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Re: MarkII
Posted: Aug 31st, 2011, 7:34 pm
by Pilikia
biglakeexile,
Thanks for the updates. Safe to say, you are boldly going where most of us haven't been!
My question about the tether, I was hoping you'd say how many wires of what size you are running, and especially how you are providing the buoyancy for it. From the pic it appears it's not all the same construction. Is there more flotation in the portion closest to the ROV? Please explain. Thanks.
Re: MarkII
Posted: Aug 31st, 2011, 9:03 pm
by biglakeexile
The tether consists of three separate cables, on 18-2 for the AC, one mini coax for the video, and one 22guage for the RF transmission. It's roughly 330ft long and only has buoyancy on the 100ft closest to the ROV. The Buoyancy material is called "backer rod" available at home improvement/hardware stores and is normally used to pre-fill a crack before you apply caulk to seal a gap. However, this stuff doesn't work too well because it is elastic and becomes compressed under pressure which reduces the buoyancy. That being said, it would still work fine for pool or pond applications. But after about 50ft or so it has mostly lost its effectiveness.
This leaves me with my three biggest hurdles:
1) The main junction box or housing which holds most of the guts leaks beyond 125ft. I'm surprised it made it that far, it's only IP67 rated. So, I'm working on building or sourcing (probably building) a new box.
2) The tether needs better management, including buoyancy. I feel it would have worked at the 280ft test, but would have hindered the ROV's movement. This will be the biggest problem as most things buoyant and flexible are soft and compressible. I'm open to anyones ideas at this point. The best I've come up with is small cylinders (maybe PVC) spaced apart on the tether. I don't like this for obvious reasons, as it would be a bear to work with but thats all I have at this point. Going to solve the leak onboard first, then I'll worry about the tether since it does sort of work for now.
3) The bilge pumps will not work forever at 300ft, I think we all know that. So I need to start thinking about plan B or maybe it's plan J now, for thrusters which will might include enclosed, oil filled brushless inrunner motors. And magic probably.