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[rsm]

The speaker with the 16" gun sound is 0.2W 8ohm, but it doesn't mention anything in the instructions about amplifiers. The best answer would probably be to ring Ralph at RamRC in the US and ask him (he doesn't do email).

[Bob K]

May I offer a couple of comments, especially having built amplifiers back in the days of Practical Wireless magazine.  Do not connect the low Ohm power output into the highly sensitive input of another amp, you could blow it up, probably both of them.  Ideally you should look for an amp with the right output, with input suitable for the sound file signal.  You can get pre-amps but matching them to power amps can be more complications than you need.

I would avoid using the hull as a 'sound box' as the low frequency vibrations are likely to damage fine detail over time, and could even crack more substantial structures such as ribs or deck mountings.  Anyone who has experienced a vibrating motor or worn double U-joints will know what I mean.  Having a fine mesh grille in the deck to let speaker sound waves exit the ship will be essential IMHO.

To properly replicate the sound will be a tough call, and probably end up as a compromise.  A real Iowa Class broadside will probably be audible for up to 40 miles.  Attaining 1/96 of that distance is virtually impossible. Bearing in mind that the vibrations of such a discharge will be more apparent than the actual 'bang'.

[derekwarner]

Hullo Bob.....yes...in real life, a firing of the 16" Iowa Class would be a night time visual at the speed of light, however the audible sound at 40 miles away may only just awaken you  from your sleep

40 miles = 40 x 2240 = 89600 ft
speed of sound = 1126 ft/sec
89600 divided by 1126 = 75.57 seconds after the firing [if you had good ears]

Derek

[tigertiger]

So the sound audible roughly 75.56 seconds after the flash then.

[derekwarner]

Well TT, yes but only in this [non scale] example only...however it highlights previous points that .................

We see the flash.......then we hear the sound......[in that order].........

The calculations of sound pressure level effect to distance is a far more complex

Derek

[Bob K]

My point was, that whilst the aim might be to get a loud(ish) bang from up to 50 feet, there is no way that you can replicate the massive sound pressure wave from a scale 40 miles.  The timing does not really come into it as it becomes 'perceived' effect (what the observer might find reasonable to expect from the lake side).  ie:  an interval of over a minute between flash and bang would be unaccountably long to a lay observer.  I would aim for a couple of seconds between flash - smoke to bang, even if the ship were on the far side of the lake. 
In practice most might miss the flash, only having their attention drawn by the bang, then seeing the smoke largely dissipated.

It is the perceived effect we are after.  The Portsmouth MBC display team have flash / smoke / bang simultaneous, and it looks OK.

[tigertiger]

It is the perceived effect we are after.  The Portsmouth MBC display team have flash / smoke / bang simultaneous, and it looks OK.

It may be that a delay is not accepted by the brain, which perceives the 50 feet and not the scale distance. The brain can be funny like that.

[C-3PO]

Hmmm

40 miles = 40 x 2240 = 89600 ftspeed of sound = 1126 ft/sec89600 divided by 1126 = 75.57 seconds after the firing Derek

I thought there were 5280 feet in 1 mile which would make this closer to 188 seconds
C-3PO

[derekwarner]

yes...a monumental calculation cockup with flat batteries using my abacus ....

The 16"/50 calibre Mark 7 – Iowa Class gun mounts had a muzzle velocity of between 2240 & 2500 ft/second ..depending on the charge loaded

So interestingly ...a projectile fired from one of those mounts would take approx. 75 seconds to travel the 40 miles and explode, yet, we still would not have heard the gun fire for another 112 odd seconds ....

Thank goodness for the speed of the flash otherwise we would all be asleep ...... Derek

[derekwarner]

Might be better to stop this nonsense  ....

The American 16"/50 calibre Mark 7 mounts could fire approx. 17 miles, the British 14" BL Mark 8 mounts could fire approx. 14 miles

'So interestingly ...a projectile fired from one of those mounts would take approx. 75 seconds to travel the 40 miles and explode'

Suffice to say lets have the firing with the flash first & the bang sometime later ... Derek

[Geoff]

I have found a sound module by "Sense Innovations" ESS ONE. Its not cheap at £80 but appears to give 20 watts output. Perhaps more importantly I have heard and seen one in operation and it is loud! Problem is you download the sound you want and its really designed for trucks and cars so:


1) I'm not sure I can down load a broadside


2) I'm not sure I can operate it just by connecting the power with a micro-switch


More investigation needed but it is really quite small about 5" x 2.5" x 1.5" complete with speaker


Geoff

[C-3PO]

Geoff,

Called a Wav trigger i.e. can trigger .wav sound files

Have a look at this product - it plays standard .wav computer sound files.

https://www.sparkfun.com/products/13660

It has an on-board 2w amp or an standard headphone socket audio out which you can plug into an amp

It's a clever bit of kit and can be used in several ways. In simple terms you load your files onto the little SD card and then there are 16 triggers pins. If you want to make sound 5 play you simple make pin 5 +5v (so you could trigger with a micro switch) and the sound will play

This example is a piano - if you consider it's just a set of switches(the keyboard) triggering sound files
https://www.youtube.com/watch?v=UUkcs_XL5x0

C-3PO

[C-3PO]

1 x 5 LITRE Vegetable GLYCERINE / GLYCEROL

£18.50 inc delivery from Amazon

Smokin!

C-3PO

[C-3PO]

Thought I'd chuck this one in the melting pot

I am currently going for the CO2 option to drive the smoke. Lots of thoughts/concepts already in my head - most will probably not work in the real world!

This product uses a Paint Ball/Soda Stream/Disposable CO2 cylinder and after the regulator has a 12volt solenoid. This may be to big/heavy but interesting none the less. I already have a 12v solenoid valve that works up to 150psi so will use this (paired with a regulator)) in the short term

http://www.co2art.co.uk - based in Milton Keynes

C-3PO

[Geoff]

Very interesting. What are the physical dimensions of the pressure vessel and do you know how many two seconds burst of gas it will provide?


Cheers


Geoff

[Bob K]

My new Sparkfun vac/air pump finally arrived today.  These are quite powerful units.
However, after coupling up an e-cigarette to the 'suck' end with heatshrink  and applying 12 volts it failed to pump any visible smoke via tubing to the 'blow' end pipe.  Rather disappointed really as it only takes a light 'draw' to extract copious amounts of 'smoke' a la normal function.

I was confidently expecting a heavy stream of smoke.

[C-3PO]

Bob,

I am awaiting delivery of some kit, having dissected a cheap disposable e-cigarette I am surprised it makes any smoke at all.

I think the solution will be cheap and easy

I'll update you more when I have the result

C-3PO

[Geoff]

For a further update please see the Iron Duke thread.


Cheers


Geoff

[Umi_Ryuzuki]

As far as E-cigarettes, It may be a battery issue, but use caution.
E-cigarette explosion.
https://www.youtube.com/watch?v=k1LjSuq0rk8
There's been more than a few occurences of faulty e-cigs.