Ryan Bao

Chemically powered car cad

I was commissioned to produce a CAD file for a school project for an acquaintance with the goal of producing a chemically powered car that runs on exothermic reaction for a prespecified distance.

In order to create the basic frame of the car, I used a tried-and-true method that was similar to many of my robotics teams robots, a double-H-frame. This frame gives each part at least two attachment points for maximum stability, and provides ample room for different attachments. Because I didn't have much experience in chemistry, I was unsure of the exact scale of the parts needed to make this car possible, so I decided to make the attachment room as large as possible.

For the actuators, we used torqueNADO motors from TETRIX. This is because I have had experience with TETRIX and had good results with their DC motors, and because the ChemCar was designed to support more weight than the average FIRST robot, I used the torqueNADO, which supplied significantly more torque then the DC motor. For a microcontroller, we used the Arduino, because it is more universal than the REV control hub or the PITSCO microcontroller, and for power supply we used relays connected to the main power source, controlled by the Arduino.

The main power supply was a three-chambered module with the exothermic reaction in the center chamber and two endothermic reactions in the side chambers. This provided a temperature difference that produced the electricity necessary to power the model. In order to fulfill the weight requirement a water tank was needed. As such, and because this requirement was communicated late, the water tank was added as a very tall cylinder. This is one of the benefits of using the larger double-H frame.

The method used to stop the vehicle was a light sensor that would detect when a chemical reaction reached a point where the fluid was opaque enough to block light entirely. In order to accomplish this, a syringe was placed on top of a tank of fluid to allow the user to inject a precise amount of chemical into the tank to make the vehicle stop at the correct time. The light sensor was built into the fluid tank and connected to the controlling arduino. A flashlight was also inserted into the opaque fluid tank to reduce dependence on natural light.

The final product, although clearly not optimized, could theoretically work as a functional proof of concept. The electronics are not pictured because they are placed on the bottom, although they are are placed in the CAD model.

Reflection

Overall, given the time constraints (I only had a week to build this entire model on top of my other extracurriculars and courseload), I am fairly happy with the way that the model worked out. The gears interlock and can be moved in CAD realisticly. Although the model is fairly simple and makes use of only simple shapes, I got good practice combining various parts and assemblies into one final product, as well as converting the CAD model into technical drawings. If I were to redo this, I would make the H-frame larger so that the water tank does not have to be so tall.

Downloads

Assembly.pdf

Full CAD files

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