Green Lightning 400mm EDF

This gigantic ducted fan was designed for and used in a go-kart called "Green Lightning" but it has an array of other applications including other vehicles or R/C aircraft. As a completely custom design, this huge fan has 12 interchangeable blades and room for a powerful motor. The motor and blade mounting plates ideally should be CNC or laser cut out of metal or carbon fiber due to 3D-printable plastics not handling well with heat. This project uses A LOT of filament (>1.8kg) so beware that more than one 1kg roll will be used up.

Performance:
I use a 7Kw 130kv brushless motor on a 12s lipo battery to power this thruster, but more powerful motors may yield better thrust. The theoretical thrust of this unit (https://rcplanes.online/calc_thrust.htm) at 4Kw is in the range of 150N -190N with a large margin of error from simplifying the blade geometry. For more power, a lower Kv motor can be used at a higher voltage. Motor may become warm, so a cooling fan in the tailcone is strongly recommended. When stress testing the 3D-printed blades out of PETG, they each could handle about 200N of force on their centroid of loading before significant deformation and withstood more than I could measure radially. This gives a safety factor of about 8 with my highest thrust scenario.

Manufacturing the two hub plates:
The blade hub and motor plate file should be used as a template only and the DXF files are provided to make the two required plates.(rotor_mount.dxf) Services such as SendCutSend are available, but personal laser cutters and CNC mills work just as well. I uploaded the DXF files to SendCutSend and got them cut out of 3mm Aluminum, which works well for my performance levels.

3D printing:
I used PETG for the entire thing and printed parts on a Creality CR-10 and a Raiscube A8r. Some parts are very large and need 300mm x 300mm bed space The CR-10 works well for this but those with smaller printers and modeling skill may need to separate it out into smaller sections.

Here are the parameters for the different pieces:
single blade - 1.6mm wall - 2mm top/bottom - 40% cubic infill - use support and brim
top & bottom blade hub - 1mm wall - 100% infill - no support - brim optional
nose & tailcone - 1mm wall - 1mm top/bottom - 20% cubic infill - no support
stator segments - 1mm wall - 2mm top/bottom - 20% cubic infill - no support
nosecone adapter - 1mm wall - 100% infill - no support

Assembly:
The outer housing is not provided in the files because it would be too large for most printers. I used a "muck bucket" lined with Kevlar/epoxy composite over foam spacer inserts. The internal diameter of the housing should be 425mm +- 3mm to minimize the gap between blades and housing. The blades once fully assembled should have a diameter of 414mm. The blades are designed to be assembled with 12x 3/8in.- 4 in. bolts (US) or M10x100mm bolts(metric) This thruster has plates that should really be cut out of metal or carbon fiber to run this thing to full power. The nacelle is also not included because it was intended to be made out of 6" (150mm) PVC pipe in a 15" (380mm) long segment.

final notes:
assembly can be complicated with so many parts. be patient and use sandpaper to adjust tolerances between interlocking parts. hasty assembly leads to damaged or cracked parts.
do not spin the rotor over 8,000 RPM or else it might suffer a sudden kinetic disassembly. Do not let any loose objects or body parts to come in contact with spinning blades or serious injury can occur.
Improper printing or use of damaged parts can also lead to catastrophic failure - inspect all parts before assembly and use.