Nova Wheel Assembly

January 3, 2021

Recently, I was tasked with modeling a wheel assembly for a drag-style RC car. I have quite a bit of experience with 3D modeling, but in order to complete this build I was going to need to step up my game a bit. The entire project has tight tolerances for all the components to line up properly when assembled. I also needed to complete the wheel in a reasonable amount of time, so I wouldn't be learning any new software. I'll be completing this build with Blender.

Introduction

The client provided me with some rough sketches and measurements that got the entire process started. I've redrawn them here to reflect the style of an engineer drafted image. I don't have any training in this field however, so they may not be exactly as they should, but they were certainly close enough to create a nicely fitted wheel.

3D Modeling

The majority of the process was simple, but creating symmetry in a 5 lug pattern proved to be somewhat difficult as mirror modifiers wouldn't cut it. I tried a few variations for getting the hole alignment right for the center lug holes and the decorative lug nuts on the edges of the rim. In the end I decided on two different methods to accomplish the task. For the lug holes, I knew the measurement from the origin to the edge and placed the first hole on that line, then just duplicated and rotated 72 degrees for a 5 lug pattern to get the proper hole alignment. I believe that the 6 lug pattern required a 60 degree rotation around the origin.

For the decorative beadlocking lugs (streetlocks) around the edge of the rim I used an array modifier set to follow a curve and a NURBS circle as the curve that would be followed. I felt that this gave the best results with the least amount of distortion to the lug mesh. I used a similar technique to create the decorative wave that surround the lugs on the outside of the rim. The rest of the modeling process was extremely straight forward, using only simple extrusions and boolean modifers to create the remaining mesh.

The entire modeling process took about 10 hours, broken up over the course of 3 days.

If this process is something that you'd like to see elaborated on in a video, I can certainly make one. Send me a description of what you think would be useful in a tutorial (preferably one that's not already easily found on the internet) and I'll see what I can do. If I do decide to make a video I'll post it at the bottom this section.

3D Printing

Typically, I create my own support material when I design parts, but this wheel assembly had quite a few overhangs on it so I decided to try Cura's built-in support generator. I was very happy with the outcome. The only issue that I have with it, and it's purely aesthetic, is that it leaves a woven pattern in the model directly above the support structure. This isn't a real problem however, as the support is on the back of the wheel and will never be seen.

Below is a link to the file that describes the print settings in full and the approximate time it takes to print each part. Also included is a description of the hardware that was used to print the models.

Testing

Below you can watch a quick video demonstrating the printed wheel assembly in action. It's purpose is to maintain the position of the tire on the rim, preventing the tire from sliding and increasing traction.

Drafting

As I said earlier, I don't have any kind of training in the creation of a technical drawing, but I do certainly think they're interesting. I wanted to put something together that seemed, to the untrained eye, like it could be the real thing. In order to create an image that looked like an engineer drawing I used the models that were created from the rough sketches and ran them through Blender's edge/line based render engine called "Freestyle". It uses mesh data to create something that appears to be hand drawn. I used two separate passes through this render engine to create an outline with a background first, then rendered again, but this time focusing on the hidden geometry. I then layered the two images to create a single composite image that appeared to be a technical drawing.

There would still need to be some measurements added to the image to really make it feel like the real thing. In order to accomplish this, I turned to an add-on in Blender called "measureIt". It's an easy to use add-on that takes measurements between points on the mesh. Simply render a separate pass for the measurements, enable the render pass checkbox in the freestyle settings, then overlay them on the final image.

At some point I do intend to learn more about engineered drawing techniques and I've already done a bit of research. If you'd like to learn more about technical drawings you can read about them here. There's also a good video that describes industry standards and best practices here.

Files

I've decided to include both the STL files and the gcode that was produced inside of Cura for this build. Feel free to check them out!

There may be some more projects related to this RC car coming, but for now feel free to browse my other projects with the link below.