Controlling Depth

[AHarris]

I am making an ROV that I shall have a maximum dive depth of 15m with a recommendation of 10m as it is only made out of an ABS Plastic Project Box (a new concept I am trying, ease and ready made off the shelf parts as my local DIY shop sells nothing but the parts you need for home improvement which means it has no unusual corner sections or larger sized pipes).

As I am using an ABS Plastic Project Box, it isn't going to stand to much pressure (10m is 14PSI) and I wanted to limit the depth. I however still want exploration tether so I can't just cut it to 15m, I was planning on using a Tire Pressure Gauge and using it to tell me when I reach 14 PSI but this has complications in itself such as in accuracies which according to reviews, the cheaper ones do have. I am working on a budget and wondered if anyone had any ideas of how to regulate the dive depth of my ROV?

Thank you

[Rover]

Controlling the length of your tether may help, or diving in water equal to or less then you max depth.

You can also pressurize your ABS enclosure with 5 to 15 psi, to give you a safety margin if you should go deeper? Another way to look at it is.... if you pressurized your box with 14 psi, it be greater then the water pressure, until you reached 10 meters. at that point the internal and external pressure is equal, just as if the project box was on the surface. As you continue to dive deeper, you will reach the 14 psi differential at 20 meters........ essentially extending your dive depth by 10 meters. MAny years ago we did this with two scuba tows we built. We installed a motor cycle valve stem, as they are threaded.

Jim

[Alaska Rov Systems]

I came up with an idea, design the ROV like a harrier jump jet so it hovers above the sea floor with a few bilge pumps pointed downwards and have a rear bilge pump in the rear that is rotatable so it gives you steering. I believe this would give depth control. Its just an inspiration that popped into my head from a dream.
Alex Stuart
Alaska ROV Systems

[derelicte]

that sounds similar to what I have done on my rov. I can adjust the speed of the vertical thruster so that it maintains the current depth. kind of like hovering a helicopter.

it actually works really well except for the tendency to slightly yaw due to not having counter rotating thrusters. I may implement a yaw trim as well to cancel it out.

[Alaska Rov Systems]

Yeah my idea was maybe to control the thrusters with variable resistors (potentiometers). That way you could control speed of thrusters and how much hover you want and you could then stabilize the ROV if it started tipping to one side during a hover.

[derelicte]

Yeah my idea was maybe to control the thrusters with variable resistors (potentiometers).

that is the same idea. I just do it digitally.

I haven't noticed a tendency for it to tip over. as long as the center of buoyancy is above the center of mass, I don't see how it could.

[Alaska Rov Systems]

I also had this other idea: make the ROV not neutrally buoyant and use the bilge pumps to control the descent and hopefully have enough power to still hover and return to the surface. I don't know if this would work.

[bossfrog]

Maybe have a dropable weight that you could let loose at the end of the dive that would then make the ROV positively buoyant.

[Alaska Rov Systems]

I will take the dropping weight into consideration! I also was thinking if one can hover over the ocean floor and stay in place, you can have video cameras and also may be able if the object is light enough do recovery of small objects!

[Rover]

I am also using a PWM variable speed control to adjust the vertical thruster for precise hovering ability.

Jim