This project was really just me having fun before I graduated from my high school, where I had access to the machining equipment necessary to complete the project. Unfortunately, I did not have enough time to finish all of the parts. However, I do have enough to give a very clear idea of what it will look like. Though the gearbox was designed to be used on a FRC robot, it will probably never see use.
This tutorial was made through the Autodesk FIRST High School Intern program.
Aluminum Hex Bar
The PDF attached to this step is a complete Bill of Materials for this project. It includes information such as the quantity, cost, material type, and vendor for many of the required parts.
Step 1: Designing the Gearbox
I designed my gearbox entirely in Autodesk Inventor before purchasing a single part. I started by choosing a gear ratio (which you can learn more about here), and then ensured that there would be no clearance issues between the rotating parts using the sketch shown in the second picture. This sketch also helped me define the exact shape of the gearbox plates. From there, I designed the rest of the gearbox, part by part. Throughout the design process, I had to ensure that I could make each part that I designed on the tools available to me.
Step 2: Milled Parts
Step 3: Lathed Parts
Photo Credit: http://www.grizzly.com/products/G8688
Step 4: 3D Printed Parts
Photo Credit: http://www.rapidreadytech.com/2012/07/university-of-nevada-reno-opens-3d-printing-to-student-body/
Step 5: Purchased Parts
Now, we can begin assembling the gearbox.
Step 6: Motor Assembly
Step 7: Motor and Bearing Installation
We also have to press several 3/8" bearings into place. Pictures four through six show the three locations where these bearings are installed.
Step 8: Output Shaft Assembly
Step 9: Case Assembly
Step 10: Bearing Block Assembly
Step 11: Final Assembly
The installation of the 1/2" snap ring is as close to completion of the gearbox as this tutorial can go. Unfortunately, I ran out of time to manufacture several of the necessary parts, leaving the gearbox in an incomplete state.
Step 12: Finished Product, Lessons Learned
Here are some lessons I learned from making this gearbox:
- Ensure that you have sized holes properly for bolts and motors - I ended up having to modify the holes the CIMs are mounted in by manually sanding them down.
- Control tool chatter when milling parts - resulted in a few parts with bad surface finishes and even caused some parts to be over-sized
- When used properly, CAD is an incredibly powerful tool. Because of it, I didn't have to redo a single part for reasons other than manufacturing errors.