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[Bob K]

Gunfire

Not sure if anyone has tried this, or even whether it’s street legal, but I am looking into attempting simulated gunfire.  Obviously pyrotechnics are out unless you have all the necessary licenses, and even firing blanks is not permitted in public spaces.

I am looking at adapting a low power BB airsoft firing mechanism from a toy RC tank, together with artificial smoke, and a 2 second sound file (which I have).  The mechanism to be housed in the RH side of a twin 15” gun turret, operated by remote control.  The LH gun to have a ‘recoil’ mechanism and powder smoke.  Thus it will appear that the LH gun is firing, even though the BB pellet comes from the RH barrel. Gun elevation and turret rotation by conventional means.

A spare gun mechanism is only £9.99 on E-Bay and looks both slim and compact. Actual firing would only be “out to sea” with a range of 25 meters.  Simulated fire (with the BB part disabled) no problem.

Any thoughts ?

[radiojoe]

Sounds interesting Bob, I'd like to see what you do with that, one of my Grandson's was round at the weekend who said when looking at  the turret on my Coventry "wouldn't it be good if you could fire a tiny bullet out of it" my reply to him was "don't think I haven't thought of it" 

[Bob K]

It is for my HMS Abercrombie Monitor.  Just one huge twin turret, so its not like trying to fire a dreadnaught broadside.  The recoil should be straightforward, a light coil spring in the barrel with a servo operated cam.

Sound:  https://www.audioblocks.com/stock-audio/distant-big-gun-sound-effect.html

[TailUK]

How about "firing" flour or talc using the airsoft mechanism? 

[rob]

I thought I'd stumbled on a thread about my favourite military alchoholic tipple !

[ballastanksian]

 

Bob, Geoff who is building Iron Duke (also in this room) is also trying out ideas for a gundfire system for his Battleship, so it might be worth seeing what he is trying to do and wether any of it would be of use for Abercrombie.

[RAAArtyGunner]

There is a group that specifically model  "firing" warships and engage in battles and try to sink their opponents.

Details of guns mechanisms etc were on their website.

Cant recall the group name, but Google should come up with it.

[TomHugill]

Those henglong or taigen bb units are horrifically unreliable m, I would avoid.

[Bob K]

I have been following his Iron Duke with great interest.  I was just thinking of a simple soundcard.
Note:  The gun firing mechanism is NOT in any way a ship combat type, but low pressure air firing a plastic airsoft pellet, from a toy tank suitable for children.  I have never seen a recoil mechanism on a model warship but thought it would look visually realistic.  Can talc be used for repeated firings?  Probably, as when I was likkle I had a toy Sherman that puffed talc from its gun.

The only working guns I have seen on ships use gunpowder.  So was seeking a more street legal effect.

[Martin (Admin)]

 
https://youtu.be/opugmmhGfTw

https://youtu.be/Yf2mCXqf-u0

[Bob K]

Very interesting video clips Martin, especially the recoil mechanism inside the tank turret.
I am trying to find the video clip I saw last week of an early battleship gun firing. Fast recoil with slow return, and huge amounts of cordite smoke.

[g6swj]

https://www.youtube.com/watch?v=hnxYMic7xG0

[derekwarner]

Hullo Bob.....this is an interesting action to simulate, however it is relative to science being the speed of light >>>> to the speed of sound >>> then to what the human mind can accept

In older photography of ordinance firing [of the period your are contemplating] are we really sure what we perceive?

a. we see the flash
b. we hear the sound
c. we see the barrel return as a function of the return from recoil

What I am trying to say is with [a.] & [b.] occurring at such a close visual/audio perception in time, that we don't really see the barrel retract into recoil, however we do see [c.] the secondary motion of the barrel returning from recoil

The video of the Henlong tanks look impressive during the firing, however viewing the real tanks firing offers a somewhat different perception in that the barrel retracting post firing is literally a milli second action

Good luck........ Derek

[derekwarner]

Bob...here is a link to 16" guns on a US Iowa Class Battleship...

BTW...the puff of smoke exiting the barrels @ 3:25 minutes after the firing is termed as the 'air blast', which blows/expels combustion gases from the barrel prior to opening of the breach...naturally this eliminates or stops the same gases from entering the gun house ....... Derek
______________________________________________________________________

https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&sqi=2&ved=0ahUKEwjngYjEjI_LAhXJp5QKHU_RApUQtwIIKjAF&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DdVvEPTYrcXA&usg=AFQjCNGX0S4MG7wRegWhRyMGfAGzU3W9dg&bvm=bv.114733917,d.dGo

[Bob K]

That was the clip Derek, I could not easily re-find it as the actual firing is a long way into it.
The recoil is virtually instantaneous, allowing for the sound / light effect as you say.
What it interesting is that the barrel dips shortly after firing, probably starting to return to its loading elevation.  The sheer scale of the flash and smoke would be difficult to reproduce without pyrotechnics.

[C-3PO]

https://www.youtube.com/watch?v=43gBsxijkU4

http://www.pmbdt.co.uk/HOMEPAGE.html - maybe these guys can explain what is involved with the pyro aspect, license etc

[Bob K]

C-3PO:  That is the Portsmouth Model Boat Display Team, I have watched many of their awesome displays.
However they do use live pyrotechnics, and have all the relevant licenses for gunpowder and public displays.  Incredibly professional and 'must see' if you get the chance, but definitely comes under the caption "Do not try this at home." 

[Geoff]

I would generally concur that the recoil happens quite fast but believe it would be visible with a gun that weights about 100 tons. As has been reported the puff of smoke afterwards denotes on British guns the breach has been opened and a jet of compressed air used to blow the remaining smoke and fumes out of the barrel.


The gun then returns to its loading position. In general it was quite possible to load at any angle but the cycle for loading was typically 30 seconds or so for a big gun and it proved easier to bring the gun back to a fixed position to reload.


On British ships this was all controlled by hydraulics basically working off a pressurised ring main which was in turn pressurised by hydraulic pumps in turn driven by reciprocating steam engines supplied by steam from the main engine boilers.


In terms of simulating this in model form I have always felt the increased complexity of a recoil would outweigh the reliability particularly as 30 feet away you really can't see it. Fun to do but in my opinion not necessarily conducive to creating the simulated effect we are all seeking on a repeatability basis.


With Iron Duke the concept is simple enough, plastic box with smoke generator, pump the smoke out the barrel. In the adjoining barrel use a very bright LED and all connected to speakers for the sound.


The devil is in the detail but I have a number of experiments on going to validate the system for Iron Duke. I have built a number of similar test systems and they all worked to an acceptable degree so the theory is valid, but they all leaked smoke everywhere which is the problem.


It sounds easy to say just put a valve in but the actual construction of airtight valves of say 8mm (for the gun barrel) and 40mm (for the PC fan) is proving challenging. If you move to compressed air (Air gun propellant) then there are other issues such as flammability and making/breaking high pressure air pipes and the volume for the air reservoir. It adds complications in different directions. I'm a believer in simple rugged systems that work all the time, every time.


One of the problems is that you can only get so much gas flow (smoke) through an 8mm" tube and beyond a certain unknown pressure there is no advantage in going higher. Does the design of the neck of the gun pipe make any difference? This is part of the reason I've decided to fire 5 shots at a time in a proper salvo. A single shot may not produce the volume of smoke but pretty sure 5 at a time will be effective!


A conservative estimate with ID is that I can fire 40 salvo's so basically 200 shots which means I can fight all day!! Ye ha!! I only need fog fluid and battery capacity to continue all day.


If anybody knows of a source for 40mm very powerful PC/server fans and/or has any ideas of how to make airtight valves do please share on the forum as if I'm successful it would be my plan to publish a "how to" so we can all do it!


I've tried flap valves and even a ping pong ball in a tube which was very promising but used too much air pressure. I liked the ping pong ball idea as it was fully automatic - I may give it another go maybe stacking the fans to increase the static pressure rather than increased airflow.


Most valved have a very positive action and need a fair amount of force to seal/unseal. I had event thought of a diaphragm valve (like a camera) - yes lets see someone make one of those! And then we have the problem of how to operate the valve - solenoid perhaps etc. This is all where it gets both interesting and challenging at the same time. Hours of work to find there is a fundamental problem in what you were building - more stuff in the junk box!!


I'll keep at it as I'm convinced the method is sound


Sorry, long post here but its an interesting topic


Cheers


Geoff

[Bob K]

Geoff:  I greatly appreciate your taking the time for such an interesting and constructive description, and in hearing about your research work on getting the smoke effect.  That's about 30,600 yards further than I've got 

Silly thought, but how about a 1" dia syringe type piston to push the smoke through the barrel.

I will continue to watch your Iron Duke build with even greater interest

[Geoff]

No thought is silly, I had thought about a syringe but for the volume it needs to be about 8" long and 1" or 2" wide plus the plunger and the drag to push it in and out plus the engine and gearbox to move it.

This is both the problem and fun in trying to develop this system, sometimes the practical engineering side intrudes!

The reason I went for the fan solution is that I can suck as much air in as I need and don't have to store it anywhere so no pressure vessels.

I have thought about using one larger fan linked by tubing to all of the turrets as a possible solution but haven't got to the point of developing a prototype. It has some advantages as one large fan will be easier to construct and more efficient than five smaller fans, also one valve etc.

Please keep the ideas coming!

Cheers

Geoff

[Bob K]

Fair enough Geoff.  I am sure you looked at countless possible scenarios.  Good luck with your gun trials - most interesting 

On recoil distance, the British 15" Mk I is stated to be 46 inches, or 12.5 mm at 1/96 so is enough I believe to be visually worth replicating if I can.

[Geoff]

I've heard of some people simulating the recoil on a crank, like a piston in an engine if that makes sense. The speed can be adjusted by the voltage.

Good luck

Cheers

Geoff

[Crossie]

Geoff, for your valve, maybe a rotary device would be acceptable, they can be leak-proof and require low energy to operate, think of model aircraft throttle bodies, or a higher pressure application as on a tap-loading air rifle , in both instances this design of valve has high reliability. For shifting more air than cooling fans, would a suitably sized and regulated EDF unit be suitable?  Good luck with your scheme, it's always fun experimenting!

                                     Trevor

[ballastanksian]

The best smoke effects could only be produced by a chemical reaction such as black powder detonation and or another reaction just to create smoke, and as both of you have mentioned requires a liscense for the former, while the latter is illegal due to the compounds required.

If only you could remember the make and provenance off your toy Sherman Bob, this might have provided prototype systems to back engineer.

The issue with syringes of such size though similar in scope to model sub flotation chambers, is where to put them. While both hulls are quite capacious due to their shape, there is competition for that space with drive train, power and control systems.

I wondered when hearing how tinny the digitised sound can be wether the speaker could be muffled with some foam to remove the higher frequencies of sound and add a bit if base to what is to be the sound of very large guns firing!

[Bob K]

R&D evolution.  Well, it was worth a try for under ten Quid.  However the 'replacement' toy tank firing mechanism is far to big and bulky to adapt into a 15" turret at 1/96.  No dimensions on web page, so was a shot in the dark based on size of tank.



Next up was the sound file.  The usual small speaker proved nowhere near adequate for this low frequency high air volume sound.  To do it justice a big bass speaker with corrugated cone base (to shift max air volume) might be needed, but they are far too big for a model ship.

Tried blowing cigarette smoke down a suitably sized brass tube.  Not bad effect.  I wonder if a motorised syringe with a flap valve to draw and expel might work?  ( He is getting desperate here ! )