Old/New CO2 system still available?

[bob_eissler]

Skip made up a nice piston system for his marlin and albacore. Using the wtc cylinder as the side wall is a very elegant design .

[thor]

That's the ticket, Bob, exactly. That is what I am doing, but I have eliminated the jack screw all together. It is a bit of an oddball system, but it is working better than I had hoped.

[JWLaRue]

BTW Jeff's piston inside the modified OTW cylinder is very nice.
Although he stole the Dial-A-Depth from me!
Hi Jeff! Knee! BD

Yup, my piston-in-a-cylinder has been working flawlessly for close to 10 years. It's been so reliable that I don't think I've even opened the cylinder more than once in all that time....and that was to replace the cylinder O-rings/seals last year.

And contrary to BD's comment about the origin of Dial-a-Depth^tm , it really does allow me to have very, very exact control. I can 'hang' the boat on just the top inch or two of the scope.

-Jeff

[bigdave]

Skip made up a nice piston system for his marlin and albacore. Using the wtc cylinder as the side wall is a very elegant design .

I remember that system. It was really top notch.
He had it at Jim's years back and we were all giving it the Oooo, Aaaaaa! BD

[scott t]

Wonder if threaded nylon rod would work for a jack screw?

[thor]

Dont need a jack screw....

Skip's system was a superb piece of engineering.

[salmon]

Rick Palumbo did a piston using a water pump to move the piston back and forth. I have that sitting on my bench. Very clever idea. I am playing with that to see if I can get it to work a little better. That would get rid of the additional gear too.

Anyways, back to CO2, I agree with Matt, the advice has been given from multiple sites, advising not to go CO2 and/or warning you about the dangers. I am glad to see you are going to try some pumps that are ordered.

[Ralph --- SSBN 598]

Tom,
The piston moved by using a water pump is similar to a pump filling and emptying a rubber bladder inside the Main Cylinder.

Exact same principle.
The moving piston is more complicated to build.
It does looks better than a plain rubber bladder. (balloon)
Works the same.
The rubber bladder expands and contracts.
The piston moves to increase and decrease air volume in the main cylinder.

[thor]

It is simply a ridgid balloon.

[bigdave]

Aaa!
A dirigible! (Ridged balloon)
Let's hope it does not say Hindenburg.
Sorry. Didn't Flip Wilson used to say, "The devil made me do it" lol BD

[Guest]

Wonder if threaded nylon rod would work for a jack screw?
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It would work okay on the bench, but I would expect you to experience problems in the field, as plastic is not very strong compared with steel, and will bend very easily under pressure.

A threaded shaft may seem a bit agricultural and inefficient means of retracting a piston, but it has a number of advantages. It offers a very high reduction and is self-locking when stopped. It's also cheap and readily available, so easy to refurbish.

Very high quality geared motors are available on ebay from the likes of maxon, portescap, pittman etc. These are usually surplus, NOS or secondhand, but will probably last forever in a model submarine, and can be purchased for a fraction of their original retail price.

Also by directly controlling the position of the piston with a screw, you have a lot of options with regards to deciding filling time, if you use a pump to fill the tank, which works perfectly well, the filling speed is dictated by the flow rate of the pump being used, and these often tend to be a on the slow side. Also the quality of many of these pumps has gone down greatly in recent years, so reliability may be a concern.

The biggest hurdle for most model submariners contemplating a piston tank ballast system is that you really need the use of a lathe to make accurate fitting parts. It does amaze me how many modelmakers will spend hundreds on kits, but baulk at the price of a small machine tool which has the capacity to pay for itself many times over in this hobby.

Having said that, if you can bench fit to tolerances of say 5 thou and under, you could make the parts for a piston tank without a lathe, along with all the other round parts on a model sub. However it does take a lot more time working this way, and you need the necessary skill which comes with a bit of knowledge, and a lot of practice.

[southern or]

Piston tanks have been employed in wet hull designs for decades here in the UK.

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They can be heavy depending on the method of construction used, but ultimately the only thing that adds weight over other forms of ballast systems is the threaded shaft for the jack screw. A CAD image of the R & R system posted below shows the piston tank is elegantly built into the end cap of the WTC, with resin helical gears, which are quiet and light in weight. The motors are fairly large, but that enable the tanks to be swiftly retracted, dive times are under 10 seconds with these modules, so you can get pretty scale looking dive times even with WWII boats.

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Engel tanks are particularly heavy I think. They are a bit over engineered, with pretty thick cylinders, metal gears, big motors etc. and it all tends to ratchet up.

The 4 tanks I have are pretty wide, but they aren't that heavy by themselves. That giant motor with reduction gears and the switch assembly does add some weight, but it isn't enough to through off things. My problem has been the off keel location of the tanks so they don't hit each other. The Oscar isn't as wide as the Typhoon.

[redboat219]

Does anyone have a link to Skip's integral piston tank. Thanks.

[bigdave]

As far as I know nothing was ever published on it.
It was a you had to see it in person type thing.
But maybe someone will prove me wrong. BD

[JWLaRue]

Well...it's the same unless you add on a control module that provides precise control over the amount of water in the piston. You know.....Dial-a-Depth^tm.....

While I can control my OTW dive system, which is pump-based, very well...the my piston-based dive module is a bit better at control.

-Jeff