Hello,
I have an ancient LEDlenser Hocus Fokus 3xAAA rotating TIR zoomie that I want to repair.
The optic is special, that’s why I want to keep it.
The TIR optic has a little crack on the side and while I like to wash my lights after use outside, this one will now get water inside.
Do you guys have an idea?
Maybe the capilary-action (thin like water, 20mPas) cyanoacrylate glue? Will that be transparent enough?
The Hokus Focus is not waterproof due to its construction. Changes is temperature can pull in water.
How big is the crack and where is it located? Cyanoacrylate should work fine with the material of the TIR. But I’m sure that any attempt to glue it will be visible in the beam.
I recommend against using regular super-glue on optics due to the risk of the glue damaging the plastic. If you absolutely must use such glue, maybe try specialized super glue designed for use on glass.
That said, I recommend against using ANY glue on an optic. TIR optics work via the reflection of light off the backside of the optic. The texture of the backside of the optic must be smooth and at the right angle. Anything that disrupts this, such as even a thin layer of glue that soaks through or a drop that dribbles down the back, could wreck the optic.
Also, most LED Lensers are intentionally not waterproof. This is because cycling the zoom mechanism changes the internal volume of the light. If it were airtight, air pressure attempting to equalize would cause the bezel to return to whatever position it was in when the battery compartment was closed. The only ways to prevent this are to have a very stiff zoom mechanism that can resist this pressure change … or to allow an opening so air pressure can equalize.
Since your LED Lenser probably isn’t more than splash-resistant anyways, sealing up a crack in the lens probably won’t make the light safe against water intrusion.
It’s not glass, it’s PMMA. Cyaonacrylate works fine with it. But only very little may be used. Never try to rub off excess glue, it will destroy the surface finish. Nevertheless the crack will be visible in the beam afterwards because the glue has not the same optical properties as the TIR lens. As long as it’s still in one piece I wouldn’t try to glue it.
I recommended “super glue glass glue”, not because the optic is glass (it’s not… its acrylic), but rather because that particular formulation is designed to leave less mess on clear surfaces than ordinary super-glue. At least that’s my experience with it.
I agree with your recommendation on that Hocus Focus: Do not attempt to glue the optic so long as it is still in one piece.
If you decide to glue it, maybe use something like this. A UV cured glue/resin. There appear to be many different brands. All seem to work best on clear or transparent objects where the UV light can actually reach the glue/resin to cure it.
I have used this and a similar product on clear glass and clear plastic with amazing results.
J-B Weld SuperWeld Light Activated Glue is a specially formulated super glue that cures instantly when exposed to blue light. Simply apply the glue, shine the included light, and in 5 seconds the glue will fully cure. Use for bonding objects of all shapes and sizes, filling gaps, and sealing cracks.
Light curing super glue and applicator for precision control
Instant cure with light, [1 minute set and 24 hour cure without the light]
Bonds difficult and small repairs
Fills gaps, seals cracks and leaks, and rebuilds surfaces
Any cyanoacrylate glue carries the risk of fogging the plastic.
I would leave it alone.