The FSCONS conference was awesome, discussion on RepLab is evolving, and I have a feeling we haven’t seen anything yet. At the same time – the core of building a pattern for replicable, post-scarcity, resilient communities is actually building it. Today we get back to the CEB automation question – and we present encouraging initial results.
The summary of results to date and calculated predictions is captured in this brick production rate table, featuring manual and automatic control runs for The Liberator Compressed Earth Brick (CEB) Press.
(note: cylinder sizes in the table refer to the soil-loading drawer cylinder, not to the main cylinder)
At about 9 bricks/minute realized (second result) and 12-18 bricks per minute calculated, this is very encouraging. I haven’t found any 12 brick per minute machines for less than $50k. It looks like a factor of 10 in cost reduction for us. This sets the mind spinning on prospects of open source enterprise replication, and transformative economics resulting from this.
Explanations of the table are found below. Here is a 1 minute video showing the automated motion of the machine – performed without soil for testing purposes, demonstrating the 6 brick per minute result in the table above. Look, mom – no hands:
Here are further details of the entire Arduino-controlled setup.
The experimental setup involved an Arduino powered by the 12 volt battery from the Power Cube.(See presentation where from which this slide is taken)
The picture shows the Arduino being programmed by the Ubuntu laptop with the Arduino Programming Environment via the blue USB cable. The Arduino is in a weathertight enclosure, and the red leads are the 4 amp power cables from the controller MOSFETS to the 2 double-acting solenoid valves. The solenoid valves control the fluid flow to the 2 hydraulic cylinders on The Liberator CEB machine. If you would like to understand the control logic, see the annotated test code which was used to obtain the results shown in the video above. The code has notes on the motion sequence used.
Here is a video about programming the Arduino:
Here is a video of the additional hydraulic components:
And here we show how they are connected to the machine:
Explanation of Brick Pressing Rate Table above:
The noteworthy feature of the table above is the predicted brick pressing rate. The real data above has been obtained with limited hydraulic fluid flow – as the automatic solenoids are rated for 10 gpm. However, we have 24 gpm available – so the next step is sourcing large solenoid valves to optimize machine throughput.
Several conditions were used. The variables are hydraulic flow rate, manual vs. automatic controls, and secondary cylinder size. We used the PowerCube and LifeTrac as power sources. The hydraulic flow rate (fluid actually getting into the cylinders) was calculated by observing the speed of the cylinders over many repetitions – to obtain a good average – based on a known cylinder size. At first, we used a 1.5″ cylinder for the loading drawer – but found that it would sometimes get stuck. Using a 2.5″ cylinder solved this problem, and we intend to stick with a 2.5″ cylinder.
The first result was done for real, with soil, and manual controls – to obtain 4 bricks per minute with 8 gpm flow. While the hydraulic pump is rated at 10 gpm, the effective flow rate into the cylinders was 8 gpm. This could be simply that the rated flow rate is not achieved under load due to to various losses.
The limit of human dexterity is about 4-5 bricks per minute for operating the two cylinders in an actual pressing situation – corresponding to the maximum achievable pressing rate with 10 gpm flow. Limited by manual dexterity and rated solenoid size of 10 gpm, we could only simulate the brick-pressing output at higher flows. The maximum flow rate that we could test readily was 15 gpm with LifeTrac – which is the max intermittent flow achieved with the 12 gpm rated hydraulic quick couplers.
To simulate brick pressing rate, we performed a number of full-cycle repetitions on each cylinder individually to obtain an average speed of each cylinder. This was done without considering the more complicated, 7-step pressing sequence – such that human dexterity limits would play a negligible role in the test. Then, we summed the motion times corresponding to the actual 7-step pressing cycle. We then calculated the number of cycles that fit in a minute – and this was our brick pressing rate. We obtained 8.8 bricks per minute for LifeTrac-powered, 15 gpm flow. Note that this was without soil in the hopper.
We did the same with 8 gpm fluid flow of the Power Cube, and obtained 5.5 bricks per minute. Thus, automatic controls increase the pressing rate in this case from 4 human controlled bricks per minute to 5.5, under the condition of limited fluid flow.
Calculations show a brick pressing rate of 12-18 bricks/min with 24 gpm fluid flow, depending on brick thickness required. See the calculations here on the wiki and comment if you think there is any error. The main challenge here is using a solenoid valve big enough to handle this flow, and rewiring the hydrauilic connection to allow for 2 output channels from LifeTrac. LifeTrac has three 12 gpm outlets, and a total flow of 24 gpm at these quick-coupled, hydraulic takeoffs.
At any rate, the calculations show a rate sufficient to keep several people busy stacking bricks, while the tractor does the hopper loading.
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