It's been a few months since I worked on the project since I've been doing a few other things around the house. I had a day off over the 4th that I could blow off the dust and do a couple of things. The big project that I have been dreading is cutting out the center crossmember on the chassis and drilling out all those steel solid rivets. It took about 6 hours to get it out but it finally came out after giving me a good fight. Next will be to box the frame and add in another crossmember to mount the hanger bearing support for a two-piece driveshaft. More to come on that effort later.
I have also been working on another smaller portion of the project in my scarce spare time. Earlier in the build I made a metal extension on the lower center portion of the dash to mount the future AC controls. I didn't really like the plastic bolt-on extension that came with the AC kit that I intended to use plus I really wanted to make the controls look as period correct as I could and integrate them into the dash. So I went ahead and bought the Vintage Air controls so I could build the extension around them.
The other thing that didn't look period correct were the knobs that came with the kit. I had always planned on replacing the knobs either by machining new knobs or finding some that fit. After searching around the internet and not seeing anything to my liking I decided to try to 3D print the knobs. After looking at what it would take to outsource the effort I determined that I could just buy a 3D printer and try to do it myself. Being a “screw-it-up yourselfer” always seems to be the road I travel.
After reading reviews I bought a cheap but decent 3D printer (Ender 3 Max Neo) that was on sale and started printing a few objects to see what it could do. Once I got relatively comfortable with it I went ahead and designed and printed a test knob. The knob is shaped pretty close to the knob on the old choke cable. I will eventually need 4 knobs. One for the fan, defrost and hot and cold adjustment. I want to just put a simple block F, D, H & C on the surface of the knobs for the labeling.
To attach the knobs to the shafts of the controls, I bought a brass press-fit grooved insert with a set screw to place into the plastic base. The first knob off the printer was basically to test if the brass insert worked and to see what type of surface quality I could expect. The insert worked great but the surface quality was a little rougher than what I expected. I had used the standard out-of-the-box settings so after reading up on it it was obvious that I needed to use a higher (and slower) printer setting. I also took the test knob and sanded on it to see how the plastic reacted to the sanding. The sandpaper that I had on hand was too aggressive so that told me that I needed to use a finer grit (600+) or higher. I also had attached the knob to a shaft mounted to a drill so I could sand it while it was spinning. I learned that if you go too fast the plastic melted and just smeared instead of being sanded smoother. So in the end the test knob was totally trashed but I learned a ton.
I increased the settings on the printer to the highest resolution settings and then printed a second knob. This time the quality was a bit better but you could still see some of the layer (which apparently is typical, especially on smaller pieces). I tried to use what I learned on the first knob by sanding the second knob and it looked pretty good but I think the wall thickness was a little thin so when I pressed in the brass insert I had some unintended deformation. The 3D printer actually only builds the outside shell and then does a lattice internally to support the shell...or that was how I had the machine set to print. The first two knobs only took about an hour each to print since they were basically empty shells. I went ahead and cut the second knob in two pieces so I could see what it looked like inside. I then decided to print a third one but this time make it 100% solid. This increased the print time from 1 hr to a little over 2 hours.
So far I have sanded it down a bit and primered it black to see how it looks. Each one is getting better than the last and the third one looks close but I have changed the profile and I'm printing a new one. I made the edges on the one being printed as I type this a little more rounded and next I want to see how the lettering works out. I think my approach will be to slightly sand it, do a high build primer on it and sand it smooth and then touch-up any of the larger voids with some glazing putty. I plan on painting the knobs a gloss black with white letters. I ordered a fine tip white paint marker that has oil based paint in it so hopefully I can dab it in the letter pocket and let it cure and then overcoat it with a gloss clear.
I'll update with some pics once I get further down the road.
1949 Chevy Panel Truck A Project Journal I'm old but I make up for it by being immature.
