----- Original Message -----From: Fly DeepSent: Friday, January 03, 2003 1:09 AMSubject: Re: [PSUBS-MAILIST] Ballast QuestionI have a degree in mechanical engineering and I’m an ASME coded high pressure pipe welder. I’m in the middle of designing another submarine. One of the submersibles that I’ve owned was the “Nekton”. I think we should all take a close look at it. Originally it had hard and soft ballast. The hard ballast was removed and used only the soft ballast for control. It has 2 tanks, one forward and one aft. The tanks have a 3 inch hole at the bottom to let the water in and out. Not like the gaping open bottom as like the Kitridge thing. It would begin to descend faster as it went deeper of coarse but the volume change per atmosphere of descent becomes less noticeable the deeper you go. After a few practice runs it’s very easy to add just a squirt of air and slow down the decent. And, as you get down towards 5 or more atmospheres the buoyancy becomes very controllable. I was concerned with the thought of having no hard ballast but found that it really wasn’t important. After you gently touch down it’s very easy to adjust the vessel to neutral or stop it on the way down. But I tend to be involved in jobs that require lots of surfacing and descending so I wanted a simple way of having a highly controlled decent to the bottom with out getting stuck in the mud. What I’ve come up with is a ballast tank that rotates. Basically it’s a tube with bulk heads from one end to the other. Not baffles because the water is not allowed to travel from one space to the other. Through the center of the tube from one end to the other is a pipe that has an orifice for each compartment or space. This is the air pressure line that blows out the water. Now here comes the trick. The tube with a slot can rotate. As it rotates the slot moves around and lets out the air and lets in the water. With just a few trips it would be easy to know just how far to set the degrees of rotation so that the slot will be right where you want it. As you approach the desired depth you just turn on the air and it automatically fills the tube until the air runs out. It also allows for rapid descent away from the surface and away from the waves. Very quickly. To surface, rotate the tube so the slot is down and hit the air. Walla, no valves to become corroded and stuck open. The tube can be made to rotate in many ways depending on the application. It can also be made from PVC or what ever works. I haven’t used this yet and I’ve never seen it done but I think a few of you might see the beauty in it’s simplicity and it’s unique applications. And just for the record, the little deep workers do have a hard ballast system. It has the ability to pump oil out side the pressure vessel into a bag therefore changing the mass of the vessel. It’s very accurate and easily accomplished. As for hard ballast in general, it may be over rated. I think most of the Personal Submarines that are being built are small and hold only one or two passengers. This requires only a little math and a trip to the pool to see how much weight should be inside the sub. If one guy is gone IE around 180 pounds or so. Then Bean Bags of lead shot should be added to make up for the weight. These can also be moved fore & aft as applicable for trim. The small sub should be very, very close to natural before it is let go over the side. In which case soft ballast will suffice. Just a little shot of air will put it right where she needs to be. This does keep it simple. I’m currently completing the pressure vessel for a submarine that will have a working depth of 1500 feet. It’s primary view port ( a spherical section) was machined by Reynolds out in Colorado, and is 3.5 inches thick and 38 inches across. The battery pods are done and will hold gobs and gobs of power for the manipulators. This particular vessel will have only soft ballast. It will have the capacity to lift 3000 pound and bring it to the surface. Keep on welding….djb
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