This project began after slaying the Tail of The Dragon’s 318 curves last October. We determined that the new Mazda 3 would benefit from additional bracing, and we are currently testing the first round of prototypes. In this blog, we will go into the development process of the Rear Hatch Brace and the steps we took to get to our current sample, which will be the design you can purchase for your hatch in the coming months.
This project began by searching for suitable mounting locations to tie the brackets and cross bars into the chassis effectively. After removing a good amount of the hatch trim panels, we found that the existing mounting locations for the seat back latch were a perfect spot to use as the location for the main cross bar brackets since they are tied into a main chassis structure. They also feature two M10 bolt locations perfect for providing a secure bracket mounting point.
After we nailed down the main cross bar’s mounting locations, we looked for another spot to tie in additional bars required to triangulate the brace. The bracket that links the rear seats back together was an obvious choice since it also offered two M10 mounting locations that were easily accessible. The CAD model depicts the brackets below, which are highlighted in blue.
Once we identified all the mounting locations, the next step was to move on to designing the brackets and cross bars. This process was considerably easier since we created the parts using the Mazda 3 hatch chassis in CAD, as seen above. The first components to be designed were the brackets. The brackets needed to match the angle of the rear seats without sticking out too far into the storage space to retain the practicality and usability of the hatch.
Retaining practicality is also the main reason why we wanted the brackets and cross bars to be separate. If you ever need to remove them for additional space, it can be done quickly without removing any trim pieces. We also wanted to provide two configurations or “Stages” of the RHB to give you more options. Once all these constraints were taken into consideration, it resulted in our bracket design, which is currently being tested on one of our shop cars. Below you can also see a comparison between the CAD model’s Stage 1 and 2 configurations.
Stage 1 – Single Bar System
Stage 2 – Triple Bar System
For the design of the cross bars, we initially started with an alternative design and material. The first iteration of the cross bars featured a round tube that would be welded to bent sheet metal end brackets to provide a mounting surface to interface with the brackets attached to the chassis. While this design would have been functional, it looked less OEM than we wanted. Additionally, it would have added considerable difficulty to the RHB’s manufacturing and overall cost.
We decided to search for a better solution that would function as expected while also improving in the areas the previous design lacked. Over the course of the design process, we moved to a rectangular tube as the stock material. The R&D process resulted in the rectangular cross bars we are testing on the car now. A comparison between the two designs is highlighted in the images below.
The last detail of the Mazda 3 Rear Hatch Brace is all the hardware tying the brackets and cross bars together, along with the coating used on the parts. For the hardware, we wanted to provide bolts that matched the clean look of the brace and complemented the look we were going for. That led to us selecting countersunk bolts and finishing washers which are stainless steel for excellent corrosion resistance and help add the extra flare we were shooting for. The cross bars and brackets are textured black powder coat, further complimenting the factory interior while providing a rugged finish. As you can see below, the results are beefy!
Thank you for reviewing the details of the design process of the CorkSport Rear Hatch Brace. If you are interested in picking one up for your 4th Gen Mazda 3 Hatch, stay on the lookout – it will be hitting the website in the coming months.
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