Hybrid Ballast Tank/Piston System

[Bob Gato]

Is the Mav-2 giving you 1/8 venting internally? many 1/2" water valves don't really open internally the .19635 sq" that gives you 1/2" worth of flow.

Consider a flow check-a timed leak down of a set volume thru an unrestricted 1/8" tube vs the same volume thru the mav-2 depressed

[Subculture]

I didn't realise that was your vent. No wonder you're getting trouble. You want the vent directly on top of the tank or higher.

[trout]

I am just spit wadding here, but I agree with your assessment. The resistance of air (surface tension) means we need an opening of about 1/8”(minimum). Even with David’s excellent Sub-Driver, there is a fine adjustment of the flap and opening. Not enough opening and the tank does not fully expel all the air. Too much and it will not seal. The simplistic path for air to escape, the better.

[Monahan Steam Models]

Maybe I have created a pee trap like the U-bend on a sink drain by plumbing it the way I have? I might try swapping the tube coming from the main tank with the barb sticking straight out of the back of the valve instead of the barb pointing vertically.

[Monahan Steam Models]

Steve,

The vent valve is a Clippard Mav-2.





The connection from the vent at the top of the ballast tank connects to the stainless steel barb in the above photo. The brass barb is where the tank is vented when the servo depresses the valve.

Nick

[SubDude]

What vent valve are you using?

[Monahan Steam Models]

What diameter is your vent valve? If it's it's less than 3mm/1/8" then the vent maybe skinning over with surface tension after the first ballast vent/blow cycle.

The ID of the vent is 1/8”/3mm.

Small steam boilers for RC boats will sometimes get bubbles trapped in their vertical water sight glasses that result in a false water level reading. A simple trick to break the bubbles tension and prevent this from happening is to insert a thin diameter length of wire inside of the sight glass. I tried this yesterday with the vent valve outlet but it did not have the same effect.

Admittedly, I was concerned at the beginning of this project during the early design phase about mounting the vent valve lower than the vent at the top of the tank for this exact reason. There might be a simple fix.

I will need to take a closer look at what may actually be occurring to cause this. Then I’ll know if there is a solution or not. If it is obvious to anyone, please point it out. I’ve been staring at this project for far too long. It’s kind of like you can’t see the forest when you’re in the trees.

Nick

[Subculture]

What diameter is your vent valve? If it's it's less than 3mm/1/8" then the vent maybe skinning over with surface tension after the first ballast vent/blow cycle.

[rwtdiver]

Finally after getting the end caps and their penetrations sealed up and thoroughly leak tested, I was able to finally do the first complete assemble WTC test tank dunk today. Feels like it has been a million years since I started this project.

The first test was simple. Just flooding the main ballast tank and manually trimming the two piston tanks. Well dag nabbit, look ma it hovers at mid depth!

https://youtu.be/cSjJs8bf1pM

First time I’ve had a WTC that can hover statically. It a novelty for me.

Once the LiPos are charged fully, I plan to do more testing using the gyro trim functions.

All was not totally perfect with the test. I did experience one small issue with venting the main ballast tank that I will need to find a solution for. On the second dive the main tank would only vent about 2/3rds then air exiting through the vent valve stop flowing. It seems to be a airflow/hydraulic issue. The water column above the vent valve opening (which is remotely mounted lower than the top of the tank) appears to create an equalized pressure with the air trying to escape. I added a tube extension to the vent to bring the outlet up higher. That helped a bit but was not the silver bullet.

Anyways, I’ll need to solve this issue.

Nick

Great job on your Hybrid ballast system Nick! I really like how well that system operated! You put a lot of time in planning, designing, and development. And it was very much successful!

Rob
"Firemen can stand the heat"

[SubDude]

Looks really good Nick! That is quite an accomplishment.

[Monahan Steam Models]

Six months of hard dedicated development ending in 15 minutes of free time to do these tests and documentation that yields 1+ minute worth of video..... Yea it’s a labor of love for the craft but sobering at times for the work put in.

[Monahan Steam Models]

Finally after getting the end caps and their penetrations sealed up and thoroughly leak tested, I was able to finally do the first complete assemble WTC test tank dunk today. Feels like it has been a million years since I started this project.

The first test was simple. Just flooding the main ballast tank and manually trimming the two piston tanks. Well dag nabbit, look ma it hovers at mid depth!

https://youtu.be/cSjJs8bf1pM

First time I’ve had a WTC that can hover statically. It a novelty for me.

Once the LiPos are charged fully, I plan to do more testing using the gyro trim functions.

All was not totally perfect with the test. I did experience one small issue with venting the main ballast tank that I will need to find a solution for. On the second dive the main tank would only vent about 2/3rds then air exiting through the vent valve stop flowing. It seems to be a airflow/hydraulic issue. The water column above the vent valve opening (which is remotely mounted lower than the top of the tank) appears to create an equalized pressure with the air trying to escape. I added a tube extension to the vent to bring the outlet up higher. That helped a bit but was not the silver bullet.

Anyways, I’ll need to solve this issue.

Nick

[Monahan Steam Models]

It floats with just the main ballast tank: https://m.youtube.com/watch?v=IiCpdk...ature=youtu.be

[Monahan Steam Models]

Thanks BG.

As hard as I try making these videos, I still manage to get the correct terminology butchered while trying to explain the functions of the system. Like I said, I dread making videos but I want to pass the knowledge the best I can. I like functions so far that have been worked out to function so far but I want to hear what you guys think about this project. I have thick skin.

Nick

[Bob Gato]

Your a freakin' magician..