Operational cannon in Ironclad Models
Steve Lund
Models like these
ironclads tend to be very “sterile” looking, lacking a lot of deck
and surface detail that
other types of ships abound in. Having an “animated” feature like
operable cannon really livens things up
and offsets that disadvantage somewhat. The effect of having you
craft cruising serenely by and unloosing a smoke-producing salvo
from her guns, can be pretty dramatic. And although I have spoken in
seemingly glowing terms about this feature, I would have to caution
anyone who desires to embark on using it to approach it with extreme
caution. First of all, the black powder used to achieve the effect,
is an explosive. And when we work with that substance and
electricity, we have a potentially dangerous situation. So, just
plan from the outset to always work with the powder in very small
quantities, keep it isolated from any potential sources of ignition,
and always wear eye protection while handling it.
Another caution; Projectiles?……Absolutely not! I tried an
experiment, once, with one of the gun
tubes on the bench, using the same small amount of powder used to
produce the smoke effect, loaded with a single piece of birdshot,
and aimed at a piece of bond paper 24 inches away. The result was
the shot passing cleanly through the paper and expending itself
against the back of my garage wall with a loud report. It was
clearly evident that the shot was capable of damaging an eye or any
other soft tissue. Likewise, one has to be very careful about using
the correct type of powder. The wrong type (which we will cover
later) produces a loud “bang”. Doing such a thing is a public park
is not a wise thing. In fact, here in the L.A. Basin, it is apt to
get you thrown out of the park, get you return fire, or both. One
final disadvantage to the whole process is that you wind up with
black powder residue inside your model. The substance is dirty and
highly corrosive. So, even though many of my models have this
feature, I use it rarely. You may want to consider the same
approach.
All that said, I’ll now discuss what you need to do to make it all
work. The essential elements of the
system are the gun tube with its mounting system, the ignition
system, and the (for lack of a better term) “fire control” system.
The first element will vary depending on whether the guns are turret
or casemate mounted. Amounts of available space between the two
configurations are dramatically different. The other two elements
are common to all configurations. It is just a matter of choosing
the method that you are most comfortable with. For the 1/72 scale
ships, I have found that ¼ inch thick-walled aluminum tubing works
best. The material is the right size, readily available at most
hobby and craft stores, sturdy enough, and is easily worked. The
guns are mounted to basswood blocks, and then the blocks are mounted
into the ship. In turrets, I leave them permanently in place. In
casements, I mount thin wall brass tubes into blocks as sockets and
slide the actual gun tubes into them. This way, the guns can be
wired for ignition and then simply plugged in as an assembly.
Speaking of ignition, I use two types; pyrotechnic and electrical.
While both are actuated electrically,
the pyrotechnic method is the simplest. I use the disposable
igniters made by Estes that model rocket builders use to set off the
rocket motors. They are a simple loop of this nichrome wire covered
with a small amount of material like that used in ordinary match
heads. When energized with as little as six volts, the wire heats up
through resistance, and set off the igniter.
The disadvantage to this approach is that you have to disassemble
the gun each time to replace the
igniter at the breech and then load the powder in at the muzzle end.
In most cases, this involves taking the boat out of the water so one
can get to both ends of the guns. When the igniter is inserted, the
breech end of the guns can be closed with a simple wad of beeswax
(since there is very little back pressure exerted) or (in the turret
application) with a transverse block pinned in place. In the case of
the transverse block, thin copper tubing passes through it to
receive the igniter on the inside and the wire from the fire control
on the outside. Both of the methods associated with the pyrotechnic
method are inherently “gas-leaky” and result in residue inside the
model, due to the necessity of having a removable breech plug
arrangement.
The electrical ignition is done two ways; with model airplane type
“glo plugs” and with purpose0built
igniters using 24 gage nichrome wire as the heating element. This
approach is the simplest and most
maintenance free because it doesn’t require servicing after every
shot and remains sealed and connected. All you have to do is load
the muzzle end and it is ready to fire again. The principal
disadvantage to this method is that it takes higher amperage than a
normal lead-acid battery delivers with six volts. So, one must
resort to using NiCad batteries. And the bigger (i.e. “D” cells vs
“AA” or “AAA” when using glo plugs) the better. Besides the
batteries themselves being a monetary investment (about $5 each for
the “D” cells), you also have to invest in a charger for them. The
best battery “package” I have found is four “D” cells (6 volts) for
the glo plugs and a 6 volt, 1.0 amp “Gell Cell” for the nichrome
wire configuration. I found out (the hard way) the 6 volts and 1.3
amps burns the igniter up (instantly). Either way, the act of
igniting the cannons poses a terrific drain on the batteries. At
best, I can get only 6 ignitions out of a single battery charge. So,
plan to use a separate (separate from the boat’s drive motor power.
You don’t want to run that battery down prematurely) power source
for ignition and to bring along spare batteries if you plan to do
repeated firings. Now, on the subject of gunpowder. Black powder
comes in three grades: FFg, FFFg and FFFFg. The courser grades (the
preferred ones) are FFg and FFFG. The finer the grade (the finer the
grind) the faster the powder burns, and that makes it more likely to
produce a “bang”.
If you don’t want it to make noise then the preferred product is
Pyrodex. This is a product that is billed
as “safer” and more “environmentally friendly”. I personally prefer
to use this stuff, and it always ignites
on cue as well. To load the powder I use tubes made from cigarette
paper, sized to slide easily into the bore. It is treated to burn
completely, usually has a glue strip on one side, and is thin enough
to ignite readily. Magician’s flash paper works better, but is
illegal in many states (California, for one) and is sometimes
difficult to find. It is also difficult to glue (it is toxic, so you
can’t lick it like cigarette paper) because of its thickness and a
surface that seems to repel some adhesives. Once you have a
functional and mounted gun suite, you can progress to the “fire
control” system that you need to fire them by remote control. My
solutions to this problem have ranged from crude to somewhat
sophisticated. It simply depends upon ones inclination and the
number of guns fitted to determine the approach.
For my first effort, the USS SAUGUS in 1/86 scale, I simply had a
servo arm with a contact on it move left or right to close the
ignition circuit to fire the appropriate gun. I used a three channel
HITEC unit with the two control sticks operating the rudder and
throttle. The third channel was operated by a twist knob. All that
was necessary was to slew the knob left or right to fire the
appropriate gun. To set the guns off, I now use servos arranged to
trip microswitches when they move to maximum travel position in
either direction. This is a simple way to fire two or more guns with
one servo. I now use a four channel R/C system as a minimum, so that
I can accommodate features such as this or operable turrets, or
both.
For multiple guns, I use combinations of paired microswitches where
half travel of the servo’s lever
trips the first switch (one with a long arm) and continued movement
causes its lever to trip a second switch. In this way, I was able to
fire eight guns (having them salvo in pairs) on the CSS VIRGINIA off
one servo. I fire her broadside guns in this way and the fore and
aft guns off a separate servo. Admittedly, the whole thing can get
complicated.
In conclusion, I’d say that these systems can be pretty spectacular
to behold………when they work.
And, as I think I have shown, there are plenty of factors that go
into that. So, if this sort of thing interests you, I’d advise that
you proceed with caution and expect to do a lot of experimentation
before you get it all to work properly.