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Hi Dean. By ''hydro motors'' do you mean hydraulic ? If so, here's a couple
of thoughts that I recall from previous discussions on this. ( I too had
originally planned on going hydraulic.)
The conversion from electric to hydraulic has a pretty high cost in
efficiency. Many tourist subs and research subs have been converted to full
electrics recently.
A hydraulic motor needs two through-hull fittings, where an electric motor
needs only one. That one fitting is sealed SOLID, while the two hydraulic
fittings have liquid moving back and forth ( in a reversible system)
and has several connections on the outside where leakage can occur. It's
true that the hydraulic system has a positive pressure as compared to the
outside water pressure, but that difference gets less the deeper you go.
You also have the noise, smell, and potential for a high pressure leak
inside the sub that a hydraulic system would entail. Would be pretty shitty if
you blew a hydraulic line inside!
Cost is also a factor, not only in original installation, but in
maintenance as well.
A full electric system has fewer parts, takes up a lot less space, and
generally is easier to replace individual components than the oil based
system.
The only drawback I had trouble with was waterproofing the motors, but
there are some good solutions to pressure compensation and I'm pretty confident
that has been resolved through previous threads.
Got any pictures yet ? sure would like to see some. Frank
D.
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