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How the Guns Operate
This section describes the operation of a typical piston interrupter type BB gun.
The gun starts out with the piston at the bottom of its' travel and a single BB siting on top of the piston. The presence of this BB prevents any other BBs from entering the vertical portion of the Interrupter assembly from the inlet. There are other BBs in the magazine and in the inlet portion of the Interrupter. The last portion of the magazine (and therefore also the Interrupter inlet) angle down (typically 10 degrees) so that the BBs in these areas will feed by gravity. The rest of the magazine can be at any reasonable angle including angled so the BBs roll away from the Interrupter.
To fire the gun CO2 (at 150 PSI maximum) is supplied to the gun at the bottom of the piston by valve controlled by a R/C servo. The gas forces the piston up blocking any more BBs from entering the gun. At the same time the gas flowing around the piston blows the BB that was already present up the vertical portion of the interrupter and into the Restrictor assembly. At the same time gas was applied to the fill end of the gun magazine, blowing one or more BBs into the down angled portion of the magazine. The Restrictor holds the first BB until the pressure inside the gun assembly builds up. When the pressure reaches a level were its' force against the BB is sufficient to overcome the restraining force of the Restrictor, the BB shots out the barrel at high velocity. The BB then has an effective range of about 20 feet. After the BB fires the valve is closed and as the gun pressure drops the piston drops back down, and the next BB in the Interrupter inlet rolls into place. Some guns have an internal spring to help force the piston back down.
The gun is now ready for the next shot to be fired.
The Restrictor assembly generally uses either a compressed O-ring or a length of model aircraft fuel line to hold the BB until the pressure builds up.
Setting Up the CO2 Gas Supply for the Guns
There are several options for supplying the CO2 to power your guns, both for the CO2 supply and for the feed to the guns. The most important consideration at any time is SAFETY!! The liquid CO2 we are using for our gas supply is at a pressure of 1500 PSI in the tank or cartridge!! Do not use anything but commercial equipment and fittings for the regulator and any parts on the high pressure side!! After the regulator the pressure is 150 PSI, so you can modify or build parts in on this side, just take reasonable precautions as to the strength of the finished parts. Any accumulator tanks made should be assembled from copper water pipe and pipe fittings, and soldered together to normal water pipe standards. Do not use butt joints in the accumulators!! Use standard end caps and other fittings!! To attach CO2 Gas fittings to the pipe either solder a nut inside the accumulator or tap the location and also solder the fitting to the pipe. If you can attach the gas fitting to the side of a water pipe cap or T fitting this will provide twice the thickness of copper to hold the gas fitting (the thickness of the side of the pipe fitting and the thickness of the pipe).
For your gas supply there are two standard setups. One uses a disposable CO2 filled cartridge, and the other a refillable tank.
For small ships that need to save weight, a disposable 2 oz (of liquid CO2) cartridge , an adapter, and a light weight regulator are used. The adapter is screwed into the high pressure side of the regulator (and stays screwed in thereafter), and the cartridges are screwed into the adapter. As the cartridge seats (and seals) into the adapter a fitting pierces the cartridge end and the gas can flow to the regulator. Be sure that the low pressure side of the regulator is hooked to the system, or you can watch the gas merrily vent to the air!! This setup has no shutoff valve as in the larger ship setup. This type of setup will generally supply enough gas for two, or possibly three, 50 shot guns (or one 50 shot and one 75 shot gun).
For larger ships a standard regulator and a refillable tank is used that screws directly into the high pressure side of the regulator. A light weight regulator can also be used, but if you do not already have a regulator the standard one costs about 50% of the price of a light weight regulator. The refillable tank has a built in ON/OFF valve and an over pressure rupture disk (in case the tank is overfilled and then the liquid has insufficient room to expand as the tank warms) (the disposable cartridge does not need the rupture disk as it is correctly filled at the factory). You will need a supply of CO2 to refill the ship tank from. A 20 pound tank is used for this purpose. These large tanks can be purchased, or rented, from most local welding gas supply houses. You will also need to purchase the fittings and hose to connect the two tanks during refilling. You also get the 20 pound tank refilled at the same locations.
The tank that fits in the ship comes in three commonly used sizes: 3.5 oz, 7 oz, and 12 oz. The 3.5 oz tank is used in the larger Cruisers and Battle Cruisers (two to three guns). The 7 oz tank is used for Battle Cruisers and small to medium Battleships (three to five guns). The 12 oz in the largest Battleships (six or more guns) or medium Battleships with high gas flow guns. The high flow guns use larger valves and hoses to increase the power (faster BB velocity) of the guns.
The plumbing for the low pressure (150 PSI) gas that powers the guns is generally made from standard or modified commercial Clippard pneumatic control equipment. In the rest of this write-up the use of Clippard parts will be assumed. These parts include valves, fittings (allow multiple lines to join together), and barbs (to go from the hoses to fittings).
To get the low pressure (150 PSI) Gas from the regulator to the gun valves a manifold is used. The manifold is typically made from one or more fittings. These are a hollow cube shaped block with a threaded nipple on one side and tapped holes on one or more of the other five sides. The nipple screws into a matching hole on the regulator or valve, the barbs for the hoses screw into the holes. The manifold is made up off one or more of these fittings, stacked (with additional fittings screwed into one of the holes in the previous one), with enough holes for the desired number of supply hoses to the valves. Due to space considerations inside the ship and minimum bend radiuses for the hoses, generally only two hoses are fed from each fitting.
From the manifold hoses connect the supply to the gun valves. There are three major setups for controlling the gas flow from the low pressure supply to the guns.
The simplest is to run a hose from the supply to a servo driven plunger valve, and from that to the gun. When the servo arm pushes on the valve stem, the valve opens and gas flows to the gun. When the servo arm retracts the valve closes. The valve typically used in this setup is a MAV-2. This valve resembles a cylinder with a stem coming out one end and an inlet hole in the other. The exit hole is on the curved side of the cylinder. The valve stem is pushed in toward the valve to open it. A spring inside the valve pushed the stem back out when the stem is released. This valve is totally enclosed so that none of the gas escapes to the atmosphere during valve operation. Is allows the valve to be mounted with the stem inside a watertight box for the servo. The major portion of the valve as well as the holes for the hoses remains outside the box. This setup provides a simple reliable method to feed the guns. Performance suffers though if a the guns are any great distance from the valve. As the length of the hoses from the valve to the gun increases the flow rate of the gas decreases. The gun then takes longer to pressurize and the rate of BB fire decreases. The gun also lacks the quick action that produces higher BB velocity. Another problem with this setup is that you must have a valve for each gun, and a servo can not reliably actuate more than one valve at a time.. With the larger ships that may have a multiple gun setup where several of the guns should fire simultaneously this limitation causes layout and servo cost problems. A servo can be used to drive up to two valves, but only if one is driven at a time. Servo movement clockwise from the centered position drives one valve, movement counterclockwise drives the second valve.
The second setup uses an electrically controlled pneumatic valve (or solenoid) in place of the MAV-2. Operation is the same, except that a servo activated switch supplies power to control the solenoid. The solenoid is mounted close to the gun it feeds, eliminating the problem with long runs between the two. The servo setup is also much easier to place inside a watertight box as only a small hole for the wires is needed rather than a large one to accept the end of the valve. Placement inside the box is also simplified as the switch can be glued to the side off the servo, rather than the servo having to be positioned carefully to mate with the valve stem. This setup also provides for the actuation of several guns simultaneously, as a single switch can power multiple solenoids. A larger diameter supply hose can be run to the solenoid inlet, allowing for better flow to the gun. Accumulator tanks can also be used (these are explained later). This system also has a few problems. Solenoids require a fair amount of current to operate, typically .6 to 1 amp. This means that the switch has a heavy load applied on it as the number of solenoids driven at the same time increases. This also places the electronic noise generated by the switching of the current inside the box, and thus close to the sensitive receiver. Both these problems can be avoided if and external transistor is used to directly drive the solenoid, with only the small drive current for the transistor supplied by the switch. The external transistor, though, must be waterproofed. I did this by dipping the transistor and its’ leads in Dip-It, a type of tool handle coating, after all the wires had been soldered. Care must also be taken to properly wire the solenoids with provisions to prevent voltage spikes generated by the collapsing magnetic field in the coil from reaching the main power lines. This is not difficult, but some knowledge of electronics is needed (see my Web Page for the information on handling this). Another problem with this method is that the solenoids add extra weight and bulk to the inside components. For small ships the added weight can be a problem. In almost all ships (no mater how big the hull looks empty) interior space fills up quickly. The solenoids are also somewhat expensive, about $15 to $30 dollars each. Gas flow is also limited to about the same as the MAV-2 above. This makes it unsuitable for those Captains who demand very high flow rates, and have the space inside their ships for large tanks and bigger valves.
The last standard setup uses pneumatically powered valves to power the guns. This setup is similar to the first, except that the servo drives a valve that supplies gas to the pneumatically powered gun valve. As one servo driven valve can power several pneumatic valves, multiple guns can now be controlled by a single servo, and the pneumatic valves can also be positioned close to the guns they power, as in the solenoids above. The valve setup is as follows:
Accumulator tanks are used to provide a larger immediate gas supply to your guns. Generally one accumulator is used for each gun. A standard hose can flow only so much gas during firing, the longer the hose the lower the flow rate. An accumulator solves this problem. It is basically a secondary supply tank. CO2 is supplied to the tank and the gun is feed by a valve mounted directly or through a short hose to the gun. The tank provides a large volume of readily available 150 PSI gas to the gun. A larger valve like the MJV-2 can really take advantage of this larger supply. The tanks are made from sections of copper water pipe and associated fittings (end caps, "T" fittings, elbows, etc.). Check valves are used on the input side of the tank so that as the supply line pressure drops due to a different gun being fired, the accumulator tank does not loose pressure by bleeding back into the supply line. The disadvantages of the accumulator are that they take up a fair amount of space, and can be quite (relatively) heavy, as well as requiring one per gun.
One or a combination of the above setups can fill all your gun supply needs.
Drive System - Propellers
The ship's propellers are turned by electric motors. A ship will typically have one, two, or three propellers powered any other shafts that were present on the real ship are installed but the props are fixed. In our scale a ship can easily be drive at the allowed speed by less than the prototypical number of propellers. The fixed propellers act as a source of drag. This means that the powered propellers have to supply extra thrust to keep the ship at speed. This extra thrust results in a higher speed flow of water over the rudder, providing superior turning ability over that without the added drag.
For smaller ships one motor drives each prop, general directly (both turn at the same speed). Larger ships use a larger motor typically through a gear reduction setup (motors turn faster than props). For the bigger ships if built without this reduction the higher speed of a direct drive setup would cause the props to provide too much thrust, even with drag props.
The prop shafts are enclosed in an outer housing to prevent water entry around the shafts. This typically consists of a brass tube two sizes larger in diameter than the shaft. At each end of the housing a short length of brass one size larger than the shaft (and thus one size smaller than the housing) is installed to act as a bearing. Grease (generally petroleum jelly) fills the space in between the shaft and housing. THis forms a watertight assembly, while still allowing the prop shaft to stick out of each end.
Rudder
The rudder is installed in a similar manner to the prop shafts. In this case, though, the housing is only one size larger than the rudder shaft. The housing is set vertically in the bottom of the hull and the free end sits above the normal waterline. Thus even without the rudder shaft present no water would enter the hull. The rudder is not under the tress of the prop shafts and does not turn as rapidly, so no bearings or grease is needed to prevent wear. The Captain can of course use grease if he, or she, desires.
The top of the rudder shaft has an arm attached that the rudder servo linkage connects to. Some ships use a gearing system to increase the throw angle of the rudder past the typical servo rotation of 90 degrees. Generally these gears provide a rudder rotation of between 120 to 180 degrees. On ships with close to 180 degrees of rotation it is not wise to try to accelerate from a stop with the rudder thrown fully over. The extra drag of the rudder and that fact that it typically blocks the flow of one of the props, greatly decreases acceleration, while not providing much of a turn rate. With this setup you stay off the rudder until the ship gains some speed, and then move the rudder to turn.
Pump
Each warship (except the really small ones, like destroyers) have one or more pumps. These pump water that is entering the ship through the holes your opponent(s) are so conveniently providing. If the incoming water flow exceeds the pump capacity, your ship sinks! This gives you the opportunity to take a cooling dip in the pond! Sinking is not a shameful occurrence, but it does allow the other side to throw in a bit of ribbing!
Pumps are built with an impeller, but not a gear or piston setup, that is directly driven by a motor that can not be physically larger than the drive motor(s). The pump output is piped to a discharge that provides an exit from the hull. The diameter of this discharge outlet is limited to a maximum of either 1/8 or 3/32 of a inch. This creates a practical limit on any pump to insure that a ship can be sunk, if enough damage is inflicted.
Power
Radio, Drive, and Pump systems are powered by either sealed GellCell or NiCad batteries. The batteries supply 6, 7.2, 9.6, or 12 volts, depending on the Captain's preference. Smaller ships generally use either a 6 volt or 7.2 volt power. Larger ship either 6, or 12 volts. The 7.2 and 9.6 volt power comes from the NiCad batteries, and is used in Heavy Cruiser and smaller ships for the higher energy density to weight ratio. Larger ships Bigger Heavy Cruisers and up use the GellCell batteries, as they cost less and are less finicky about the way they are charged and discharged. The GellCell battery capacity ranges from 6 volts at 7 AmpHrs to 6 Volts at 36 AmpHrs or 12 volts at 18 to 20 AmpHrs. AmpHrs is a measurement of the energy capacity of the battery. The higher the AmpHr rating the more total energy the battery can provide.
These batteries provide power to the drive motors and pumps. The radio receiver is powered either by these same batteries, or the dedicated receiver battery that comes with the radio. Opinion on the best set for the radio is widely debated, though personally I prefer to use the main power batteries.
System Waterproofing
The radio receiver, throttle switches, and most times the radio servos are protected in a BB proof and watertight box. The rudder servo is often provided with its' own waterproof box as it is generally installed close to the rudder, while the main box sits closer to the center or bow of the ship. Alternately the servo can be individually waterproofed and installed without a box.
The drive motors, pump motor(s), batteries, and gun systems are out in the open. A dunking does not overly effect them. Piston springs and motors are fairly cheap and are replaced every year or so. In fact it would be almost impossible to seal up a pump motor and still allow water to get to the pump inlet.
Hull and Superstructure
The hull is made from "Bullet Proof" material (except the skin) and superstructure from relatively "Bullet Proof" material. The superstructure also has to be light in most ships, so is not as heavily reinforced as the hull. Superstructure pieces are not typically hit anyway as damage to them is not counted in the scoring. However greatly detailed superstructure is not encouraged as it does get hit at times.
The hull is built with a mandated amount of open space along the sides. These openings are then covered with a replaceable 1/32nd balsa wood skin. The BBs penetrate this skin to cause the holes. The skin is covered with model aircraft silkspan and paint to seal it from the water and reduce the tendency to split over large areas rather than have a small hole created. This skin is typically replaced once a year. Holes are patched with a piece of silkspan and paint or glue. This repair generally takes less than 15 minutes between battles.
Radio
Ships require a standard R/C radio of four to six channels. The left stick (2 channels) control the throttle (front to back movement) and rudder (side to side). The right stick controls the guns (front to back - bow and stern guns) (side to side - side guns). The pump is controlled by widely varying methods somewhat depending on how many free radio channels are available.
Units
Each ship is categorized by a strict set of standards, based on year constructed, physical size, gun size, armor thickness, and displacement. Each ship is allowed a fixed number of units based on this rating. A unit is either a single gun (50 BB magazine) or a pump (with a 1/8th inch outlet). Thus a standard WWII Heavy Cruiser such as the USS Wichita would be allowed three units. The typical setup for this would be two guns and one pump. The USS Arizona is allowed 5.5 units. She is setup with one pump and four guns. The extra 1/2 unit is used to give one gun a 75 BB magazine rather than the regular 50 BBs per gun.
Gun Positioning
The rules also specify allowed gun positioning. Smaller ships have a greater tendency to rock while maneuvering, and are for safety reasons limited to having their guns pointing only forward are backward. Larger, wider and more stable, ships can additionaly have guns pointing to the side. These sidemount guns can be angled down more (due to deck configuration) and thus are much more likely to inflict more dangerous (to the ship) below the water holes. The drawback is that they also by the same virtue are a closer range gun. The bow and stern guns will not inflict as damaging holes, but can do so from a longer range. So you trade off between greater damage and greater range.
Additionally ships that are allowed the sidemounts have rules restricting how many sidemounts can be installed per side. Larger ships in general can have more sidemounts.
With the fore and aft guns you can due damage from a distance, a good thing for smaller ships anyway as they being smaller can absorb less damage before sinking, and can not fit the battery capacity to run "super" pump with a high current draw motor.
The sidemounts being more powerful, but shorter range require that you get "Up Close and Personal" with your opponent, thus exposing yourself to his sidemounts. That is unless your opponent happens to be one of those smaller ships whose Captain has not been paying sufficient attention to where in the battle his ship is.
My First Ship - What Type do I Pick?
The present wisdom is that a new (Rookie) Captain should select a four unit ship (Battlecruiser).
Anything smaller than a Cruiser (3 Unit) is very difficult to build due to both size and allowed maximum model weight limits. They are also limited in fire power. Sorry to all those who want a destroyer!! Real life makes these unsuitable for all but those on the extreme edge of both building and fighting ability!!
A five or more unit ship is harder to maintain and build as the number of individual parts climbs. They also take more skill to fight in battle, as well as taking more damage that must be fixed between battles.
The Cruiser was the beginners choice in the past as it was the simplest to build and fast enough to get out of trouble. With the rule changes that increased the speed of some Battleships, though, this speed advantage has gone away. They are still a good starter ship, but most Captains desire to get more fire power after a few battles.
The Battlecruiser is now the recommended ship to start. It allows you to install one or two sidemounts. while only adding one additional gun assembly to the mix. So you start with more firepower and thus probably not feel the desire to build another ship after the first year. The smaller ones are a little slower, but more maneuverable than the Battleships, so are more forgiving of the new Captain learning the "Ropes".
The real choice is yours though! If you want to build that Iowa or Yamato, more than anything, do so. But realize that you are going to send a lot of time getting all the systems right the first year, and will be spending a lot of time patching the hull!! The best thing for any new Captain is to get on the water and practice, practice, practice!!!
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