THE SHOP

November '19

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56 THE SHOP NOVEMBER 2019 Manufacturers validate side impact air- bags with an array of deployment tests whenever a condition exists that changes any aspect of how the seat is constructed. This is done even when changing manu- facturing locations, despite using the exact same materials and thread for construction. The tests vary by manufacturer, but typi- cally consist of deploying airbags in very cold, very hot and ambient temperatures to verify that the chosen materials perform equally well in all climates. Cold tempera- tures can cause some materials to crack or break, decreasing deployment times; hot temperatures can cause some materials to expand, therefore delaying deployment. Failed tests are studied and changes to materials, stitching or other aspects are made to bring the seat into spec to ensure passenger safety. THE ANATOMY OF SIDE IMPACT AIRBAGS Not all airbags are designed the same, have the same parts, or are intended to deploy in the same manner. However, here's how most typical airbags are constructed: Aside from the actual airbag and its charge, there's also an airbag chute, break- away or functional seam, and chute rein- forcement around surrounding areas. The airbag chute is what directs the actual bag out of the seam and toward the passenger in a reliable manner. The ends of the chute are typically sewn into the seam by first tack-sewing the edges and then completing a join sew. Airbag chute material can vary, but is typically a woven nylon material with sili- cone coating on one side, which extends the life of the material and prevents burn- through during charge explosion. Aside from the airbag itself, the chute takes the brunt of the charge force and makes a clear path for the bag to deploy. Although strong, tearing can happen if the material is over-perforated by way of resewing the chute. This is one of the many reasons why you see warning labels on airbag seams instructing you to not resew. It's not some conspiracy from corporate America to keep you from getting work or fixing things yourself. A weakened chute could alter the path of the airbag deploy- ment to an area that is not beneficial. Worst case scenario, it could even allow the bag to deploy within the seat, squeezing On the left, the original seat sewn correctly from the factory. On the right, a trimmer's incorrect attempt to resew the chute. The thread and sew pattern are sloppy, and loose threads from the old stitching remain. Aside from the airbag itself, the chute takes the brunt of the charge force and makes a clear path for the bag to deploy. Although strong, tearing can happen if the material is over per- forated by way of resewing the chute. This is one of the many reasons why you see warning labels on airbag seams instructing you to not resew. Understanding Side Impact Airbags

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