How long thether can i use?

Any miscellaneous pieces and parts that don't fit in the above forums.
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Atle.norway
Posts: 41
Joined: Mar 15th, 2013, 7:57 pm
Location: Norway

How long thether can i use?

Post by Atle.norway »

Im thinking of my new project
I want to go deeper.
I know with bilgepump thrusters my limit will be aprox 30 meters.but i want to go 50-60. Meters
I use dc current.will i loose much current if my tether is 60-70. Meters.
Its either tether or wireless .wireless is more demanding regarding waterproofing and either way i will need a radio line up to the surface
Zaibach
Posts: 48
Joined: Aug 13th, 2013, 9:50 am

Re: How long thether can i use?

Post by Zaibach »

I am exceedingly new so you will have to forgive me but I wasn't aware that bilge pump motors had such a short operational window.
Is it because of power transfer issues or that they just mechanically fail much past 30 meters?

If it isn't a mechanical issue you could always put most of the batteries used to power the ROV in the ROV itself and used some Power over Ethernet to run a data repeater or two.
Not 100% sure how far you can push a signal over a cat cable, just that I have never needed one long enough that it required a repeater before.
Atle.norway
Posts: 41
Joined: Mar 15th, 2013, 7:57 pm
Location: Norway

Re: How long thether can i use?

Post by Atle.norway »

To my knowlegde the bilgepump motors can only take a certain amount of pressure about 30 m.
Because the pressure will push the bearing that is located around the drive shaft.so hard that the driveshaft will stop.and this is only hear say.i hope somebody knows better and can prove me wrong.so i wont have to buy new motors
njs552
Posts: 61
Joined: Jun 10th, 2013, 6:22 pm
Location: Sacramento, CA

Re: How long thether can i use?

Post by njs552 »

Hi,

Are you pressure compensating your bilge pumps with oil? If not likely they will leak at some point (maybe 30m? for these) and short the motor and melt the copper windings. I have seen this happen with more than one bilge pump. It might also be that the bearing is jamming the shaft, and it is not leaking.

If you want to go deeper, you will probably need to run brushless motors completely unprotected in the water, and then you will not worry about pressure at all because there are no exposed electrical contacts in brushless motors like the brushes in brushed motors.

Also once you go to a 100ft+ tether you cannot power the ROV from one 12v battery. You need to send power at 24,36, or 48v, etc and buy a step down converter to convert the 12,24,48v to 12v. That way there is not as much current draw and you do not have so much voltage drop.

Thanks
njs552
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ROVER3D
Posts: 128
Joined: Nov 9th, 2012, 7:45 pm
Location: Wuppertal, Germany

Re: How long thether can i use?

Post by ROVER3D »

but i want to go 50-60. Meters
I use dc current.will i loose much current if my tether is 60-70. Meters.
Please think about your tether! If you want to dive to 50m depth, you will need:
About 5m on land
About 100m horizontal tether on water
and vertical to 50m depth!

150m tether! This is what you need minimum! There is no place to dive to 50m Depth from land where you will need only 50m tether!

If you can supply your ROV over 150m tether AND the ROV is strong enough to pull the complete tether in water (!) you can build you ROV.

If not, think about your concept...
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