Hi

I plan to print the 55mm FJD Jet Drive, and I wonder what printer settings are recommended? Layer height and anything else?
Is that info somewhere around here? I searched a bit but didn't find it.

Thanks

Hi

It said in the beginning of the FJD thread that one requirement for the project was that supports should not be needed.

I notice when I slice the Impeller, that the blades are slightly elevated compared to the hub. This causes supports to be printed. Should it be like this?

The first two layers shown, looks like this will cause some issues as the supports also don't go all the way out to the ends.

The tips of the blades contact the surface at the same level as the hub bottom. But this is not critical and you can lower the impeller slightly below the bed level if needed to negate the use of supports. Impellers can be difficult to print depending on the printer. You may need to use a raft or supports for impellers and you may not be able to print these at all (I have difficulties) and may need to have Shapeways make one for you.

When I started this project I used PETG because it was impervious to water leakage but there are now PLA filaments that won't leak when the correct settings are used - you'll have to play with your settings. 0.2mm layers are fine but you can go finer if you have the time and patience.

Thanks for your response.

The impeller was not at all as flat as shown in your pic, when I got it into Fusion 360, it looked really strange in the bottom part. I cut away a bit to make it all flat and get a good start for the print with the blade end flat to the bed, just as the blades are at the top.

It'll be interesting to print the impeller. Using a wide nozzle with a thin layer might do the trick, I'll try 0.08 layer thickness, it's a 3 hour print for me, that's not much

Printing the intake now, estimated at 14 hours at 0,32 layer height.

I downloaded the same one you did and posted it, didn't change a thing (nothing 'strange' on the bottom). You asked for recommendations on layer height and decided to do it differently. Whatever. Good luck with your endeavors.

I had already started the print with 0.32 layer height, being a bit eager 😉

I'll see if I can get a pic posted of what it looked like in my case later today.

hi. trying to print the 75mm jet drive
however its FAR to BIG for my printer
is there any way someone can slice it cleanly in half and add lip with bolt holes for m4 bolts so i can print in two pieces and bolt it together again afterwards.
i tried but the STL completely fried and half the walls are now missing

@OctaneX: the impeller was never meant to be printed with an FDM type of printer, but SLS instead at 3D print companies like Shapeways.
Nevertheless some people managed to print usable impellers with an FDM machine.

At this moment I am working with the 45mm FJD.
The nylon 12 SLS printed impellers seem to have ahard-time when 2kW of power is applied to them.
To a certain amount of rpm/power they work fine, above that they presumably flex too much.

Edit: checked the original 45mm impellers in my CAD software: they are perfectly flat at the back as designed.
Indeed the footprint is a single line thick since it ends on an edge, which is perpendicular to the helical spline the blade describes.

Originally Posted by itsthegeek

hi. trying to print the 75mm jet drive
however its FAR to BIG for my printer
is there any way someone can slice it cleanly in half and add lip with bolt holes for m4 bolts so i can print in two pieces and bolt it together again afterwards.
i tried but the STL completely fried and half the walls are now missing

Please tell me the application for this drive, I am curious

Originally Posted by itsthegeek

hi. trying to print the 75mm jet drive
however its FAR to BIG for my printer
is there any way someone can slice it cleanly in half and add lip with bolt holes for m4 bolts so i can print in two pieces and bolt it together again afterwards.
i tried but the STL completely fried and half the walls are now missing

Did you find a solution? You can re-download the files if you mess them up - no worries. How tall can your printer print?

The Thrasher is going for $1K now. Sheesh....

Originally Posted by sundogz

The Thrasher is going for $1K now. Sheesh....

It is a very well designed jet-drive and a true Ready To Run RC.
However this is more expensive than a 1/7 scale SC truck RTR including 6 or 8S batteries and a charger!

Nevertheless made in the USA, or at least assembled and designed.

Wonder what will happen now with the cost of our hobby now cost of labor is rising in Asia, transport cost from there multiplied with up to 10 times as it was before the pandemic. And do not forget the cost of raw materials.


Anyway, found this inspiring movie (you can skip the introduction by going straight to 1:05 minutes)

Mini Supercharged Jet Boats Take On HUGE RAPIDS!!! (Mini Boat Mafia Episode 2) (10 min 11 sec)

I can see it pays to buy high quality seats! Great drone work there, thx for posting.

Saw this recently on Youtube. Multi-finned stator. Axial pump with long overlapping blade impeller. But the graphics department didn't re-adjust the angle of the steering nozzles in the dual drive setup (1:41) to pivot vertically. I made that mistake once, it causes exaggerated heeling over in turns (even on a catamaran - imagine the impact on a V-hull) Funny that design engineers didn't catch that little faux pas.

Introducing the new A5 Series waterjet (2 min 9 sec)

Originally Posted by sundogz

Saw this recently on Youtube. Multi-finned stator. Axial pump with long overlapping blade impeller. But the graphics department didn't re-adjust the angle of the steering nozzles in the dual drive setup (1:41) to pivot vertically. I made that mistake once, it causes exaggerated heeling over in turns (even on a catamaran - imagine the impact on a V-hull) Funny that design engineers didn't catch that little faux pas.



https://youtu.be/ERCnq43HN4c

That's the problem between engineers who design these products, and the artists who make this animation. They miss technical know-how.

The reason why a former employer of me ask us to learn how to do these animations too. No more mistakes, but quite a slow learning-curve!


Did you notice the shape of the inlet channel?
The overlapping very high pitched impeller is made for marine diesel engines I assume. Very low rpm high torque machines.

Did you notice the stator housing? Looks like one of a mixed flow jet, like a Berkeley for example or American turbine.

Originally Posted by unusual_rc

Did you notice the shape of the inlet channel?

Yes, it looks strikingly familiar to me There are certain design features that if you veer one way or the other, you lose something in the process.