Final Design

Figure 1. Final Design Solution

Figure 2. Step 1-2

Figure 3. Steps 3-4

Figure 4. Steps 5-6

Figure 5. Steps 7-8

Figure 6. Step 9 (Fully Collapsed)

The final design of the container includes: a bi-folding wall, a single folding wall, a ceiling that would be folded down onto the single folding wall, lifting hooks, forklift pallet on the bottom, four doors, and an inner support. Each wall and bottom floor panel is attached to 5 aluminum support columns, as shown in Step 7 in Figure 5, which structurally enhance the container by reducing the deformation of the container when loads are applied. At each folding edge, 90 degree hinges are attached to the wall panels, as shown in Step 3 in Figure 3, allowing the wall to be able to fold inward. When fully extended, the wall is held rigidly together by straight brackets, removable angle braces, and quick-release pins which lock the supporting beams together. The quick release pins allow for tool-less locking of the container, thus eliminating the need to unscrew any bolts when collapsing. The inner support is separated into 2 parts, with the lower part fixed to the floor while the upper part is connected to the support column by 90 degree hinges which allow the inner support to fold flush in between the support columns, as demonstrated in Step 6 in Figure 4 above. There is also a forklift pallet attached to the bottom and 6 lifting hooks attached to the 4 corners of the ceiling for lifting, transporting and collapsing the container.

The final solution was designed to have all doors rotate 270 degrees outward and lock onto the walls before collapsing the container, as shown in Step 2 in Figure 2 and Step 3 in Figure 3. After all doors are locked, the bi-folding wall collapses first while the other side wall and ceiling are held up by a crane. After the bi-folding wall collapses down to the bottom panel, the ceiling panel folds down to be flush with the standing wall, as shown in Step 7 in Figure 5. The standing wall with the ceiling panel then folds on top of the collapsed bi-folding wall. The single folding wall with larger panels have a fixed step up part to allow the standing wall to fold flat onto the bi-folding wall when fully collapsed, as demonstrated in Step 1 in Figure 2 and Step 8 in Figure 5. The inner support folds into the wall and in between the support columns before collapsing, allowing the collapsed container to be flat.

This design was able to reduce the original volume by 73%, which is slightly lower than the goal of 75% reduction. Also, the design was able to withstand a 9G horizontal load and a 2G vertical load, as shown in the structural finite element analysis. Moreover, there would be a forklift pallet on the bottom to allow the container to be transported and lifted by a forklift. In addition, the lifting hooks attached to the container allow the container to be lifted and collapsed using a crane.

The final design was decided upon after thorough analysis of each possible design. FEA analysis was performed on each possible design, and the pros-and-cons for each design are demonstrated in detail in Multimedia page. The sliding wall design was too heavy and did not achieve the goal of reducing 75% of the original volume. The scissor link could not self-contain all the removable parts when collapsed, and the processes to collapse the container were too complicated and troublesome. The folding wall design was not structurally sound after performing FEA analysis. Furthermore, overhang created large deformation (about 8.9 cm) and a high stress of 729 MPa for the two bi-folding walls design, demonstrating that modifications on the bi-folding design to reduce overhang is necessary. As a result, the final design solution is the single bi-folding wall design, as shown in the figures above, improved from the two bi-folding walls designs to reduce the large overhang.

Figure 7. FEA of the Wall Panels and Support Columns

Figure 8. FEA of the Quick Release Pins and Angle Braces

Figure 9. FEA of the Inner Support and Stress Singularity

To strengthen the structure of the container to withstand the 9G hard-landing load, the final design includes the removable supporting angle and corner braces to distribute large amount of stress on the quick release pins, as shown in Figure 2, 7 and 8. These angle and corner braces are also attached to the supporting columns using quick-release pins to stay consistent with the tool-less locking design of the collapsing mechanism. Before collapsing the container, all the angle braces need to be removed and stored in the open space, as indicated in Figure 3. Adding the braces reduces the stress on the quick release pins from 8.66 GPa to 153.13 MPa and the support columns from 6.68 GPa to 112.16 MPa as shown in Figure 7 and 8. The stresses that all of the individual components experience are under their yield strengths.

Additionally, two types of locking mechanisms when collapsing the container are incorporated in the final design. One is to utilize the quick-release pins to lock the ceiling onto the wall and the inner support onto the wall during the collapsing process. The pins are also used to lock the bottom and top parts of inner support together rigidly. The detailed reason behind choosing quick release pins over bolts and nuts is explained in the final report. The other locking mechanism utilizes padlocks to lock doors onto the walls to prevent them from swinging open when collapsing and to keep the doors closed when shipping the container is fully extended, as shown in Step 3 in Figure 3.

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