Experimental Brushless Outrunner Motor for RC Projects

thingiverse

**WARNING:** This is an experimental design. Be aware that no magnetic analysis has been conducted and the design has not been tested, so performance results are uncertain. The only guarantee I can make is that it will rotate. That's all. **Non-printable parts required** * 2 ball bearings measuring 8x4x3 mm. A minimum of 30,000 RPM rating is necessary, with a preference for metal caps on both sides to prevent dust accumulation. Metal cap designation is ZZ. * 12 neodymium block magnets measuring either 8x4x2 or 7x4x2 mm. Any heat-resistant class will suffice since the printed parts are the limiting factors. Opt for powerful magnets, with a good choice being anything in between N48-N52. For high-temperature resistance, look for designations like M or H at the end (e.g., N52H). * A half-threaded M4 bolt as a shaft. You can also use precision DIN pins and thread them yourself. Feel free to be creative and make it work with any standard M4 part. * 0.6 mm insulated winding wire, such as enameled copper or similar. * 2 M2 set screws. **Manufacturing** There are two different manufacturing methods that can be employed: * 3D print the entire thing. * 3D print parts as a master for epoxy/resin casting. For a quick but inefficient result, you can 3D print everything. If so, consider the following: * The stator core should be printed with a magnetic compound capable of withstanding high temperatures. Thinner layers may yield better results. * The bell should be sliced to maximize radial strength as centrifugal forces at high RPM will attempt to disassemble it. My 3D-printing-inexperienced recommendation would be to use: * Ferromagnetic-PLA for the stator core. This appears to be the only magnetic filament available, but it is not resistant to high temperatures. * Nylon or Polycarbonate for the housing, bell, and spacer. If you desire a stronger and potentially more efficient motor, consider using the 3D printed parts as a master to cast the production part in epoxy/resin. Keep in mind: * There exists a core production method called SMC (Soft-magnetic composite) that can be used to create the stator core from fine iron powder and high-temperature epoxy/resin. * The bell should be cast from a strong material, with analysis indicating that at least ABS-level tensile strength is required. Certain epoxies can provide this. **Assembly** * Wind the stator in dLRK combination with 7 turns per tooth (See [this](https://www.bavaria-direct.co.za/scheme/common/#prettyPhoto) for more details). * Glue the spacer to the inside of the housing and attach the bearings on each side. * Glue the stator to the housing. * Attach the magnets to the bell. * Place the shaft and the bell into the housing. * Use M2 set screws to constrain the bell to the shaft. **Links** For the CAD designs, click [here](https://cad.onshape.com/documents/1d82d48e1a626e89a966ae87/w/84fcab2a456c5856b1c34b16/e/3229e4f6269fb42a7bce95c6) For the bell analysis, click [here](https://www.simscale.com/projects/tapirath/2207_rc_brushless_motor_v1-2/)