I'm jumping in!

[fryslan76]

Compared to the other parts you need a childs bike inner tube is so cheap that even replacing it often to be sure is no problem. And the best part is has a nice attachment point added to it allready.

Enjoy.

Fryslan

[olegodo]

One thing that always seems to happen to me is that when I think I have a lot of spare time to spend on whatever project I am working on. Some other stuff always pops up and takes away that time.
However my test shroud and prop combo is finally printing now. 46% and 1h55mins in at this point. If assembly goes ok, I hopefully can do some testing tomorrow.

I have gotten around to testing and thinking about my manipulator arm design though.
I really wanted to use servos because of the precise control it would give me, but I really don't think thew will be powerful enough when used directly. And as they can only rotate 90 or up to 170 degrees (at least for the ones I have) I cant gear them to get more torque either as the movement range will be far to small.
What I am left with is to convert them to continuous rotation servos. This means disconnecting the potentiometer inside the servo and replacing it with normal, static resistors. This allows them to spin continuously, pretty much just making them geared but sealed motors. I will still be able to adjust speed and direction on the fly.
The big downside to this is that is that you lose the precise angle control. But I think this will still be ok as I can make gears to increase both the torque and range of movement.

I still have one servo that has been filled with mineral oil for months now, and it's working fine.

Stepper motors would also be an option if the servo route fails. I have 3 Nema 17 steppers, shaft seals and a pretty good idea to seal and oil fill them. Problem I see with that is the weight and general size.

Thruster pictures:

Printprop.JPG (48.25 KiB) Viewed 3054 times

2014-08-19 20.09.32.jpg (353.03 KiB) Viewed 3054 times

Printing done.
Still need some finishing touches, but came out pretty good. 3h 40min print time @ 0.2mm layer height. The surface looks a lot rougher then it feels.

2014-08-19 22.34.28.jpg (249.83 KiB) Viewed 3039 times

[olegodo]

Also!

My Battery and electronics housing arrived. Two Fibox 180x180x100mm cases. IP 67 rating and actually came with a vacuum in them. Was really hard to get the lid of, but at least they are even air tight
I also got lucky and scored some subsea connectors to use between the battery box and the electronics housing.
The company a friend of mine is working for had ordered them by mistake and couldn't return them. According to him they are rated for 64 amps and waterproof down to 300m. Really good stuff! Will post pictures when he comes by with them.

Picture of battery and electronics housings, Six 4cell batteries in the one to the right:

[scubersteve]

Wow, that shroud looks great!
Can't wait to see what kind of results you get out of the assembled thruster.
Keep up the good work.

[Bubbles]

Really nice work with the shroud!!!!

[Bubbles]

One question because I am a bit confused .which direction your propeller spin?Because I think you should reverse the shroud 180 degrees .

[olegodo]

Thanks Bubbles!

The nozzle will be most efficient in the direction on the picture you posted. However according to the literature you can find about the rice nozzle on the web, it should increase the efficiency in both directions.
Also, the propellers I am testing with, witch is the ones in the rendered pictures are 100% symmetrical and should perform equally in both directions. The nozzle and flow obstacles like the motor will change this though. Test will show by how much.

Printed the rest of the parts now, but I think I will have to go back to the drawing board again. The arms that was intended to hold the motor became to weak and hard to assemble. And if this thing can max out at a couple of kilos then I think the arms will flex too much and the prop will end up touching the nozzle.
I have a new idea and working on modeling it now.

[olegodo]

New day, new design.

I removed the arms that I intended to use to mount the motor and have now replaced them with one mount (Shown in blue in the pictures)
This thing is a lot easier to print and will be 10x stronger. also making sure the motor and nozzle is centered will be a lot easier.
As you can see in the pictures the two pieces slot together so that they are all lined up and secured with one M6 bolt on each.
Downside is that I need to print a new nozzle

Also added a cone for the motor.

[TigerShark]

Looks great, only thing is what parts of your outrunner motor are spinning? I couldn't mount mine that way since the back of the motor is the only part that doesn't turn (end you have the dome/ fairing on).

[olegodo]

This is the same style of motor I have (mine are 28-36 750kv)
The part where the cables enter the motor is stationary. Same side as the shaft.