Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[warspite]

Would there be enough room to fit two micro servo's either side of the pivot, i.e. servo drive the pivot for each gun, could then be individually raised and lowered either by linkage or direct, the back box could then contain a servo limiter of some kind if not programmable from the ardino, the servo's down each side then are using dead space (assuming its dead space)

[ballastanksian]

I have been avoiding anything too technical for a single turret, but it may come to that.


Still, I will dabble more next weekend and see what occurs.

[Geoff]

To clarify, with ID I only have one working barrel per turret due to the internal space being limited and the need for insulation. Basically everything hangs off the bottom of the turret which is then inserted into a large diameter tube (75mm external diameter) with a central brass pivot tube to take the cables out on the center line. The large diameter tube then also acts as the fluid reservoir and sits flush on a false deck. The turrets are then winched round using a servo sized sail winch.


Exact details and dimensions of the pumps are in the ID thread with plans but again none of this is really critical. Probably the only thing is the pumps need to act quickly both to prime them (the valves aren't perfect) and to shoot the fluid in quickly to the heat exchanger so you get instantaneous flash vaporization which in turn pressurizes and shoots the smoke  out of the barrel with an audible whoosh! The combination creates the effect as otherwise if injected slowly the smoke will pour out rather than rush out.


I would counsel you build a gun and test it as slight modification may be needed to fit. Fundamentally the alloy acts as a heat capacitor heated by the thermistor. When the fluid is injected the energy dumps and flash vaporizes. Basically it takes "x" amount of energy to flash vaporize "y" amount of fluid in "z" fraction of a second. This will also depend on the surface area of the heat exchanger so a little thought will show provided you have this combination the actual shape doesn't matter too much.


You may find if you are trying to run two thermistors off the same battery the battery may not be able to supply the initial current which could be as high as 18 amps - this also impacts the thickness of the cables etc and there may be some imbalance between the thermistors such as one drains the energy from the other and neither gets to the right temperature, This is why I use separate batteries in ID.


Its all goof fun, enjoy!


Cheers


Geoff

[ballastanksian]

I am going away from having the barrels elevate to concentrate on gun smoke. A thought I have just had is to have a battery for each thermistor. This means that ampage is reduced to the level of draw shown for a single thermistor.


But yes, I need to test all the thermistors to make sure they work and also make fluid vaporise.


I made the dimension of the barbette on HMS Raglan 92.5 (93) mm, so depending on the wall thickness and thus inner diameter, that is what I will have to play with. I can laminate a tube from thin plastic and frames.


Anyhow, off to speak 'Car' with the garage....

[warspite]

When you mentioned putting fluid on the thermistors - one of these popped into my head    god knows how I would tackle that problem

[warspite]

My internets been playing up

[ballastanksian]

Geoff has done a build log of HMS Iron Duke in Warships R&D which covers his development of smoke generation finishing up with a great system using thermistors and pumps.


Have a search for it, its pretty extensive, and Geoff is adding bits here as well while I bimble about.

[warspite]

I have seen the turret system using the ardino's thread, and will leave suggestions to the more experienced 


I have never built anything bigger than a corvette so BIG guns are an oddity to me for making them work, just got caught in the moment.

[tonyH]

Of course, you could always experiment with General Wolfe and her open 18" mount!

[ballastanksian]

One of the Clive's is on my long list. Nick let me have a 12inch majestic turret so that part is difficulty lessened. Mind you, an Abercrombie was also on it but got scooted ahead of Cochrane.


Not to worry Warspite, all ideas and thoughts are welcome here. I read it all and if anything pops out as useful, I will try it.

[Geoff]

One thing to consider is that the actual working gun is only 4mm in external diameter so much smaller guns can be made to work provided you have the room for the batteries. There is no reason why the pump and servo needs to be in the barbette (its just how it evolved with ID) and can be remote from the turret.


As an experiment I used the thermistors and a long 4mm tube and pumped the fluid in in little spurts and it went Puff, puff, puff, puff just like an anti aircraft gun!


If the barrel is bent 90 degrees and the thermistor and heat exchanger is nearly vertical it will work with much smaller turrets as the gubbins can all be below decks provided the external barrel diameter isn't more than 4mm.


At times it sounds quite complicated but in practice its really quite a simple system because of the thermistors which are self regulating.




One experiment I did try was using 3D printer heaters. They are not thermistors and have no upper temperature limit and reached yellow hot in 20 seconds - my temperature gun registered 500 C before I had to put the fire out! However once installed in an alloy heat exchanger it never overheated as the heat was drained away too quickly. Candidly I couldn't get it to work well due I think to the heat path being less efficient than a flat thermistor on a flat heat exchanger which gives a very good surface area to transfer heat.


Still at some point I intend to try again as I think it has some potential as its smaller and the maximum current draw was flat at 3.5 amps vs 9 amps at start and 3.5amps running for the thermistors so a potential saving in current which equals more shots!


Cheers


geoff

[ballastanksian]

I plan to get dabbling again on Saturday.

[ballastanksian]

Sorry not to have done any more to this since July. The new business and having eyes bigger than brain meant that I have stalled.


I hope to get back to it later this year, probably reining in my aspirations to a single barrel or fixed elevation barrels (mid angle elevation to make them look reasonable.) Mind you, using a servo to elevate them will be simpler than the cam system so all is not lost!


Happy new year folks.

[T888]

Happy New year Ian,nice to see your active again. 


Myself I’ve lost a bit of the modelling drive, so taking a brake from it.