250 Series Modular Sub Driver (MSD) for all RC subs
  • 250 Series Modular Sub Driver (MSD) for all RC subs

    View and download instructions here. 


    The evolution of the SubDriver has arrived!


    The all new Modular Sub Driver (MSD) has underwent significant upgrades over the first generation SubDriver units. The new MSDs feature a completely modular layout, which allows for much easier access to all areas of the cylinder for upgrade, repair or maintenance. 


    MSDs are also now powered by high-efficiency and high-torque brushless motors. Single shaft variants run direct-drive, while dual-shaft MSDs run through an integrated gear reduction splitter for simplicity and reliability. 


    These cylinders feature 3 servo outputs at the rear, a fully assembled SNORT ballast system with integrated emergency gas backup. 


    The SNORT ballast system is ideal for most RC submarines and offers superb reliability and simplicity. The ballast system brings the boat from full surfaced waterline to "decks awash" state, retaining slight positive buoyancy. With the addition of a small amount of forward movement and dive plane commands, the model easily submerges. In the case of emergency, the model will always re-surface, simply by putting transmitter controls to neutral and waiting for the submarine to re-surface. 

    Conversion to full static-diving SAS ballast is possible, but is challenging in models of this size with limited volume available in the sail area. Please email me for more info or details, if desired. 


    The 250 Series MSD refers to the diameter of the rear motor compartment and the forward battery compartment. MSDs are ordered using three values, each representing one of the compartments: Motor Compartment / Ballast / Power Compartment. All ballast tanks come standard with a 12" length. This ballast tank can easily be cut to size for your specific application. Instructions to do so are included in the instructions.

    IE: An MSD with 2.5" motor compartment, a 3.75" diameter ballast tank, and a 2.5" power compartment would be a 250/375/250 MSD. 




    • How to size your ballast tank

      Each MSD250 comes with a standard 12" long ballast tank. The tank and wire conduit is easily cut to size using standard hand tools.

      To determine what size of ballast tank you need, you need to determine the weight of your fully assembled submarine model above the surfaced waterline. To this weight, add another 10% as a safety factor.  

      Each inch of length of the ballast tank will provide a set volume of ballast. Take the target weight that you determined above, and divide it by the appropriate ballast tank volume value below in order to determine your ballast tank size, rounding the length up. 

      2.5" diameter tanks offer 2.57oz or 72.9g of reserve buoyancy per inch.
      For example, an 8" long tank of 2.5" diameter will offer 20.6oz (584g) of reserve buoyancy. 

      3" diameter tanks offer 3.76oz or g of reserve buoyancy per inch
      For example, an 8" long tank of 3" diameter will offer 30oz ( g) of reserve buoyancy. 

      3.75" diameter tanks offer 5.97 oz or g of reserve buoyancy per inch
      For example, an 8" long tank of 3.75" diameter will offer 47.8 oz or g of reserve buoyancy.

      Real world example:

      Let's say that you have a 48th scale WW2-era fleet boat model you are building. These boats have twin motor shafts. 

      You determine that the weight of your model above the surfaced water is 22oz. We will add another 2.2oz and round up, giving us 25oz as a target volume for our ballast tank. 

      Measuring the interior of your sub, you determine that you can fit a 3" diameter ballast tank without issue. 

      Using the values above, we take 25oz and divide by 3.76oz/inch, offering us a target ballast tank length of 6.65", or 7" when we round up. 

      So, what we're after is a 250/300/250 twin-shaft MSD with a 7" ballast tank.

    • MSD Package Contents

      Main SubDriver Unit:

      ❏ Motor bulkhead: Either single or dual motor, with external gearbox that produces two counter-rotating output shafts or without, depending on what you’ve ordered. This bulkhead has the motors, motor shaft seal(s) and pushrod seals pre-installed and tested, and the equipment tray connected.

      ❏ Motor compartment cylinder - polycarbonate tubing

      ❏ Motor compartment ballast union bulkhead with pre-installed Low Pressure Blower (LPB) with attached and tested Motor Pump Controller (MPC), ballast servo, and servo pushrod watertight seal on the after ‘dry side’; a mounting flange for the optional emergency gas backup blow valve, and pass-through nipples for the induction and discharge SAS plumbing on the forward ‘wet-side’

      ❏ Ballast tank cylinder with pre-installed and tested ballast vent linkages, flood-drain holes, vent, hole to accept optional emergency gas backup bottle, and 5/16” o.d. Brass conduit

      ❏ Power compartment ballast union bulkhead

      ❏ Power compartment cylinder - polycarbonate tubing

      ❏ Power compartment forward end cap with integrated servo tray and seals

      ❏ Two installed servos with pushrods

      ❏ Three, 1/16” diameter brass linkage rods

      ❏ Mounting screws for servo tray

      ❏ Electronic Speed Controller

      ❏ BEC (battery eliminator circuit)

      ❏ Spare 1/16” pushrod seal

      ❏ Three, magnetic Klik-On linkage connectors

      ❏ Power cable, 16-gauge two-conductor zip-cord, 24” long

      ❏ Two servo extension wires for the forward servos

      ❏ Two sets of mini-Deans connectors for equipment tray disconnect

      ❏ One set of standard Deans connectors for battery

      ❏ Mini fuse holder and 15A fuse

      ❏ Heat shrink

      ❏ 5 mini servos (2 of which are pre-installed)

      ❏ 3/32” i.d., 26” long, flexible hose for antenna and leak testing

      ❏ 1/16” i.d., 20” long, flexible induction hose between MSD and snorkel

      ❏ Various extra mechanical fasteners

    • What You'll Need to Supply

      What you’ll need to finish up your cylinder:

      ❏ Radio and radio receiver on appropriate surface frequency (75mhz in North America, 40mhz in Europe - check your local laws regarding allowable frequency ranges). GHz radios do not penetrate water. If you use one, you will need to extend the antenna above the waterline and keep it above the waterline during operation of your submarine. You can view a photo catalog of the GHz conversion methodology here.

      ❏ Optional pitch controller. I recommend our AD2 (Automatic Depth) pitch controller

      ❏ Optional failsafe device. I recommend our BLM (Battery and Link Monitor)

      ❏ Optional Depth Controller. I recommend our DC (Depth Cruiser)

      ❏ Optional waterproof lighting connector

      ❏ Optional switch. Either a standard toggle switch with waterproof boot, our MM10 (Magnetic Mission) switch, or our remote on/off switches

      ❏ 11.1-volt Lithium polymer battery of the highest capacity that will fit within the power compartment

      ❏ Silicon grease, AKA distributor grease (available at car supply stores)

      ❏ RTV silicone adhesive/gasket maker

      ❏ Two-sided tape for mounting electronic components

      ❏ Hand and power tools including side-cutters, a rotary tool, wire strippers, soldering iron, drill and drill bits, flat blade screwdriver (for prying cylinders off unions), needle-nosed pliers

    Shaft Outputs
    Ballast Tank Diameter


    The Nautilus Drydocks is the world's premier supplier of kits, parts, components and resources dedicated to the hobby of remote controlled submarines. 



    983 Tivoli Dr
    Naples, FL  34104 USA
    Phone: (239) 877-4280

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