double o-rings?

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I like double o-rings myself. Stabilizes tailcaps w/ rear pressure switches (better feel) and makes accidental activation less likely with twisties.

IIRC the 6PN shipped with 2 orings for water resistance, but I haven't seen any of those firsthand.
 
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The rationale is that the joint with the most activity gets the most reinforcement. It is that a second ring is more protection, but one ring is still quite a bit, but one ring can still fail and will fail more often under more use. So just think of the second ring as a built in back up seal - redundancy.
 
My Armytek Viking Pro V3 has two o-rings on the head and two o-rings on the tail cap. I imagine other Armytek lights are the same. AT uses the head tight for turbo and the head loosened for all the other modes. I have never been a fan of having to unscrew the head slightly but this setup is very solid and has a good feel to it. I have no problem having the head loosened slightly.
 
If the o-ring gland area is properly designed a single o-ring is all that's needed for water resistance.
If the machined area is too wide, instead of capturing the ring, the tension on the ring is lessened and will leak.
There is a fairly new series of o-ring called a quad ring which has four sealing surfaces instead of two of conventional round o-ring gland material.
 
I see Oveready stopped by already. I was coming to say talk to them. They do a really spectacular double O ring upgrade to some of the bored Surefire bodies.
 
dealgrabber2002 said:
Hello,

If the light has one oring on the body but it has room for 1 more. Would doubling it help or ruin water proofness? Or it's a waste of an oring?
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My one and only dive light is double o-ring. :) Uranusfire. Surprisingly, build quality wasn't bad except for an unscrewed pill that I had to tighten.

I don't see how it could do anything but help water resistance.
 
Theortical question: In the absence of wear and tear, if the two o-rings and their interfaces with the tail and cap are exaclty alike, and the o-rings' deformation under pressure are also identical (think 2 identical instances of an o-ring), would 2 o-rings then increase (double?) the maximum depth at which the joint is waterproof with only 1 o-ring? In other words, does the additional o-ring increase the allowable submersion depth rating? I think this is actually the question some folks mean to ask.
 
If the light has room for another o-ring...yeah.

But example:
The lens of my Alpha doesn't really have room for a second one. But placing teflon tape on the threads would help if that is practical...couldn't really do either with my Streamlight TL at the front.

But at the rear either could have either or both.
 
I'm surpirised no one has said "one is none and two is one"...

My Armytek and leupold flashlights has two, thus the higher guaranteed water resistance.
 
I guess the real question is if the gap is large enough for two o-rings. It may appear to be so when the original ring is uncompressed, but how much does it expand sideways under compression. Since pressure is applied from the side, so to speak, one o-ring will start to compress before the other. If there is not enough room, the second ring might be forced to remain taller in the groove than is designed, where it could either tear itself or possibly keep the cap from seating all the way due to resistance. Unless one is an o-ring designer, I guess the only real way to test would be to add the second ring, and then open and close the fitting several times, then check for any damage, especially to the inner ring. Truly a trial and error process.
 
Timothybil said:
I guess the real question is if the gap is large enough for two o-rings. It may appear to be so when the original ring is uncompressed, but how much does it expand sideways under compression. Since pressure is applied from the side, so to speak, one o-ring will start to compress before the other. If there is not enough room, the second ring might be forced to remain taller in the groove than is designed, where it could either tear itself or possibly keep the cap from seating all the way due to resistance. Unless one is an o-ring designer, I guess the only real way to test would be to add the second ring, and then open and close the fitting several times, then check for any damage, especially to the inner ring. Truly a trial and error process.
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Surefire C2/3, Z2/3, 6/9P, M2, M3, M4 all have double o-ring grooves at the tail not a larger gap that can accommodate two o-rings, stock lights came with one o-ring but many CPFers put in another o-ring in the second groove.
 
You'd have to be sure that the lens is sealed well enough to withstand greater pressure than the light is rated for. And it would depend on how much the body around the o-ring would warp from the o-ring. If it could warp at all from the pressure of two o-rings at some point within the lifetime of the light (which could be decades) then neither o-ring will be pressed as firmly against the body as if there were just one. You'd have to re-test everything to see if it meets the specs you want it to meet. I wouldn't do it.
 
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