Any Mechanical Engineers out there with advice!

[gcbryan]

Here is the light in question for reference:

DealExtreme: $95.00 Diving Cree MC-E (K-WC) 3-Mode 640-Lumen LED Flashlight Kit (2*18650/4*CR123A/4*16340)

It's being used as a dive light (somewhat successfully) but really was tested only to more moderate water resistant standards.

My question is not whether to buy it or not. It's already on it's way. My question is about o-rings and potentially stronger lenses.

The light uses 2 silicone o-rings in the removable tail cap section of the light. By all reports these o-rings are very soft. I'm sure this makes them seal quickly at lower pressures but at higher pressures they're more likely to bottom out. What durometer should I look for as a replacement given it's application as a dive light?

In addition, the lens is a coated glass lens and is approximately 2-3 mm. This thickness can't be changed given the existing space without thread. Is there a material in that thickness that would still function to let the light through that would be stronger than glass for this purpose? Plexiglas or something?

Just curious if any ME's have any surefire ways to beef this up a bit. Supposedly it's statically pressure tested (dry in a pot) to 300 fsw and dynamically to 180 fsw (not sure how that was done) but it doesn't exactly appear to be over engineered so I'm looking for any easy fixes if there are any.

 

[wquiles]

From various searches here in this forum and over the Internet, the most common answer is to use duro 70 O-rings, either EDPM or Nitrile.

Here is a good link on the duro values:
O-ring USA ...

and here are some older post from Packhorse, who is very experienced with light builds:
O-rings for Mag conversion ...

Packhorse also uses duro 70 o-rings in his W200 conversions:
Ultrafire W200 conversion


The question on lens thickness I don't know much. The only data point I can offer is that the dive-rated lights from Barbolight are tested to 200 meters, and they use a 2" dia polycarbonate 5 mm thick lens, and that at 200mm there is less than 0.5mm deflection on the lens. Glass is stronger (although not impact resistant as the poly lens), so you should be able to make it thinner than 5mm - how much, I don't know. This is also the type of information that I am also looking to learn more about.

Will