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Don't use a sledgehammer! There's a better tool for ramming earth into earthship tires.

 
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I've been meaning to make this post for a while now.  Whenever I read about anyone looking to build and Earthship style structure using the traditional rammed earth tires I cringe at the thought of trying to do that with a sledgehammer.  In fact, this is often used as a point to dissuade people from doing it, the advice being, "go get just one tire and ram it full of dirt with a sledgehammer, then imagine doing hundreds of them."  I can understand why some people don't want to use tires for this purpose at all, that's a whole other issue.  For those who do want to try making an Earthship style building I strongly suggest getting a better hammer for the job!

I suspect Michael Reynolds went with the sledgehammer because it probably is the best commercially available hammer for the job.  I work as a metalsmith, basically using all sorts of different hammers to form metal all the time.  So when I went to use a hammer to ram my tires with dirt I quickly realized the sledge wasn't the right tool.  The face is way too small.  What you want is something with a similar weight, but with a broad curved face that more closely matches the curve of the tire you are trying to pack tight.  Even better if you had an entire circular face so anyway you happen to pick up and swing the hammer it will hit correctly.  You also want a large flat surface for tamping down the central part of the tire once the side walls are rammed full.  

As far as I know you can't buy a hammer with these characteristics, but you can easily make one for a few bucks.  If you don't feel you have the skills to make one, then I'd strongly reconsider building an Earthship structure as that job is going to be WAY more complicated than making your own ramming hammer!

I'll attach a picture of the ramming hammer I first made over a decade ago when I started my first Earthship style structure.  I was pretty much using scrap material.  I grabbed a solid hunk of scrap maple for the handle.  Down at the end I drilled a few holes and wove some old electric fence wire through it so it was sticking out in various ways.  I also partially screwed in some screws, getting them solidly embedded in the wood, but still sticking out.  These protruding metal bits essentially acted as my rebar, and helped to more strongly bond the concrete "hammer head" to the wooden handle.  I didn't really want the head flying off.  After pounding hundreds of tires with it the head hasn't budged at all.  

Once the metal protrusions were made I used an old 1 gallon pot that some plant had come in.  I duct taped up the drainage holes in the bottom.  This was my form for the concrete hammer head.  I mixed up the concrete, held the prepared handle in the pot and poured in the cement around it until I had a dept that felt right for ramming into the tires. The dimensions of my hammer head ended being roughly 8 inches in diameter and 3.5 inches thick.  Once the concrete has fully set up simply pull of the plastic pot, or cut it away as need be.  Now you have a superior hammer for pounding dirt into tires!  Mind you tire pounding is still hard work, but it's less hard work.  I found the relatively small face of a sledge hammer would loosen up almost as much dirt as it packed in.  This concrete hammer on the other hand pretty much just packs dirt in an efficient manner without loosing much to either side of the head.
Earthship-hammer.JPG
[Thumbnail for Earthship-hammer.JPG]
 
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If only there were a way to build rammed earth walls without using tires. No tires, no hammer.

Some people get around this by bagging dirt. I mean, plastic is going to be less toxic and easier to work with than used tires. Some press their dirt mix in a machine to churn out bricks.

I would just build using concrete framing, an appropriate soil mixture, and a tamper just  narrower than the width of my walls. No fuss, no muss, and you calculate time spent by the one-foot-height courses of wall tamped rather than individual tires packed and laid.

-CK
 
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Chris Kott wrote:If only there were a way to build rammed earth walls without using tires. No tires, no hammer.



We built the buildings at our school of rammed earth, using wooden forms. We set up the form, filled and rammed it with a tamper much like the one above but welded metal, then after a day or two removed the wooden formwork and move it up to a new spot. I had my house built of it too. I love the thermal, humidity and acoustic properties of it. Out school building is 23 years old this year and there don't seem to be any structural problems with having used rammed earth that had no cement.
 
David Huang
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Thanks Rebecca.  I was going to note that those who want to do rammed earth without the tires could still find creating a hammer like this useful.  You would just adapt it's shape to work best in whatever form you are ramming the earth into.  Welded metal could work great if you are just tamping, and have the skills and access to a welder, which aren't that hard to come by.

Can I ask how thick the walls of the school and your home are?  For me I'd worry how well rammed earth without a retaining form would hold up to earthquakes.  They are rare by me, but do happen.  Actually I'd just worry about the constant minor tremors I feel when large vehicles like school buses, garbage trucks, UPS delivery, etc. go roaring down my often bumpy dirt road.  I can feel the whole house shake from it and wonder how well a simple rammed earth wall would hold up to that.  
 
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Chris Kott wrote:If only there were a way to build rammed earth walls without using tires. No tires, no hammer.



There are some pretty advanced block-making machines out there that create a product that is basically rammed earth.





Vermeer is a company out of Iowa that builds chippers, farm equipment, etc.  They've taken this on as a passion for a low-cost solution to developing world housing challenges.  They send their machines all over the world to help people build quality lasting housing.  Its just compressed soil -- other than the fuel needed to run the compactor, the environmental footprint is completely benign.  I'd love to see this gain widespread adoption here in America, particular in the hot southern states where rammed earth construction makes so much more sense.
 
Rebecca Norman
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David Huang wrote:
Can I ask how thick the walls of the school and your home are?  For me I'd worry how well rammed earth without a retaining form would hold up to earthquakes.  They are rare by me, but do happen.  Actually I'd just worry about the constant minor tremors I feel when large vehicles like school buses, garbage trucks, UPS delivery, etc. go roaring down my often bumpy dirt road.  I can feel the whole house shake from it and wonder how well a simple rammed earth wall would hold up to that.  



I've seen in various sources that for rammed earth, a ratio of 1:10 width to height should be pretty good for most earthquakes. That means 1 foot wide per story, approximately. Our older buildings were 1.5 feet thick if one story, or 2 feet thick on the ground story and 1.5 or 1 on the upstairs. It helps to have a good number of corners and intersecting walls (not just long straight walls), and we tie the corners together in various ways, most recently with a tough plastic "geomesh." We've had a lot of 4.something earthquakes in the past ~25 years that the building has been standing (the type that not everybody feels) but none of them seemed to cause any cracks or anything. There are no destructive earthquakes known in history in our region, but it's certainly a risk -- supposedly our part of the Himalayas is rising a centimeter per year.

We use tie beams too for some seismic protection. In our older buildings they were wooden beams running on top of all the walls, supporting the rafters above each story. More recently we've done RCC tie beams, at plinth, lintel and ceiling level.
 
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Rebecca ,I'm curious, how are foundations of those buildings made?
I'm thinking concrete over a rubble trench?
 
Chris Kott
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Marco Banks wrote:

Chris Kott wrote:If only there were a way to build rammed earth walls without using tires. No tires, no hammer.



There are some pretty advanced block-making machines out there that create a product that is basically rammed earth.





Vermeer is a company out of Iowa that builds chippers, farm equipment, etc.  They've taken this on as a passion for a low-cost solution to developing world housing challenges.  They send their machines all over the world to help people build quality lasting housing.  Its just compressed soil -- other than the fuel needed to run the compactor, the environmental footprint is completely benign.  I'd love to see this gain widespread adoption here in America, particular in the hot southern states where rammed earth construction makes so much more sense.



That's incredibly useful information, Marco, thank you.

I discovered compressed earth blocks about the same time I read about methane digesters in India for human and animal wastes, for the production of biogas as an alternative to open-flame cooking, in a Mother Earth News paperback from the 70s, old even then, when I was a child of about 10 in the 90s. They even mentioned a "new" technology, the CINVA ram, that allowed for the manual pressing of bricks in an efficient manner, allowing a half-dozen people to mix earth, press blocks, and build with them, virtually right out of the press, with a no-mortar application in which you wet the bricks before setting them in the wall with a wet slurry of the earth mix. The resultant structures  cured quicker than cement, and solidified over time, such that it acted less like a brick structure and more like a monolithic one.

Here is the Open Source Ecology version:


While I always thought that they would be the best method of working with compressed earth as a building material, I have, for a while now, thought that a hydraulic tamper working between appropriately spaced forms, as for the pouring of concrete, would yield the most efficient result. I would expect to have to do corners and finicky bits with a manual tamper, but were I designing it, I think I would want something just small enough to do the job, but designed so that one or two people could jump up and down on it for proper compaction, seeing as how the long, straight runs of tamping would likely already be done.

It also allows, in temperate climates, for the use of insulated concrete forms, though I suppose one could use regular, removable forms and then backfill with some biomass or mineral wool-based insulation, which technique, I suppose, could also be used with the Compressed Earth Blocks.

I might be incorrect in this assumption, but I always thought that if I was working with an earth mixer as large as a cement truck, and loading it with a backhoe or front-end-loader, depending on terrain, then the forming of bricks would be the first bottleneck, and if a machine were used that operated as fast as it could be loaded, the unloading and placement of the bricks would be the bottleneck. So what's best would change depending on how much free or cheap unskilled labour is available, and the rate at which the raw materials can be mixed.

But if it were just me, I would go the tamper route. Fill the mixer and set it to mixing, set up the forms for the first few feet to be tamped, pour the mixed earth mix into the forms, and tamp with a hydraulic tamper, to finish with a manual one in the tight spots. After the mixer is empty, it gets refilled, to mix while the tamping of the last pour is being finished, and all the steps are repeated until the day is over or the work is done.

For tamping, though, even before I decided that tires were too toxic and cumbersome to be of any use, I had happened upon the realisation that the tamping of the tires wasn't well-suited to the use of a sledgehammer, and that the best thing to do would be to remove one of the sidewalls and build a tamper plate to fit snugly inside the tires being used, perhaps with a pogo-like arrangement, or with a two-plate setup, the bottom with a rod sticking out from its centre, parallel to the direction of travel, and a second plate with a hole through it to accomodate the rod, and a tube welded similarly, so the two would fit together. I would employ either one large spring, or four to five smaller ones, between the plates, such that when they were jumped on, the top would compress the springs, the momentum would tamp the mixture under the tamping plate, and pack the tire.

This setup could be used in a form-filling earth compaction, just by using it like a pogo stick. Enough momentum in the bounce could transfer to a forward motion for the skilled and careful.

But yeah, I would say don't use tires, and especially if you do, don't use a sledgehammer.

-CK
 
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Or just make a hydraulic press to compact tyres.

http://web.archive.org/web/20110916050825/http://homepages.callplus.net.nz:80/~b.gubb/tyre_press.html
 
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great concept, I have used it in Australia for many yeras
 
David Huang
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Graham Chiu wrote:Or just make a hydraulic press to compact tyres.

http://web.archive.org/web/20110916050825/http://homepages.callplus.net.nz:80/~b.gubb/tyre_press.html



That is another approach.  I've read about others doing similar things.  Personally it looks much more complicated to me, esp. custom making the limited use tool.  Then they are partially filling the tires and rolling them into position to finish filling.  They mention a time estimate of 10 minutes per tire.  I wonder if that is doing the full job of strapping the constraining metal band around the tire, filling it with a dirt that will compact and remain compacted when rolled into position, then rolling it up onto the wall for placement, and finally filling and doing the final tamping?  I'm also wondering what the do to deal with the open spaces below in the final tamping?  I would first jam scrap cardboard into my tires prior to doing any dirt ramming.  This allowed me to fully fill them.  Anyway, I'm wondering if their 10 minute estimate is just to strap, fill, and compress the first stage, or if that is the time with two people working on a tire?  

Doing it myself with my cement hammer I would lay all the tires out right on the wall to fill and hammer in place.  It was taking me about 15 minutes a tire working by myself until I got so high up on the wall that I had to start bringing the dirt up a ladder in 5 gallon buckets.  That slowed things down quite a bit.  A second person would have greatly helped at that stage!
 
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