Wow, I don't quite know what went wrong with my update - okay I'll try this again to delete the gibberish!
All turrets now work and on a calm day there is a good discharge of "smoke" which is certainly visible from a distance and leads to the same question, where's the bang? I'm working on it!
I have now fires something like 150 shots in a session (30 salvos) without issues so the system/process definatley works but like most systems the devil is in the detail.
However curiously I set fire to my fourth funnel smoke generator which is built along the same lines - a wick in a bath of fog fluid wrapped with nichrome wire. The first two caught fire because the top cover was plastic and a small piece fell onto the wire. The third was less certain and the fourth a real puzzle as the roof is brass with copper piping to the funnels, so whats to burn?
I tried some tests:
1) Is the fire rope I use for the wick really fire proof or just fire resistant? I put a piece in a gas flame and it wouldn't burn so is fire proof.
2) Is the non flammable fog fluid flammable? - much to my surprise the answer is yes! The same test set fire to the wick with a small flame despite what the data sheet says flash point Not Applicable. It was a small flame but even so a lot of heat is produced.
3) Further checking on line revealed that if the fluid is not completley vapourised it can undergo a chemical change (don't know why) and leaves a residue. Once the residue reaches a certain concentration it can catch fire if conditions are right (wrong). A guy on line put some fog fluid in a pan over the gass and it produced copious amounts of smoke but then caught fire!
4) My fog fluid was 10 years old so may have gone off a bit
This has the potential to be quite serious for obvious reasons however I believe I may have the solution:
1) The funnels were being used for an hour at a time which creates a very different set of dynamics to the guns which are used for 12 seconds at a time.
2) I was extracting unused fog fluid and putting it back in the bottle which is why the liquid took on a yellowish hue which I then re-used. Inadvertently I was systematically increasing the concentration of residue
3) I now only use fresh fog fluid
4) A small funnel fire isn't too serious as water can be dropped down the funnel putting it out but a fire in the "magazine" is rather more serious and awkward to get to.
5) Redesign of the smoke box (magazine) mans the actual unit is now on a tray and can be slid out for inspection and replacement without a major dismantling exercise. This also lets me experiment with alternative heat sources (PTC Heating elements).
6) Remove the remains of the plastic slide valves to minimise combustible material
7) Additional alloy heat shields in the magazine
I purchased some Kapton self adhesive tape - this is used in 3D printers and can withstand 350 degrees centigrade to line the roof of the magazine. To be fair I've never seen any signs of burning but better to build in more protection.
9) Most importantly I now have a filler tube which can exit above decks. This places fog fluid directly on top of the wick. I can also pump water down the tube to extinguish any fire. This will be disguised as a ventilator. I also have a drain tube which is accessible when the deck is off.
10) I'm hoping that by using fresh fog fluid the problem will be solved for the guns but with the additional precautions I'm now more comfortable in managing any issues.
11) More experiments with the new fog fluid for the funnel smoke generators.
The biggest puzzle is that the fog fluid caught fire at all when all the fact sheets say otherwise!
Either way I have decided to pursue the experiments as the potential for 450/900 shots is too great to ignore
Cheers
Geoff