Update README.md

README.md

@@ -41,6 +41,11 @@ The rear gear system is 0.5 module. It uses the standard 8 tooth spur gear that
 A bill of materials and build video are to come.
 
 # 3D Printing Notes
+I used the original Elegoo Mars resin printer to print the car. Contrary to popular belief, you can absolutely print robust car parts, even on a resin printer. For many of the parts I used standard resin, especially if they were non-critical like the spoiler, or if I intended for them to be weaker anyway, like the bumper. For parts where strength is needed and for the gears there were two approaches I took that worked. One option is to use ABS-like resin, which I found acceptable. The other is to mix flexible or strength resins to the standard resin. I found 30% of Sirayatech Tenacious mixed with 70% of Standard Shine Tough Grey worked well and I favored that approach. For the standard resins, ABS-like and even the blend you can use pretty normal exposure and support settings if you limit the Tenacious to 30%.
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+Lastly, the TIRES! At first I tried standard resin and printed the wheel and tire together. As you can imagine there was no grip. Then I tried a "flexible" resin and used 100% Sirayatech Tenacious. Unfortunately, this was far from actually being flexible and still was very smooth and plastic like and did not provide any real traction either. Then I found Wanhao Rubber-like resin, and best of all it came in black. I would disagree that the resin is "rubber-like" in truth regarding flexibility. It's still actually pretty inflexible unless you are printing something thin. But it did provide enough flex to be able to print he tire separately and slip it over the wheel. The best part is that it did provide a rubber-like texture and feel and so it does provide grip and in the end worked well. 
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+The Wanhao took me four tries to successfully print as I had no real guidance. I found that I had to use 300% of normal exposure for the bottom layers, and 400% of normal exposure time for the remaining layers. My lift distance was 7 mm, bottom lift speed was 25 mm/min, lifting speed was 40 mm/min, and retract speed was 40 mm/min. The rubber-like resin really needs robust support. I had to double the diameter of my medium supports and the amount of contact depth, and I had to add large supports throughout the model. I think with good support I could probably back off on the exposure times a bit. The rubber-like prints take a very long time.
 
 # RC_Car_CONTROLLER
 Uses an Arduino NANO with two analog joysticks (right and left). Sends to the nRF24L01 on the car being controlled. I use this controller right now for all my RC projects. It is highly adaptable. I will upload my PCB and INO files for the controller also. I have some plans to improve the controller in the future. When I get around to them I will update the files.