The wheels bolt onto this hub, which has a set screw to grab on to the 8mm drive shaft transferring power from the servo drive actuator module.
CAD source Wheel Parts
3D Printing STL File: Wheel Hub.stl
3D Printing Notes
- The set screw hole is identical to that on the servo coupler and shares the same issues. See servo coupler instructions for more details.
- We will need 6 of these, one for each wheel. Also: consider having one or two extra on hand as spare parts.
- Example print durations:
- Fast PLA rough draft: 14 minutes each * 6 hubs = 1.5 hours total.
- Slow PETG final draft: 30 minutes each * 6 hubs = 3 hours total.
Post-processing
Estimated time: 10 minutes per hub * 6 hubs = one hour total.
Tools:
- Drill
- 8mm reamer
- Soldering iron
- 10 to 14mm long M3 bolt, with washer and hex wrench.
Parts:
- 3D printed wheel hub
- 4 * M3 heat-set insert
Use 8mm reamer to clean up the center hole for the drive shaft.
The M3 thread heat-set insert for the set screw going in to the side is installed the same way as the identical part in servo coupler. See servo coupler instruction for details.
The remaining 3 heat set inserts are for us to bolt the wheels onto. Since they are easy to install we do not need the extra M3 bolt tool. We do, however, still have to be careful about maintaining alignment. In this picture, the heat-set insert is starting to lean off-center and n eeds to be corrected before it cools and sets at an angle.
Depending on exact dimensions of heat-set insert and 3D printer settings, the hole may be too small or too large.
If the hole is too large, the inserts will not be able to hold itself in place. try using epoxy or other adhesive to glue the insert in place, or try printing hubs with smaller hole dimensions.
If the hole is too small, it will push too much plastic while it melts. "Too much" is when the bolt hole is no longer accessible from the other side, which is the direction we'll be bolting the wheel from. In this picture, the hole on the right was too small and there's excess plastic that needs to be removed. (Try an X-Acto blade.) To resolve a slightly too-small hole, use a drill bit to remove some material before installing the heat set insert. This was done for the hole on the left, which shows the desired lip of plastic being pushed ahead of it (which will help keep it in place) without too much excess that blocks bolt access.
A successfully completed wheel hub will have the heat-set inserts level and flush to one side (shown here) and all M3 threads accessible from the reverse side. (not shown)
