The Liberator – Open Source Compressed Earth Brick Press – Prototype II Complete

Time is ticking before Product Release of The Liberator. Some last minute adjustments are forthcoming, before we release Beta Version 1.0. Here are some scenes from field testing.

First, we carry it over to the work place with the LifeTrac forks. LifeTrac makes for Air CEB, but The Liberator Prototype II weighs 1922 pounds total.


The machine was buried 3 feet down to facilitate soil loading, while the support legs rest on the surface. The soil grate was added.


Second, we use the Soil Pulverizer/Loader for the first time in the CEB workflow to grind a pile of soil. Since rainy weather did not allow for a single day of soil digging for this entire month, this soil is from inside the workshop – we’re lowering the floor.


Then the Soil Pulverizer/Loader dumps the soil into the 6′ wide hopper, which is getting its first use under real working conditions:


Third, we turn on the Power Cube – which you see in the background in the above photos riding on MicroTrac – for the first time in the real CEB application, and press bricks using 10 gallon per minute hydrauilic flow at 2400 PSI.


Compared to the Liberator Prototype I, the bricks are thicker and smoother. Both are features of the finer soil filling the compression chamber  – achieved by both the Pulverizer and the grate. The compression chamber fills more completely and leaves no traces of grain boundaries in the pressed brick:


The white spots are gravel chunks, care of our workshop floor.

Our observations so far are:

  1. While an auger for preventing soil bridging appears to be unnecessary (and is not used, though we thought we needed it initially in the concept drawing), a screen shaker is critical. Soil does not flow readily through the top screen of the machine when >1″ particles are dumped into the machine. The top screen is 1″ mesh, so a garden rake helped the soil go through the screen.
  2. A stronger cylinder is needed for the soil-loading drawer. Right now, we’re using a 1.5″ cylinder, and we should probably use a 2″ or 2.5″ cylinder. Under certain conditions, the drawer locks up and it has to be wiggled to move it. Avoiding lockup is critical for automatic controls – forthcoming as an addable module in the product evolution – which would waste significant time for overriding the lockup. The lockup observed so far was caused by soil sticking to the drawer’s pressing surface – where a large force is required to unlock the brick prior to ejection.
  3. The motion guides are functioning well. The pressing characteristics of the machine are excellent, without using any protective liners. Prototype 1 featured Nylon 6/6 liner for abrasion resistance, but attaching it to the compression area was problematic. We eliminated this by using the roller guides, which allow the loading drawer to float: (1), above the table, (2), under the top stops, and (3), away from the side walls – by keeping a small air space – without direct contact. Morevover, 4 bolts fixing the main cylinder in vertical alignment allow for ‘frictionless’ up-down motion. The bolts keep the pressing plate a small distance from the pressing chamber sides, so the only abrasion is caused by soil-on-metal contact, and not metal-on-metal. We are aiming for 1 million brick pressing capacity before wear issues must be addressed – enough to build yourself 50 homes.


  1. Joel


    Do you suppose coupling the powercube’s engine vibrations to the grate would be enough?

  2. Lenita

    What kind of rates are you getting so far? I’ve very excited for you!

  3. Lenita

    That is, *I’m* very excited for you. 🙂

  4. […] for 8% stabilization), and we would mix and load the soil in one step – ready to be used in The Liberator. We plan on using stabilized brick for walkways, base courses in buildings, and we are considering […]

  5. Dan

    What kind of soil is used? Are there better mixes, poorer mixes, some that don’t work at all?

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