Helical Gears for VEX Robotics
Entry ID #: 9231
Created: Wed, Dec 9, 2020 7:16 PM
For our entry to the VEX Robotics "Make It Real" CAD challenge, we decided to design a set of helical gears that could easily be used in place of the stock VEX spur gears. These gears needed to use the same hub design as the stock gears so that they could fit in the same spaces and be mounted interchangeably. In addition to this they needed to have all the advantages that helical gears bring over spur gearing:
- Lower backlash
- Higher maximum loads
- Smoother operation
- Less wear
Although helical gears do have some disadvantages in the form of:
- Slightly higher friction (compared to spur gears)
- Higher manufacturing cost
- Discrete left and right gears
Despite these disadvantages, helical gears offer advantages in systems such as drive bases where lower backlash can help with maintaining reliablilty during autonomous operation. The smoother operation that helical gears provide is also helpful in drive bases because of it makes movement more fluid, which can both save time while accelerating as well as allowing for faster operation. Helical gear also provide an advantage in high load systems such as lifts. In these sytems the higher load capacity of a helical gear as well as the decreased wear are both helpful in making gearing more reliable and robust.
To create this part I used an Educational liscence of Fusion 360 version 2.0.9439 and an open source add-on. This add-on generated the gear form easily however it could also have been accomplished by using a gear hobbing profile, a sweep/ loft operation, and the circular patterning feature. After the gear profile was created, I combined the teeth with the hub of the different vex gear files to create the final body. To create the discrete left and right handed gears, I used the mirror feature to mirror the gear body about the ZX plane and saved it as the left side gear.
This project inspired me to look into the many different gear profiles that are used including: spiroid, fishbone, helical, worm, spur, rack, and more. Using CAD helped my robotics team by letting us design and optimize our ideas when we were unable to access buiding materials. We were able to optimize multiple parts of our robot such as the drive base as well as speeding up the building process once it began. I plan to use 3D design software in the future throughout my career in mechanical engineering which will help me to visualize and bring to life my ideas.
Links / Videos
I created this simple test to show the difference between the backlash in standard VEX spur gears and the helical gears I designed and 3D printed. Although this is a qualitative test, when compared to the video of the Spur Gear Backlash Test, it is clear that there is significant improvement in backlash.
I created this simple test to show the difference between the backlash in standard VEX spur gears and the helical gears I designed and 3D printed. Although this is a qualitative test, when compared to the video of the 3D Printed Helical Gear Backlash Test, it is clear that the helical gears provide a significant improvement in backlash.