Touchscreen Chassis

I finally got a couple of nice days in which I tore the center console, the trim piece on the dash, and radio /audio head unit out of the car. I measured everything and, sure enough, the unit is completely different is size from the early C-4. It’s also a bit challenging in that the four attachment points are offset differently from the front of the radio. One is set back 3/4″, one 1-3/4″, and the others in between. They are irregularly distributed around the face as well. This means that I will have to redesign model.

First and Second Sketches

The first step in the process was to gain access to the dash and measure the existing unit as well as the mounting points. In my C-4 model that meant pulling out the plastic shifter console, the center vent unit and the plastic radio trim piece for the center part of the dash. Once those were out, I found two bolts holding the head unit in place.

Once everything was clear, I measured and made a rough sketch.


With measurements in hand I fired up Progecad, an AutoCAD clone that is pretty affordable. I created a two-dimensional plan view, printed it, and took it out to the car to field check it.

Now armed with updates and additions on paper, I modified the drawing and then transferred the plan view to Autodesk Fusion 360 via a .dfx file. If you’re not familiar with it, Fusion 360 has a really reasonable license for makers i.e. it’s free. It’s also easy to use although there is a bit of a learning curve. I realize that sounds contradictory but the software requires a shift in thinking for me, and that’s a slow process. I’ve been gradually working it into my workflow, which is why I started in a more conventional CAD package.

3D Model

In Fusion, I moved the sketch into three dimensions, generated a model (for posting) and then generated a .stl file for my 3-d printer. The original Comvette chassis is designed to be cut from acrylic but I’ve chosen to go with a 3d printed one, at least for the prototypes because it’s “what I’ve got.” I have a CNC router in the works, so I might wind up cutting a final version, but there’s no real time-line and I want to keep the project moving. Additionally, while the original C-4 audio system looks like it mounted with four bolts, all on the same plane, this one features each one at a different depth, as the model shows.

I uploaded the new file to Slic3r and discovered that the object was too large for my build surface, So I had to cut it in two for the printer. Once that was accomplished and the design sliced, I started the printer.

Printing took about seven hours. I won’t have time to try it in the car until the end of the week, but it fits the screen well enough. If it fits into the dash, I think that I’ll reinforce across the top and bottom to alleviate any strain on the screen.

Fresh off the printer with the supports still attached.
Started removing the supports
Left-hand piece (upside down) mostly cleaned up.

The next step for the prototype is test fitting, after which I make modifications as necessary to the model and reprint. In the mean time there’s a lot of setup and configuration to do on the Raspberry Pi, as well as a radio and a power management system to build..

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