O rings for maglite D size

[mastou]

I am planning to modify my 4D maglite (the new version with D in front of the number) into a dive light, and would like to have an advice on which size o rings I should buy. What I have read so far (e.g. here: http://www.scubaboard.com/forums/do-yourself-diy/272038-o-rings-mag-light-conversion.html) it seems like I should go for:

1) Outside lens - NBR70 ID 48mm x 2mm
2) Inside lens - NBR70 ID 48mm x 2mm
3) where the head connect to the tube - ?
4) Tail cap - NBR70 124 or 1 3/16 ID X 3/32 c/s

I have a some doubt about the inside lens (number 2) since when I measure the original o ring it seems to be closer to 50-51mm than 48mm? Furthermore, what is the sizes I should look for for number 3 and 4 NBR70 124 doesn't say me much and 1 3/16 ID X 3/32 c/s according to this conversion table (http://www.broadleyjames.com/o-rings-size-chart.html) is 29.87mm and the original o ring seems to be around 33mm in inner diameter?

My guess (from what I have measured) would be to use:

1) NBR70 ID 48mm x 2mm
2) NBR70 ID 50mm x 2mm
3) NBR70 ID 37mm x 2mm (but this is more or less similar to the original)
4) NBR70 ID 33mm x 2mm

I should say I don't know if I can get these sizes, and it doesn't have to be metric this is just what I figured could work, but what do you say...:shrug:

Thanks, Magnus

 

[jspeybro]

about the O-ring that is closer to 50-51mm, I had the same issue. However, I went to rubber shop where they have all kinds of O-rings, and 48x2mm was the closest match that they had, so I bought that one. Haven't tested it though, but Packhorse seems to use it without problems.

about the O-ring between the tube and the head, since most people cut a part of the tube and then use JB weld or something similar to reconnect both parts, an O-ring is not necessary at this place. I read somewhere (scubaboard I think) that someone used the original O-ring from the tailcap to replace this O-ring and this seemed to work for him.

The thing is, when you use a thicker O-ring with the same inner diameter as the original one, chances are that it is not going to fit as the outer diameter will be bigger. Using a thicker but slightly smaller ring, you will stretch the ring a little so that it will be a tighter fit and still be a little thicker than the original O-ring.

 

[mastou]

Thanks for you answer jspeybro I'll go for the 48 x 2mm for number 1 and 2 :)

Do you have any idea which o ring will fit best for the tailcap?

Packhorse seems to go for one that has an ID of 1 1/4 and a CS of 3/32 (corresponding to an ID 31.42mm and CS of 2.62mm in metric) if I guess correct with NBR124 (see size-chart linked in first post).

Whereas bradsab (see first link in first post) uses an o ring that has an ID of 1 3/16 and CS of 3/32 (29.87mm x 2.62mm) which must correspond to NBR123?

I think the one packhorse mentioned will fit best since the one bradsab mentioned are much smaller than what I measured. I think I'll try to order a couple of different sizes for the neck (if I decide not to weld it).

The light is going to be used for spearfishing at night so it will probably never be used deeper than 10m (I mainly spearfish at a depth of 1-3m)

Thanks again, now I just have to decide between 3xXP-G, 3xXR-E or 1xP7 :thinking: :)

 

[Klem]

Magnus,

Just a thought, but I don't use O rings unless needing frequent access to that part of the torch. The logic being, that fewer O rings lessens the chance of accidental flooding.

The only part of the torch you need frequent access to is where the batteries are, for re-charging.

Trying to source replacement O rings for the Maglite lens is an example of what I am suggesting. Why not affix the lens permanently to the bezel with epoxy putty, so the bezel and lens becomes one solid waterproof part. Then discard the thin factory O ring on the head and screw the bezel/lens on, sealing it with silicone liquid gasket (e.g. Silastic). Wipe off any excess that squeezes out as it tightens and voila!

If you need to service the front of the Maglite you can still get back in by 'cracking' the seal with a bit of elbow grease. I made two pieces of wood that can evenly grip the head in a vice that helps here (see the photos on the link). Gives a nice even grip that doesn't mar the finish, or dent the bezel.

The head to the body can be waterproofed by again discarding the factory O ring and using polyeurathane glue instead (e.g. Sikaflex Marine). Polyeurathane is a stronger more permanent seal than silicone, and so I recommend using it when there's even less chance you'll ever need to open the seal.

Here's an example of a modified 2D Maglite. It has only one O ring remaining, which is where the batteries are.
http://groups.yahoo.com/group/hiddivelights/photos/album/683013969/pic/list

Hope this helps

Klem

 

[mastou]

Hi klem, thanks for your reply (I can't make the link work). The reason for only using o rings was so that I can use the same host for different LED setups (3-4 XR-E/XP-G or 1 P7). This is because I am in doubt about how focused beam pattern I will prefer. The danish water often is unclear thus a tight beam might me preferable (e.g. including aspheric), but since I mainly spearfish at night I might need a bit of spill or a less focused beam for orientation.

I am new to homebuild lights so focusable lights is way over my head, I need some learning time first ;)

/Magnus

 

[Klem]

Magnus,

OK, understood.

Try this link this time
http://groups.yahoo.com/group/hiddivelights/

You will need to register to join the goup but once in there's a good bunch of torch ideas in the "Photos" section. Look down the first page of the photos albums for, 'Mac's Maglite 12Watt LED'.

As for focusable lights, if you can make one that is focusable underwater then you will be fairly unique amongst the rest of us, as very few torches are made to be focusable. Divers usually choose a degree of spread and build this as fixed.

Particulates in water tend to scatter light, so whatever beam angle you choose will spread it wider below water than above. A common night combination is to have the narrowest beam angle on your main torch so you can punch maximum distance, and a smaller face-mask affixed torch with a wider angle to see your instruments and the area immediately surrounding you.

I do a fair bit of scuba prawning on summer nights here in Australia and that combination works for me. You go on the moon cycles so you don't get to choose the visibility, so it varies. The main torch is swept from left to right looking for the little suckers and the smaller torch on the face-mask comes into play when you home in to use a net on them.

Years ago we used to make canister torches using MR16 halogens They'd invariably blow (especially when overdriven to 16V) at 20 metres depth at night. You'd be left with your small face-mask torch while you fished around in the gloom for a spare, or finished the dive with 1 metre viz:candle:.

All good fun.

Klem