Week #40 - Cutting Costs

This week we spent providing solutions to some of the most common problems that plague filter production. Willie and I have also come up with some new designs that we will test further in the weeks to come.

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One of the biggest problems is broken corners and rough edges along the top and leaks at the bottom.

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This is the cause of broken corners at the top. You are looking at the mold for the filter. When that space of light is filled with cement and the mold is pulled out, it breaks the cement leaving the three broken corners in the above picture.

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Another problem is cement that leaks out of the molds during the vibration to remove air pockets. This causes a rough edge along the top and side of the filter. We fixed this by putting in a gasket at the bottom and the sides of the mold.

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Fissures at the bottom of the filter are the number one problem with small molds. We found that the mold had the same problem with the bottom as its top; an indentation that fills with cement and then pushes out when it is removed. For this problem, we decided to cut it out and then add a larger taper to the mold.

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Something else we wanted to try was adding a 45° fillet to the bottom of the filter. This is to change the stresses on the filter when the cement is curing. We'll have to let you know but our first tests didn't have leaks.

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Also by putting the pipe in this way we have been able to reduce the number of elbows needed. In this picture you see two but in later versions we use only one elbow instead of five normally needed to reach the water bottle. We did this by changing to a smaller, stiffer hose that is glued into the pipe. Its pull proof also, I tried my best to pull the hose out of the pipe.

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Here is what the inside of the filter looks like with the small slotted pipe. An advantage to this design is we do not need to use large gravel to allow for water flow. With the small slotted pipe we only need the smaller gravel, which is sized not to clog the slots and still suspend the sand above it. This eliminates one bag of gravel.

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Robert Kent Jr- robjkentjr@gmail.com
Wat/San/Health Consultant
www.RobRasa.com/hisblog/
Cell: +504 9871-5318
Work/Home: +1 (631) 458-1119