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Thread: Diving with "The Moderator"

  1. #1
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    Default Diving with "The Moderator"

    Diving with “The Moderator”

    Part I

    I returned a couple of weeks ago from a diving holiday with my family, but it’s taken me that time to get around to doing a write-up about it.

    Naturally, being a conscientious CPFer, I made sure I was fully tooled up with adequate underwater illumination equipment. Some of you may remember the modifications I made to a Navy dive light, which (until recently) I have been calling the “Yellow Monster”.

    The full story of the light and the mod can be found in this thread, but its brief details are:

    Originally made in 1993 for the British Royal Navy (looks like it could have been made in 1893, lol)
    · Bright yellow
    · 12 inches long
    · 3 ins wide at bezel
    · Solid ¼-inch thick cast aluminium body
    · Heavy stainless steel tailcap
    · A whopping 3 lbs 4 oz (1.5 kgs)
    · 4.5V bulb (75 lumens)
    · 3x alkaline D-cells
    · Crappy reflector

    Modded by me to take:
    · Fivemega G4 bi-pin socket
    · WA 1185 bulb (1,200 lumens)
    · 3x AW protected ‘C’ Li-Ion cells
    · Fivemega MOP reflector
    · Other internal fittings, spacers etc

    Before I went on holiday, I was thinking about labelling it with my name, but I realised this would be pretty pointless, as nobody else would be likely to have a light even remotely similar to this ancient dinosaur of the deep.

    On an impulse, I instead reproduced the “DM51 / moderator” info as it appears at the top of my posts in CPF. I printed this on to a clear waterproof adhesive label and stuck it on the body of the light. It looked appropriate, and IMO really quite smart.

    I fully expected some questions about this unusual label, but no-one, not even members of my family, seemed to realise what it signified. Perhaps they thought the light had come like that. I decided not to explain. Strange as it may seem, my family seem to be unaware that I visit this forum. They do not know what a moderator is, either. They know that I have an interest in flashlights, but that is all. So, much to my amusement, the light itself became known as “The Moderator”, and that is what I now call it.

    Here is a pic of it disassembled (while the batteries are on charge). You can see what I mean by the label.




    You can see I have fitted the light with 3 bolt-snaps – 2 to clip to D-rings on my harness when it is not in use, and a 3rd one which remains attached to prevent loss when it is in use, on the end of the safety cord (that is the original cord the light came with, BTW).

    Here is another (not very good) pic, taken underwater, of the light attached to my harness.




    It proved to be a fine dive-light. That big chunky twist switch is superbly easy to operate. The light is obviously as solid as a lump of granite. It is however about pounds negatively buoyant underwater, which is quite a lot.

    And of course, with a WA 1185 bulb, it is BRIGHT!! At ~35 Watts and ~1,200 lumens, it demolishes most other dive-lights, and it is very gratifying to see the surprise on other divers’ faces when they see what looks like an obsolete relic blasting out so much light.

    Here is a large eel (~5 feet long) which seemed pretty surprised too:




    Many divers nowadays use LED dive-lights. When you just need to see where you are going at night or in caves, these are fine, and the long run-times / brightness / compact size make LED lights very useful indeed. However, they fall down badly in underwater color rendition – the weakness of the red component of the spectrum is even more pronounced due to its absorption by water.

    Red will not penetrate more than 5m (15 ft) of water, so at even quite modest depths, recreational divers will never see any red colors unless they carry a light. Orange disappears at 15m, yellow at 30m, green at 60m and finally blue at 80m. Below that, it is pretty much black.

    A powerful incan will bring back the missing colors in a startling way, especially the reds and oranges that are not otherwise seen even at normal recreational dive depths, and the Moderator certainly proved its worth. The pic of the eel above was taken during daytime, BTW, not night-time.

    After the first dive, I was very pleased. I had run the light for nearly 40 minutes without noticing any problems, and it had more than lived up to my hopes for it.

    However, there was to be an intriguing and totally unexpected problem with this light, which for a while had me totally baffled. It proved a fascinating problem to deal with – something very unusual, which has probably never been experienced before by anyone, with any light.

    I will continue the story in a later post in this thread…
    Last edited by DM51; 04-27-2008 at 09:54 AM. Reason: Edit thread title
    Resistance is futile...

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    Default Re: Diving with "The Moderator"

    Oh, come on! You left me hanging!!! I gotta know what happens!
    WWII 60" Anti Aircraft Carbon Arc (Sold), Short Arcs: 1.6KW NightSun, 1KW VSS-3A, .8KW TrakkaBeam, 600 Watt M-134 Gun Light, 500 Watt X-500-14s, 500 Watt Starbursts, 300 Watt Locators, Megaray, 150 Watt Set Beam & Communicator, Maxabeam Gen3, LarryK14@52V

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    Default Re: Diving with "The Moderator"

    DM come on man, i've followed this light from the start of your mod and you're going to leave me hanging like this?!?! I could wait while you were doing the modding, that takes time, but this....you know the rest of the story!
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    Mad71 Re: Diving with "The Moderator"

    Now this is just cruel......
    " I reject your reality, and substitute my own!"
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    Default Re: Diving with "The Moderator"

    Part II

    Oooh, we have some impatient people in this thread. Guys, you have to give me a chance to write this stuff before I can post it, lol. I’m a slow typist, too.

    Anyway, to continue the story…

    Back on dry land after that first dive with the Moderator, I unscrewed the tailcap to remove the batteries for recharging. The interior of the light was bone dry, so no water had got in anywhere, but I noticed the tailcap threads seemed no longer to be bright and shiny. In fact, they seemed slightly corroded). But this seemed only a minor problem, so I ignored it.

    I should make the point here that seawater can get into these threads – the way this light is designed, the O-rings to seal the body are ‘after’ the threads, if you see what I mean. The disadvantage of this is that the threads themselves are not protected from sea-water, but they are big and chunky, so it shouldn’t matter. On the other hand, the big advantage is that the vital O-rings are protected, so particles of sand or other debris cannot get on to them.

    When the batteries were fully charged, I reassembled the light for the next dive. On the boat, I tested the switch, and… nothing. Not a glimmer. Not a flicker of light! I hurriedly unscrewed the tailcap and checked the batteries were making a proper contact. There seemed to be nothing wrong. But no light. Damn! Too late to do anything about it. The 3-pound weight was already factored in to my calculations, so I decided to take the light as ballast anyway, or I would have been underweighted for the dive.

    Shortly after starting the dive, something strange happened. I noticed the light was now ON (even though it was day-time, you do tend to notice it when a WA 1185 light is on). Furthermore, the switch was operating properly, as normal. I had obviously left it switched on before entering the water, and maybe a jolt from my backward roll off the boat into the water had given it the kick-start it needed. I thought no more of it at the time, beyond being very pleased that for some reason it had decided to start working again. It continued to operate without a problem for the remainder of the dive.

    Later that day, I prepared to recharge the batteries again. Before unscrewing the tailcap to take out the batteries, I checked the operation of the switch again. Nothing. Very odd. It had worked underwater, but not out of the water, either before or after the dive.

    The interior was again bone-dry, as before, but now corrosion and pitting was very pronounced on the bare Aluminium tail-threads, while the steel tailcap seemed to have acquired a white coating. I also noticed some quite heavy pitting on the body of the light – in places where the yellow paint had worn off and the bare Aluminium was exposed – the pitting was black, and quite deep. That had not been there before. My first thought was that the light had been made out of some really inferior Al alloy, if seawater could do that to it. The pics below illustrate it.

    Threads (Al body) before and after diving:




    Tailcap, before and after diving:




    Pitting on body where paint had chipped off, exposing bare Al:




    I was now very puzzled. I used my DMM to check every part of the circuit – bulb, holder, batteries, spacer, switch… all the voltages and resistances were as expected. By process of elimination, the contact between the tailcap and the light body had to be the problem. But why had it worked underwater, and not on dry land?? That raised an intriguing possibility.

    Could it be that there had been a chemical reaction, caused by the electric current, between the steel tailcap and the Al body, causing corrosion where the 2 different metals met, and thus breaking the circuit? Even more intriguing, could that explain why the light worked when immersed in seawater but not out of it? Was the electric circuit being completed by the seawater itself?!?

    The saline content of seawater makes it electrically conductive, so it was a theoretical possibility. If this was what was happening, it should be possible to observe electrolysis taking place, and the production of oxygen and hydrogen molecules. I had not noticed this during the dives, but then I hadn’t been looking for it, and it might be difficult to observe it in open seawater anyway, with current movements and a fairly high concentration of water-borne particles present. And at depth, where the gases would be compressed to a fraction of their normal volume, there might not be much visible sign of it at all.

    The salt content of seawater is predominantly sodium chloride. I tried to remember some elementary chemistry. During the electrolysis of seawater, there would be hydrogen and oxygen, but perhaps these gases might in turn react with the sodium chloride to produce hydrochloric acid (HCl) at the +ve terminal (the Al body) and sodium hydroxide (NaOH) at the –ve terminal (the SS tailcap).

    It seemed to make sense. The HCl at the Al ‘anode’ might explain the pitting noticed on the body – it certainly looked as if the action of an acid had caused that. However by now, the more learned and scientific CPFers among you will no doubt be shaking your heads, keen to correct me. Please do so! I would dearly like to know exactly what chemical reaction it could have been!

    The dive the following day went as expected. The Moderator had not worked before the dive, when it was dry, but after it was submerged I switched it on and it worked fine. There was light.

    There were also bubbles!! These were literally streaming off the light near where the tailcap meets the body. A large quantity of hydrogen and oxygen gas was being produced (along with whatever other noxious chemicals the learned CPFers will tell me below). The pics below illustrate this bubbling:





    The impressive thing was that the light still worked. The energy going into the electrolytic reaction had to be considerable, and that was energy that should have been going into the bulb filament. I wanted more lumens, not more bubbles! What could I do?

    I decided to experiment. For the next dive, I would reverse the polarity of the batteries, to see what would happen.

    However, rather than reveal at this stage what actually did happen, I am sure the learned ones will be eager to seize the opportunity to predict the result of reversing the battery polarity, so I will take another break and hand over to them to tell us…
    Last edited by DM51; 04-27-2008 at 09:53 AM.
    Resistance is futile...

  6. #6
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    Default Re: Diving with "The Moderator"

    hmmm sounds like a electrolysis to me. if you change the cathode and anode during anodizing this is what might happen. with the direct current you force the Al to react with the Cl ions from the salt water. the AlCL3 now solves into water (not really sure about this) together with the Na-ions and there is your corrosion.

    Correct me if i am wrong........chemistry lessons were long ago
    proud Fenix T1 aspheric R2 owner

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    Default Re: Diving with "The Moderator"

    From working on AL Airplanes all of my life, I know exactly what is happening, Galvanic Corrosion. You should never use dissimilar metals in a corrosive environment.

    Instead of explaining it, I'll direct you to this great article:
    http://www.corrosion-doctors.org/For...-corrosion.htm

  8. #8

    Default Re: Diving with "The Moderator"

    I'm almost surprised that such a well-built light doesn't have a sacrificial anode (or whatever you use to offset the galvanic reaction).

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    Default Re: Diving with "The Moderator"

    I'm going to venture that the corrosion stopped (steel is far more noble). Sounds like you need to recoat the body rubber to prevent the electrolysis from occuring.

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    Default Re: Diving with "The Moderator"

    i bet you can remove any HA III or other anodizing with your method
    proud Fenix T1 aspheric R2 owner

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    Default Re: Diving with "The Moderator"

    Congratulations/condolences!

    I'm thrilled to see the results of that light - I've been drooling and searching high and low for one like it. As a diver, myself, I've been thinking about making/modifying a light of my own (with no luck so far). My plan is for several Crees and a couple UV LEDs to get the corals to fluoresce.

    Where did you go? The eel looks to be the size of a green moray, but the color is a little off...

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    Default Re: Diving with "The Moderator"

    Ha ha like on a boat in the salt water you need ZINK at any bait shop or refueling station on th sea they will sell little and big chunks of Zink, they will corode first instead of your flashlight or boat!
    Diver, boater, flashlight nut!
    Stick the zink to bare metal poof problem solved.
    It aint dark in here no more, not with 25 lights!

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    Default Re: Diving with "The Moderator"

    Quote Originally Posted by stansbrew View Post
    Ha ha like on a boat in the salt water you need ZINK at any bait shop or refueling station on th sea they will sell little and big chunks of Zink, they will corode first instead of your flashlight or boat!
    Diver, boater, flashlight nut!
    Stick the zink to bare metal poof problem solved.
    zinc



    Really hope those threads aren't permanently damaged, DM.

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    Default Re: Diving with "The Moderator"


    Quote:
    Originally Posted by Essexman
    Will the beamshots be underwater ??

    LOL, yes, eventually I will post some underwater ones.
    Thankyou!
    Great light, great posts, from modding to using-the complete story.
    Nice to see a torch being used well. Hope you can sort out the samll problems and have many years of use.
    cheers

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    Default Re: Diving with "The Moderator"

    Part III

    One of the great things about CPF is that there is always someone who knows the answer to practically any question, no matter how obscure. Many thanks to those of you who were able to tell me what was going on with this light. I would never have known about Galvanic Corrosion. I would not have known a piece of zinc was the cure for it, either.

    Evidently, neither did the British Royal Navy, when they designed and made this light! One would have thought that navies ought to know things like this, but there you are.

    Anyway, time to tell/show you what actually happened when I reversed the polarity of the batteries. To recap, on previous dives, +ve had been to the Aluminium head/body, and -ve to the stainless steel tail.

    I simply inserted the batteries the other way round for the next dive. This was partly out of interest, to see what happened, but also because for obvious reasons I wanted to stop that alarming corrosion, which was swiftly eating away at the Al body of the light.

    As before, the light did not work out of the water, but as soon as it was immersed, it worked normally. The electrolysis was still going on - I could see the bubbles - but the 2 gases were now presumably coming off reversed ‘terminals’.

    The surprise was seen on resurfacing. Where the exposed Al parts of the body had turned black and pitted before, these same areas now looked as if they had been partly filled in by a white material. You learned fellows will no doubt tell me what it is. These comparison pics below show the difference.

    Before - normal polarity (+ve to head)


    After - reversed polarity (-ve to head)


    Before:


    After:


    Before:


    After:



    The other big surprise was the steel tailcap. Did I mention above that this was Stainless steel? Yeah, right. Sure it was. This shows before and after. Before, with normal battery polarity, it had acquired that harmless-looking white coating. After… well, I don’t think I need to be all that learned, to know what that is. See for yourself:

    Before (normal polarity):


    After (reversed polarity):



    Furthermore, it wasn’t only the “stainless” steel tailcap that had been attacked. The hex bolts securing the bezel had been got at too:


    Worse was to come. When I tried to unscrew the tailcap, I found… well, I couldn’t. It was stuck fast. I am reasonably strong, but despite all my efforts, I was unable to budge it one millimeter.

    The other people staying at our hotel were a frindly lot, so I set off to initiate a “strongest man” contest. There was an enormous and very powerfully-built South African who I would have bet a few $$ could do it, but after turning bright red, with muscles bulging and sweat popping off his forehead from the effort, even he had to admit defeat.

    I was making my somewhat morose way back to my room, when I bumped into the hotel mechanic, who dealt with all the machinery. He looked a bit like the engineer who bangs on Groucho Marx’s cabin door with the hammer in ‘A Night at the Opera’. Large, capable and well equipped with suitable implements. Just the man!

    He obviously regarded this tailcap as a challenge, and disappeared with it to his workshop. He was gone for 15 minutes, which seemed to me like an eternity.

    Finally, he returned in triumph, having managed to get it off. He had had to use a vice and a massive wrench to do it. He had also used… well, dear readers, I don’t know exactly what it was, but it had obviously been liberally applied. The smell was extremely pungent, and yes, it was clearly some form of… petroleum product. Aaaaarghh! My poor O-rings!



    Thanking the mechanic profusely, I hurried back to my room to take that pic of the infected threads, wipe all that stuff off, and clean the light thoroughly. Fortunately, none of it had got in anywhere it could have done any damage.

    Reflecting on the episode, it was clear that reversing the battery polarity had been a disaster. I obviously couldn’t repeat it. Either the tailcap would soon rust solid on to the body threads, or the mechanic would get fed up with having to free it each time – or, most likely, both of those things.

    The alternative was to revert to using it with the batteries in their normal polarity, and watch the Moderator being visibly eaten away by this pernicious corrosion, which I had no doubt would eventually eat right through the Aluminium body. I had no idea how long that might take, but at the rate it had been going, it didn’t look as if it would take very long.

    Bear in mind here that I knew nothing about the remedies mentioned above by learned and scientific members. What could I do to minimize the electrolytic reaction? Was there a possible solution, or at least something that would help keep the corrosion at bay? Or was there nothing to be done?

    Tune in for my next post in a day or two, and find out!!
    Resistance is futile...

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    Default Re: Diving with "The Moderator" - Part III added!

    I'll bet there is someone talented enough here to make you a aluminum tailcap. It would be more of a challenge to make a waterproof switch.

    It appears that now the reversed polarity causes the AL to oxidize.

    A Stainless Steel tailcaps resistance to corrosion is due to a very thin chromium-rich oxide film which is formed on the surface, but when the layer was eaten away, it exposed the carbon steel beneath to the sea water forming the brown iron oxide, or rust, on the surface.

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    Default Re: Diving with "The Moderator" - Part III added!

    So much interesting stuff here.....
    When I go diving I use a silacon grease to cover my dive knives blades and even smear some on my watch, just in case my bdy with all of the metal in it has the same reaction as your light. Any dive shop should have just the trick for you, but I dont think it will help as well as the zink will, but what the heck its worth a try.
    It aint dark in here no more, not with 25 lights!

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    Default Re: Diving with "The Moderator"

    such an interesting story. I think after seeing it eaten away I would have been very reluctant to go back in the water with it.

    This thread really shows the expertise of the forum. Amazing what you can learn here.

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    Default Re: Diving with "The Moderator" - Part III added!

    I think the most impressive part of the whole story is that you made a label for a Dive light that said DM51 Moderator ! LOL!

    That is a sad tale of woe. Such a nice looking light, and so much work you put into all the parts. I'm crying for you....damn, what a shame.

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    Default Re: Diving with "The Moderator" - Part III added!

    I feel like i'm watching a sitcom, waiting a week between episodes..haha.

    Do you think it's all the extra voltage you have here causing the problems? Obviously the light was designed to have a LOT less electricity flowing through it than you have here. Maybe you're speeding up the reaction past the point the original engineers ever expected. With 2D's (or whetever it originally ran on) this reaction took place so slowly that it was a non-issue.
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    Default Re: Diving with "The Moderator" - Part III added!

    Quote Originally Posted by LuxLuthor View Post
    I think the most impressive part of the whole story is that you made a label for a Dive light that said DM51 Moderator ! LOL!
    And, you can't forget that it shows he's offline.

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    Default Re: Diving with "The Moderator" - Part III added!

    This is very sad!
    WWII 60" Anti Aircraft Carbon Arc (Sold), Short Arcs: 1.6KW NightSun, 1KW VSS-3A, .8KW TrakkaBeam, 600 Watt M-134 Gun Light, 500 Watt X-500-14s, 500 Watt Starbursts, 300 Watt Locators, Megaray, 150 Watt Set Beam & Communicator, Maxabeam Gen3, LarryK14@52V

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    Default Re: Diving with "The Moderator" - Part III added!

    I, too, am intrigued to know what actual affect the voltage has on the problem. The galvanic reaction would occur between the two metals even if there was no current from the batteries, but I imagine the extra voltage serves as a catalyst.

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    Default Re: Diving with "The Moderator" - Part III added!

    Part IV – my $0.02

    Thanks to all for the interest shown, and for the kind expressions of sympathy for my (p)light.

    In the last episode above, you will remember that reversing the battery polarity had resulted in the stainless steel tailcap rusting badly, and this had all but fused it to the Aluminium body of the light. I had decided to revert to normal battery polarity, although this would mean corrosion would resume eating away at the Al body instead.

    Judging by the speed of the corrosion during the first 3 dives (total time a little over 2 hours), I doubted the Moderator would last another 2 weeks before it corroded almost completely away. I had to do something about that, if I could. Remember, I didn’t know then what I know now about the chemical processes that had taken place. Nor did I know what remedy there might be, or even if there was one. I had to make a guess about what to do.

    It seemed to me that the key was somehow to stop the electrolysis. Although it was a big waste of electrical energy, that was the least of the problems it caused. Far worse was the fact that it was producing sodium and chlorine ions along with the hydrogen and oxygen. I was sure these were somehow combining to form the acid that was causing the corrosion. If the electrolysis could be halted, or at least reduced, then the rate of gas and ion production would also be reduced, and in this way the corrosion might be slowed too. That was how I reasoned it, anyway.

    I deduced that the electrolysis was occurring because the early stages of corrosion had formed oxides (or whatever) on the steel and Al threads, breaking the electrical contact between the two metals. Conduction had from then on been via the seawater, with its saline content completing the circuit. It was the current passing through the seawater that was causing the electrolysis.

    If I could reinstate a physical metal contact between the body and tailcap, then the voltage between the tailcap and body would drop to zero, and the electrolysis should stop. What was the best way to make that contact?

    There was a small gap between the tailcap and the body of the light, before the threads engaged with each other. The gap was about 1/10 inch (~2mm). The obvious thing to do would be to jam a piece of metal in there to make the required contact. I would scrape off some of the protective yellow paint to expose the bare Aluminium in that spot, and bridge the gap between that and the steel tailcap with some suitable metal object. What did I have that would make a really good electrical conductor?

    Silver was the best conductor, I remembered. Looking back on it now, I think that if I had had a nice pair of silver cuff-links or some other fancy item, I would probably have willingly sacrificed them there and then to save this light. But I didn’t have anything like that with me. The next best conductor after silver was copper. Maybe a piece of copper wire… but how would it be realistically possible to attach it and make it stay there?

    A copper coin! That was the answer. It would need to be a small coin, to be jammed into that gap. I rummaged around in my bag. At the bottom were some coins, and among them was a British 1p piece. I tried it out. It looked as if it would fit OK, and could be hammered into place so it wouldn’t fall out. I scraped away some yellow paint off the body so that the coin would be able to make a good contact with the bare Aluminium.

    Reassembling the light with fully charged batteries, I pushed the coin into the gap and gave it a couple of good hard whacks with the back of my adjustable wrench to jam it in place. I tried the switch. Contact! The light came on! It worked! But what would happen during the dive? Would the copper cause an even more peculiar reaction?

    I need not have worried. The dive went well – the Moderator seemed brighter than before, and although I could see a few bubbles coming off the contact areas near the coin, the effect was very much reduced from the rate I had observed before.

    Here is a pic of the coin in place during that dive:




    After the dive, I could see the coin had become coated with the same white material as the tailcap:






    It was clear there was still a reaction going on, but on inspecting the previously pitted parts of the Al body, there had been no visible deterioration. Using the coin seemed to have helped.

    Subsequent events proved the cure had worked. After each dive I removed the coin to open the light, and later, after recharging the batteries, I jammed it back in place again for the following dive. The corrosion of the Al body was brought almost to a standstill. I saw no more bubbles. The threads never jammed again. The Moderator continued to work perfectly.

    Here you can see it hanging on a line from my surface marker buoy during a decompression stop at 6 meters, with one of its admirers photographing it.




    By the end of the 2 weeks, the Moderator was looking a bit more battered – definitely well-used – but it was the toughest piece of equipment on that dive-boat. It had come through the test triumphantly. It is still working perfectly today.

    As scottaw has said above, it was almost certainly the increased voltage and current that had led to the accelerated effect of electrolysis. With the stock low-power 4.5V bulb running on alkaline cells, this effect might only have been very slight, and possibly not noticeable at all. I rather wonder how these lights did actually perform with the British Royal Navy – did the Navy divers notice any problems with them after a while? Could that be why they were withdrawn from service and sold, with one of them ending up in my hands? It would be fascinating to know more.

    Just one other thing to round off this tale: At the current rate of exchange, the 1p coin I used (UK £0.01) is almost exactly equivalent to 2 US cents.

    So I can truthfully say - this story really is just my $0.02¢.

    Thanks for reading it!
    Resistance is futile...

  25. #25
    Flashaholic*
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    Default Re: Diving with "The Moderator" - Part III added!



    Next week, on Days of our Flashlights, DM51 will tell the tale of his trip to Tunisia and how a brass washer and super glue saved the day.

  26. #26
    Super Moderator
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    Default Re: Diving with "The Moderator" - Part IV added - my $0.02!

    Lol, S-dude! And well spotted for noticing that the label showed I was offline.
    Resistance is futile...

  27. #27
    Flashaholic* schiesz's Avatar
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    Default Re: Diving with "The Moderator" - Part IV added - my $0.02!

    I thought the red light was funny also. Mine is either green or not lit. Red is obviously reserved for mods that are out diving.

    Great story, and such a cool light!

    schiesz

  28. #28

    Default Re: Diving with "The Moderator" - Part IV added - my $0.02!

    So, was the coin dissolved at all? I think 1p coins are actually mild steel these days, but if it's an older coin it would be bronze. In either case, it should not have served as a sacrificial anode (I think).

    Maybe it worked by creating a better electrical path and changing the difference of potential between steel and aluminum parts.

    I don't know. I'm intrigued.

  29. #29
    Thread Killer Illum's Avatar
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    Default Re: Diving with "The Moderator" - Part IV added - my $0.02!

    something tells me the royal navy light you have is a clone of the real thing....and that when the light was made the seas had lower salinity...or the light was made to be a "fresh water" dive light

  30. #30

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    Next week, on Days of our Flashlights, DM51 will tell the tale of his trip to Tunisia and how a brass washer and super glue saved the day.

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