Fire Control

(I'll probably regret this, but here goes

I gather that there are several people working on fire control systems. Would anybody care to collaborate, maybe "divide-&-conquer", or just compare notes? If you want your project kept confidential, but want to talk about it all the same, I can keep a secret. E-mail me at johnmatskytexdotnet, include "SHIPFIGHT" in the Subject, to be sure to clear spam filters.

JM

 

Well, sure I'll speak up here. Yes, I am developing a system for "director-based fire" using the basic design premises mentioned on the Yahoo Big Gun group. Just for recap, here's the basic idea:
*indicate the range and bearing to target
*positionally controlled guns automatically aim at indicated point
*upon pressing the trigger, all guns that are on-target fire, all others do not

I am building the system into a Viribus Unitis class dreadnought as a testbed for future projects. For the initial version, I am using as much "stock" equipment as I can, for example using BDE guns with large gears on top of standard servos for rotation, a standard hobby radio (if I can) and a Picaxe microcontroller. It's basically a proof of concept, that allows me to experiment later with different human interfaces and levels of control. I also hope to find out how much of an improvement the Director-based fire control works.

I have several Picaxe 18X chips, a board to experiment with, two tandem triple BDE cannons specially built for a VU, and a beautiful wooden hull. However the project is on hold until more pressing projects (PUMA, repairing and selling Spahkreuzer) are completed. I estimate that the Viribus project will be ready to sail and fight during the 2009 combat season, but I really won't know until I actually seriously start on it.

I would be very interested in collaborating with other people. If anyone can build an improved controller, positional-control cannons, or even volunteer your ship as a testbed, I'd be more than happy to help out. Just let me know if there's anything I can do to help, or anything you can do to help me.

 

Carl: What have you got worked up so far? Have you got an architecture defined? Any other features besides the basic ones you noted?

JM

 

What I had in mind was, if there were several interested parties, we might be able to agree on a common architecture & interfaces. Everybody could go off & build parts, & all end up with basically the same system, but a lot sooner than working alone.

Kind of like how it works on a "real" job, but for fun instead of pay.

JM

 

John,

I would like to co-operate on this sort of development but there seems to be hugely conflicting requirements between Big & Fast gun.
As an example , most Big gun targeting is for distances between 12 and 30 inches from the gun in order to get enough angle into the water to score a below. Similarly , underwater torpedo tubes have a range of about 1 foot.For these sorts of distances a lookup table for each of the gun mounts is probably sufficient. In a way similar to the ladies in WW1 etc who calculated elevation tables once, by hand , plotting bearings to and depression angles for converging fire is probably best done once empirically . Using a laser pointer strapped to each turret to converge on a paper target placed at the appropriate location and monotonously plotting the results would be boring but would only have to be done once per boat .
It could be simplified by allocating a number of "aiming points" to calculate for eg : 0,15,30 , 60, 90 degrees in each quadrant . If you then placed buttons at these locations around your controller , hitting the button for , say , port 30 degrees would cause all turrets that could bear to elevate to parallel to the water surface, traverse to the bearing required to hit in the target box for that location and depress barrels the required amount.This then becomes a quick "read the table", transfer the result to the bearing/depression variable pair for that mount, move mount to new location. Fire ! Hopefully all fire will converge in about a 5 x 1 inch target box. Microprocessors can do lookups much faster than they can do math.

Small gun however seems to have , for the most part, fixed gun positions & aiming points and aim the boat. I'm not quite sure what their requirements for a "Fire Control Assistant" would be.

Kevan M

 

JM, I'm not quite sure what you mean by "architecture". Do you mean how would I write the program? I've got a pretty good idea about how to do it because I've done some programming in C, visual basic, and basic before, but I haven't begun applying it to the Picaxe language yet.

What I need right now is some bigger gears. The BDE cannons I have include a small gear at the base of the magazine, and a large gear to go on top of a servo. Trouble is, the ratio is only suitable for a little over 180 degrees range of motion, when I really need about 270 degrees. Once I get that, I can set up a test system and begin programming. No sense writing a program if you have no way of testing it. I'm taking a machine shop class right now, and next quarter I will be taking a CNC class, so hopefully I will be able to make my own gears soon.

Right now, all I want to do is get both my front guns and aft guns pointing in the same direction. Convergence, depression, and ranging can be added later, as long as I leave room. I know how many inputs and outputs that will require, so I can leave enough pins free on the pic, but for right now I'd rather get a perfectly working sample without convergence and ranging than a glitchy specimen with them.

My biggest limitation right now is human interface. I do not have the knowledge or expertise to either modify a radio, or build a whole new controller unit. I would love to have a 360-degree dial to indicate direction to target. Heck, I'd even love to have a 270-degree knob to show what direction the front gun is facing, then make the back gun turn parallel. But I don't know how to do the necessary modifications. If anyone has the know-how to do that, I would gladly give a working sample of the fire-control circuit.

 

I mean, the design of the system; its parts; their inter-relationships to one another; interfaces; what each part is supposed to do.

Do you have a design that's far enough along to consider that yet?

I wish that Pickaxe had been available several years ago. It seems to be a "better" Basic Stamp, & cheaper too! Not sure if it's appropriate for a "production" system, but that's the sort of question that would get answered as the architecture is defined.
...
JM

 

I don't know if that's necessarily the case. The payoff may be less with non-rotating guns, for sure. Whether it's worth the effort would be for each captain to decide. Figuring out exactly what the requirements should be is the 1st step.

Where I think a fire control system has the most benefit is where there are multiple, rotating guns (perhaps including some fixed, too), of different calibers & reload times. Imagine a multi-rotating-turret main battery with 8-second reloading, multi-rotating-turret secondary battery with 2-second reloading, & a pair of fixed torpedo tubes with 30-second reloading. Trying to manage all of that can be overwhelming to the operator (captain) & is really the biggest reason for developing a fire control system other than just wanting to take on the challenge for its own sake. 1:72 could be the biggest beneficiary, since larger hulls could take on more/different weapons.

JM

 

I don't. I've got a Nelson with main battery armed only. It has had 2 secondaries rotating & 4 secondaries fixed armed at various times, but now removed because it's just too much trouble to manage them & they're worth more to the enemy as sink points than to me as weapons. Never added torpedoes. I figure Nelson is just too slow & poor-turning to ever get close enough to use them. I've got other ships, too, & plenty more in the pipeline (if I can ever get around to building them).

What I have or don't have is irrelevant, though. I'd like to see something built that can work on any ship. Otherwise, if everybody is just going to build one-off units, that only work with 1 specific ship, there isn't much point in collaborating.

How does that work where only part of a battery fires? For instance, only the forward main guns fire & then have 8 seconds to reload, while aft main guns are still eligible to fire at any time. Or port-side torpedoes fire while starboard-side torpedoes are still ready, etc.

JM

 

I run one of the timers, and they can limit servo timing differently between clockwise and counterclockwise firing servo rotation. For example, when my firing servo rotates clockwise, it fires the main battery of three triple 1/4's, limited to one servo movement per 8 seconds. If the servo rotated anticlockwise to fire any secondaries fitted, it can have a different timing to allow for that type of weapon. (30, 8, 6, or 4 seconds).

 

JM
Each gun/battery that can be fired independantly has a line in the reporting script:
Forward main back in 8
Port torps forward back in 30
Aft triples back in 4 .....
etc.
Even if you have :
Forward Main
Forward Port Secs
Forward Port Torps
Forward Starboard Secs
Forward Starboard Torps
Midships Port Secs
Midships Starboard Secs
Etc etc etc you will find that the audio review can cycle in less than 2 secs , which is the smallest cycle time.
Most people only a maximum of 4 or 5 independantly firing batteries.

Kevan

 

MWC and IRCWCC both outlaw these types of systems.

 

Yeah, I don't think that MWC and IRCWCC would benefit from a "fire control assistant" in the same sense that the Big Gunners want. I remember hearing that stuff like rangefinders that automatically adjust the depression of your cannons are illegal though. Probably all that you fast gunners need is a triggers that you can press faster. Although I bet the Treaty combat guys could benefit from a rate-of-fire restrictor.

 

Would somebody please post the relevant rules? Let's see just exactly what is outlawed.

JM

 

Before we start dividing up tasks, it might be prudent to decide: Build "what", exactly? I recommend starting with the required features & letting it all flow out from there. So far, I've seen the following features described:

1. Indicate the range and bearing to target.

1.A. Allocate a number of "aiming points" to calculate for eg : 0,15,30,60,90 degrees in each quadrant. If you then placed buttons at these locations around your controller, hitting the button for, say, port 30 degrees would cause all turrets that could bear to elevate to parallel to the water surface, traverse to the bearing required to hit in the target box for that location and depress barrels the required amount.

1.B. Have a 360-degree dial to indicate direction to target. Heck, I'd even love to have a 270-degree knob to show what direction the front gun is facing, then make the back gun turn parallel.

2. Positionally controlled guns automatically aim at indicated point.

2.A. Get both front guns and aft guns pointing in the same direction.

2.B. Convergence, depression, and ranging can be added later (rather get a perfectly working sample without convergence and ranging than a glitchy specimen with them).

3. Upon pressing the trigger, all guns that are on-target fire, all others do not.

Is that OK so far? Anything else?

JM

 

1.C. Simulate "velocity" control over the front gun, and have the aft cannon stay parallel.

This one doesn't require modifying the transmitter. While it's not as intuitive of a human interface, it is a nice starting point. I was planning to use this in my Viribus Unitis class dreadnought.

Also, consider for possibility:
3.A. Restrict each cannon to its proper rate of fire. Pull the trigger before it's allowed to fire, and nothing happens.
3.B. Measure rate of fire and inform the skipper when it's safe to fire, but do not physically limit firing.

Rate of fire is pretty important in a fire control system, but you also have to keep in mind the opposition. In my club, nobody actually follows the rate of fire rules, so there's a target then they pull the trigger as soon as the accumulators are recharged. I personally would not want a physical limitation on my rate of fire unless I know that EVERYONE has the same limitations.

 

Can you expand on this? I don't understand what you mean by "velocity control".

There's an implication here that any system must work within the framework of existing hobby R/C technology. This is more of a "how" (it gets done) than a "what" (is to be accomplished), & I'd really like to get all the "whats" defined 1st. Those will go a long way toward determining the various "hows". It may be a legitimate requirement, though, to make use of hobby R/C. We should be able to justify all requirements.

I think it's important to consider those who DON'T have a comparable system installed, & what they may think. I don't think it's unreasonable to expect some people to have a little fear of some unknown (to them) system that somebody else is using, justified or not. I think that a good way to counter that sort of potential ill-will is to include some features that help enforce rules or improve overall safety. It's a matter of give & take: "In exchange for letting me do ____ to help myself, I'll do _____ for you." While everybody may not have enforced rate-of-fire limitations, everybody also does not have guns that "automatically" place all shots from multiple mounts into a 1" x 5" rectangle, either. I don't think anybody wants to build a system that their club won't let them use, thinking it would give them an unfair advantage (whether it actually will or not may be debatable).

I'd define it something like: Restrict rate-of-fire by requiring a minimum amount of elapsed time between shots fired by a given mount. The minimum time between shots needs to be configurable, per mount, using a range of 0-x seconds, with 0 being no restriction. Provide feedback to the user, per mount, indicating whether each mount is aimed/not aimed at a target and eligible/ineligible to fire due to "reload".

This also brings up another question: What, exactly, should be the "top level" or "30,000 foot view" objectives? I'd like to suggest the following, for starters:

1. Primary Goals:
a. Simplify User Interface
b. Manage Multiple Guns
2. Secondary Goals:
a. Avoid building something that others won’t want to fight against, or make rules to outlaw

JM

 

For both MWC and IRCWCC:

"8. Automatic-tracking and automatic-ranging systems for the cannons are illegal."