage processing augers in the $50,000 + range that have the strength required. I watched a midsized unit chop up furniture and appliances. ---------------------- If I end up building something it will most likely be based on a large post hole auger inside a giant pipe. Basically a clay pug but with several inches clearance to allow rocks to pass between the blade and pipe wall. One advantage of a pug is that the material can exit at height and be loaded onto a vehicle or allowed to plop back into the hopper for another run through the auger. I described this mental marvel to my dad yesterday. Turns out he built one in the 60s for pumping manure and to suck up mucky water that would destroy most water pumps. It was pto driven and he figures it moved manure at several hundred gallons per minute.

Dale,
Are you wanting rocks in the cob mix simply as an aid to break up any clay lumps?

Consider this: What if an auger was constructed with a (using arbitrary figures) flight outside diameter of 12” and a tube inside diameter of 15”. This would allow the rotation of the outer tube around the auger eccentrically. The lumps would be squished into the outside edges of the flights as the outer tube rotated eccentrically and the rotation of the flights would “scrape” the inside edge of the outer tube. I think it would work way better than the mixer in the videos below.

http://www.youtube.com/watch?v=XeSFw_auTp0

http://www.youtube.com/watch?v=TyGCloAxeFo

The machine in the videos seemed to be having trouble moving a very thick cob mix to the output end unless they added water which resulted in a too wet mixture exiting. I believe that what I’ve proposed (perhaps the diameters need to be larger to allow a larger volume of cob to be mixing at one time) would result in an ability to fill the machine up and get a very thick mixture exiting which is something the machine in the videos could not do because of the open top. What I’ve proposed can also be shorter in length.

I’m sure what I have proposed is not a completed machine. A lot of detail will need to be specified. I’m willing to collaborate. Perhaps you can spot weaknesses.

Here is a site with some photos of a custom made vertical auger cob mixer. Actually, I can see where the tapered vertical auger achieves the same thing I was suggesting since the chunks travel up to a certain point and then must fall back down into the mixing action again.

http://minnesotaeconaut.blogspot.com/2008/09/mixing-up-cob.html

I've seen the cob cannon before. I like the idea of a 16 inch auger inside an 18 or 20 inch pipe. The effluent could dump into a wheelbarrow or it could plop back in for further processing. I'm not tryin to add stones. Just dealing with any that inadvertently enter the mix. If a sufficiently robust pipe and auger were used they could effectively reduce the size of woodwaste and some rocks.

A large diameter auger has the ability to fling material off of itself when the speed is ramped up. None of the mixes I've made are as sticky as the Cob Cannon goo. It may be that this type of machine is best used without the straw. It could mix the sand and clay and the straw could be incorporated in a trommel. But then , why not build a bettter trommel and have one machine?

The stickyness of cob is comperable to dough. Commercially mixed dough is usually made in paddle mixers. Paddles move the material so it doesn't remain stuck to the drum. Mortar is also made in padddle mixers but they aren't robust enough to move cob. I'm going to monkey with an auger and if it clogs with goo I'll weld some paddles onto an old auger or a steel tractor wheel. Something like this which is PTO driven inside a drum would have the power to mix a good thick cob. With huge power available the thing could be sped up to clear the paddles if the material wants to go for a ride without mixing properly.

Look at the last link posted by C.J. Murray. That machine is the best I've seen. Vertical auger adapted from feed mixer. The base is more cone shaped than on typical mixers so that the auger takes up most of the floor space. If this unit were trailer mounted it could be taken around to many build sites. This type of auger could be installed on a tow behind mixer, the type used for papercrete. Since cob is not fluid like papercrete the container should have a smaller base. A sweeper paddle could be mounted beneath the auger to draw material toward the auger. -------------- With any hopper type machine where material may stick to the sides the material may be helped along by vibration. Any electric motor with a pulley can be turned into a vibrator simply by adding bolts or other weight to the pulley. For longer life the offset weight should be separate from the motor and belt driven. See lapidary shaker tables. They vibrate hard enough to loosen teeth.