Hybrid Ballast Tank/Piston System

[QuarterMaster]

Yes Sir. That and I mainly want to explore what is possible using a system like this and Arduino.


Two jack screw driven piston tanks was the original goal but the packaging of all the components in a 17” long WTC upon initial review, looked like that wasn’t going to happen. So I thought I might explore the syringe and peristaltic pump idea for fun. Main ballast tank will only have two states. Completely flooded or completely empty. If the piston trim system fails the main tank can be blown to get the boat back to the surface. The overall piston tank capacity is more than what is needed for trimming. Total ballast with 10% added is 850ml. Ballast capacity was subtracted from the main tank and added to the pistons to make more room available in the WTC.

Looking forward to the development, build, and testing!

Ed

[Monahan Steam Models]

Did some more testing tonight with the peristaltic pumps. Had one hooked up to the power supply set at 11.1 volts to take an amp reading. Amps read In the range of 0.455. Tried to manually stall the 100ml syringe during pumping to get a max amp reading. Amps jumped to the 0.53 range for a significant time before the out let hose blew loose from the pump. No around the tube clamp was used to secure this connection.

Now considering moving the pumping side of the peristaltic pump into the wet to eliminate WTC floods in this situation. This will decouple the motor/driven side into the dry via one seal. I’m using this same methodology with the main ballast tank. Vents and blow of the main tank will be external and operational by a single pushrod. The work ED did with his “skeletal dive system” is a well thought out and executed example to follow.

[Monahan Steam Models]

A little bit more design work done on the WTC.

Added the lower pump shelf and upper equipment shelf in the forward compartment. Swapped the 4 relay pump circuit board out for a much smaller dual channel esc to control the pumps. (The esc is not proportional. It’s on or off each direction like the relays) Moved the twin LPB pumps to the forward upper equipment shelf. (Idea is to keep all the noisy interference stuff away from the other components) Added the port and starboard out runner brushless motors to the aft WTC bulkhead. (This is a first. Normally I like to keep these in the dry space)

Found spots to place the forward compartment servos. These will be converted to a linear motion. Moved the pass through ballast conduit and added a second one. Central conduit will be for low voltage signal wires. Lower conduit will be for high current wires to the motors and such.

Rear compartment servos need to be moved slightly forward and linear conversion mechanisms added to each as well. The central ballast tank will be keep sealed from the fore and aft compartments of the WTC. The venting and blowing of the central tank will be connected externally.

Also moved the syringes slightly inboard of the fore and aft bulkheads so that their flanges rest against the inner bulkhead’s walls. Designed the part that will secure each trim syringe to it’s bulkhead an provide a base for the laser distance sensor to mount to. These also act as a hard stop to keep the trim piston from pushing out the end of the syringe cylinder. They allow the air behind the floating piston to pass into the WTC and provide a mounting surface for a limit switch to be installed incase of a last ditch shutdown of a malfunctioning limit sensor or pump.

If you see any flaws in the design please point them out. I’m presenting this experiment as a WIP not as an example of here’s how you do it.

Still more components and systems to add to the design. There will be water detectors added to each compartment.

Also if anyone can recommend a solenoid Valve for the main ballast vent. I’m going back and forth on venting via a servo and mechanical valve or using a solenoid valve.

Again thank you!

[Bob Gato]

Nick-I am so glad that you are doing this.. its a great idea! I am so far behind your engineering but am holding on tightly to the tip of the rudder as it fastly moves along..one suggestion regarding your wet running outrunners, if you can, try to leave access to the back end of the motors (stand offs?) to allow lubing the back of the back bearing after running the boat. (corrosion x, WD-40 or whatever)-unless , of course if you are planning on using ceramic bearings then that's would be non issue.

[Monahan Steam Models]

Bob,

Thank you for spotting that and pointing it out. That helps a lot! There is plenty of room available in the boat to move the outrunners further aft to gain access to the back bearing.

[Monahan Steam Models]

A delivery of bits and pieces from Bob M arrived a couple days earlier than expected.....today!

The two micro LPB pumps were in this shipment. After spending a good part of the day working on the CAD drawings for the hybrid WTC, I thought I’d take a break and mess around with the one of the LBM pumps using the bench top power supply.

Prior tests using the benchtop power supply, I was able to test the peristaltic pump hooked to 100 mL syringe to gauge the rate of water filling the syringe overtime at a given voltage. At 9 V the peristaltic pump would fill the 100 mL syringe in 30 seconds. At 11.1 V the peristaltic pump would fill the 100 mL syringe and 22 seconds.

Today was time to test the micro LPB pump moving air. I set the benchtop power supply to 11.1 V and connected the outlet of the pump to the 100 mL syringe with its plunger set at 0 mL. Impressively, the pump moved the plunger to the 100 mL mark in seven seconds.

The main ballast tank in the hybrid WTC design is 650 mL. If the displacement of air is equal to the displacement of water, then this would assume it would take 45 1/2 seconds for one pump to completely empty the main ballast tank. With two of these pumps connected in parallel, (as planned in the current design) the main ballast tank could be pumped dry in 22.75 seconds.

Assuming (for now because I’m tired, it’s late and I’m too lazy to dig deeper into the science) a 1 to 1 ratio of displaced air to water, that potentially two LPB pumps can pneumatically displace the total volume of the main ballast tank in roughly the same that each peristaltic pump can displace each trim tank is at this early stage a very interesting thing.

[Monahan Steam Models]

Made a small but significant mistake earlier on in describing the overall system function. The main ballast tank will operate as a SNORT system. Not as a S.A.S. system. I had the two systems mixed up.

Made a small amount of progress on the design today. Worked out the positions of the forward and rear pushrod penetrations with bushings and u-cup seals. The servo pushrods are stainless steel. Figured out the placement and penetrations for the intake and outlets for the peristaltic pumps as well as for the LBM pumps in the forward WTC end cap. Started work on the forward compartment linear pushrod to servo mechanism. Spent a good part of the day going down the rabbit hole on IP68 multi pin connections and cable glands in preparation for making a plan to get power and signal wires through the forward WTC bulkhead for the torpedo system.

Still have yet to decide and act on, how I will set up the externally mounted main ballast tank vent valve along with the emergency gas blow valve. Have a few ideas but none that I’m completely satisfied with yet. Wanting to keep the high pressurized gas circuits out of the main WTC as best I can. Mainly the primary torpedo gas circuits and the emergency main ballast gas blow circuits.

The aft compartment needs attention too. Need to update the motor mounts as per BobG great input as well as add the rest of the components. More that needs to be worked on.

[Monahan Steam Models]

Starting to marry all the bits together in 3D land and in the real world. I know these posts of 3D CAD models are not as exciting as photos of real work, but they are still a documentation of the many hours of pre planning work that goes into a build. Creating the 3D CAD models takes time, skill and most importantly accuracy. Each part and assembly needs to be accurately created. If the 3D model doesn’t accurately reflect the real world thing in every regard then it is useless as a tool for planning out complex assemblies.

I started out in my youth drafting with a pencil and paper when it came to figuring out an idea. The manual skills I had learned at the time and knowledge of tools dictated how I would draw out and plan to build something. Decades later, and after much knowledge gained in what technology and tools can be utilized to make white, this is how I do it.

It’s all in the planning and knowing what you design envelope is.

The real world looks more like this:





Lots of planning and experimenting. Seeing what fits and what doesn’t.

In the above 3D CAD model, the grey bulkheads represent the actual model’s cast in place bulkheads inside the moldings that I am stuffing all this **** into. The spacing and shape is dead nuts to the original real world thing. Just to recreate this in a 3D environment takes a learned knowledge on measuring and plotting an object accurately with simple measuring tools.

The results yield you the physical design envelope you have to work with. The other design fundamentals such as weight and buoyancy force on the overall assembly come from how accurate you are in your measurements as well as the black art of a wizards knowledge in his craft.

[trout]

Saw this and thought of you:

https://www.pololu.com/blog/894/new-pololu-distance-sensors-with-digital-and-pulse-width-outputs?utm_source=newsletter&utm_medium=email&utm_campaign=2102DS

[Monahan Steam Models]

Great find!!!

Thank you posting this! Looks like they’re using the same Lidar sensor chips as the sensors I’m using currently. The overall foot print of the board is much smaller too.

[Monahan Steam Models]

Got some parts made today for the piston trim tanks while I was busy figuring out other aspects of the WTC design. Got the floating piston gland backing made. It turned out great and with a quick OD turn on the lathe it slides down the syringe bore like butter. Also got the syringe distance sensor/hard stop mount made today. Everything fits together perfectly. Couldn’t be happier. Soon will be testing the distance sensor readings. The floating piston was already tested and works perfectly. Probably spend tomorrow back on the hybrid WTC design as there is still much to work out.

[redboat219]

Some inspiration

https://youtu.be/-85Y8T0ZYU8

https://youtu.be/sPFJZFGQ03E

https://youtu.be/4CEz3rMzV18

[Monahan Steam Models]

Good find Redboat!!!

Thanks for sharing these links! I enjoyed watching them. They give a great example of what is possible with fine trim adjustments of the pistons.

[Monahan Steam Models]

More stuff added to the experiment.

Some updates on the hybrid WTC design. Got the bow plane mechanism worked out as well as the main ballast tank vent/blow and emergency gas back up valves mechanism worked out. Still need to focus in n the plumbing of all this together in the model and add the torpedo circuits. Getting there slowly but surely.

[rwtdiver]

More stuff added to the experiment.

Some updates on the hybrid WTC design. Got the bow plane mechanism worked out as well as the main ballast tank vent/blow and emergency gas back up valves mechanism worked out. Still need to focus in n the plumbing of all this together in the model and add the torpedo circuits. Getting there slowly but surely.

Hi Nick,

Can I ask you what CAD system you are using! I really like what you are doing with your designing of the WTC and the components first, and then building off the concept you have designed! Nice work you are doing here! Thanks for sharing!

Rob
"Firemen can stand the heat"