First Build - Work in Progress but feedback welcome

[beekeeper5]

Re: First Build - Work in Progress but feedback welcome - update

Mine too. Are you running W7x64 like me? I open Notepad, hit enter twice, copy and paste into the post and get new lines. I would be grateful if someone offered a better solution.

Yes.

 

[beekeeper5]

Re: First Build - Work in Progress but feedback welcome - update

I found some Sikaflex and 3M 5200 marine:

Sikaflex 295 UV - $20
Sikaflex 291 - $12
3M 5200 Marine Adhesive Sealant - $13

Which one do you think I should put around the bezel and the lens?

I'm thinking of either the 291 or the 5200. Any comments?

Also, the lens is really stuck on the bezel and I can't get that stubborn silicone out. I'm thinking of just cutting the side of the bezel, cleaning the silicone off the lens, and putting it in a brand new maglite bezel.

PS - I'm writing this in notepad to be pasted in to get the newlines. :duh2:

 

[Klem]

Re: First Build - Work in Progress but feedback welcome - update

I use none of them. I prefer to use two-part epoxy putty (Aqua-Kneadit by Selleys). I find the two part putty is easy to woek with. Seems to work on both glass and synthetic lenses. Pays to scratch-up the inside of the bezel and edge of the lens a bit to help the glue adhere to the surface.

I daresay the Sikaflex will work also although you will need some decent pressure from the body to push the lens against the bezel to maintain the seal at depth.

 

[lucca brassi]

Re: First Build - Work in Progress but feedback welcome - update

You use plastic or glass lens ? Some sikaflex types are agressive to polycarbonates.

 

[beekeeper5]

Re: First Build - Work in Progress but feedback welcome - update

You use plastic or glass lens ? Some sikaflex types are agressive to polycarbonates.

I'm using borolens (from 350xfire).

 

[johnohuk]

Re: First Build - Work in Progress but feedback welcome - update

Disaster almost strikes.... water behind the lense after 27m (88ft) dive....

Not sure what to do next... Seal lense rather than o-ring at the front? Still works mind ....

 

[Klem]

Re: First Build - Work in Progress but feedback welcome - update

This happened to me also...using the supplied O ring to seal a glass lens to the bezel. It leaked.

Anyone else had bad a experience with O ring on glass lenses in a Maglite?

 

[DIWdiver]

Re: First Build - Work in Progress but feedback welcome - update

The MAG was never intended to seal against pressure. The water pressure tends to push the lens AWAY from the o-ring, opening the seal.
Make sure you have enough compression on the o-ring and that whatever is supporting the lens from behind is VERY rigid so the lens can't move under pressure.

Also, the original O-rings may not be the best quality. I don't dive with my MAGs, but I just took a look and while I don't see any problems, I'm not impressed either. Replacing them with quality rings may help. Slightly thicker rings may help as well. They may make assembly harder (or impossible if they are more than a bit thicker). I wouldn't be afraid of using soft rings either. 50 duro can handle water depth pressures without issues (while 90 duro is now common, 70 used to be standard and is still in use for tank pressure).

Seems like I remember a discussion of replacing the rings in MAG heads. Maybe a search could turn up some old advice.

I dive with a lot of photographers, and they (at least the good ones) are VERY meticulous with cleaning and greasing the O-rings. And they still have leaks on occasion. I try to be conscientious with my lights, but I've flooded several after years of reliable service. These failures are clearly due to maintenance issues, not design. Obviously, a maintenance mishap can overcome even the best design. That's why double rings are becoming popular. They don't overcome design flaws, as an identical design would likely cause both to leak under the same conditions. But a maintenance issue is at least somewhat likely to affect one and not both, and to be corrected before becoming a catastrophe.

Could your problem be that simple?

 

[Klem]

Re: First Build - Work in Progress but feedback welcome - update

If you are asking me the answer is, no. I have 30 years diving experience so am well familiar with greasing O rings.

The oversize (supplied) O ring was not adequate in two instances. I suspect the first one was because the reflector head was pushing it against the bezel to seal, not the lip of the head-thread, and this was simply not enough so 'my bad'. The second one was the Maglite head-thread-lip so I can only imagine pressure compressed the O ring into the bezel in a way that worked against sealing, as opposed to commercially designed O rings channels.

My theory is that as the O ring in a maglite bezel sits on the front of the glass and is completely exposed to pressure it is comressed equally to a narrower diameter. If this is the case it pulls away from the glass, forward. I'm thinking the only thing that would prevent this from happening is to screw the bezel up in the workshop to the equivalent compression as a diving would... with the strength of a thousand guinea pigs.

 

[lucca brassi]

Re: First Build - Work in Progress but feedback welcome - update

Don't know mags , but it is possible to modify prolonged bezel for proper O-rings and thicker glass ?

http://www.amazon.com/dp/B002TMRCVC/?tag=cpf0b6-20

 

[Klem]

Very interesting Lucca...haven't seen that one before.

Anyone have any experience with this bezel replacement? Does it have enough surface area for a workable O ring?

 

[johnohuk]

Ok, on closer investigation the water was between the drop in and the lense.. it hadn't gone back any further...

It was using upgraded o rings... which are slightly thicker that the originals...the new ones are :

Nitrile Rubber O-Rings 48mm x 2mm 48 ID x 2 Thick NBR70

I took the o rings out and expected them, there seemed to be a lot of salt crystals and general muck on the front most ring... so it might be a maintenance issue...they were still greased up though...

So what next.. well I think I will clean everything up for starters... and secondly.. I'm not convinced the front most ring in the bezel is making a good seal at all times.. I could tighten the head a bit more but it was pretty tight to start with but i've decided to increase the o ring cross section size to 2.5mm... I've ordered them so will try them out on my next dive...

fyi my previous testing of the head was only to 15m (50ft) so going to 27m was untested... ( i was lucky!)

 

[DIWdiver]

Re: First Build - Work in Progress but feedback welcome - update

If you are asking me the answer is, no. I have 30 years diving experience so am well familiar with greasing O rings.

The oversize (supplied) O ring was not adequate in two instances. I suspect the first one was because the reflector head was pushing it against the bezel to seal, not the lip of the head-thread, and this was simply not enough so 'my bad'. The second one was the Maglite head-thread-lip so I can only imagine pressure compressed the O ring into the bezel in a way that worked against sealing, as opposed to commercially designed O rings channels.

My theory is that as the O ring in a maglite bezel sits on the front of the glass and is completely exposed to pressure it is comressed equally to a narrower diameter. If this is the case it pulls away from the glass, forward. I'm thinking the only thing that would prevent this from happening is to screw the bezel up in the workshop to the equivalent compression as a diving would... with the strength of a thousand guinea pigs.

Two minutes of research confirmed my suspicions that solid rubber materials in o-rings have negligible compressibility.

Also, because the o-ring is in front of the glass does not mean that it is completely exposed. If all sides of the o-ring are exposed to equal pressure, there is no sealing function to begin with. The o-ring is squeezed between the back side of the bezel and the front of the lens, forming seals, so the ID of the o-ring is exposed to water pressure and the OD of the ring is exposed to the interior air pressure in the light. Water pressure pushes the ring against the ID of the bezel. This is what's known as a static axial seal with internal pressure, quite common in commercial use. In fact there are quite a few of those in a scuba regulator.

If the reflector is supporting the lens, and the reflector can distort or be pushed back a little under force, i.e. the reflector is not firmly supported by the head, this is almost certainly the problem. At 27m, that's over 50 kg-f pushing on it. The question is, could that much force push the lens far enough to uncompress the o-ring? That's exactly what I meant when I said "whatever is supporting the lens from behind is VERY rigid so the lens can't move under pressure".

 

[DIWdiver]

Ok, on closer investigation the water was between the drop in and the lense.. it hadn't gone back any further...

It was using upgraded o rings... which are slightly thicker that the originals...the new ones are :

Nitrile Rubber O-Rings 48mm x 2mm 48 ID x 2 Thick NBR70

I took the o rings out and expected them, there seemed to be a lot of salt crystals and general muck on the front most ring... so it might be a maintenance issue...they were still greased up though...

So what next.. well I think I will clean everything up for starters... and secondly.. I'm not convinced the front most ring in the bezel is making a good seal at all times.. I could tighten the head a bit more but it was pretty tight to start with but i've decided to increase the o ring cross section size to 2.5mm... I've ordered them so will try them out on my next dive...

fyi my previous testing of the head was only to 15m (50ft) so going to 27m was untested... ( i was lucky!)

Sounds like you have good O-rings already. If you dive the light in salt water, rinse, let it dry a while, then take it apart, the O-rings almost always look nasty, and by the time you get it apart it's hard to tell if any of that was inside BEFORE you took it apart.

The question of tightening isn't only about how tight you have it, but what is tight against what. If the bezel bottoms against the head, you can tighten it with the strength of a million hamsters, it won't improve the seal. To improve the seal you have to increase the compression of the o-ring, meaning you have to tighten the bezel against the lens. To achieve this, the bezel must not bottom against the head, or at least not until sufficient compression of the o-ring has occurred.

To check that you are getting this, stand the light on it's tail, loosen the bezel a bit, place a flexible 50 kg weight on the lens (or maybe 80 kg if you want a safety factor), then tighten the bezel. If it tightens abruptly, it's bottoming against the head and not compressing the o-ring. If it tightens gradually, maybe followed by a sudden stop, you've compressed the o-ring.

If this sounds absurd, it is. Kind of. But if you're not sure of the support from the head to the lens, you can't be sure of the seal, without doing some kind of similar test. It's much better the lens should rest on a ledge on the head, instead of on the reflector. Or, as with my un-modded MAG, the reflector has a rim that rests on the head. That way you are sure that the lens can't move.

 

[Klem]

The question of tightening isn't only about how tight you have it, but what is tight against what. If the bezel bottoms against the head, you can tighten it with the strength of a million hamsters, it won't improve the seal. To improve the seal you have to increase the compression of the o-ring, meaning you have to tighten the bezel against the lens. To achieve this, the bezel must not bottom against the head, or at least not until sufficient compression of the o-ring has occurred.

To check that you are getting this, stand the light on it's tail, loosen the bezel a bit, place a flexible 50 kg weight on the lens (or maybe 80 kg if you want a safety factor), then tighten the bezel. If it tightens abruptly, it's bottoming against the head and not compressing the o-ring. If it tightens gradually, maybe followed by a sudden stop, you've compressed the o-ring.

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I agree, how tight we screw it in makes a lot of difference, and if we tighten it to the point the metal of the bezel makes contact with the lens then that's as tight as that O ring is going to be compressed . My understanding is the tighter the bezel the more it compresses the O ring against whatever surface it is sealing against. As you tighten, more surface area of O ring is flattened against the lens surface with more tension to defeat the external water pressure trying to force it's way between the two. Also, the more you tighten the greater the surface area of compressed O ring becomes which lessens the chance any anomalies like run-out between the bezel and head will cause leakage (i.e. sealed on one side but not as much on the other due to to factory tolerance).

The 80kg test agains the glass...If the glass is resting against the lip of the Mag head then I'm at a loss as to what this achieves. The glass will be hard-up against the lip of the head regardless of how much weight you place against the (essentially) incompressible head. This effort will only be of use if you are using the reflector to support the lens and this then ensures any 'give' in the support system is displaced.

My thoughts are more towards considering the path taken around the O rings by water under pressure. It can go one of two ways; between the O ring and glass, or around the O ring in the bezel. If you can permanently seal the edges of the lens to the inside of the bezel then that's now one seal instead of two. Plus you remove the potential of the O ring stretching as you screw it up with the risk that some sections of the O ring are more stretched than others (hence the need for silicone grease to mitigate this). As some sections strech more than others so then will it thin at those sections, alolowing water to ingress if water pressure can overcome the seal of the thinner O ring.

 

[Klem]

Re: First Build - Work in Progress but feedback welcome - update

Two minutes of research confirmed my suspicions that solid rubber materials in o-rings have negligible compressibility.

Here's a thought for you...

If O rings are essentially incompressible (when pressure is applied evenly from all dimensions) what about in a Maglite situation where pressure is not even on all surfaces of the O ring? In this case it has the potential to be displaced by water in a similar way to how it is displaced as the bezel is tightened.

Or in other words, the only situation where the O ring is incompressible is when the torch is fully flooded.

 

[lucca brassi]

Re: First Build - Work in Progress but feedback welcome - update

:thumbsup: after all that time ....

 

[Klem]

Re: First Build - Work in Progress but feedback welcome - update

:thumbsup: after all that time ....

Meaning?

 

[lucca brassi]

Re: First Build - Work in Progress but feedback welcome - update

maglite is still not diving lamp :devil:

 

[DIWdiver]

The 80kg test agains the glass...If the glass is resting against the lip of the Mag head then I'm at a loss as to what this achieves. The glass will be hard-up against the lip of the head regardless of how much weight you place against the (essentially) incompressible head. This effort will only be of use if you are using the reflector to support the lens and this then ensures any 'give' in the support system is displaced.

The point of the test would be to learn whether the glass can move sufficiently under pressure to break the seal. I agree the test is not necessary if the glass is directly supported by the head, because...

That way you are sure that the lens can't move.

Oh, wait. I said that in my last post.