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Registered Member #29
Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500
Great project! I am also "lurking" in the background watching your progress..
regarding communications with your underwater vehicle: have you considered acoustic signaling (ultrasonic)? Acoustic signals can travel great distances underwater, experiencing far less attenuation than RF or optical signals. If you are doing simple telecommand and telemetry, it could be a suitable method...
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040
WaveRider wrote ...
Great project! I am also "lurking" in the background watching your progress..
regarding communications with your underwater vehicle: have you considered acoustic signaling (ultrasonic)? Acoustic signals can travel great distances underwater, experiencing far less attenuation than RF or optical signals. If you are doing simple telecommand and telemetry, it could be a suitable method...
ultrasonic control is a nice prospect I would love to explore, but alas i have two considerations that make it unusable: the first is that this will, in the long run, have a basic sonar. The second, and more key reason to use a tether, is the two live video cameras that will be streaming to the surface - even if ultrasonic transmissions could carry a feed, it would not be live by any means, which is imperative to hovering.
tomorrow I start the FULL water tests with Electronics and basic control, minus the Buoyancy Control. I finished the electrical soldering and circuits today, and finally got the regulator adjusted to the 5V for my fiber media converter (don't know why it took me so long)...
I ran the fiber optic cable through 80 feet of vinyl tubing, and sealed the entry port into the unit with a LOT of silicone (filled an entire PVC end cap with it). I am only waiting on two patches of sealant to dry, one on the third Cooper Waterproof Electrical Connector I installed today (this makes one for the left/right bilges, one for forward/reverse bilges, and one for Ballast dive/surface control and later I will add a fourth for "accessories"). For these patches of sealant, as well as a few others, I used Gorilla Glue because of its expansion properties which make it very suitable, in my experience, at waterproofing because as it expands it fills all gaps and compresses itself against the surfaces. If you've never used gorilla glue, if you smeared a layer on the bottom of a coin and left it on the ground (with nothing holding the coin down) the glue can expand around and cover the coin and you won't be getting that coin up without a prying tool
-Jimmy
p.s: pictures up tomorrow after the first full water test.
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
Just a thought after reading all the updates, have you considered how water-resistant the bilge pumps will be at depth? From what I've read the seal on the axle is just a pressure fit o-ring with an interior filled with air. My advice would be to carefully drill a small hole, then take a syringe with silicone or vegetable oil (ie: not harmful to aquatic life) and fill the internal cavity, then clean off the hole and re-seal the pump. Since fluids are incompressible, it should be functional to a much greater depth and have better heat dissipation.
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040
aonomus wrote ...
Just a thought after reading all the updates, have you considered how water-resistant the bilge pumps will be at depth? From what I've read the seal on the axle is just a pressure fit o-ring with an interior filled with air. My advice would be to carefully drill a small hole, then take a syringe with silicone or vegetable oil (ie: not harmful to aquatic life) and fill the internal cavity, then clean off the hole and re-seal the pump. Since fluids are incompressible, it should be functional to a much greater depth and have better heat dissipation.
Rule bilge pumps are rated "submersible" on their packaging, and most hobby ROVs use bilge pumps unmodified unless they decide to modify it to be a propeller drive rather than an Impeller drive (which it normally acts like because it is a pump)
and Conner is right, it would create a drag and on such small pumps would be significantly affecting performance
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
Homebuilt ROVs has done some testing on bilge pumps, you can read about it here:
Awesome project, Jimmy! It's interesting to see how you've chosen to solve some of the design issues. Your ROV is certainly going to be a heavy fecker! I'm working on my own ROV right now, though it's taken much longer than anticipated. I've only recently finished the tether/reel and surface controller, yet I hope to have it ready for the summer holidays. I was hoping to put a depth sensor in my ROV, but I couldn't find anything cheap enough, what are you using to measure depth? Is it all handled by the BCD?
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040
Uzzors wrote ...
Homebuilt ROVs has done some testing on bilge pumps, you can read about it here:
Awesome project, Jimmy! It's interesting to see how you've chosen to solve some of the design issues. Your ROV is certainly going to be a heavy fecker! I'm working on my own ROV right now, though it's taken much longer than anticipated. I've only recently finished the tether/reel and surface controller, yet I hope to have it ready for the summer holidays. I was hoping to put a depth sensor in my ROV, but I couldn't find anything cheap enough, what are you using to measure depth? Is it all handled by the BCD?
only the highest end BCDs have their own computerized parts, otherwise they are a bag with a couple of valves.
I do not yet have a finalized plan on measuring depth, that will be determined after my school grade when I can really start experimenting with the thing
I thought about using a small air container with an air pressure sensor and a flexible diaphragm, as air pressure sensors are cheaper - then again, I could always use a liquid based meter and have the readout in front of the camera.
and yes, this is one heavy sucker especially with the ballast weight needed to get it to dive! - the BCD will only control about ten pounds worth of ballast at best, only enough to make the change from surface to neutral and start to sink, so the ballast is centered around it and tests with empty cases give around 60 pounds to sink it (which I don't want really, I want neutral for the most part) but with the space consumed by the electronics and added weight of the battery and since the PVC's had holes drilled in it to remove it's buoyancy, I think I'll be fine, but I do plan to replace the PVC with Steel pipe in the not too distant future so it is stronger and the frame would be it's own ballast
-Jimmy
p.s: a good place for sensors is Sparkfun, they have a lot of easy to use parts at a pretty good price, I'm sure they have some kind of pressure sensor.
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