New hypothesis ballast system - Comments appreciated

[skip asay]

Carl -

Thank you for the

Carl -

Thank you for the heads up. I stand corrected.

Skip Asay
SubTech

[slats]

To all those people who

[color=#000080]To all those people who have contributed - many many thanks.
These comments are great and have given me loads to think about. Thanks so much for your efforts.

Skip,
you stated]

[Guest]

Slats,
This discussion mentions comparisons of

Slats,
This discussion mentions comparisons of available ballast systems.
As you might know, I use a different ballast system in my 1/72 L.A. and Alfa. The following URL has a video of my Alfa, utilizing the Recirculating Compressed Air Ballast System. You might have to join my MSN Group to view the video, if you can access it]Art Broder's Models[/url] . There is no automatic depth controller on this model. It can be brought up from the bottom even if your prop is stopped by weeds, or if your ESC has blown a fuse. The 6 or 12V system uses an air pump, not a water pump, and is simple and effective. Go to www.groups.msn.com/ArtBrodersmodels , if the above link does not work, and click on Documents, in the left column, click on the ballast system and read the 32K doc. file. and then view the pictures. Hope this stimulates more discussion.

[koeze]

@Skip,

You do realize I hope

[color=#000000]@Skip,

You do realize I hope that with a rigid ballast tank and and a few ml of air bubbles left in a tank you would have to draw an alomst absolute vacuum to draw more than a more water out that there is air.
Suppose the pressure inside the tank is 1 bar. The sub is near the surface and wants to pump out the tank. There is 20ml of air in the tank. In order to get that 20ml to expand to 40ml you have to have half the pressure ie. 0,5 bars. That is a LOT of vacuum allready and that only enables you to pump out 20ml of water. That is near nothing. A medium sized seringe holds 20ml.
If however the tank is flexible than not only the little pocket of air in the tank can expand but the entire volume of the submarine can expand. This requires MUCH less vacuum and can be done.
I however cannot see a waterpump (gear of piston) pump more than a couple of 10th of bars vacuum resulting in maybe a couple of ml of water being pumped out.

My idea of safe pump operated submarines is]

[skip asay]

Koeze -

In referring to "vacuum"

Koeze -

In referring to "vacuum" holding the snorkel closed, I should have said "pressure differential". This would be the case with a ballast tank that has absolutely no air inside. If there is an air bubble, then "vacuum" would be appropriate and some water would, in fact, be removed from the tank, although not very much. The amount of pressure differential would still be the same and the snorkel float would still be kept closed, even though it's above the surface. This is wanted I wanted to explain.

Skip Asay
SubTech

[safrole]

KD6HQ was kind enough to

KD6HQ was kind enough to do a better job than I depicting the "carburetor float" style of seal. He points out that the float would need to have a bit of weight to break the vacuum when the boat surfaces.

[koeze]

@Skip,

Point taken.

What I was

@Skip,

Point taken.

What I was referring to is this quote

“Surfacing - when fully dived at depth beyond the reach of the snorkel, the snorkel vent remains closed. To surface the 6 v geared pump runs in reverse and starts pumping out water. In doing so a vacuum forms in the ballast tank as its not vented, but the geared pump can overcome this. When the ballast tank has only pumped out 30% of the water, the boat is or should be close to decks awash, and the moment the sail breaks the surface the snorkel valve opens automatically, the vacuum is then released and the pump then empties the full contents of the tank.”

I have very serious doubts that any (usable) pump can pump out more than a few ml. I thought you meant that a geared pump should be able to pump out +/- 30% of the volume of the tank.

EJK

[ramius-ii]

I disagree that you get

[quote]I disagree that you get a smaller battery. The issue isn't current draw, it's power consumption.

P=I*V (power=current*volts)

For motors with similar power consumption, a 12V motor will consume half the current. This is true. But overall power consumption is roughly equivalent.

So lets say for a 6V pump motor you need a 6V 2AH gell cell, but a 12V pump motor would let you use a 12V 1AH gell cell. This is not a smaller battery. Both batteries output about the same amount of power, and so they are roughly equivalent in size.

Here's an example]

A little clarification:
Back on July 7 of this year there was a discussion on motor theory. RAALST explained the factors very well. Basically, while it is true P=E*I, you first must determine I (current). Two 500 series motors with the same power (torque and RPM) one a 6 volts draws 3.5A the second a 12 volt motor draws 0.8A. This all has to do with the size of the wire used to construct the motor, number of poles and the motors internal resistance when turning. 12v motors are more efficient. If this were not true, then commercial building would use 110v motors and not 480v motors. Subway system could use 100vdc rather than 600vdc.Thus the I squared R formula is the most correct.
As for battery size, take the height times the width times the depth and the 12v battery is slightly smaller at 12.6 ci vs 13 ci.
I would like for slats to be successful in his project and my input was intended to provide him every advantage. Sorry for starting a motor theory debut.

Ed

[slats]

Gee - you guys are

Gee - you guys are terrific.
This is what I love about remote control subs - pooling of heads together, frequent but constructive disagreement, -this what I think is the attraction to subs is that skimmer skippers don't or cannot understand.
Thanks again a whole bunch.
Subcommittee Membership has its privaleges.
All the best
Slats

[kd6hq]

Hi Slats

I know that this

Hi Slats

I know that this is off topic but do you have any close up pictures you could send me of you Alfa?

thanks

Don