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Monday, November 19, 2007: Some Lessons Learned
I have been in Antartica for coming on 18 days, and we have had VideoRay in the water 10 of them. Including the last 6 days in a row. I call that reliable.


I have been in Antartica for coming on 18 days, and we have had VideoRay in the water 10 of them. Including the last 6 days in a row. I call that reliable. Since as ussual I am behind on my blog, I thought it would be a good idea to send Marcus a Operations Report and post it as a blog. I figure Video Ray will like this since they sent out a press release quoting my last blog. If I make this one long enough maybe they will make a feature film...

The sonar is the black cylinder at the front of the floatation block.

The TriTech sonar has been invaluable. Mounting it was a little tricky... I ended up adding a half wrap of electrical tape to the OD of the base and press fitting it into the hole provided in the foam. It is wonderfully secure. Marcus Commented that this was the way he ussually mounts the sonar, too!

It can be difficult to identify small targets as the slider system for setting contrast and sensitivity requires considerable tweaking, and on the fly the pilot doesn't have that time. It is very, very useful as a way of determining heading. Most work is done on a slope, and the direction of "up-hill" is known. Setting the sonar on polar (360 degree scan) and "High Speed" to keep track of which direction it gets shallow in has been critical to efficiently driving the VideoRay.
The sonar has been useful in making small scale maps showing how groups of objects relate to one another. Below is a map/photo of several sample cages we discovered with Video Ray while looking for Stacy's experiments at Cinder Cones.

The corrals are too close together for seperate nav positions of each one to be very useful, but the sonar image allows the scientist to easily see their spatial relationship.

After adding both the sonar to the Nav Ducer above the center of gravity of Video Ray, I was concerned about stability. I added some flotation up high as well, and extra wieght down low to compensate.

Peque, the World's Most Technically Astute Penguin, proudly displays the new Nav Transducer mount with added flotation.

I have noticed that VideoRay tends to roll a bit in turns even with the attempt to increase the metacentric height. I lack the time, inclination, or information to compute Stabilty for the vehicle, and it occurs to me that most 'casual' operators would rather just have the answer instead of the problem. It might be a good idea to include a stabilty adjustment with any piece of semi-standard add-on equipment.

I have been operating positively bouyant and using the vertical thruster to hold the vehicle steady on the bottom. It has gotten a lot of run time. I think this has contributed to a low oil level in the shaft seal. The aft thruster's seals do not have low levels. I'll be topping off the level in the Vert's Shaft Seal tomorrow. We get a day off from diving! Hooray for maintenance!

Marcus commented that VideoRay recommends replacing rather than refilling the seal cartridge.
After I had it apart I found the oil level was not low after all. I reinstalled and dove it to 30 meters with no problems. I have dove three different VideoRays for three different scientists and I have yet to see a real problem with these seals. In my experience, they are the best idea for sealing a prop shaft I have seen, easy to check, dependable, easy to change. Lovely.

The integrated laser package Marcus sent us has performed flawlessly. We only notice them when we need to measure something. Perfecto.

The single biggest improvement that could be made to the ROV opertion is a dependable heading indication. We can use the sonar to keep track of up-hill, and watch the nav to see which way we end up travelling, but real time heading information would make the job significantly easier and intuitive. VideoRay has heading indication provided by a magnetic compass, but it suffers from the geographical location of our dives (we are south of the south magnetic pole) as well as nearby thruster magnetic fields. Operating in Antarctica doesn't help but in my experience with other VideoRay operations, far from the Poles, I have seen the same rapid compass swings. It is an agile little vehicle and can swing very quickly for real. I long for a laser ring gyro to provide a steady heading... It would only perhaps quadruple the cost of the VideoRay. Maybe if I'm good I'll get one for Yule.

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This material is based on work supported by the National Science Foundation under Grant No. ANT-0619622 ( Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.