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[Bob K]

A technical quandary.  How to simultaneously rotate seven main armament gun turrets. 
Some of you may guess what ship this is for.

To get more than 180 degrees rotation on a turret I will need a servo plus a control arm to increase the angle over the normal of about 90 degrees.  It would be nice to slow the rotation down, if possible.
It may be possible to rotate two adjacent turrets from one servo by adding linkages, but trying to add enough servos to a single receiver channel will be far too much load for the Rx, even with splitter leads which do not reduce the channel loading.

Any ideas ?

[Tug-Kenny RIP]

Two things spring to mind here with your question, Bob.

Would this normally be seen in action on the real ship and also how close are they together  ?

My first reaction was a rubber drive belt. Is this any good. ?

ken
 

[Bob K]

Thanks Ken.

Seven centreline turrets spread along around four and a half feet of a seven foot dreadnaught, made more complicated by my needing to split the hull in half for transport.  3 in the front half, 4 in the rear.
I realise that turrets do not train in exact unison, but achieving that effect may be a bridge too far.  ie: building in short time delays.

[John W E]

 

Obviously there are going to be several ways to do the movement you require of the gun turrets - I can suggest a couple of ways I achieved this on 2 or 3 models - the first way I did it:

on HMS Ajax - I had 3 old Futaba Servos (they were the very old ones) which I stripped the electronics from and this left only the motor and the gearing.    I also removed the physical stops from the plastic casings of the servos - so that the 3 servos could rotate.   Then I purchased a new Futaba servo, opened it, and soldered onto it 2 fly-lead wires from the contacts of the motor.  These 2 fly-leads from this servo, which was to become the main lead servo - were wired up to the three old servos in parallel, so, basically the 3 servo motors would mimic what the first brand new servo would do.  Then, the other thing I had to do was to modify the new servo by taking the variable resistance pot out and adding 2 resistors.   This isn't as complicated as it sounds and there are plenty of videos on YouTube, which show you how to do this.  Each servo was mounted underneath a gun turret - the only problem with this is that sometimes the gun turrets do not line up on the centre line.

the second way I did it on HMS Exeter was I purchased 2 servo stretchers from Technobots and 1 from ACTion:   These were mounted obviously in the hull and connected to 3 standard servos, which in turn were mounted underneath each individual turret.  This was the easiest solution I have found, with the least problems.   

The bugbear is (and it doesn't matter which system you use) the low speed of the turn of the turrets tends to produce a jerky movement.   

If you look at my HMS Exeter build there is a section there where the turret build is explained.

http://www.modelboatmayhem.co.uk/forum/index.php/topic,33734.75.html

john

[Bob K]

Lovely build.  Very interesting 

But how to I couple seven servos to one receiver channel ?

[Netleyned]

Using two sail drum servos and Kenny's
Elastic Band  with a Y lead connected
between the two hull sections might
work from one channel Bob.
Not tried it myself, just a suggestion.


Ned

[John W E]

Hi ya Bob, what model is this actually for?    I have had a quick look through your postings to see if I could see which model this would be for, but, I am unsure?

Generally speaking though on a warship, not all the turrets will turn at the same time.  Also, they will not all be pointing in the same direction - there will only be a select amount of guns which point outwards at the same time.   If the guns on the starboard side of the ship are facing outboard/starboard - the guns on the portside wouldn't (I am sure) traverse and fire across deck - they would stay in a fore and aft position.

Really, you should be using 2 channels for your gun movements and these 2 channels could be split with Y leads accordingly.   

I did forget to mention, I added the Y leads before the servo slowers - also, I used 2 channels.

John

[Netleyned]

He's got Deans Marineitis
Seen the new Grey Machine
and fallen for it.
Its bigger than his car so
a split hull is needed.
Ned

[Bob K]

Hello John,  I intend building one of these during 2017.  Correct Ned - Yes, I am crazy.  Over 7 ft long

http://www.modelboatmayhem.co.uk/forum/index.php/topic,56290.msg584168.html#msg584168

I looked up servo slowers, they use them for model aircraft landing gear retract.  Bookmarked it. 
http://modelradioworkshop.co.uk/shop/servo-control-devices/5-servo-turret-controller/
Thanks.
I guess I can have one slower per turret or pair, slightly different timings, to bring all guns to a broadside firing position.  Guns barrels raising using a guide inside turrets. 

[Plastic - RIP]

With that number at that scale, I'd be putting a little dc motor in each turret with microswitch & diode travel limits - with gearboxes, you can make them move nice & slow. Drive them all from a single speed controller so they all track at the same speed - they would synchronise position when they all reach an endstop.

[dreadnought72]

Lovely build.  Very interesting 

But how to I couple seven servos to one receiver channel ?

Arduino would be my first choice, and use miniature geared steppers instead of servos.


Andy

[John W E]

Hi Andy

What we must remember is not everyone is capable of programming and writing software for these systems.   Some people, including me, prefer to keep it as simple as possible to understand  .

I appreciate where you are coming from though but also we have to remember stuff like this does literally terrify some people 

John

[Colin Bishop]

I rather think that any electro mechanical system will struggle to keep seven turrets accurately synchronised, particularly in returning them to a properly aligned fore and aft heading. Maybe each of the three turret groups could have its own 'gearbox' though. But then again you have to take into account the fact that the different turrets all had their own training arcs, point in different directions when at rest and not all would fire on the same bearings.

Logically Andy is right. The turrets should be computer controlled. You would send a signal to the model stipulating the target bearing and then each turret would need to 'decide' whether it could achieve that bearing and, if so, train round to it. Of course this would take no account of the movement of the model itself which would require another level of computation to keep the guns bearing entailing comparison of the target bearing with the ship's heading. An interesting programming problem!

I think the most you could realistically achieve with a simple system is three positions: 1: turrets aligned with the ship's keel; 2: trained out 90 degrees to starboard and 3: trained out 90 degrees to port.

Colin

[John W E]

hi there Colin

There was no way I was trying to run Andy's system down.   I was just trying to put it into perspective for everyone on the Forum.    If someone was to design and build a module; similar to a receiver, where you plugged in say several motors or servos; and you could make adjustments and it was pre-programmed similar to what Andy is describing - that would suit a lot of people.   When you think about the average model boater and this is coming from reading this forum, they struggle with where to put a fuse in the electrical system of the model; they struggle about how to wire speed controllers up and in general they struggle with electronics.

 You mention only obtaining 3 points of movement of the guns - to be honest with you - if we had more control over the positions of the guns - who would really notice, apart from those controlling the model and those who knew about the electronics inside the model, but the average onlooker from the public would think 'oh look at Bismark's guns turning, and hey Mr is that the Titanic'.

John

[barriew]

Providing you will have the capability of multiple links between the two halves of the hull (servo leads) there are a number of people on Mayhem who I am sure could provide an Arduino based solution (including me) and I think it would cost less than £20. This would also provide power for each servo independent of the Rx battery.
The only problem I would have is having that number of servos to do the testing.
Barrie

[Colin Bishop]

John, I appreciate what you are saying but my feeling is that the geometry of all those turrets is a bit of a nightmare unless you just want to do something simple. Unlike the relative simplicity of say, a Queen Elizabeth class with two forward turrets and two aft, the Agincourt has the two forward turrets pointing in one direction, the middle two at 180 degrees to each other and one of the aft turrets pointing in the opposite direction to the other two. The only thing they all have in common is that they can train on either broadside and I reckon that would be easier to achieve than trying to make them line up on intermediate bearings. As you quite rightly say, the simple fact that they can move and all point in the same direction on one broadside or the other would be pretty effective visually. Having the barrels automatically elevate using guides would enhance the effect as long as you don't knock the flying bridge off!

Even so, it would still be quite a fiddly job and I reckon you would need one mechanism for the forward two turrets, two for the middle two (although you could introduce a linked contra rotation maybe) and another two for the after group.

As said previously, the mechanisms would need to have a good degree of mechanical and electronic (servo) precision with no backlash to ensure that the guns are correctly aligned in the three stop positions.

It's not impossible but anyone attempting to do this needs to understand that there is no quick fix! Some pretty precise model engineering and a good working knowledge of servos systems is a basic requirement even without venturing into the realms of computerisation.

Colin

[Bob K]

Andy, I have followed your Arduino info with interest, but I don't think programming them is within my personal ability.  I have seen a ship train her guns to a relative bearing, and adjust aim as it turns, but that requires some serious computer control.  Especially when one or more reaches it's maximum arc of fire.

Just to make life interesting, in order to split this massive hull for transport I need to cut it between the centre two turrets under the flying bridges.  Three turrets in the forward half, four in the rear.

Many thanks everyone.  Certainly some good food for thought.  I would be happy just to train them all 90 degrees to port or starboard, with barrels elevating using ramps/guides.  Plenty of room inside for a gunfire sound system, maybe LED's in the barrels.  I would stop short of smoke effects though ( Tee hee ).

What makes this ship impressive is the sheer quantity of turrets, so I would like to show them off if I can 

 

[unbuiltnautilus]

Right, first thoughts..KISS. Treat the fore and aft sections as separate models. Put a receiver in both the fore and aft sections, both bound to the same transmitter. Plug your turret gizmos, morphs or whatever, into the same channel on both receivers. This will reduce the load as you will have either three or four servos only per hull, connected to your individual receivers. This also eliminates any awkward hull plug connections, also eliminating any access holes having to be waterproofed. I followed this route on SS Ohio, two Rx's with only one Tx.
Servo chatter as you slow the output down could be a bit of an issue, as could re-aligning on the centre line after broadsides, but that's what modelling is all about!
I could show you a turret rotation mechanism with seven stop positions, using micro switches, working through a bank of relays. Very effective, but a pig to make. Servos, nice and easy

[dreadnought72]

Hi John - not feeling 'run down' at all. More like 'fired up'. 


I'll start a new thread after Christmas & the New Year. Cheap, easy and accurate microprocessor fire control.


Andy

[Bob K]

Right, first thoughts..KISS. Treat the fore and aft sections as separate models. Put a receiver in both the fore and aft sections, both bound to the same transmitter. Plug your turret gizmos, morphs or whatever, into the same channel on both receivers. This will reduce the load as you will have either three or four servos only per hull, connected to your individual receivers. This also eliminates any awkward hull plug connections, also eliminating any access holes having to be waterproofed. I followed this route on SS Ohio, two Rx's with only one Tx.

Now that is a good idea -  2 x receivers. 
KISS indeed.  It will also give the big SLA ballast in the fore part something to do.

[RAAArtyGunner]

Hi Andy

What we must remember is not everyone is capable of programming and writing software for these systems.   Some people, including me, prefer to keep it as simple as possible to understand  .

I appreciate where you are coming from though but also we have to remember stuff like this does literally terrify some people 

John

Yes 

[derekwarner]

Bob...this is a very interesting scenario.....however in todays world the direction of the movement of the turrets in the thread is heading toward a controlled precise ballet symphony

The vessel did have state of the art for the day gun control systems [an Officer in the Crows Nest ] relaying messages to a Senior Weapons Officer in the Fire Control Bunker....who would relay these massages to the Captain......so eventually a command is given to each Gun Captain to train and elevate the mount to the directed positions

I suggest the turrets in their day would not have resembled the orchestrated ballet movement of today

As previously suggested, each turret having the ability to very slowly train and elevate to an athwart or midships position and return to the in line home position would suffice.... and be far more realistic 

The elevation could be via a fixed spring loaded cam within each turret and require no electrical of mechanical input

Certainly a few [3] ACTion P96 controllers and some Y leads would provide the progressive slow speed and also the final set points for turret train, and the return home position

Derek   

[RAAArtyGunner]

Interesting topic and some good suggestions/solutions.

Talking Gunnery, don't dismiss the "broadside" that Bob is trying to achieve,  it would be perfectly logical for all guns to train and fire a broadside.

In that situation all guns would fire "parallel' with say the central gun being the "aiming' gun.
Resultant explosions would overlap if using HE and destroy the "ship". Field/Anti Aircraft artillery do like wise.
If concentrated one misses, they all miss.

Even on land bombarding, a broadside may be required to smother/suppress the target along a frontage.

Also at maximum ranges you would not notice any bearing changes between individual turrets/guns for concentrated engagement if the ship was engaging broadside to the target.

Any Naval Gunners????

[Bob K]

I would love to replicate this ships broadside ability as most dreadnaughts of the time could only fire four turrets broadsides as echelon turrets on the far side tended to create damage if fired across the deck.

Although Agincourt’s superfiring guns could not simultaneously fire within 30 degrees of the centreline due to the rangefinders mounted on the turret hoods, full broadsides were possible.  Without a Dreyer fire-control table the seven turrets probably trained independently, aided by commands from the foretop control centre.

The rate of fire of these guns was 1.5 rounds per minute.  When a full broadside was fired, "the resulting sheet of flame was big enough to create the impression that a battle cruiser had blown up; it was awe inspiring”.   No damage was done to the ship when firing full broadsides, despite the common idea that doing so would break the ship in half, but much of the ship's tableware and glassware did shatter when Agincourt fired her first broadside.

At Jutland she fired 144 twelve inch shells, although it is not known if any hits were made. 

[malcolmfrary]

Small sailwinches are currently available at not much more than a standard servo.  As much or little angular travel as needed.  A 2-turn winch with its standard 1" drum gives about 7" of linear travel.  Use a continuous loop (easy, the winches come with a double drum)large pulleys to gear down at the turret, hook the line onto a notch as was done on old radio dials to ensure that everything stays in sync.  Excess travel can also be sorted with a servomorh or EPA on the transmitter or both or just be disciplined.  Probably one winch per half of ship and a simple Y lead.  Since the winches are slower than servos, the speed issue  and is taken care of.