JWT Custom Water Tank Design

In August of 2007 we received a call from a colorful entrepreneur living in Australia who sounded a bit like Crocodile Dundee. He asked us to assist him in designing two lines of water tanks for the exploding Australian water conservation market.

This product was intended to function as a reservoir for rain water running off from the roofs of residential homes. As climate changes continue, similar products will begin to appear in the US, South America and Europe.       

Initially the project didn’t appear to be too difficult until we were informed of the desired shape for one of the lines.  Instead of a conventional cylindrical shape which evenly distributed stress around its circumference, these half round tanks would undergo an asymmetrical stress distribution. 

In addition, the design was further complicated by the fact that the tanks were required to nest within each other while being shipping from China to Australia. Sizes were to range from 1000 liter to 10,000 liter for the round tanks and 1000 liter to 3000 liter for the half round tanks.

When we were first introduced to the project, we had the opportunity to review numerous ideas proposed by other designers. Some of these concepts are shown here. Unfortunately, all of the ideas were rejected because of impracticality, poor aesthetics and insufficient detail.

After reviewing many alternative designs for the half round tanks, our client proposed his vision to us which was based on a series of reinforcing stainless steel bands surrounding  the tank. Although this initially seemed quite obvious and offered a distinctive look, it did present numerous structural, technical and economic challenges.

Concurrently with the development of the half round tanks, we also designed the full round tanks. Early sketches were used to develop details between the lid and main body..

Eventually the complete line of 10 different sized full round tanks was designed and released for production based on the CAD designs shown here.

Shortly after the CAD files of the full round tanks were released to vendors in China, production design of the half round tanks began. Optimizing dimensions for each size proved to be difficult due to considerations for tolerances, structural considerations, overall dimensional constraints and overall volume requirements.

Eventually the designs were refined and rendered in colors that would eventually be offered as shown here.

Numerous finite element analyses were conducted before the design was released to verify overall structural integrity as shown in this animation. It should be noted that the deflections shown in this animation have been intentionally exaggerated for purposes of clarity.

After the design was verified, production design details were completed for each rotationally molded tank, injection molded plumbing hardware all steel reinforcing sub-assemblies. Upon approval, all files were released to Chinese molders for construction of sheet metal molds.

We even provided camera ready artwork for the product name. This artwork was specified for use during the engraving process within the molds.

Photos of first molded parts were emailed to us within six weeks after the files were released. The following pictures show units being molded and viewed from different angles.

First molded samples were assembled with the reinforcing belts. 

They were then filled with water. 

Incorrect rivets used in the assembly between the belt and rear reinforcing bars resulted in premature failure of the joint between each.

The test was applied to two samples of different sizes and wall thickness.

Minor changes to design included the addition of two more steel belts, slightly larger tubing and thicker tank walls. These changes were recommended by us as shown in the picture to the left.

These changes eliminated all the bulging and distortion problems with earlier units that were tested.

The final product resulted in a highly innovative and truly unique product that successfully represented our client’s ambitious objectives.

The units nested within each other as specified and defined by our design team.

The completed units were identical to the proposed designs. The final products looked great at all levels of detail and functioned as specified by our client.