Re: [PSUBS-MAILIST] Sub launched ROV

[irox <irox@ix.netcom.com>]

Hi,

one thing to keep in mind is that we are wanting robots for different
purposes.  

When I'm out in my sub and I'm on-site somewhere worth exploring, I
do not want to be spending that time sitting around waiting for the ROV's
batteries to recharge.  If I have a reason, I want to be able to run
it around the clock (for several days).  So it must get power from the
sub.  I did consider having the sub trickle charge a battery on the
ROV via the tether, but I see little value in this right now.

Carsten's specs are very similar to mine.  300meters, fiber gives you
great bandwidth for sonar/cameras/etc..  Fiber gives great bandwidth
and flexibility for future gizmos/expansion.  One fiber pair and one
copper pair for power should give a pretty light cable.  Bonus if I
can 300meter fiber/copper cable from some other ROV.

I want it to be as solid state as possible, so where one where it's
unavoidable will solenoids.  I'm planning on the ROV having an on
board computer (embedded linux), ethernet over the fiber, talking
to another computer on the sub.  

I'm also considering that it might be cheaper/easier to buy at
used ROV.  There was one ebay a couple of days a going that sold
for $3500, seemed nice.  I've seem other small ROVs on ebay from
around $20,000 (I think the Sea-otter or something like that)
with lots of spare parts and cable.

I spent some time looking at slip rings for eletrical/fiber use,
and there is quite a bit out there.  Last time I looked only
manufacturer had slip rings which had a high enough signal
transmission quality to run digital protocols like USB, FireWire
and Ethernet over them.  Now they are much more (and I hope that
means the price came down a little).

Cheers,
  Ian.

-----Original Message-----
>From: ShellyDalg@aol.com
>Sent: Jun 20, 2008 3:19 PM
>To: personal_submersibles@psubs.org
>Subject: Re: [PSUBS-MAILIST] Sub launched ROV
>
>Hi Ian. A reel would need the connection to swivel, and would attach to the  
>sub in a simple multi-prong electrical through-hull. A possible option  would 
>be a cone shaped cable holder, where the cable spools off, but it would  still 
>need to curl up the cable. Retrieval could be accomplished by rotating the  
>cone shaped spool. ( simple motor drive ) 
>If the sub was say 200 feet deep, and the cable was 100 feet long, you  could 
>cover an area about 100 feet around the sub, or go deeper with the ROV (  but 
>with less area )
>It seems like a fiber-optic cable would be prone to problems. Wouldn't it  
>work to use coax cable for the video feed?
>As for power, I would rather see a battery on the ROV so no heavy power  
>cables are needed from the sub to the ROV. Just low voltage wires so they could  
>be cut if needed. 
>The pressure proof container is the easy part. Just a stout piece of pipe  
>with a window in the front, camera and battery inside, control panel for motor  
>drive and dive plane positioning. Make it neutrally buoyant with a drop 
>weight.  It would be small enough so you could make the whole thing from stainless 
>at a  reasonable cost. Something about 24 inches long and 12 inch dia. for the  
>pressure container would be enough if you packed the stuff inside right.  
>Some fixed ballast tanks to achieve neutral buoyancy, and with a grabber arm on  
>the sub, you could make a simple docking mechanism so the ROV could be stowed  
>away in it's holder after retrieval. 
>Low voltage solenoids inside the ROV for powering switches so no heavy  
>cables are needed from the sub.
>Seems like an eight pair cable would be enough for the minimum, plus the  
>coax video feed.
> One problem is voltage drop over a long cable, but with the  right 
>solenoids, that would be solved. I had some info on an off-the-shelf video  device that 
>was posted earlier this month here on the psub mail thing. It was  pricey but 
>was a complete system including cable, camera, and monitor. I  think it was 
>built to be deployed from the surface like from a boat or  maybe ice fishing.
>   The cost of a simple camera( about $150), a small TV monitor (  like the 
>small TV/VCR combo made for a motorhome, 12 volt, $99 at Best  Buy ) and your 
>own pressure cylinder as a start. Then add the motors  and controls, the cable 
>and connections, spooling reel, and various mechanical  things like dive 
>planes and drop weight. Doesn't Steve Pierce have something  like that he's been 
>working on? I think you can buy an off-the-shelf tiny ROV  for about $2500. 
>There's a guy here in Santa Cruz that has one he rents out to  boat owners. I 
>remember seeing an advert on it a while back. Anyway, lots to  think about. Frank 
>D.
>
>
>
>**************Gas prices getting you down? Search AOL Autos for 
>fuel-efficient used cars.      (http://autos.aol.com/used?ncid=aolaut00050000000007)




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