Pump Jet (32mm Prop) by N7_Cat

Last crawled date: 3 years, 3 months ago

An offshoot of my project https://www.thingiverse.com/thing:4606971 RC Pump Jet boat, I modeled a stand alone water jet originally intending boat to be modular in design. After consideration I decided to just integrate the pump jet with the boat body rather than try to seal the modular parts against water ingress.
This model might still be useful for someone though. I've also kept the motor separate from the pump jet in case you want to model your own motor housing for different motors.
Note this design has inlet and outlets for water cooling, you will need to plug or remove these if not needed
BOM:
Motor: 2212 if using the provided mount https://www.aliexpress.com/item/32672300112.html
Prop: 32mm with 100 mm shaft (note get the 10 cm one with 3.18 motor as the 2212 shaft is 3.175 mm - I initially tried to model an axial flow impeller but I found this purchased item to be far more sturdy. Advantages are it has built in high speed bearings and replacement props can be purchased from here as well. I also added provisions for a diy 3mm shaft using 623 bearings) https://www.aliexpress.com/item/32714017489.html https://www.aliexpress.com/item/32528668718.html
Servo: sized for 9g servo (important you will want to waterproof or find an alternate waterproof servo) https://www.aliexpress.com/item/33005962141.html
M3 X 6 X 5.3 Embedded Nuts (old link no longer works - possible substitution M3 X D5 X L6) https://www.aliexpress.com/item/4000232858343.html
M3 Machine Screws (Button head and Flat head) https://www.aliexpress.com/item/32798146322.html or stainless https://www.aliexpress.com/item/32934186482.html
Thrust vector nozzle, stator and motor cooling impeller should be printed in TPU for layer adhesion qualities.
For post processing pics please go to https://www.thingiverse.com/thing:4606971
Note that the embedded nuts go on the inner side for this model while they go on the outer face for the boat project due to access issues. The boat model also has an alternate motor mount with base which might suit some builders better as well as a template for custom motors other than the 2212.
Josh at Flite Test did a good vid about waterproofing RC electronics with Peter Sripol (Flite Test | Waterproofing Electronics)
Enjoy >^.^< also let me know if there are any issues as my main focus for the near term will be the RC boat project and changes / improvements there may not make it here.
Updated 10/3/2020, removed the bar surrounding the servo to improve printability.
Updated 10/7/2020, improved printability by modifying the fillet around the shaft support
Update 10/9/2020, After a print failure of the protective grid on the intake as well as impact durability test failures I have replaced with a filament heat stake method as shown in my boat project post processing pics.
Insert 1.75 mm filaments into the slots and use a low temp soldering iron to melt the ends into the inlet - you could also use servo wire and glue in place...unless you like grinding baby fish into a pulp...u monster
Updated 10/11/2020, increased clearance for the prop shaft
Updated 10/15/2020, motor mount was a tight fit, increased clearances - note if print elephant foots you will still need to trim mount a bit
Updated 10/18/2020, Added a variable trim ride plate. A bent 1.5 mm servo wire serves as the retention and adjustment mechanism, backup retention provided by an embedded nut and M3 X 10 screw + spring. Joint held by filament joint. Note stator profile carried over from my boat project and outer gasket allowance missing :P caturday cat prefers to nap >^.^< it is a feature not a deficiency
Updated 10/20/2020, some weird artifacts were cropping up in cooling impeller during slicing, increased to high resolution stl and fixed wall width
Updated 10/21/2020 increased prop clearance on stator bowl
Updated 10/25/2020 improvements to trust vector nozzle to allow M3 X 5 X 6 mm embedded nuts to ride on the inner race of the 623zz bearing
Update 11/6/2020, feedback on my boat project suggest that a thrust vector nozzle with a slight pitch up would be beneficial - added a thrust vector nozzle with a 5 degree pitch up. If you find that your own boat is going nose down this new nozzle will help :). Added a 10 deg pitch nozzle if your CG/CB requires it
Update 11/18/2020, first functional test of the waterjet - I found that even with TPU gasket air and water would spray out thus sealing the stator bowl to inlet duct body with silicone or glue is necessary. I found an issue with air locking - I don't fully understand the cause but experimentally determined a way to resolve this via a pending modification to the thrust vector nozzle. Update uploaded (Thrust Vector Nozzle Variable Pitch) but untested - I'll hopefully get a chance to print and test by tmw. Testing confirms the air lock issue is resolved with this new nozzle - there is some loss of efficiency. I don't really know why this fixes the air lock but I suspect the stator bowl fins were not redirecting enough of the rotational energy generated by the prop resulting in an area of low pressure which would draw air in from behind the outlet...without high speed cameras or CFD I can't really say. N7 Cat says "wut he trying 2 say iz I putz mah paw ober da nozzle and dat fixes it"
11/21/2020 did some more study on propulsor units and updated the pitch and number of stator vanes - 5 vane stator uploaded - will test later and delete original if testing displays improvement. Test showed marked improvement in both trust and elimination of air lock using the 5 vane stator - original deleted. For anyone else designing or trouble shooting other pump jets on thingiverse the number of stator vanes needs to be a prime number and different than the number of prop blades otherwise a standing wave can develop. At some point in the future I might experiment with a properly designed axial flow prop and stator - salt sintering might be able to create a strong enough part for use as a prop.
11/25/2020 reverted thrust vector nozzle to neutral pitch