Sealing the Lens

[ShoalDiverSA]

I am working on an alumin(i)um handheld torch. I would like to seal the lens to the body as simply as possible.

Initially I was thinking of screwing a collar onto the front of the body with an o-ring behind the lens (see attachment - left). Maybe a screw-in collar would be better because it would be easier to keep from protuding beyond the body (see attachment - right).

However, I really would like to get away from the threaded solution. Kowalski handheld torches seem to have a neat seal.

Canister Torch

Handheld Torches

Any ideas how their lens sealing works?

Perhaps a circlip can be used to hold the lens in place...

Any ideas?

Thanks,

Andrew

 

[mddolson]

We were faced with the same problem.
So we just drilled and tapped 4 holes to secure the front clamp ring with 4 ss cap screws. (see photo)

Mike D

 

[ShoalDiverSA]

Thanks Mike,

Unfortunately, I am machining the body from aluminium pipe, with a wall thickness of 3mm. This does not leave me enough material for the mounting of an o-ring as well as mounting holes for the lens cover. The thickness (thinness?) of the wall is where the challenge lies. Sorry that I did not specify this at the beginning.

By the way, I may be able to get away with an internal snap ring holding the lens. I am open to suggestions...

Cheers,

Andrew

 

[ShoalDiverSA]

I've narrowed my design down to two options:
1) screw-on collar to hold lens in (external thread on pipe), or
2) screw-in collar (screws into torch face - internal thread on torch pipe)

[Mike, I tried to apply your advice, but just could not fit the machine screws and the o-ring into the wall thickness - thanks for the idea ut:. By the way, it looks like Gilan (www.gilan.nl) use the same system of fastening their lenses on. The only problem is that solid bar costs six times more than pipe!]

I am going to find out which of the above options is easier (read: cheaper) to make and go with it.

I am planning to use 5mm thick borosilicate for the lens. Any suggestions/calculations to support a different lens thickness? For (purely) interest's sake, the crush depth on the alumin(i)um pipe is 700m! Well in excess of the crush depth of my noggin .

I would think that a design working depth of 150m would cover all eventualities. The selection of borosilicate glass is so that the torch can be used out of water without risking damage to the lens.

Thanks,

Andrew

 

[nickjb]

I made my markII lighthead using the sealing method you described and I made an external screw on cap to hold it all together.

I did think about just using circlip to hold it all together and relying on the water pressure to squash the o-ring but I thought it might leak at shallow depths. A piece of foam behind the circlip might help to apply a bit of force.

If I make a markIII then I might try an internally threaded design. I think it'll be a bit more elegant. This is also what I plant to do on my camera housing if I go for a glass lens, rather than plastic.

I've been to sort out some pictues for ages. Maybe I'll get round to it this week

Nick

 

[scuba-punk]

Most commercial dive lights use some sort of 1/4" - 5mm plate glass. Borosilicate (Pyrex) would be my choice too for the lense. What about machining a groove on the inside of the cover (facing the glass) for an o-ring to seal against the glass. Should probably cushion the glass on the other side too. Maybe a small groove on the facing edge of the pipe for a smaller o-ring? Just a couple of thoughts.

We expect pictures when you have it together! Good Luck!

-Frank =-)