Building a R/C Combat Model of the SMS Hindenburg

Well, now that you've gotten your feet wet it's time to get back to the shop, set the boat to the side, and start working on the guns. There are several schools of thought when it comes to the guns in our hobby. Many will buy pre-made guns, the main supplier of which is Swampworks. Others get their guns second-hand from other battlers, these may be Swampworks guns or home-made. The hardest, but most rewarding, method is to build your own guns from scratch. Why rewarding? Simple - when you build something you know more about it. Where every piece goes, how it's "supposed" to look and feel. You can tell if something doesn't seem "right." This is critical at the lake, when the gun is firing weak or intermittently and the second sorte starts in a few minutes.

Before we get to building the guns, there is something I would like to stress - SAFETY!! Though we mount these guns on model boats and our girlfriends and wives think of us as "big boys playing with big toys," these guns have the potential to injure and maim if not handled with respect. Please read this article by one of the "old men" of the hobby before going any further.

That said, let's get to work.

First thing to discuss is the basic operation of a RC Combat BB gun. For this I'll refer you to the above diagram of a typical poppet-valve operated, piston-interrupted, O-ring style BB gun made up of standard 1/4" compression fittings. There are other methods of building and firing the guns, involving slave valves or electronic solenoids, but for the purposes of this article I'll keep the set-up simple.

From bottom to top (which in our case is the direction of gas flow):
• You start with a CO2 source, usually a 3.5 or 7 oz tank in 2 gun cruisers or larger and illustrated here, or a CO2 cartridge like those used in commercial BB and pellet guns for smaller boats;
• Per the rules of the International Radio Warship Combat Club (IR/CWCC), guns systems are limited to a working pressure of 150 psi, so some sort of commercially manufactured regulator is required to bring the bottle pressure down to that level;
• After the gas leaves the regulator it travels via a supply hose, usually of 1/8" inside diameter (ID) but sometimes other sizes, to a distribution manifold (to split the gas among several guns) or to a single gun as in this case;
• The supply gas goes to the poppet valve, a Clippard MAV-2 is shown here, which stops the gas flow until the button to the left is depressed, usually by a servo;
• The gas then flows past the valve up into the bottom of interrupter assembly via 1/16 ID tubing. Here the gas splits along two paths:
  • First the gas pushes the interrupter piston up, allowing only the BB sitting on top of this piston to move toward the breach and blocking those in the magazine;
  • The rest of the gas will travel to the end of the magazine and then travel down the magazine tube and push the other BB's forward toward the interrupter, then flow past them to carry the BB poised on top of the piston up to the Breach;
• The BB on top of the pistion will be carried up to the breach, in this case an O-ring compressed between the inner wall of the 1/4" "L" fitting and the end of the barrel;
• The BB will be stopped by this compressed O-ring, blocking the gas flow and allowing the pressure behind the BB to build;
• Once sufficient pressure has built up the BB will force its way past the O-ring and out the barrel of the gun, hopefully to strike its target ;-)

First, the parts and tools you are going to need:

• Parts
  • CO2 source
    • Disposable CO2 Cartridge (small boats with 1-3 guns)
    • Refillable CO2 Tank in 3.5 to 12 oz sizes (larger boats with 3 or more guns)
  • One Regulator to attach to CO2 source, max 150 pounds per square inch (PSI) output
  • 50 feet 1/8" ID Urethane Hose
  • 50 feet 1/16" ID Urethane Hose
  • Two Clippard 1/8" Hose Barbs w/ 10-32 male threads per gun
  • One or Two Clippard 1/16" Hose Barbs w/ 10-32 male threads per gun
  • One Clippard MAV-2 Poppet Valve per gun
  • One 1/4" Plumbing Union Tee per gun
  • One 1/4" Plumbing Union Elbow per gun
  • One 1/4" Plumbing Union per gun
  • Several feet of 1/4" OD copper or brass tubing
  • 3 feet each of 1/16", 7/32", 1/4", 9/32", and 5/16" OD Round Brass Tube per gun
  • 1 small sheet of thin brass (1/16" or 1/32" thick)
  • Piston material - penny nail, brass/aluminum rivet, etc.
  • 1/4" (2-3 coils) of a small spring (large enough to fit over stem of piston)
  • Teflon Pipe-Tape
• Tools
  • Propane Torch
  • Solder
  • Flux
  • Tube Cutter
  • Metal Cutting Shears
  • Drill or Drill Press
  • Vise or other support for solder work
  • Lathe (for best results)

How the guns are built varies from person to person, region to region, varying mainly based on the experience level of the battler and the parts available to them. To give you an idea of the different construction techniques I'll refer you to two other sources of information on building your own guns: