Mounting a window (lens) in a custom light

[Mick]

This is a ghosted view of a 3D CAD drawing showing the window (red) and a o-ring (black) in a housing (blue). The housing and o-ring are semi-transparent to show how the glass contacts the o-ring and is forced against the seat as well as centered in the pocket.

The window can be replaced by prying out the o-ring which may damage it but I feel it is an easy way to get a water proof lens installation.
Please comment?

 

[Morelite]

McGizmo (Don) uses a method very similar to that, but he has an Oring on both sides of the window and it seems to work very well.

 

[PEU]

I think your design depends on the "desire" of the oring to be there and not move...

If I were you I would use a two oring system and the lens in the middle, like a sandwich that keeps itself in place. I just sketched it:

a proper drawing would show the orings "copying" the shape of the lens, and presing the lens from top and bottom, I used an Oring I had previously modeled

[edit] While I was drawing morelite gave you the same idea :nana:

Pablo

 

[Anglepoise]

I have used this exact method on a couple of LED task lights on machinery.
However the lights in question were not exposed to water. I suspect that this method would work for very shallow submersion, but the clamping pressure of a threaded bezel would be needed if greater depth was desired.

 

[PEU]

If I recall correctly, barbolight dive flashlights use this same method, and these are rated for 100m deep at least


Pablo

 

[Mick]

One of the problems I saw when working on this design was the o-ring was not exactly the right size and the window was only available in certain sizes. I was trying to use standard pieces. On my design the o-ring needs to be stretched a bit as it is forced into the groove. I think that a flat rubber gasket on the bottom would make the assembly easier, but I agree that rubber on both sides is the best situation. With my light design (at this time) I can't get to the bottom of the window to push the o-ring in the groove.
Thanks for your thoughts.

On second thought what I could do is use the next size smaller o-ring and let it just sit on the flange. The upper o-ring would provide a little seating pressure. This could be somewhat controlled by using a higher durometer o-ring. This would mean I would not have to cut a groove right at the flange which could be a problem. McMaster has a quad o-ring in just the right size.
Thanks again for the comments.

 

[65535]

What you need is a thick O-ring sized exactly right for the groove, and a piece of glass sized to cover roughly 33% of the O-rings cross section. The groove should cover 67% of the O-rings cross section.

IMO that would give you the best fit, but it must be kept under tension.

 

[Anglepoise]

Mick,
I think you will just have to experiment to see what combination works.
The fact that Barbolight and Don's Lunasol use a similar system means it can be done. Just make sure your grooves are well machined, no chatter marks, and the 'O' rings fit deeply and firmly. I agree with others, two 'O' rings will be better than one.

 

[collector]

Quite interesting...

 

[gadget_lover]

Are you doing this to make it water resistant, toilet proof or water proof to depth X ?

The design you originally suggested should be water resistant.

It might be able to withstand a quick dip in a sink, puddle, etc, but the impact might compress the o-ring and rorce water past it.

It would not withstand any depth, as the o-ring will be pushed into it's groove and water will bypass.

Adding an o-ring groove to the shelf in the original picture will allow an o-ring that is forced against the glass by the water pressure, making it water proof. That would probably be the best solution, IMHO.

Daniel

 

[Mick]

Water pressure will cause the o-ring to flow towards the gap between the window and the housing causing a tighter seal. The window will break from the pressure before the seal will leak.