Nyange Tile Press (2017)

Overview

The overall goal of the tile press is to compact the clay and remove air bubbles, ultimately creating stronger, higher quality roof tiles. The hydraulic tile press was designed and implemented by EWB-SCU in 2017, replacing a purely mechanical tile press implemented in 2015. Without a press, the community scrapes the top of clay in a roof tile mold. Because the clay is not compacted, air bubbles remain in the clay weakening the integrity of the tile. By increasing the quality of the CO-OP’s tiles, the community could sell their tiles for more money, increasing their income without spending resources.

diagram

Background

After harvesting clay and carrying it to their cooperative building, the community must form wet clay into the tile shape to prepare it for drying and kiln firing. Without a press, the community scrapes the top of clay in a roof tile mold. Because the clay is not compacted, air bubbles remain in the clay weakening the integrity of the tile. Additionally, the scraping is very labor intensive, meaning that only the strongest men in the community could mold the tile.

In 2015, EWB-SCU attempted to improve the pressing process as their first project. The original team had not visited the community before and struggled to understand the tile making process, lacking critical details such as the density and thickness of the clay. They did their best with the limited information they had to address the clay press problem and traveled for the first time bringing a table, an arbor press, and tile molds to the community.

In 2016, EWB-SCU returned to the community and saw that the tile press was too weak to sufficiently compress the clay and did not distribute load evenly across the tile. Additionally, it was prone to dirt getting in the mechanical components, adding friction and making the system more difficult to use. As a part of EWB-SCU’s long term commitment to the community, the team realized that the press would need to be redesigned.

Design: Hydraulic Jack

EWB-SCU returned in 2017 with an improved press that could mediate the deflection of the table and apply up to 4,000 lbs, more than 15x the force of the arbor press.

To create the press, the team started by brainstorming ways to press the clay. They ultimately decided to use a hydraulic jack because of its small profile and ability to produce massive force. To contain this force, a custom frame needed to be designed. Steel was chosen due it its high strength, and standard cross sections (1x1 in & 1x2 in) were used to cut costs. Standard off the shelf Unistrut brackets were chosen to connect the steel tubing because of their strength. The frame and brackets were analyzed using finite element analysis (FEA) and hand calculations for bending and bearing stresses. Taking into account the strength of the frame, a 2 ton hydraulic jack was selected because it would have enough strength compress the clay and would leave a margin of safety to ensure that the frame would not bend or suffer from fatigue.

After the design of the frame and press had been reviewed, the team began to machine the components, drilling holes for the bolts that connected the brackets. To mount the hydraulic jack, the team needed to modify the jack. Hydraulic jacks do not typically work upside down, so a custom straw needed to be added allowing the hydraulic fluid to move.

Implementation

In Summer 2017, EWB-SCU traveled and brought the hydraulic press and frame. A user manual was created and translated into Kinyarwanda to help the community understand how to assemble and use the tile press. Additional tile molds were created to better fit with the new press and create more consistent tiles.

Testing the new tile press, the tiles were found to be smoother and more compressed than those scraped by hand. The community was excited to have the press, explaining that it would empower the women to make tiles more easily.