Deep Water ROV Brain Storming.

[ermaclob]

So i do alot of scuba diving and explore the underwater quite often. My diving normally falls within normal recreational limits of 130 ftsw with the occasional decompression dive to 150 ftsw. i would like to explore deeper depths of any where around 200 to 500ft if possible, with out dealing the relatively large cost going into trimix diving and rebreather diving to gain the extra depth not to mention the dangers. i figured i could probably make a ROV to get to see stuff at those depths.



i have this older underwater camera housing that would make to my assumption a fairly good starting point to make a ROV body. The housing is rated to 300ft and would have more then enough space to hold all the necessary components to run the ROV. Im thinking i can even pressurize the housing on the surface to give it some extra depth. the housing is pretty big tho. i dont know if this would cause any issues when it comes to picking propulsion.





My biggest challenge if i decide to peruse this is my lack of knowledge with underwater thrusters, as well as what to use as and umbilical for such depth. Im thinking that CAT5 Cable will be to short as its transmission distance is 328ft, would fiber be a better option. i dont know how much thrust the trusters need produce as well as how to waterproof for those depths.

and of course i dont know what i dont know so if any one has some extra advise to give, i would happily take it.

[Bennachie]

Hi and welcome!

Your camera housing would make a very good starting point for an ROV. However, DO NOT attempt to pressurise it! The housing is designed to withstand external pressure, not internal. I doubt the over centre catches would be able to withstand much, but it's simply dangerous however you look at it.

You say the housing is rated to 300 feet, so I'd say it would be able to go quite a lot deeper than that before actually failing. Probably several times deeper, as there will be a safety factor built in.

Fibre is a good idea for comms, you can get cheap units designed for CCTV cameras.they have a video uplink and a comms downlink. I don't know if they have a comms uplink however, as I've not looked at them in enough detail yet.

Thrusters are trickier. I'm using brushless DC motors which can run wet, however that's for fresh water. I'd expect salt water to have a serious impact on their lifespan, however they are so cheap you could almost consider them semi-disposable. Others on here will be able to give you a lot more info on sealed thruster design.

[Bennachie]

I forgot to add- regarding transmission distances, it's not cat5 that limits the distance, it's the Ethernet signal. You can send RS-422 / RS-485 signals for over half a mile down cat5 cable at 9600 baud. More than enough for ROV telemetry.