At the beginning of the 2019 season my team wanted to use a drivetrain with high mobility opting to do swerve. However, with no previous experience with this drivetrain we decided to do Vex’s VersaDrop instead, which ended up causing many issues. Due to these issues and lack of mobility of the octocanum drain train relative to swerve, I began designing my own swerve module, hopefully for future use.
The overall goals of this swerve design were to be light, small, modular, simple/easy to build, and well-priced. I feel that this design accomplishes these goals but there is still room for improvement.
Unlike many other swerve designs that use large thin-section bearings my design uses a bushing method very similar to 2067 design. The rest of the module is designed around this bushing. A 38T pulley connected with a 1:1 ratio to a versaplanetary articulates the module and a NEO with a 4.71: 1 reduction drives the two 3” wheels at 15.76 ft/s (free speed). The entire design is quite modular so if a larger or smaller reduction is needed, the drive motor assembly can be easily modified.
Most of the custom parts are to be 3D printed out of either PETG or Alloy 910. The other custom aluminum parts, specifically the c-channel mounting plate and the swerve saddle legs, will be CNCed on our router. For the modules we made this summer the bushing was made using a manual lathe but once our Haas VF2 comes in, it is likely we will mill them instead.
Furthermore, the modules we build this off season were based on version 75 of the design which utilized ¼” thick 4” wide rectangular tube stock for the saddle. The CAD linked is version 81 which replaced the tube stock with a 3D printed azimuth and two connecting aluminum “legs”. This was done to reduce the weight of the module and to reduce its swept area for better integration into the chassis. Additionally, if this design were to be used in a competition season, we would likely use a VP lite with a banebots 550 instead of a 775 to save more weight.
Cost Per Module: $247
Speed: 15.76 ft/s free speed 12.77 ft/s adjusted speed
Size: 3.5x6.5”, 5.48” tall, and 3.43” of ground clearance
Weight of V75: 4.9 lbs
Weight of V81: 4.4 lbs (estimated)
There are only three main things (as of right now) that I would like to change about this design: the height of the module, the amount of ground clearance, and switching the steering motor to a NEO. With the height of module being 4.6” above the 2x1 it mounts to, there will need to be something preventing the motor/VP from begin hit. The other two changes are not too much of a concern, but I feel that if would possible help improve the design.
During my redesign of the module (75->81) I was concerned that the 3D printed azimuth would not hold up, so I ran a linear static simulation of the module. Under a robot that weighs 200 lbs, the max deformation is less than .009 mm with a high factor of safety. If you would like to see the exaggerated results you can find it here.
Link to CAD: https://grabcad.com/library/2834-swerve-module-1
Special thanks to 910, 2067, and 2767 for sharing their designs and answering many of my questions!
If you have any questions, comments, or thoughts I would love to hear them!