16" Turret and Mk38 GFCS Director Animation - Introduction

29MAY16 - First let me say this portion of the project has been a lot of fun: it involved basic mechanical and electrical design, along with some microcontroller coding thrown in for good measure. But let me back up a bit and define this task...

Prior to ever starting the actual build of this model, I've always assumed I would include as much animation as practical - and maybe even some impractical features "just for the fun of it." The first and most obvious feature to receive animation effects is the 16-inch gun turret. This means creating a mechanism to rotate ("train") the gunhouse clockwise/counter-clockwise and elevate/depress the barrels. Requirements I established for this effort include:

• realistic motion: the prototype turret trained at a rate of 4-degrees per second, and the guns elevated at 12-degrees per second,
• must be fully-programmable, providing operation without (or minimal) intervention from the R/C transmitter,
• operation must be realistic in terms of director/turret relationship,
• completely modular: the entire assembly must be self-contained and easily removable from the model for servicing/adjustment,
• must be able to disassemble to a reasonable level for repair/adjustment
• should preferably use off-the-shelf components, and
• must be externally indiscernible.

The "primary gun system" as I call it comprises the three 16-inch three-gun turrets, and the two Mk38 Gunfire Control System directors. Conceptually, while the model is underway, the directors will independently train to a random angle. Occasionally, the turrets under control of the given director will train to the same angle, simulating a gunfire exercise on a target designated by the director. I will probably also program in the ability to control a director directly from the Futaba transmitter. The forward director ("Sky One") will control turrets One and Two while Sky Two will control the aft turret Three.

My first step - as usual - was to begin creating a virtual mockup in Solidworks. This inevitably led to my learning about suitable products available for purchase. I broke the components down into three categories:

• motors
• driveline, and
• electronics.

For the motors, I wanted to use standard Futaba servos (I'm using a 14SG radio for this model). I had no idea of what to use for the driveline, but anticipated a challenge given the required (slow) rotational speeds I would need. For the electronic control components, I knew I didn't want to design my own circuit board ($$$). Fortunately I became aware of the Arduino line of boards and must say I am very impressed with their quality and ease of use: if I'd had something like this when in school I'd have finished a few labs in days rather than weeks.

So... I began modeling components and (re)learning about gearing. For the turret, I ultimately wound up with two major subsections: the gunhouse would house the barrel elevation mechanism, and the barbette would house the training works. One concession I made early on was giving up on the notion of having independently-controllable barrels: on the prototype, each of the three guns in a turret are independent of the other two: they may be loaded, fired, and (most importantly) elevated independently. However, given that I wanted to retain realistic motion (ie., proper speed and smooth operation), I decided to treat the three barrels as a single unit. I may revisit this strategy at a later date.

Three renderings of the final turret mechanism appear below: click on any thumbnail to view a larger image.

	Here's the Solidworks model of the turret control system: training in the barbette and elevation in the gunhouse.		Another view of the SWx model with the barbette omitted.
	This is an exploded view showing the two main subassemblies.

Next up was the director module. Ironically, even though the director only requires training motion, it proved to be more challenging to design from a packaging perspective. I wanted the mechanism to sit as low as possible and be removable as a unit. Given that the superstructure is already built, whatever I came up with would have to be "cut in" to the existing structure. I settled on the design shown in the renderings below. See Part n for more details on why and how I arrived at this design.

	Low-angle view of the forward Mk38 director mechanism.		Top view...
	This render shows the forward director mechanism mounted in the superstructure.

Continue to Part One: Turret Training mechanism.