Aspheric mag.

Packhorse

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I'm not a big fan of twisting myself but I'm not seeing how it's any different than the W200.

Yes its the same with the W200. Except the W200 has 3 ( or 4 in my case ) O rings and they can easily be checked each time you change the batteries.

When you turn the head the head moves closer to the body. This reduces the internal volume and so all other things being equal the pressure will rise. Sure its not that much. And maybe its of no concern. But it does happen and needs to be considered.
I do have another focusing system design floating around in my head and it also changes the pressure in the head but not by as much. But the focusing system will also be effected by the pressure differential from out side to in and as such may not work in a dive light application.
 

gcbryan

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OK, sure the internal volume is reduced but that's no different that when you screw the head in when you're at the surface so it's nothing related to diving (it's not somehow more important in a diving environment).


I'm not trying to be argumentative here, I was just trying to see where you were coming from.
 

Packhorse

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As I said, it may be of no concern but I do think it needs to be considered.
I know focusing of the MB Sub does not effect the internal pressure. Im not sure if it was a design concern or not.

I guess the bigger issue I would be concerned with is the constant movement when focusing. Especially with such different pressures of inside and outside. This may cause the threads to wear. After all you would need a full 20mm of travel or more to have the full range of focus available. Im not sure what the thread pitch on the Mag head is but I guess its less than 2mm meaning at least 10 full revolutions which may not even be possible with out the head coming off.
 

gcbryan

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Yeah, I'm sure you're right regarding the Mag. I would think that a light designed as a variable focus light from the outset should be able to change the focus from tight to wide with very little movement.

I'm sure with the MB sub design full deflection must be just a quarter turn or something like that right?

I have a variable focus light on it's way from DX. I had in an order and just added this to experiment with. I've seen a video of it in action but it's not designed for underwater use.

It's a sliding tube design. Hanachan was able to make his work underwater however so we'll see. It's only 100 lumen and only cost $10. It has an aspheric lens so there's plenty for me to experiment with there for the price.
 
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naimis

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I guess the bigger issue I would be concerned with is the constant movement when focusing. Especially with such different pressures of inside and outside. This may cause the threads to wear. After all you would need a full 20mm of travel or more to have the full range of focus available. Im not sure what the thread pitch on the Mag head is but I guess its less than 2mm meaning at least 10 full revolutions which may not even be possible with out the head coming off.

You are correct, sir. The 2D mag has, at best around 10mm of travel.

I suppose you could move the emitter back and forth, but then I'd be concerned about the thermal conductivity and whether the emitter's heat could be properly dissipated.
 

Roland

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Fascinating thread.

To comment on some theory: From UK the mini Q40 and the SL6 both have only one O-ring in the head for watertightness. The plastic head turns off from the palstic body to access the batteries. With the mini Q40 the turning of the head is even used to turn the light on or off. Many have taken these lights up to 100 meters deep without problems.
Difference with a mag D is that the head of the mini Q40 and the SL6 is smaller than the mag D. But in theory one O-ring might be enough.

The turning of the head to close the described UK divelights does increase pressure inside the lights because volume inside gets smaller while air cannot escape. This is however of no concern. The pressure change is small.

Warm air has more volume than cold air. Surface air is usually warmer than the diving water. The cooling of the air gives much more pressure change than the screwig down of the head.

We are talking about insignificant marginal pressure changes here. These changes give only a few % of pressure change. Diving to 40meters creates a pressure differential factor of 5. In other words at a depth of 40 meters the outside water pressure is 500% higher then the pressure inside the diving light.

I think for screwing a head 20 times underwater I would like to have more than one O-ring. Screwing increases the risk of leaks. And 20 whole turns underwater is a lot. The UK lights are usually not turned underwater or just once a few turns near the surface in the case of the mini Q40.

Even a light pre-focussable for a dive at the surface would be great.

Hope this helps anyone.
 

Roland

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What is of more concern to me is that UK uses a katalyst of some sort. This is included in the bulb assembly.

Water is supposed to destroy the katalyst. I once had a few drops of water inside the light which according to the UK marketing would render the katalyst material useless. The used alkaline batteries caused a gas buildup inside the light. That gas buidldup caused the head to fly off several meters when unscrewed to take out the batteries.
 

Packhorse

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Ok, its been awhile but I have finished this light.
In the end I used 2 DX 2.8a drivers paralleled up.
Since I potted them before I made any measurements I couldnt get any out put amps but input amps was 1.25a using a 2p3s LiIon pack and just over 3a for 2!
So the sum of the parts was greater than the individual drivers??

Anyway I am guessing 6 amps to the SST-90.
I cant compare it to my quad aspheric R2 mag but my feeling is that its a cleaner beam thats a little larger but just as intense.
Pics on the previous page pretty much sum it up really as nothing much has changed except the driver.

I ran it on the bench and it got a little too hot to handle after about 15 minutes.
In the end I intend to run it with a 2P3S 4000ma Li Mn Ni pack so that should give it a 3 -4 hour burn time.
 

jspeybro

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Hi Packhorse,

Are there any heat problems with this setup when using it in the water, or is it able to transfer the heat via the slip-fit heatsink to the maglite and to the water when running for about an hour?

If the heatsink is in the handle of the light with the LED on top of that (which is then fixed in the head), is the led in focus or did you modify things to get the LED in focus?

Johan
 

Packhorse

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To be honest I have only dived this light once and it flooded due to a incorrectly seated O ring. Even though the LED and driver sat in salt water for 30 minutes ( power off) it still ran fine after I flushed it with fresh water. None the less I have rebuilt it but with a SST-50 instead for a smaller beam( the same SST-90 is used in my W300 style can light now).


Heat transfer is excellent in this light due to the large slip fit heat sink.
Obviously I cant feel the heat sink during the dive but from my experience on the bench with this light and a bowl of water I believe the sink will remain at a relatively low temp.
I can move the sink up and down in the handle to adjust the focus when dismantled. I intend to use this as half of a video light set up.
 

Packhorse

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No. I used the cannister for another light and have only just got around to building a dedicated cannister for it. I will probably use it on my next dive.
 

shao.fu.tzer

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Interesting... I wonder why I never thought of that,, Using a smaller lens and epoxying it in... It sure beats the heck out of trying to raise the LED up and down until you get the focal point right! I have a 50mm aspheric in a Brinkman that I'm about to raise the star up with a few pre-1982 belt sanded and soldered penny risers to get a useable beam. It's horrifically ugly right now...
 

dakyone

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Im going to try a similar design once i get a heatsink made. Hoping to have a slug if aluminum in the mag handle that can slide in there as to make raising the led for adjusting easier, plus added surface area for heat sinkage.
 

Packhorse

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I have just changed this from a SST-50 to a XML running off a 3 (?) amp DX driver.
Result is a tighter beam (8deg??) but more intense.
Lux is 3 times higher than a XML with a 35mm reflector and twice that of a XR-E and 28mm Horton aspheric.

Its very similar to my original quad aspheric mag but much simpler in design slightly tigher beam and more intense spot.

CANT WAIT TO DIVE IT!

I also tried a triple XML reflector drop in. The beam being very different. Wide with wider spill. But lack of a working boost driver and a lack of simple heat transfer method resulted in it being relegated to the "for future use" bin.
 

little nick

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Thread resurection time!

I am part way through this mod - XML with the 44mm aspheric lense from DX.

DX has had a batch problem with the lense - they sent some lenses of the right diameter, but not aspheric. They were slightly curved (convex) with a maximum thickness of 12mm, so the focal length was in the region of 100-150mm, not the 15mm expected!

They are sending me an alternative batch now -so fingers crossed they get it right this time!
 

Packhorse

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That sux.


This is still one of my favourite lights. It gives a very similar beam as my original quad aspheric ( 4 XR-E's) but a much more simple build and more efficient.
 

little nick

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That sux.


This is still one of my favourite lights. It gives a very similar beam as my original quad aspheric ( 4 XR-E's) but a much more simple build and more efficient.

It was your passion about the light that made me give it a go. I am hoping it will be better than my XML / Ahorton 28mm aspheric Diverite conversion
 
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