ROV Thruster and propeller for brushless motor T-MOTOR MN2212 KV780

Thruster for ROVs (or floating stuffs)
This thruster structure and propellers (CW and CCW) are design for the brushless motors T-MOTOR MN2212 KV780 V2.0.
Two figures show some performance tests using unmodified BlueRobotics Basic ESC 30A R3 @15V (the fit equations are in the files).

The thruster structure is made of 4 pieces: 1) the main body (where the motor is attached by 4 screws) with cables exiting on the left or right side, 2) the front and 3) rear caps providing hydrodynamics and propeller protection, and 4) a piece to be inserted from the bottom which provides extra hydrodynamics and protection for the cables arm.

Extra parts required:
- 6 x M3 brass/stainless steel threaded inserts (<= 4 mm long) which allows an easy an frequent assembling/disassembling of the front/rear parts.
- 6 x 6 mm M3 nylon/stainless steel screws (to attach the motor and propeller)
- 6 x 12 mm M3 nylon/stainless screws (to attach the front and rear parts)
(optional: 2 x M3 stainless steel washers could be added to increase the safety distance between propeller screws and motor windings)

=> Total plastic weight : 52.3 g
=> Total weight (w/ screws & motor): 128.7 g

Thruster fixation:
- 4 x M4 stainless steel screws (maximum 10 mm length inside the thruster structure part, i.e. to attach on a 6 mm thich support, use 16 mm screws)
- 4 x M4 stainless steel nuts (prevailing torque or not) to be inserted from the inside of the thruster structure

The brushless motors will need extra protection for intensive use in salt water. As a general recommandation for a lasting use, avoid salt and dirt with these motors. Rince the motors with fresh water after each dive, and eventually pulse some air inside to help drying and remove dirt. Front/rear caps and propeller should be removed for this process.

On this example, parts were printed using a Bambu lab X1C 3D printer.
All the structure parts were printed with PLA, 100% infill (to work at any depth), with 0.12 mm layers (but 0.2 mm is enough), with some support for the thruster body. The propellers were printed with PLA-CF (wich helps a bit for printing quality) but basic PLA is sufficient for a good stiffness and resistance. A quick sanding has been done on the leading and trailing edges. Note that ABS or ASA could also be used, followed by a short exposure to hot acetone in order to improve the surface state.