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Click on the picture for RC submarine and ship conversion examples
See the latest RC subs with proportionally controlled ballast tank.

Ballast System

Click here to watch piston ballast tank video.

(9/29/2007) There are several types of ballast systems for model submarines. Piston type ballast system was selected by Puremtc for the following reasons:

1. Parts and components are widely available. Almost all hand air pumps (ball pump, bicycle pumps, ..) can be converted into a piston type ballast system. Piston type toy water gun is also a good candidate. See picture below:

2. Easy construction. The operation principle of a piston ballast system is fairly straightforward: the piston moves back and forth to draw water in and force water out of the cylinder just like a syringe. Note:The potentiometer is for position sensing and proportional control.

3. Good performance. Piston type ballast system is superior to other type ballast systems in that the volume in the ballast tank can be more precisely controlled. With a position sensor such as a sliding potentiometer, it can be made to proportionally control the amount of water in the ballast tank with a RC transmitter.

Piston type ballast systems have 2 variations:

The first type is threaded rod-action piston ballast system(TAPBS). A threaded rod-action piston ballast tank relies on a rotating threaded rod to push or pull the piston in and out.

The second type is winch-action piston ballast system(WAPBS). A winch-action piston ballast tank pulls the piston back and forth by a reversible winch.

Thread rod action piston ballast tank(TAPBS) have been employed by some submarine modelers for quite some time. Winch-action piston tanks are relatively new. Puremtc is probably the first one(or first few) to adopt this type of piston tank.

Threaded rod type piston ballast systems(TAPBS) have several disadvantages:

1. Space must be allocated for the threaded rod.

2. Threaded rod can be heavy. Compensation of center of gravity shift due to threaded rod moving back and forth may not be easy. Some model submarines use 2 thread piston tanks(moving in opposites directions) to cancel the shift.

3. Construction can be a bit involved. Suitable parts such as thread, nuts, bearing are not widely available.

Winch type piston tanks(WAPBS) more or less solve these issues. The only drawback of WAPBS is the need to replace or refill sealing pad or sealant in the front regularly.

Click here to watch piston ballast tank video.

The schematic below illustrate how a winch type ballast tank operates: