Demotech, design for self reliance

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Making the Cement Pot for the Solar Bathroom Box

The base for the SolarBathroomBox is a stable square cement pot. Making it from cement allows to give it the most functional form. Production can be done small scale in a way well known in shanty towns. Local capacity and local need for proper sanitation comes together this way.
This was a first test to learn to make such a toilet pot. The result was very already very useful, also indication where many improvement could be made in the next experiment: 30% less weight, less taper, round top, easier production.

The wooden mold filled with concrete
We had no experience how to make a mould to cast such a toilet pot and -after setting of the concrete- how to remove the cement pot from the mould. The picture shows the mould top up. Dark brown is the top of the core mould. Lighter brown are the sides that are anchored together with metal pins that fit in holes drilled in wooden blocks.
Remove the inner core
Taking out the core was difficult due to sticking of the cement to the core. Only by hammering wooden wedges gradually with more and more tension between the core and the box mould, we succeeded in pulling out the core.
The quality of the surface was very good.
A different approach is to split the core into a surface metal sheet that wraps around a similar wooden core. After setting of the concrete, the core should slide out easily away from the smooth and oiled inner side of the metal sheet. After that the metal sheet can be peeled off.
Taking off the sides of the mold
Taking off the sides was easy to do. After drawing out the metal pins from the wooden blocks, the sides just folded open.
During the casting of the concrete a running hammer dril was pushed against the mold. This made the concrete flow easily into all the sharp corners of the mold. The result looks very good.
Judging the result
To have this prototype was very helpful to give an overview of the total of the Solar Bathroom Box. It looked good, was stable because of the four 'legs'. The size also seems about good.
The wall thickness should be reduces from 3 cm to 2 cm. to lower the weight from 35 kilo. The top is now too sharp for folding over the plastic liner bag. Thanks to a different split in parts it can become rounded off. The core should have less taper and a flat bottom decorated with mosaic.