Tether- 2 X 18awg equipment wire twisted with a 4h nylon cord to reinforce.
The tether is twisted with a home made rope twisting machine.
The tether will need floats attached to make it neutrally buoyant. I am know thinking of micro glass balloons mixed with hot glue as the extruded Styrofoam i was planning will shrink to much under pressure.
I tried heating the ends of a Hep2o barrier pipe and squashing them together for floats but small floats weigh 5 grams and displace 10 grams of water so only provide 5 grams of buoyancy.
I am also thinking about the idea of having a standard 2 core PVC flex 2.5mm with 2 conductors attached to a plummet weight and a thinner tether to serve the sweep area. This would allow the ROV to reach depth much quicker (it would sink like a stone) and reduce power loss in the cable.
I hope to transmit 10 amps down the tether at 48 volts with an expected voltage drop of 50% so there could be 250 watts available at the ROV to charge batteries or power the motors. DCDC converters would be used to step up 12/24v (2X 12v) car batteries to 48v and stepped down to 12v for charging the batteries or running the motors. Some sort of charge controller would be needed to stop the batteries overcharging.
