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Old Feb 19, 2013, 02:05 AM
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Adelaide,Australia
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Self leveling pumping/ballasting electronics for a Floating Dry Dock

G'day All,

A while back I drew up some plans (Old school on graph paper...) for a 1/72 Floating Drydock with the basic dimensions (600mm beam x 2.6m length with a usable dock width of 390mm).

I recently saw in Model Boat magazine a small working 1/72 Floating dock with a Flower class Corvette in it, but it only had a limited write up on how it works....

So I invite creative discussion for how to set up an RC self levelling ballasting system using available electronics....

Cheers Bruce

PS I have discovered an ebay seller for submersible 12v dc pumps if anyone needs some.....
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Old Feb 19, 2013, 02:11 AM
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Vlaardingen, The Netherlands
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Hi Bruce,

Might I suggest making a slightly curved track on which you place a moving weight.
Place some switches in the track in such a place that only a small list will be enough to engage the switch.
Use that as input for a microcontroller which will then slightly increase the power on the pump on the other side or slightly decrease the power on the pump on the first side.
You could also place more switches along the track to counter larger amounts of list more accurately.

Greetings Josse
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Old Feb 19, 2013, 04:16 AM
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Australia, WA, Garden Island
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More expensive than Josse's idea, maybe, I haven't priced it.

But perhaps a combination of a couple of small 3 axis g sensors like these (the same as the ones cellphones and tablets use to determine the location and angle of the device in "space").

http://www.freetronics.com/collectio...e#.USNQz1oY1Jk

$19.95 each, you'd probably need 4, one for each corner. These ones are good in that they output their data in a known format, without the need for extra programming on the sensor side by the user.

You could tell water depth by having the simple cut-wire water sensing system i'm using at however many points you require, both for tank depth and external depth.

At a guess, a single mega with the right shields could do the lot.
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Old Feb 19, 2013, 04:34 AM
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Thx fellas,
I had considered using the Orange RX3 flight stabilzation gyro from Hobby king as it has multiple servo outs for port n stbd ailerons, port n stbd elevators and hook these outputs to control pumps in four ballast tanks....

Keep the ideas rollin in!!
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Old Feb 19, 2013, 07:21 AM
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I finished drawing the plans up tonight for the Basic design of the dock hull (I will run it by a mate who is a retired Marine engineer....see if I need to make any changes)

I have changed the original design slightly making the drydock modular for ease of transport. It will be in 3 pieces, a bottom section with the sides attached to the sides of the bottom and all electronics will be located (at this stage....) somewhere in the upper dry section.

Now I just need to cost the materials for the build (9mm and 6mm Plywood sheet) and some reversible pumps (the one's I had in mind are not reversible and it would be simpler to have reversible ones.....we shall see)

Cheers Bruce
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Old Feb 19, 2013, 09:02 AM
Ulf Harmason
Joined Aug 2009
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Bruce,you need attitude-only sensing with heavily over damped response.
Even gyros with anti-drift will just keep the pumps sloshing water back and forth with any rocking.
Put the question to a wider audience if you must.
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Old Feb 19, 2013, 09:53 AM
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Back in the 60s I seen one model that used parts from the old style thermostats, which had a glass tube with Mercury in it.
Regards,
Gerald.
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Old Feb 20, 2013, 11:15 PM
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G'day All,

Did a redraw of the redraw last night after a trip to the hardware store in the afternoon!! Revised the dock length down to 2.4m from 2.6m and beam to 620mm with an inner dock width of 460mm. Shortening the dock saves some dollars as a sheet of Ply is 2.4m x 1.2m so I applied the K.I.S.S. principle.!! I can get all the main hull skins out of 2 sheets of 7mm ply.

Looks like I should be able to build the hull (a Floating dock would still be a hull I think!) for less than $100.

There will be either 5 large ballast tanks evenly along the dock (11 frames 220mm apart) or 3 tanks in the center with 2 trim tanks at each end Port n Stbd. (for 7 tanks)

I figure that being 2.4m long with a dock inner width of 460mm it should be capable of holding and lifting a ship model of up to 2.7m long with a maximum beam of 400mm.....I might even try lifting USS Long Beach (3.05m x 310mm and 65kg!!)

The control system needs to be able to kept the dock level as the dock floods and when the command is given to pump out.... Most pumps I have come across seem to be one directional may have to use pumps to pump out and solenoids to flood it.

Cheers Bruce
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Last edited by HeavyCruser9; Feb 20, 2013 at 11:21 PM. Reason: added ideas.....
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Old Feb 21, 2013, 05:05 AM
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Question??....... Theoretically could an off the shelf control unit such as the type used in Quadcopters for flight stabilziation ($20 bucks from HK) be utilised to control the ballast trim tanks on the Floating Drydock?? Is this possible?? I have stuff all knowledge of how these electronics work so any advice and help is mucho appreciated!!

Bruce
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Old Feb 21, 2013, 05:21 AM
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Quote:
Originally Posted by HeavyCruser9 View Post
Question??....... Theoretically could an off the shelf control unit such as the type used in Quadcopters for flight stabilziation ($20 bucks from HK) be utilised to control the ballast trim tanks on the Floating Drydock?? Is this possible?? I have stuff all knowledge of how these electronics work so any advice and help is mucho appreciated!!

Bruce
From what they've said above, it could work.

Regarding lift capacity, that should be equal to ballasted-down displacement - unloaded displacement, minus 5% from that.

EDIT:

It could be used to give data to an Arduino controlling the tanks. The quadcopter leveller is designed to work with only 4 motors, thus probably 4 outputs. No problem to equate those to the four corners of the dry dock and go from there, i'm happy to help programming, not due out to sea for the rest of the year.
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Old Feb 21, 2013, 10:53 PM
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Thanks Mate!

I will start a build log for the FDD hull once I can scrounge some extra bucks!! Shouldn't take too long to build....
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Old Feb 22, 2013, 07:18 PM
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Maybe a potentio meter attached to a pendulum can give some sort of a signal to a servo controlled valve. The valve will control the flow between two tanks, thus controlling trim or heel angle.

thats my two cents....

Cheers
G-O
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Old Feb 23, 2013, 10:44 AM
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What about a small dish with a drop mercury in it with one wire in the center (common) and wires at the edges in your cardinal directions, so that when it tilts the mercury contacts both the common wire and one or more of the edge wires which activate pumps.
Regards,
Gerald.
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Old Feb 23, 2013, 02:20 PM
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United States, NJ, Frenchtown
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Can it be done with a reversable pump for each axis ? 6 vdc or 12 vdc car woper pumps.
A DPDT float switch on each axis ? Any long armed Microswitch mounted in a compartment sealed at the top. Water comes up from the bottom. Switch can be controlled by a float, weight & string. Lenght of the switch arm controls sensitivity...Wiper washer motors pull little current.

Big full lower & lift could go to bigger toy or R V water pumps. If you need to do several gallons in a minute. Too fast on 12 vdc..........Use 6 vdc on a 12 vdc pump/

You can run the trims totally by themselves & in a fully automatic mode with a SPST switch.

Run the big raise & sink pump from a channel on the transmitter.
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Old Feb 23, 2013, 09:31 PM
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United States, TX, Tomball
Joined Jan 2006
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One option that you can do, actually made something like this back in school days, but controlled stepper motors to level a gyro mounted platform. Swap stepper motors out for water pumps, same concept.

Build a platform with 2 bubble levels, one laying in each axis. Put a set of IR emitter / detector pairs on the ends of each bubble level. If the platform goes off of level, the bubble will come between the emitter / detector. While small, there is a voltage difference between the anti-freeze fluid and the air pocket between the emitter / detectors. Feed this into an A2D converter of your choice and you have your control signal for which axis needs more / less water.

I wish i would have kept pictures of the contraption, it was pretty slick with no SW involved. All was controlled by logic circuits.
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