Victor III

[bwi 971]

As the ballast tk priciple is working I make a new one with all the protusions at the right positions (Ballast pipes, P/V valves, breather pipe). When cutting the acrylic tube the cut is often not perpendicular to the tube.
I find it not optimal when the caps are plased at the ends of the tube.

It can be made perpendicular on the lathe but in my case I need a steady to support the tube, and that I don't have, so I designed one, the goal set was to make it printable, the purpose is to face the tube in this case this is a low load operation and I guested printing will be ok.

All the parts for the steady



Assembling the base by tapping 4mm rods trough all 3 parts (additional the base parts are glued together)





Assembly of the roller pins (a 12mm bearing is used, kept in place by 4mm shafts)



The 6mm hex nuts were inserted into the provided recess.



The assembled steady



Mounted on the lathe



And in use, the steady works fine and is more than sturdy enough to do the job.



Grtz,
Bart

[bwi 971]

I designed a housing for the P/V valves to conform with the other ballast tank appendages. The P/V valve will be pinched between an upper and lower housing, both of which will be secured with SS M3 hex bolts.





The other appendages were also adapted. Previously, the bolt holes on the inner piece were open; now they are capped.



The breather line was provided with a larger bore. Instead of a smaller one, I decided to use an orifice at the end of the breather line that will be located in the sail. This way, it is easy to test the dimensions of the hole and to clear it when it becomes clogged with debris.

The tech rack of the pump was also redesigned. Now it is more sturdy and is bolted to the intermediate ballast tank cap.










Regarding the pump, I conducted some vacuum and pressure tests, which revealed that the pump seal was failing. The housing cover was bent between the bolts, resulting in insufficient downforce on the o-ring at those locations. Since I had P/V valves installed, the pressure did not cause a leak in the WTC, but the negative pressure was low enough to pull air from within the WTC.

My opinion is that the cover will deform over time even if I add thickness to it. So, I decided to make a backing plate out of 1.5 mm aluminum. After installing it, the pump cover does not deform anymore, and the vacuum and pressure tests were ok.













Grtz,
Bart

[bwi 971]

cherry poped...the WTC was tested.

Filling the Ballast Tank:
The gear pump fills the ballast tank with water. Air escapes through a 1mm breather line. When the ballast tank is full, water escapes through the breather line. However the small diameter breather line cannot cope with the displacement from the ballast pump. To prevent overpressure in the ballast tank, P/V valves were installed. I wanted a simple P/V valve, so I opted for a duck valve after testing several options. As shown in the video (timeline 0:30), they work efficiently (water comes out of the breather line and the three P/V valves). The pump can be switched off once the sub reaches the diving draft.



Emptying the Ballast Tank:
The gear pump removes water from the ballast tank. As the breather line is open, water will be drawn back into the ballast tank. However, the pump's displacement is greater than the amount of water entering through the breather line. Water is pumped out of the ballast tank despite the small intake through the breather hole. An underpressure is created in the ballast tank. Due to water displacement, the WTC will rise to the surface, and when the breather hole breaks the surface, air can enter the ballast tank, allowing further emptying by the pump. You can hear the suction when the breather tube breaches the surface in the video (timeline 1:38).

Things to Redesign: As you will notice, the time required to surface is quite long. This is because one of the P/V valves was dislocated, allowing additional water to flow into the ballast tank through the opening. I attached the P/V valves using blue gasket sealant, which was not strong enough to withstand the underpressure in the ballast tank. The additional inflow of water nearly matched the pump's displacement. To ensure better performance, I will also use a breather line with a smaller hole, as the test shows that the P/V valves work.



Additionally, during the emptying of the tank, a small flow of air bubbles is released together with the discharge water (you can see it in the video timeline 1:00). Since the suction line is at the deepest point of the ballast tank, this must be due to a seal issue in the pump housing or the gland seal. While this is not critical, I need to inspect it to identify the cause and if possibly resolve it.

Grtz,
Bart

[bwi 971]

I had to add the footholds at the bottom. First, they were scribed with an old stencil of the Akula.









The little propellers of the creeper motors were also designed and printed. I designed a four-bladed propeller and then cut off two of the blades.




Before decanting the paint, I want to finish everything that needs to be painted. I will have two sails: one for operating the sub and one for presenting the sub on dry land; the latter will have all the masts. I printed all the mast parts. I put a lot of effort and time into designing them to be as close as possible to the real thing by using pictures. I even incorporated the bolts. Below are pictures of the more complicated ones.



























The hatches on the display sail have been cut out. I did the same with the doors because I wanted to reveal the reinforcements that I have integrated.











The hatches were thinned at the edges, but I left the base as it is to provide a sufficient surface for gluing them in place.









I'm waiting on several ordered parts, such as the 3.5mm aluminum tube for the thicker masts and the overpressure valve for the ballast tank.

I think the next step will be applying some paint.

Grtz,
Bart

[bwi 971]

Would it matter if you placed th anti-siphon tube inside the ballast tank instead of outside?

as long as its position is higher than the watersurface when the boat is sufaced it will be ok, but I like to have some additional head so I maximised the distance by bringing it out of the WTC into the sufaced dryspace of the boat.

[redboat219]

Would it matter if you placed th anti-siphon tube inside the ballast tank instead of outside?

[Tom Spettel]

Wow this is looking good.

[bwi 971]

Various Progress

I reprinted all parts with the new resin as it withstands water.




Servo Linkages
I don't like the Z bends to connect the rods to the servo horns. Especially in combination with brass horns, I find it a PITA. I opted for a 90° sharp bend by grinding a corner out of the rod. After bending, I applied some soft solder to give it back some strength. I designed a snap-on retainer to prevent the rod from working its way out of the connection. To prevent the rod from bending when the servo horn turns, I provided a hinged setup. The O-rings for the link bulkhead penetration came in. The bulkhead penetrations were fixed in place with blue Loctite sealant, which was also used to seal the holding bolts of the motor.

















The oilite bushings for the prop shaft were pressed in place, and the collar of the outer bushing was turned down to fit into the provided recess.







All the new ballast tank appendages were glued in place using the Loctite blue sealant.









The forward endcap was prepared with a connection for the pressure sensor and a recess for the WT toggle switch.









Grtz,
Bart

[Subculture]

Never had much luck with geared pumps using plastic gears. Sadly not a lot of choice for smaller metal geared pumps now. Kavan make a nice geared pump, but it's fairly large, could fit a smaller motor to the pump head of course.

Also seen pumps from China which are pitched for use with hydraulics (oil) so not sure if the parts will be compatible with water, but small and brushless. e.g. https://tinyurl.com/5yx35pm5

[bwi 971]

I had a new insight regarding 3D resin.

The pump was left with water inside, and a few days later, I tried to turn it, but it was seized. After opening it up, I noticed the gears had become soft and were squeezable. I directly linked this to a message on a Dutch forum where a fellow modeler had experienced the same issue with water-washable resin on a 3D printed shroud. Since I don't use that kind of resin, I thought I would be okay. The parts were unpainted.

I did some research on the web and found out that depending on the brand and type, some printed resins can expand significantly and become quite soft when submerged. The good thing is that they will return to their hard state once they dry out.

I did not find the critical submersion time before the effect takes place, but my pump is a critical part and will contain water for a longer period of time. I'm reprinting the pump with a different resin and will run some more tests.

Meanwhile, I traced all embedded lines to make them more pronounced and working on the fwd dive planes.
I was very happy that I managed to position on of the frames right on top of the rods of the bow planes, so I needed to partly crop the frame.

























Grtz,
Bart

[bwi 971]

Inserts in place, motor attached.



Servo link bushing glued in place shaft seal fitted.



Servo rack attached to endcap (3 servo's)





test fitting ballast tank and aft compartment


ESC for propulsion and pump will also live in the aft compartment, space is available.





Ballast tank layout.



Grtz,
Bart

[bwi 971]

I noticed that the holes in the motor endcap are too large to accommodate an M3 thread. Instead of redoing the endcap, I decided to enlarge them to 3.5mm and fabricate M3 threaded inserts, and press/glue them in place. Eight pieces need to be fabricated.

In the endcap, the M3 bolt just drops into the hole (one of the inserds alongside).



The existing holes were opened up to 3mm; they just miss the inner edge (left 3,5mm, right 3mm).



Bushings are fabricated from 10mm aluminum rod that I had lying around.













Grtz,
Bart

[bwi 971]

Having no access to a 3D resin printer. I, would have done the piping by hand. Annealing brass tubing with a torch then eye balling the bends.

I would have done the same, now its 3D CAD, estimate the tolerances/clearances, add supports, slicing and hope for the best.

Grtz,
Bart

[bwi 971]

Neat! End product or master pre-casting?

Jörg

End product, did the prototyping in PLA to verrify all was ok.
Grtz,
Bart

[redboat219]

The end caps of the ballast tank are ready... Perhaps my reasoning behind making a custom water pump did not make sense. Routing the tubing inside is tricky, as the minimum bending radius of the tubing is relatively large. The last picture shows that both the discharge and suction of the pump and the lines integrated in the intermediate cap are in line. This was my aim; this way, no bending of the tubes is required. It will only require a small straight piece of tubing.











Grtz,
Bart

Having no access to a 3D resin printer. I, would have done the piping by hand. Annealing brass tubing with a torch then eye balling the bends.