Gwen's Nautilus design as described by Jules Verne - Discussion- Everyone welcome.

[neitosub]

Hi Gwen,

Is the air pump also located in the aft compartment where the leak occurred? If so, I would also check if there’s air leak happening somewhere along the pump housing. Your pushrod seals being pushed out to the water means that there’s an overpressure happening somewhere inside the dry compartment of the WTC.

Nate

[rwtdiver]

Hi Gwen,

Is the air pump also located in the aft compartment where the leak occurred? If so, I would also check if there’s air leak happening somewhere along the pump housing. Your pushrod seals being pushed out to the water means that there’s an overpressure happening somewhere inside the dry compartment of the WTC.

Nate

What Nate says makes a lot of since! And the type of material that your bulkhead (endcap) is made of they may have just used a pressure fit on the brass bushing with no adhesive which would normally work unless the pressure that Nate is talking about did accrue that might have pushed the bushing out far enough to cause a leak!

Rob
"Firemen can stand the heat."

[GwenB]

The bulkhead came with the WTC I bought from Bob. It's obviously 3D printed, and I believe it's resin. CA should stick to it well I imagine.

[GwenB]

Hi Gwen,

Is the air pump also located in the aft compartment where the leak occurred? If so, I would also check if there’s air leak happening somewhere along the pump housing. Your pushrod seals being pushed out to the water means that there’s an overpressure happening somewhere inside the dry compartment of the WTC.

Nate

Yes, the air pumps are in the same compartment. Thanks, I'll try to check them. Do you have any recommendations about how to confirm a problem like that, other than an obvious air leak?

[Bob Gato]

I see what you are saying about the cup seal housing not secured to the bulkhead. I have always used thin CA to secure the housing to the inside of my PLA 3D printed bulkheads, I then applied silicone around the EXSTERIOR portion of the brass housing coming out of the bulkhead. Not sure what material your bulkhead is made of, so you would need to see if CA would apply here or not!? It works great on PLA. If it will work just make sure you scuff up the outside of the bushing before installing.

Rob
"Firemen can stand the heat."

It sounds logical that air pressure in the compartment pushed the brass seal housing out-although I have to ask...does the boat have standard servo setup or are they the linear servos that Bob uses now. Any possibility a servo side load when actuated caught the guide bushing and pushed the assembly out?-BG

[neitosub]

Yes, the air pumps are in the same compartment. Thanks, I'll try to check them. Do you have any recommendations about how to confirm a problem like that, other than an obvious air leak?

I would spray some soapy water on the pump housing/hose connections and let the pump run to see if any air bubbles appear. Is your WTC equipped with a silicone hose housing the receiver antenna on the outside? If there is an air leak/overpressure, you should be able to feel some air escaping from that antenna hose. What Bob said can also be the cause, could be as simple as a servo pushing the bushing out of its bulkhead.

Nate

[GwenB]

It sounds logical that air pressure in the compartment pushed the brass seal housing out-although I have to ask...does the boat have standard servo setup or are they the linear servos that Bob uses now. Any possibility a servo side load when actuated caught the guide bushing and pushed the assembly out?-BG

No they are not linear servos. They're standard servos with the arms clipped short and yes they do cause a bit of side loading on the bushings, which has concerned me a bit from the start. My WTC is a SubDriver 300 V2 I bought a few months ago from Bob. Honestly I would like to upgrade them to a linear setup. I asked Bob about that a few weeks ago but he doesn't have anything to do that with the WTC I have.

Here you can see how the servos are set up:

​

[GwenB]

I would spray some soapy water on the pump housing/hose connections and let the pump run to see if any air bubbles appear. Is your WTC equipped with a silicone hose housing the receiver antenna on the outside? If there is an air leak/overpressure, you should be able to feel some air escaping from that antenna hose. What Bob said can also be the cause, could be as simple as a servo pushing the bushing out of its bulkhead.

Nate

Thanks Nate, I'll do this and see what I find. Though the more I look at my setup the more I think the problem was caused by the servo side-loading.

[rwtdiver]

Gwen,

Possible option if the issue is the bushing and seals!





I use ONLY the rubber bellows on all my scratch-built WTC. It save having to be so precise on your protruding linkages. They work great, and I have never had a leak using them. If you could pop out the existing brass sleeves and install new sleeves, then locate on Amazon (or other places) the appropriate size bellow to fit over the sleeve and the push rod opening.

This is just a suggestion that may or may not work for your application. I now design ALL my WTC (sub drivers) using the rubber bellows for control surfaces!

Rob
"Firemen can stand the heat."

[GwenB]

Gwen,

Possible option if the issue is the bushing and seals!





I use ONLY the rubber bellows on all my scratch-built WTC. It save having to be so precise on your protruding linkages. They work great, and I have never had a leak using them. If you could pop out the existing brass sleeves and install new sleeves, then locate on Amazon (or other places) the appropriate size bellow to fit over the sleeve and the push rod opening.

This is just a suggestion that may or may not work for your application. I now design ALL my WTC (sub drivers) using the rubber bellows for control surfaces!

Rob
"Firemen can stand the heat."

Thanks Rob, I'll take a closer look at that.

[JHapprich]

Hi Gwen! I'd say you need longer and more ri gid intermediate levers between servo horns and pushrod, also the joint should be closer to the seal. Decreases lateral shift and lateral force on the pushrod.
only my opinion.

[Bob Gato]

Well, weather its air pressure or servo side load -I would remove the rods from the seal assemblies anyway and chuck them in an electric drill and spin polish them with a soft cloth and a little polishing compound so they wont tend to grab the bushing-also I am assuming that the seal that came loose was on the right side in this picture? I am seeing a figure 8 drill hole (double drilled or worn?) in that pivot hole for the servo link. That doesn't look like it would pivot too smoothly...Maybe replace or fix.

I like the CA idea on the/both seal housing/s and reinsert to the proper depth....while out for maintenance-maybe I would also cut the next concentric size of brass tubing to fit over the seal housing and with a dab of epoxy smeared around the inside, slide it on to form a shelf/stop so the seal housing can only move in if needed to remove it and any wayward air from those pumps will blow the end cap off before blowing the seals out LOL...
With that done-lube with some grease upon reassembly ... You got this Gwen!

[GwenB]

Well, weather its air pressure or servo side load -I would remove the rods from the seal assemblies anyway and chuck them in an electric drill and spin polish them with a soft cloth and a little polishing compound so they wont tend to grab the bushing-also I am assuming that the seal that came loose was on the right side in this picture? I am seeing a figure 8 drill hole (double drilled or worn?) in that pivot hole for the servo link. That doesn't look like it would pivot too smoothly...Maybe replace or fix.

I like the CA idea on the/both seal housing/s and reinsert to the proper depth....while out for maintenance-maybe I would also cut the next concentric size of brass tubing to fit over the seal housing and with a dab of epoxy smeared around the inside, slide it on to form a shelf/stop so the seal housing can only move in if needed to remove it and any wayward air from those pumps will blow the end cap off before blowing the seals out LOL...
With that done-lube with some grease upon reassembly ... You got this Gwen!


​

Thanks Bob,

I think I have made a pretty good start at fixing the problem. I removed the bushing/cup seal assemblies and pushrods from the bulkheads. Polished up the pushrods and greased them with lithium grease, carefully crimped the ends of the outer bushings inward to prevent any problems with cupseals popping out, CA'd the outer bushings back in place in the bulkhead, and reinstalled the cup seals, inner bushings, and pushrods. I have some silicone glue arriving today which I will add an exterior seal with around the outer bushings. The pushrods are definitely moving smoother through the bushings/seal than before and I think the grease will also help keep a good seal. Now I just need to do the same thing with the forward bulkhead.

Here's how they look now:

​

[GwenB]

OK, whew... The WTC is all reassembled with everything working and [hopefully] flooding problem taken care of. I think next that I will power up the WTC and dunk it in the tub to test moving the servos a lot and make sure there aren't any leaks.

Update: I did a tub test and ran everything for a while including flooding and blowing the tank and running the motor, lots of servo movement etc. Everything checked out just fine. No leaks, everything operating smoothly. So I'll keep my fingers crossed for finishing the trimming and doing dive testing in the tank outside tomorrow.

[GwenB]

Updated Nautilus drawings version 4.3 Nautilus-Gwen43.pdf

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