COMPRESSED EARTH BLOCK MACHINES
W. C. Powell
The Learning Curve of Design
A long time ago, the thought of being able to make dirt building blocks quickly so that the blocks would enable many more people to have affordable housing really caught my attention and since then, we have built and designed many earth block machines, each one improving on the last.
Some of our designs and different types of block presses included:
Block presses that incorporated a rotary mold with four cavities;
A press that had the press cylinder above the mold and a drawer to put dirt in the mold;
A press that pressed from the bottom and had a drawer that put dirt in the mold; and
Presses that pressed horizontally
We discovered that there were advantages and disadvantages to each design.
The presses that were vertical or pressed from above or below usually had to press on the biggest side of the block while the horizontal presses could press the smaller side of the block. The result is a press that has a far lower tonnage requirement.
For instance, pressing on a 10" x 14" surface requires 140 square inches x 1,500 PSI or 105 tons of pressure for the vertical press. For the horizontal press, pressing on a 4" x 14" surface requires 56 square inches x 1,500 PSI or 42 tons of pressure.
We also found that it was difficult to nearly impossible to make blocks that were all the same height with the vertical press.
The horizontal press has two fixed dimensions: the height and the length. If the height of the blocks are uniform, it eliminates having to utilize heavy mortar to level the courses. The width of the horizontally pressed block is usually not a problem because one or both of the sides of the block have a stucco or plaster coating and if your wall is the dimension of the fixed length then any difference is irrelevant and can actually be exploited by making custom sized block for ends, fillers and electrical and plumbing runs.
One of the drawbacks of the horizontal press is that the block is usually less dense on the side away from the press foot making a crumbly, round-cornered block at the eject end.
To deal with this variation in density, we have perfected the double press which eliminates the crumbly, rounded corners and softness of the block as well as pressing a uniformly dense block.
The vertical press requires carefully manicured soil because it utilizes a belt and drawer fill system. Even though it is advantageous to have carefully prepared soil, the horizontal press will perform satisfactorily with marginal soil. Its fill system simply drops the loose soil into the fill area with no other devices required. The horizontal press then ejects the freshly-made blocks on the opposite side of the press from where the loader is operating (for safety purposes).
The horizontal press, not only a less-complex block press, also lends itself to a lower height of the top of the hopper, making it easier to load with dirt.
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