I got the latest copy of CREG (Cave Radio Electronics Group) journal yesterday and there was a really interesting article about an open source ROV project that was developed for exploring a flooded cave in California.

The whole design is available to download to build and source yourself or a kit can be purchased as well a complete unit.

I know a few of you have built your own on here, but it still might be a very good reference point.

http://www.openrov.com/index.html 

https://www.kickstarter.com/projects/openrov/openrov-the-open-source-underwater-robot 

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Got one. :)

Blober constructed it for us last year. While we're still ironing out a few issues, it is looking very promising.
This clip shows a trial in Vivian quarry last Thursday:

http://pages.bangor.ac.uk/~oss108/Jemima_2.mov 

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This is very interesting, we have been involved (in a small way ) with a group building an autonomous ROV. You put it in the water and off it goes and hopefully comes back.

There are a few shafts I would like to send one of these down. Perhaps it might be my next project.

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Got one. :)

Blober constructed it for us last year. While we're still ironing out a few issues, it is looking very promising.
This clip shows a trial in Vivian quarry last Thursday:

http://pages.bangor.ac.uk/~oss108/Jemima_2.mov 

Ah, yes I saw the pics a while back, but did not clock what the ROV was. I like the view on the GC.

What problems have you had?

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Not problems as such, just learning how to get the best out of it and ensure that it doesn't get stuck at the bottom.

The umbilical is just 2-core twisted ethernet cable which is very prone to tangling so at risk of snagging. Adding the green float seen in the movie reduces this risk considerably.
Higher quality, neutral buoyancy cable would be ideal but expensive.

Next we want to improve the light coverage. The two banks of LEDs and the camera lens are all on the same panel which results in a lot of flare. I'm hoping we can rig up some form of lens hood to reduce this, but ultimately we'd probably be better off with external lights fitted to the outside of the ROV. We'd lose the ability to tilt them up and down along with the camera, but that might be a price worth paying.

I'm sure Blober will be along shortly to explain more. He's the captain and the ship's engineer!

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what sort of quality images are you getting ?

I do wonder about once the machine is in the water, stirring up the silt etc the visibility goes, do you get anything back.

Extra diving lights may be a way of adding lighting, in the same way as other ROVs ?

I do wonder about the use of ethernet cable too. If the machine were to die, could you pull it back out on that cable ? or would something a little stronger be required like so thin wire.

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Stirring up silt is always going to be an issue. The motors are far more powerful than needed so the first modification was to turn them down from their default, Magimix setting.
Image quality up close is pretty good. We could identify coins on a ledge during last week's trial. But anything beyond a couple of metres is pretty hard to make out with the current lighting.

The cable isn't very strong. The first thing we did was to try stretching a length of it between two of us. I reckon it snapped at around 15lbs of pull (unscientific guess). So it's sufficient for hauling the ROV back if it's floating freely. But if it gets snagged, we'd have a problem that probably wouldn't be resolved with a stronger tether.

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Incidentally, this was the first test a couple of months ago:
http://pages.bangor.ac.uk/~oss108/ROV.mov 
The motors were at full power then, making control difficult. And the cable sinking around all that loose slate on the floor proved a major worry, hence the float on our next trial.

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Have you got any recordings of the actual view coming back from it? Bet you wish you kept quiet!

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For the future, but features that have proven valuble on the Shropshire Caving and Mining Club "Mine cam"
Compass so you know where you are looking.
Laser range finder to give scale.
http://www.shropshirecmc.org.uk/minecam.html 

I don't have any on-board footage yet, though some was recorded on the first trial.
The "mine cam" looks a useful bit of kit.
Our ROV does have a compass to show orientation - the red marker on the scrolling ruler at the bottom of the display.
There are two also lasers to calculate distance but I'm not sure if we have them figured out yet.

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Hello!

If I never have to assemble anything like it again, it'll be too soon! Although truthfully she wasn't that hard to assemble just the first big project I've done since college.

The tether/umbilical is an issue, we're currently looking to try and change it to a system where by we can change the cable as we see fit to different lengths or types of cable. You can apparently switch the umbilical to a 300 meter one before you begin approaching any issues, so that's handy for going along tunnels and what not. Although you wouldn't want to dive your ROV to 300m depths, they're rated to around 100m, which is still deep!

Lighting is going to undergo a change at some point thats for sure, short term plan is as agricola said, attach a few dive torches to the payload bars and long term we'll be looking at some proper wired up lighting.

The camera inside is basically a 1080 HD webcam, and does produce some nice images.

Silt is definitely an issue but the thrusters can be adjusted easily using the 1-5 keys. 1 being fairly slow and 5 being ridiculous!

You can record the video feed coming from the ROV using VLC player, although in my excitement I neglected to record our last adventure in Vivian quarry! ::)

She does come with a compass and a depth meter that you reset right before you dunk her in. The laser on her is a scaling laser placed between 10cm but they need adjusting again!

Any more questions just ask :thumbsup:

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Hi Blober,

Don't forget next time to record the view ! I would be really interested in seeing that.

I know your experimenting with it all still, but have you done any 'real' dives to look at anything proper down a mine yet?

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She went down Cwmorthin once before but some disasters were encountered!

We have plans to take her back somewhere very soon, Probably drop some flooded chambers first. from the top down. Then when we have sorted the umbilical issues probably take her down some inclines and further along tunnels!

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I do ROV operations from time to time but they are with full-on, commercial systems which is rather different. Sometimes I see smaller units, sometimes referred to as "suitcase" units and these often navigate using a sonar display and compass heading (this would be for jobs around rigs and the like).

They usually have cameras - the most common job for ROVs is visual inspection - but visibility can be a serious problem.

Larger ROV often have Tether Management Systems (TMS) which consist of a submersible reel of umbilical which is lowered to depth with the ROV suspended below, so the only umbilical attached to the ROV is from the TMS

I'm most intrigued by the idea of a build-it-yourself AUV, though

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Larger ROV often have Tether Management Systems (TMS) which consist of a submersible reel of umbilical which is lowered to depth with the ROV suspended below, so the only umbilical attached to the ROV is from the TMS

We have had the offer of a length of neutrally-buoyant single twisted pair cable, but the supplier has to wait until he reaches the end of the drum before he can afford to "write-off" the final 150-ish metres of cable, as it is horrifically expensive to buy. But still a good offer in return for a bit of free advertising (put a sticker on the side of Jemima and name-drop occasionally 🙂 )
Our Tether Management System is the green float that you see in the video. It seems to work great for dropping vertically down quarry faces or shafts (or oil rig legs...) as the float tends to move around on the surface and remain above the ROV but it remains to be seen if it helps when descending a flooded incline. I thought that this would be where the NB cable would help. As Blober said, we will probably end up with a system for changing cable quickly and easily but the details need ironing out.

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A significant limitation, especially with smaller ROV, is the effects of drag resulting from the cable (I'm assuming that there are no significant currents in flooded mine workings)

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The twisted single pair cable is very light and the ROV is, if anything, a bit TOO powerful in its current configuration! Not actually recorded speed as yet but imagine the speed of a decent radio-controlled toy boat and its somewhere near, so drag is not an issue so far but when it gets re-configured with additional lighting etc it may be!

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I have no experience of ROV's, but does anyone know if there is a different thruster design to using propellers - I am thinking along the lines of a more passive one that does not stir up the silt. So that confined spaces like in a flooded mine etc... don't get murky.

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The problem is the only thing you have to react against is the water which in turn moves and stirs up the sediment.

The thing to do is move slowly and gently, the underwater equivalent of treading lightly on false floors...

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