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    Piston Ballast Systems

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    salmon

    Posts: 160
    Join date: 2011-09-02
    Age: 54
    Location: Las Vegas, Nevada - USA

    Piston Ballast Systems

    Post  salmon on Tue Sep 06, 2011 5:44 pm

    Can you help me figure out how to build a piston tank?
    what or how do you make a spindle nut? and how does this connect to the motor?
    I notice that it is used a lot in Europe and not so much here across the pond, but it looks like the best choice for static diving in the sub I want to build. Can you help me or point me in the right direction? are there any drawings?

    I have access to a lathe, granted it is older than most of the submarines we are building models of, but it is functioning.


    Thank you!
    Regards,
    Tom

    Giovanni LiCalsi

    Posts: 170
    Join date: 2010-11-15
    Age: 63
    Location: Alameda, California, USA

    Re: Piston Ballast Systems

    Post  Giovanni LiCalsi on Wed Sep 07, 2011 3:27 am

    Hi Tom,
    You may also want to register at www.rcboot.de
    They have lots of different piston ballast tank custom designs there.
    Regards,
    Giovanni

    salmon

    Posts: 160
    Join date: 2011-09-02
    Age: 54
    Location: Las Vegas, Nevada - USA

    Re: Piston Ballast Systems

    Post  salmon on Wed Sep 07, 2011 7:14 am

    Thank you for the direction. I went looking, but I am having trouble even with Google Translate finding articles. Can you guide me on ones you have found?

    Cheers,
    Tom

    david f
    First Officer
    First Officer

    Posts: 1141
    Join date: 2010-11-10
    Age: 63
    Location: Cumbria

    Re: Piston Ballast Systems

    Post  david f on Wed Sep 07, 2011 9:57 am

    I've only just started making my own - so I'm no expert on piston tanks. They are probably the most difficult dive system to build - because the pistons/cylinders need to be machined.

    The original document I found very helpful was by Lothar Mentz in Sonar. The original link to the website no longer works(It was 2009) but this reference from his document may help you track it down. (You will need to translate the document from the German - Google Translate does quite a good job.) (I don't want to send you copies because that would not be with Lothar's permission.)

    Kolbentank im Selbstbau Piston Tank in DIY
    von Lothar Mentz aus SONAR 9 Lothar Mentz from SONAR 9

    I wouldn't contemplate making one unless I had access to a lathe. (I have a Taig/Peatol which is small but OK) So don't start unless you have access to machining, I would say. Plenty of other dive systems available with all their advantages and disadvantages - see the AMS website for a description.

    Nigel E is also a dab hand with piston tanks and will hopefully chip in.

    david f
    First Officer
    First Officer

    Posts: 1141
    Join date: 2010-11-10
    Age: 63
    Location: Cumbria

    Re: Piston Ballast Systems

    Post  david f on Wed Sep 07, 2011 10:33 am



    A photo grabbbed from the original article (I'm sure that Lothar wouldn't mind.) It shows the general idea.The central gear is threaded internally and runs in a ball race bearing.

    Giovanni LiCalsi

    Posts: 170
    Join date: 2010-11-15
    Age: 63
    Location: Alameda, California, USA

    Re: Piston Ballast Systems

    Post  Giovanni LiCalsi on Thu Sep 08, 2011 4:28 am

    Here you go.
    These ballast piston tanks were found on www.rcboot.de
    I have just received a 4"OD x 12"length x 3/8" wall thickness 6061 aluminum tube for my piston tank cylinder.This will have a capacity of 1500ml.I will gundrill through the length of the wall thickness for internal compression rods to compression fit a 13" length polycarbonate wtc on each end of the tank cylinder.There will also be extra gundrill bores for air relief and wiring chases.The drive motor will drive the piston rod with it having a threaded hollow-core shaft.This will fit in my Engel Gato.
    I will post photos soon.
    Giovanni










    salmon

    Posts: 160
    Join date: 2011-09-02
    Age: 54
    Location: Las Vegas, Nevada - USA

    Re: Piston Ballast Systems

    Post  salmon on Thu Sep 08, 2011 6:31 am

    Giovanni,
    Wow, great photos! and I see the threaded center (that is the area I need to learn to build). There are two relays that I will believe limit the fully extended and fully retracted piston by turning off the motor.

    Thank you so much for finding these! I will keep looking as well. Does anyone have a plan or drawing that they are willing to share?

    Peace and Cheers,
    Tom

    david f
    First Officer
    First Officer

    Posts: 1141
    Join date: 2010-11-10
    Age: 63
    Location: Cumbria

    Re: Piston Ballast Systems

    Post  david f on Thu Sep 08, 2011 8:22 am

    Very nice photos.

    Looking at them, it occurs to me that piston tanks are always shown with the threaded rod retracted.

    Is this to try and gloss over one of the major disadvantages of pistons tanks -a whacking great screwed rod taking up all your scarce internal space?!

    I will get down off my "soap box" now but they are not the perfect system that seems to be a commonly held view. Oh and the internal pressurisation problem and the power failure that leaves your sub sunk. But they don't half control your sub well!

    salmon

    Posts: 160
    Join date: 2011-09-02
    Age: 54
    Location: Las Vegas, Nevada - USA

    Re: Piston Ballast Systems

    Post  salmon on Thu Sep 08, 2011 8:50 am

    David,

    I see your points and maybe I do have a misconception. My application is for a small sub and I thought a syringe type piston would offer enough ballast control, be compact, and allow static diving. I am certainly open to ideas. My wtc would have to stay 37mm OD x 250mm.
    Any suggestions?

    Richard

    Posts: 2945
    Join date: 2010-11-05
    Age: 64
    Location: Sussex, UK

    Re: Piston Ballast Systems

    Post  Richard on Thu Sep 08, 2011 10:01 am

    Hope these help you?

    (Posted on behalf of Nigel Edmonds.....)






    These are the same tanks as Nigel uses in his Turtle.


    _________________
    "number one...periscope depth if you please"

    Giovanni LiCalsi

    Posts: 170
    Join date: 2010-11-15
    Age: 63
    Location: Alameda, California, USA

    Re: Piston Ballast Systems

    Post  Giovanni LiCalsi on Thu Sep 08, 2011 3:43 pm

    The ballast comparisons:
    The piston tank is the most reliable ballast system for any boat, period. "Oh, but you'll run out of electric under water!" This is a scare tactic. Aside from signal loss, the controller has undervolt failsafe and there is a trimmer pot where you can even adjust the safety cutoff voltage if you really want to. Mine pops up with plenty of surface playtime left, and that's after an hour of normal running. This brings me to another point: electricity. The tank uses some electricity, but it's not that important because it's not constantly running the way your main motors are. The tank is not an electric hog the way some people like to portray it.
    If someone's selling gas systems (which are completely viable systems) but they're knocking the piston tank or kits that employ it, ask them why Engel has sold over 30,000 piston tanks! And don't let them tell you it's because the Germans are short-sighted lemmings who can't let go of yesterday's technology. It's because they have enough of a fan base to support the manufacture of a superior, reliable turnkey system. You should also suspect anyone who attempts to abuse your lack of knowledge for commercial purposes.
    Please don't think I'm down on gas. If you have a couple (or ten) gas boats, then why switch now? If you're already stocking propellant for your other boats and you already know the system then sure, stick with it. If you want to make an friend of a vendor, then buy their kit. If you only want to go with gas because it's cheaper, then build an RCABS. Maybe someday someone will actually build a commercial RCABS. Who knows, maybe reason and commerce could finally coexist.
    Let me break down some negatives and positives to try to present some fairness.
    Gas ballast negatives:
    • There is no failsafe to keep you from diving when you do not have sufficient gas to surface again. If you have a gas failsafe and dive too deeply and lose signal, it goes off.
    • Open surface (loose water) in the ballast tank means as the boat pitches forward, water rushes forward and pulls the bow down even more. This instability is lessened by the installation of baffles but it's always there.
    • Airbrush propellant costs money.
    • Filling the onboard resevoir every XXX number of dives is a pain.
    • Counting the number of dives is a pain, and a risk, and if you don't get the onboard resevoir completely filled then your dive count is off anyway.
    Gas ballast positives:
    • Cheap
    • Generally smaller WTC's
    • Cool bubbles when you blow ballast
    Piston tank positives:
    • Your failsafe keeps you from diving if it's not safe to do so
    • Your failsafe can go off as many times as you want and it resets when signal is regained, so there's no trip back to shore to refill the gas failsafe if you dive too deeply.
    • If your receiver battery dies underwater, the BTS uses the main batteries (which are monitored for undervoltage) to empty the tank.
    • No air is in the tank, so ballast water does not slosh forward and send you standing on your nose.
    • You only change the batteries, and you get an hour of playtime per set.
    • You dive as often as you want, without worrying about counting.
    • The Engel tank in particular is a very high quality product. The selection of plastic materials and microswitches are all heavy duty. The construction leaves nothing to be desired. They dominate the market for this reason.
    Piston tank negatives:
    • Expensive
    • Threaded rod travels in WTC using up space akwardly.
    • Internal higher pressure but most subs have suffered no ill effects.
    • Tank geometry is a fixed cylinder
    • CG shifts a bit with a single tank
    RCABS is in many ways the best of both worlds. It's cheap. It's all electric, so there are no gas hassles. You can run it with a BTS for undervolt and signal failsafe. The bladder can be arranged such that the center of gravity doesn't shift during filling.
    Regards,
    Giovanni





    salmon

    Posts: 160
    Join date: 2011-09-02
    Age: 54
    Location: Las Vegas, Nevada - USA

    Re: Piston Ballast Systems

    Post  salmon on Thu Sep 08, 2011 4:19 pm

    @ Richard - YES,YES, something like that! Would Nigel share his knowledge with me? I will build a larger unit if it means gaining the knowledge to tinker in the smaller range! Are there any plans out there? Would he sell me one of his? Or I can buy the parts from hime and assemble it myself or ????

    @ Giovanni - I love your passion! In the U.S. there is a saying "6 of one, half a dozen of the other". In other words, they are the same and if your sub comes up and returns to you, that is a good ballast system. Thank you for explaining so well the pluses and minuses. I have seen with each system that the owners have considered the "What if" scenarios and built failsafes.

    You guys are the best! Thank you for helping me understand and sharing information!

    I am still on the hunt......

    Richard

    Posts: 2945
    Join date: 2010-11-05
    Age: 64
    Location: Sussex, UK

    Re: Piston Ballast Systems

    Post  Richard on Thu Sep 08, 2011 5:02 pm

    Tom, best thing you can do is ask Nigel...send him a pm and ask. He's not a bad lad really... :-)


    _________________
    "number one...periscope depth if you please"

    salmon

    Posts: 160
    Join date: 2011-09-02
    Age: 54
    Location: Las Vegas, Nevada - USA

    Re: Piston Ballast Systems

    Post  salmon on Thu Sep 08, 2011 5:39 pm

    Richard,
    Thank you again! I will do that now.
    Cheers,
    Tom

    Richard

    Posts: 2945
    Join date: 2010-11-05
    Age: 64
    Location: Sussex, UK

    Re: Piston Ballast Systems

    Post  Richard on Thu Sep 08, 2011 5:51 pm

    No worries...


    _________________
    "number one...periscope depth if you please"

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