Homebuilt ROVs Forum

Hi everyone!
I'm currently in a class in which we're building an ROV. It'll go (at most, probably less) 1000ft down, and my goal is to get a bunch of sediment,mostly marine snow, from the seafloor. Therefore I pretty much need just sediment on the top layer.
I also need about 5kg, dry, of this. So that's a fairly significant amount.
Our current plan is to use a design something like this one:

I don't think bilge pumps exist that can handle this type of pressure, but what do I know?
Thoughts?
Thanks so much.

Hi Patricia.

Maybe a small thruster, rated to that depth, inside the suction pipe. You could make an adaptor out of PVC plumbing fittings to suit the thruster diameter if the pipe itself is too small. Use a bigger area filter than that shown in the picture, and place it across the top of the drum.

I'd be keen to see some pics and other details of the ROV project, and I'm sure others on the forum would be too.

Cheers,

Ross

Thanks, Ross!

Why would I use the thruster? I'm just curious. Also, I don't have the materials yet, so the pipe size isn't a problem.. yet. Also, why across the top?

What kind of container should I use? I'm totally new to this and a little bit over my head.

I'd be happy to post pictures once we're a little further along. I'm personally making a module to measure radiation off our coast. The problem is getting samples from the seafloor. Other people have other projects, a lot of them involving A/V. It should be fun!

Thanks again.

Hi again Patricia.
Small thrusters are available whose specs claim are suitable for that depth/pressure. Do a google search for "ROV thruster depth". Instead of using the thruster as a thruster, you would be using it as a pump, fixed inside the suction pipe. Bilge pumps would probably be crushed at that depth, or would leak water in and so not operate very long. Having said that, modifying a bilge pump by oil-filling it (oil not being compressible) could be a cheaper solution, but you would have to get your organisation's engineering department onto this, as there are potential hazards involved if not done properly. Depends on your budget - $100 with free engineering help - or maybe $1000 for the thruster. Whatever you do, you will need some sort of strainer or mesh over the end of the pick-up tube so pump or thruster would not get clogged up by anything bigger that what you are aiming for. Also, consider the power requirements of pump or thruster (connection to ROV, available voltages etc).

The filter at the top is better being bigger because there is less risk of it clogging up too quickly. Being across the top of the drum will help this also, I would think. Just thinking about that, you could put the fine filter part way down in the drum, and put the thruster or bilge pump in the lid. Can do you a sketch if you like.

You have to work out the wet and suspended volume of the "snow" then come up with a drum size. Plastic screw-top drums are available from beer home-brewing shops. In Australia, they sell 60 litre ones.

Ross

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Thanks again, Ross!
We definitely don't have the budget for a thruster. As we're a high-school class, we're looking for things that are on the cheaper side. A bilge pump (hopefully done safely!) will have to do.

We've got 12 volts available, and I've found some bilge pumps that do 500GPH that should work with that.

A sketch would be awesome if you don't mind, but your help so far has been amazing. Thanks so much for all this.

I don't know what sediment is like at the bottom of our coast, but I'll try to work it out. I guess I'll end up erring on the side of safety.

I honestly can't thank you enough, I'm so lucky to have found this site!
Patricia

No worries Patricia - maybe just acknowledging the forum in your project, whether you use anything from here on not, would be good.

There are a few unknowns involved as I see it:

Sample material size and therefore what filter type.
Flow rate of pump required.
Just how to oil-compensate a suitable pump.

I would be going for the largest bilge pump flow as you can afford. 2000 GPH sounds better than 500. Note the current draw though - make sure power on the ROV is up to it. Not having had anything to do with bilge pumps other than in their designed application myself, maybe others on the forum have tried pressure-compensating them or know of ways to do it. Any ideas guys?? Something like a "shop-vac", but rated to 1000'.

Refer attached conceptual sketch of what I was describing earlier. Once again, get someone suitably qualified to do any mods to the pump, cutting holes in the drum etc if you decide to go this way.

You've probably considered some kind of miniature trawl net the ROV could drag around, or are there too many obstacles on the bottom? Would be much simpler if it worked http://www.scotland.gov.uk/Resource/Img ... 092231.jpg


Ross

This is way easyer than u think it is. You need a small dredging nozzle. A small pump will work for what you are trying to do with it. Here's a pic to help explain how it works

Patricia,

Did you say 1000ft in your original post?

That seems a bit deep for any homebuilt ROV to function. Even 100 ft is pretty deep but I hope the 1000 was a typo.

a_shorething wrote:Patricia,

Did you say 1000ft in your original post?

That seems a bit deep for any homebuilt ROV to function. Even 100 ft is pretty deep but I hope the 1000 was a typo.

I was thinking the same thing....

What would you use for a tether? At that depth you would have to use onboard power. What battery would you use that would last to that depth and back? Lights? You may want to aim for a shallower depth.