$100 ROV

A very fine design for an inexpensive ROV, but I have to wonder why they don?t add a propulsion system to make it a true ROV for just another couple of hundred bucks. I would also have say that it is a poor design for a boat tow able underwater camera. I would use a torpedo design platform for the camera if all you plan on doing is towing it behind a running boat.
Another problem that I see with this project is the decision to place the weights in the buoyancy chambers. This will make the CG (center of gravity), way too high, and as a result the tow able camera will be very unstable, and will cause it to roll over on its back while underway. The quick solution to this problem will be to lower the CG by securing the weights to the bottom of the platform.
Other than that, these guys have put a lot of pride into this project, and it looks like outstanding craftsmanship.
This project looks very much like the Seafox ROV, the plans for which are available in the book ?Build Your Own Underwater Robot? by Harry Bohm and Vickie Jensen. I will recommend this book to anyone interested in building your own ROV, and you don?t have to be a geek or a rocket scientist to build this project.
 

Just a thougt - If the ROV is hanging over the side of a small dingy horisontal movement can be achieved by mving the dingy. Vertical movement can be achived raising or lowing the ROW. One advantage of this would be the simple and cheap constructiondue to the lack of trusters another advatage could be that the "exact" position can be detirmined using dGPS or standard navigation systems. My gues is that this could be a valuable tool when mapping a wreck.

Of cause this design would need to adress other problems such as orientation in water the need to pan and zoom with the camera.

Let me know you guys think

DKD
 

dk-diver, there are much simpler and less expensive ways to accomplish what you are describing, a basic drop camera. It?s as easy as taking the underwater camera housing they built, attaching the camera to a horizontal piece of PVC pipe with a flashlight, a couple of weights and a rope to reach the depth you want to observe. Determining you orientation is as simple as placing a small button compass in the field of view of the camera. As for the camera, Cornelius is correct, a color CCD camera can provide you with a direct feed to the bottom. The KISS method would dictate that you pre focus the camera to the desired distance before potting it in a water tight housing.
 

Wreckdiver - Your right that would be the KISS way of doing it. Have you used this method for drawing maps of any wreck and is iit worth experimenting with?

DKD
 

I understqand what youre saying, but if you want to know the exact location of the ROV then you need an expensive navigational system - right?

The reason im asking is that I plan to map a wreck site with an area of at least 100x100 meters. Beside beeing on a budget :'( i need a system that can be used from a small craft (6m RIB) with a crew of only 2.

I know it can be done be extensive diving - but since we both have full time jobs theres is no time to conduct such a mapping.

Does anybody have a bright idea that work?

DKD
 

My recommendation would be to build a Seafox ROV, or similar design, and add a button compass in the field of view of the camera. Utilizing dead reckoning navigation techniques I would just run the ROV across the wreck site in a grid pattern starting at a specific location at one end of the debris field. I really don?t see the need to be too concerned with an expensive navigation system. However, one thought is to just have a hand held GPS on your boat, and have your partner run the boat just behind the ROV on the same heading. Using the tracking function on the GPS will create a visual record of the search pattern, and should you run across a specific target you want to revisit in person, all you have to do is mark the location as a way point on the GPS. This method should put you within just a few yards of any target you want to dive on.
 

Wreckdiver - the problem with that aproach is the sea condition in the wreck area. There is a strong current and the ROV can not be seen from the surface. the dept is 27-30 meters and the vis is 5-10 meters. Current is estimated to 3 knots.

Our sollution is a towfish that can be controlled as a model airplane. A mock-up was tested today - it is fun to fly underwater. For this to work we need to be able to control the camera, which is next step.

Does anyone have a smart sollution to recording the video vithout using the households VCR? Today we only used a LCD screen for monitoring.

I warn you all to get into these kind of projects as they are highly addictive ;)

DKD
 

Wouldn't a 3 knot current push a small non-powered ROV all over the place?
 

Firstly I would like to congratulate the guys on a great job for a prototype towed camera or ROV if they go further. It looks very professional and could be developed further with a sound plan of what is required from a Suitcase ROV.

To record the video, get a video splitter and connect to a portable cam corder and you will be able to record as long as the batteries work and you have space. By using the splitter you will be able to watch the data as it comes in as well (you may lose a bit of definition).

Any kind of tow fish is difficult to control without good water dynamics and correctional fins. Unless it is reasonable heavy it will pitch, roll and yaw. This is very annoying and no easy to cure without test trials and solutions. To control the depth requires the umbilical to be either adjusted longer or shorter to suit the depth required and the speed of the boat altered to make the changes.

As for navigation. without high tech solutions such as DGPS and sub sea transponders and gyro compass accurate positioning is not possible. However if you split your search into to kinds.

1/ Searching a large area, you can use a normal GPS and compass to give the approximate location and allow for the length of umbilical you have out and also the compass heading, this way you will get close.

2/ Searching a small area, then you should place four marker buoys in a rectangle over the area you want to video, making sure that you are working up and down stream, then tow the camera back and forth and again using a normal GPS in an orderly set pattern. and as above allowing for the length of umbilical you have out and also the compass heading you will get closer.

However there is no substitute for good equipment only the ability to get close. Searching using an ROV or tow fish is not the way to go to find things, only to survey after you have found things.

Over 20 years of working directly and indirectly with ROV's and Sonar?s etc. have shown me that subject to the water depth and conditions, a side scan is the way to find targets, and drop a buoy in the water when you pick up a target and then throw a diver in to check it out.

I had a Phantom ROV for 12 years and only used it occasionally and only when I knew where the target was. My side scan was used weekly for many years, often finding nothing but getting great pictures of nothing so I was sure that what I looked for was not on that track of the search.

The towed camera really only sees a small area so in my own opinion is not very useful as a stand alone tool, it must have mobility to become a search tool. If the water visibility if poor then you do not have a useful tool for the job at all.

I am sure the use of thrusters would bring the thing to life, there are other threads on this site which offer advise on using economical means of propulsion. Of course the more you have the more you require in terms of power, controls and weight.

But judging from the quality of the design and engineering I am sure these guys could come up with a way to give it mobility.


Sorry for rambling on a bit

Great job guys.
 

Cablava said:
Firstly I would like to congratulate the guys on a great job for a prototype towed camera or ROV if they go further. It looks very professional and could be developed further with a sound plan of what is required from a Suitcase ROV.

To record the video, get a video splitter and connect to a portable cam corder and you will be able to record as long as the batteries work and you have space. By using the splitter you will be able to watch the data as it comes in as well (you may lose a bit of definition).

Any kind of tow fish is difficult to control without good water dynamics and correctional fins. Unless it is reasonable heavy it will pitch, roll and yaw. This is very annoying and no easy to cure without test trials and solutions. To control the depth requires the umbilical to be either adjusted longer or shorter to suit the depth required and the speed of the boat altered to make the changes.

As for navigation. without high tech solutions such as DGPS and sub sea transponders and gyro compass accurate positioning is not possible. However if you split your search into to kinds.

1/ Searching a large area, you can use a normal GPS and compass to give the approximate location and allow for the length of umbilical you have out and also the compass heading, this way you will get close.

2/ Searching a small area, then you should place four marker buoys in a rectangle over the area you want to video, making sure that you are working up and down stream, then tow the camera back and forth and again using a normal GPS in an orderly set pattern. and as above allowing for the length of umbilical you have out and also the compass heading you will get closer.

However there is no substitute for good equipment only the ability to get close. Searching using an ROV or tow fish is not the way to go to find things, only to survey after you have found things.

Over 20 years of working directly and? indirectly with ROV's and Sonar?s etc. have shown me that subject to the water depth and conditions, a side scan is the way to find targets, and drop a buoy in the water when you pick up a target and then throw a diver in to check it out.

I had a Phantom ROV for 12 years and only used it occasionally and only when I knew where the target was. My side scan was used weekly for many years, often finding nothing but getting great pictures of nothing so I was sure that what I looked for was not on that track of the search.

The towed camera really only sees a small area so in my own opinion is not very useful as a stand alone tool, it must have mobility to become a search tool. If the water visibility if poor then you do not have a useful tool for the job at all.

I am sure the use of thrusters would bring the thing to life, there are other threads on this site which offer advise on using economical means of propulsion. Of course the more you have the more you require in terms of power, controls and weight.

But judging from the quality of the design and engineering I am sure these guys could come up with a way to give it mobility.


Sorry for rambling on a bit

Great job guys.
Click to expand...

www.underwaterrov.com
Remote control color camera you can pan around with motors from above control box.
 

There is a www.underwaterrov.com that has a color camera you can control from above using a control box. Pan the camera
around 360 degrees using motors up to 100 ft depth.
 

DKD

My 2 cents

Taking into consideration 25-30 mtrs depth, 3 knts current (it may be worth actually measuring to get an exact figure), and operating from a small craft. I would probably side scan survey the site, then complete the picture with diver held camera footage. Small rov's dont handle that kind of current very well . If you were to persue the option of constructing it yourself you would need substantial (in relation to size of vechile) thrust capabilities to work in that kind of current.

Check here: http://www.tecnadyne.com/

In that current and from that size vessel I would either use scooters or drift dive in set intervals (using the current to your advantage) Is the wrecksite a snagging hazard and/or standing proud above the seabed?
If surface conditions allow and with the shallow depths involved you could lay a 4-6 point mooring spread allowing you very accurate control of a drop camera (here slowly slowly is the key) and remember it only gives small coverage area and is a "birds eye" view but once all runs are joined up it should make sense.

Be careful of magnetic compasses if the wreck is steel, Another cumbersome but proven method for small Rov's in strong currents is to utilize a drop weight system with only 30-40 ft of tether on the lower end this is easier for the vehicle to contend with but it allows you to keep control of distances and positions from centre point which if the weight is heavy enough might be only a slight distance from the vessel.(allowing mapping to be done from support vessel)

best of luck in your project
 

sorry I forgot to mention

The umbilical size is critical when working with small Rov;s in strong currents:
Always consider the surface area of the tether!!!
At 90 ft you will have out about 150 ft (if your lucky) of umbilical assuming you are not using Fibreoptics and such the cable may end up being 1/2" (again if your lucky) then unless it is armoured you will probably need some kind of strength member again increasing Diameter.Take Diameter and multiply by the length of cable in the water then divide by 2 (we wont count the trailing edge although its not exactly half more like a third that is not really affected) Put that into square inches then cut a piece of sailcloth the same size, tie it like a parachute and see if you can hold it against a 3 knot current .

Of course using the drop weight system eliminates this (tether managment systems are essential on larger , deeper vehicles to allow them to operate without having to fight against their own tether)

In 3 knots you may also find you need to add weight to get the ROV down to depth and prevent it from being lifted off the seabed.

A simple test to assist in thruster choice is to carry a rope of similar thickness to the ROV tether you intend to use then as a diver go down and see what it takes to pull around 150 ft of that rope on the site.
 

As it turned out we did it by drift diving. We have mapped out the site but but we are not going to work this site any further. It is located in a major shipping lane and we had some scary encounters with large merchant ships.Those rusty russians change course for nobody smaller than themself >:(

Further more my RIP was stolen from my front yard this weekend - they drove off with everything excluding the cut padlock >:( All i have left is the tank rack that was taken off for modification. So now im gonna spend my time fighting with the insurance company instead of diving.

The rest of the season will be spend exploring the close to shore sites in my 4m inflatable :-\

I hope that the rest of you had a better weekend than me.

DKD
 

My heart goes out to you,dont forget to remind the insurance company of that side scan and mini ROV that was onboard.
 

dk-diver said:
Does anyone have a smart sollution to recording the video vithout using the households VCR? Today we only used a LCD screen for monitoring.
Click to expand...

I understand what you are saying dk-diver about projects being addictive!!! :)

As far as your recording question. I'd recommend a cheap video capture card on a laptop/PC -- or possibly even a PDA. With a video capture card, you will be able to capture your video directly to a file. I'm assuming your camera has a standard NTSC video output on it. I've seen video capture card for PC's as well as laptops. I am pretty sure I also saw an SDIO capture card for a PDA once...

Once you have video in a file, it's real easy to cut sections out of it, or individual stills.

TS
 

YOU'D BETTER HAVE A MONSTROUS HARD DRIVE
Direct recording can be done straight onto A drive but most times its cheaper just to record onto a $50 vcr and edit at home.
 

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