Hybrid system

[Guest]

I'm just wondering about something as I design my WTC. Is it possible to pump air into a rubber bladder. And as it reverses so air goes back into the WTC to pump water into the chamber? Or is this just redundant and a waste of space and battery power?

[JWLaRue]

Re: Hybrid system

Pumping air to/from a rubber bladder is what folks know as the RCAB system (ReCirculating Air Ballast System). This is a very reliable system that does not depend on consummables like Propel.

When the air is withdrawn from the bladder, it collapses so there isn't a(ny) need to backfill the bladder with water......

-hope this helps,

Jeff

[giovanni]

Re: Hybrid system

Jeff,
What is your opinion on the OTW WTC and ballast systems?

[JWLaRue]

Re: Hybrid system

I really like the OTW dive modules. From both an engineering quality perspective as well as the type of ballast system used.

In my opinion these modules are well designed and crafted from quality materials. Of the many instances of these modules that I have either owned or am aware of, I do not recall hearing of any out-of-the-box problems...no leaks, no other fitment issues. Drop in your servos and receiver and it's good to go.

The water pump-based system provides a very good level of control over the level of ballast. It's not capable of the *exact* ballast control that a piston with appropriate electronics can do, but it is very close.

The one consideration that one needs to be aware of is that they only come in two diameters: 90mm and 110mm. This essentially limits use to medium to large boats.

-Jeff

[giovanni]

Re: Hybrid system

The only thing that i can complain about is the acrylic tube, at this time. I have the OTW made for my 1/12th scale 32nd parallel USS Holland but haven't installed it yet. I bought it from a friend but when it arrived the tube was shattered. I'm planning to exchange the acrylic tube for a polycarbonate. I am going to use 3/8" wall aluminum tube for the ballast tank section with the polycarbonate tubes on each end of it. This will allow me to drill several 3/32" chase bores through the wall of the aluminum ballast tank for the wiring that is now chased through the center tube of the ballast tank. The WTC tube will be 5" diameter. The ballast capacity will be 1000ml.
I have a really unusual way to compress the WTC tubes for a high-pressure seal. I will be applying for a patent and will post images soon. My wife is a patent specialist paralegal, so this should be simple.

[JWLaRue]

Re: Hybrid system

Sounds like whomever shipped the dive modue to you did not pack it well. I've always received mine packed in sturdy tubes....whether directly from OTW or an individual.

You may wish to reconsider using aluminum (or any metal for that matter) for the center ballast section. You'll likely have problems with the water sensor probes grounding out.

-Jeff

[giovanni]

Re: Hybrid system

How does the water sensor work? I could epoxy coat the inside of the ballast tank cylinder interior.

[Guest]

Re: Hybrid system

Water is conductive to a degree, so if you have a very sensitive input that's amplified, you can sense a small short across a pair of probes. The OTW system uses three probes, with one common and two other probes to detect when the tank is empty or full. These probes are usually fed with an AC current so they don't plate-up.

Sounds a bit like over engineering to me with all that aluminium. The OTW works on fairly low pressures, and acrylic only gives problems if you drop it on a hard surface. Polycarbonate definitely is tougher, but it scratches a lot easier, and here in the UK is much more expensive, hence why clear modules tend to be fashioned from acrylic.

[giovanni]

Re: Hybrid system

You have convinced me to only change out the broken end tube with acrylic material.
Thanks.
I will save my aluminum ballast tube for a scratch build for my other hulls.
I do have a spare eFlite 245KV motor and 120amp Castle Hydra ESC that can exchange for the stock drive. I plan to use internal Lipo batteries under the tray, instead of external pack.

[thor]

Re: Hybrid system

I wouldnt use acrylic tubing for anything in a model submarine. Please consider using Polycarbonate.

[giovanni]

Re: Hybrid system

I trust your expertise, Matt.
I may as well change it all out to polycarbonate.
Thanks.

[thor]

Re: Hybrid system

Good move, Sir! Acrylic is much to fragile and prone to fractures.

Matt

[giovanni]

Re: Hybrid system

Many years ago I was a spa and hot tub retailer and every acrylic spa that was delivered was micro-fractured. They now manufacture spas made from better materials.