Hood Pin Press Molded Plates
A well known feature of the E30 is the forward opening hood. Unfortunately, I rarely have a hood on my car, and the hinge designed for the forward opening hood is very difficult to install and remove. While rebuilding the front end of my car, I decided to ditch the hood hinge and switch to a set of AeroCatch Hood Pins.
One of my main concerns while designing the hood pin mounts was designing a mount that would be able to secure the hood at high speeds. A common tool found in almost any fabricators toolbox is a variety of dimple dies. Dimple dies offer a very aesthetic look, but the real purpose behind them is provide rigidity and strength within a thin sheet of metal.
From the dimpled design, a flat profile can be created. Keep in mind the dimpled portions needs a small amount of material to be created, so, it is suggested to slightly oversize the outside flange and trimming to fit. On a production run, the flat profile could be adjusted to account for this.
The final design was created using 16 ga. steel, but provides the same bending strength and deflection as a flat piece of 11 ga. steel.
With the use of additive manufacturing, it is possible to create a press die containing a hybrid of 3D printed shell and resin. The press die is also created keeping in mind that the driver and passenger sides mirror one another. The die incorporates a separate hole locating pin that can be swapped to either side.
Each press mold is printed out of ABS Filament with a hollow bottom and gradually increasing infill mesh. The hollow bottom and infill mesh create a cavity for the Resin to be poured into. Adding the resin is a quick and inexpensive way to add rigidity to the press molds.
To press the profile into the sheet metal, a 20 ton hydraulic press is used. Thick steel plates are placed on top and below the press molds to distribute the force across the whole mold. After the the stamp portion is done, the 90 degree bend is added in a standard sheet metal brake.
Once formed, the plates are welded to the rest of the tube structure and ground smooth. After grinding, there is a small amount of pin holes which are filled in with body filler before painting the finished structure.
With the mounts complete, everything is bolted onto the car. The hood pins are bolted into the holes, allowing the hood to be set onto the car to determine where the pins are located. Once drilled, the remaining profile of the hood pin can be marked out, cut, and installed.
