Shock Isolation..How?

[Robocop]

During a recent discussion involving a cracked lens I began searching old posts for shock isolation finding very little. I see many makers who advertise shock isolated bezels however do not really say how it is done.

I know many make good bezels that rarely break however is a shock isolated bezel mainly for the benefit of the glass lens or for the benefit of the actual lamp assembly? I also am curious as to who makes the best shock isolated light? I saw an incredible video of the TigerLight taking an amazing beating and never failed so how do they do it?

I have a light that has a sealed bezel that does not allow one to replace the lens. I have cracked several lenses on this light and wonder if the sealed bezel actually makes it easier to crack the lens. Is it possible that no light using a sealed bezel is shock isolated? I ask this because it seems to me if a lens is sealed it has no play if dropped and may break easier.

So basically are the best isolated bezels sealed or does a truly shock isolated bezel obtain the title by allowing some cushion somehow?

 

[Lightraven]

Someone will answer this better, but. . .

Surefire isolates the lamp assembly. Since the filament is the most delicate part of the light, especially when running, shock can break it. The reflector sits atop a closed cell foam donut under the pyrex window. The lamp assembly pushes forward into the reflector which moves into the foam, minimizing the impact.

Under the lamp assembly is a spring that prevents the batteries from impacting the lamp assembly, or vice versa. In the M6 is also a shoulder that prevents the battery carrier from moving into the lamp assembly.

Surefire has a diagram of this feature in one of their catalogs, I think.

The pyrex window doesn't seem to be protected in any special way.

I've dropped my M6 from about 3 feet onto rocky dirt and got only a small scratch on the window.

 

[Robocop]

Thanks for the reply Lightraven and from most of my searching it does appear that Sure-Fire does indeed make the best shock isolated bezels. It also seems that the shock isolation is aimed at protecting the filament rather than the actual lens.

My main reason for asking this question was to determine if it would do me any good to replace my broken glass lens with another glass section or keep using the spare plastic material I have found to fit it with. Simple logic tells me that a fixed lens that is not replaceable would not do as well with a drop than would a lens sandwiched between two 0-rings.

I have basically taken a bezel that was designed to be a sealed lens design and made it now where I can interchange lenses however if the use of o-rings has nothing to do with shock isolation it would do me no good anyway and thus I should stay with the plastic material lens.

As far as a glass lens is concerned some lights I have used with glass seem to last forever with no breakage as others break so easily. I wonder if the bezel design has something to do with that or is it most likely the type glass used.

 

[cy]

robo, surefire M series isolates the entire interior mass, end to end.

batteries are isolated by beefy springs on bulb base and tailcap. M series bezels are shock isolated by foam on both sides of bulb. you can feel bulb's cushion by gently pushing bulb's base.

depending upon model, there's 1/4in+ of travel provided. It's not by accident Surefire M series are considered military grade.

grade of glass used makes a huge difference in impact resistance. you can take a hammer to some tempered glass and have it bounce off. it's pretty safe to assume Surefire uses tempered glass in M series bezels.
http://en.wikipedia.org/wiki/Toughened_glass

 

[lightr07]

This will give you a slight understanding on how they work. The head you see is from a SureFire M6.

http://youtube.com/watch?v=Pr1Tj2kY-ZI

 

[Size15's]

lightr07, thanks! The video shows the shock isolated bezel's isolation of the Lamp Assembly well.

Yes, the Pyrex windows used by SureFire are tempered (another term for toughened). The main reason for this is so that the glass can handle rapid and extreme changes in temperature.
Toughened glass is able to bend and flex, and even twist a small amount compared to annealed glass (normal glass) that will snap rather than deform. However, the extent to which the glass can deform is severely reduced when in a flashlight bezel not least because of the small surface area but also due to it being constrained around its circumference.
It will still fend off impacts better than annealed glass of the same thickness with the exception of hard, sharp pointed objects that will be able to break it.
When it breaks tempered (toughened) glass will not shatter into shards - it will fragment into dices. The size and shape of the dices will depend on the surface area of the glass and the extent to which it has been toughened. Overall there is less risk of cutting or piercing injuries as a result of glass breakage.

Anyway, a few points about SureFire's shock isolation system:

- The primary function is to protect the Lamp and batteries from the influence of recoil as a result of the light being mounted on or attached to a firearm.
The forces inflicted on the WeaponLight which is mounted parallel to the firearm's barrel are axial and result in the contents of the flashlight moving forwards and backwards inside, slamming into each end, and into each other.

- The first part of the shock isolation system prevents the lamp assembly from slamming into window by means of a Neoprene strip buffer ("Compressive Recoil Damping Sleeve"). The Lamp Assembly locates against a metal ring that floats on the Neoprene strip.

- The second part of the system braces the lamp assembly against the body by means of the outer spring contact (negative contact).

The Lamp Assembly is suspended between the Neoprene and spring allowing it to travel forwards and rearwards. It is not directly in contact with the wall of the flashlight offering some (but limited) isolation from forces applied off-axis.

- The third part of the system is the negative spring contact in the TailCap that prevents the batteries from slamming into the back of the flashlight and effectively suspends the batteries between it, and the Lamp Assembly's inner (positive) spring contact.

- The fourth part of the system is what makes a SureFire illumination tool a WeaponLight rather than a flashlight (note there are several exceptions such as the M6). The body has a neck ("Machined Battery Barrier") preventing the batteries from being removed from the bezel-end of the body. This neck prevents the batteries from slamming forward into the back of the Lamp Assembly.

- The fifth part of the system is the shock isolated battery stick (now largely not required due to the low cost of SF123A batteries and related to that the increase usage of batteries resulting in them needing to be in the WeaponLight for less time. Anyway, the Shock Isolated Battery Sticks featured the individual SF123A (previously DL123A) batteries contacts welded together by a metal connector, and a fibre washer between and the whole assembly shrink-wrapped together. This resulted in more reliable contact and prevented the batteries from being crushed through the influence of weapons recoil etc.


The overall result is that the Lamp Assembly (with it's bulb) and the batteries are suspended within the flashlight significantly reducing shocks transmitted through the flashlight being attached to a firearm.

 

[Robocop]

Size15s thanks for the detailed reply and I never imagined it was that complicated however it does seem to work the best in the Surefire lights.

I am checking a local source for some correct size lenses to use in my Raider D36 bezel however I just realized how hard it is to find odd sizes of better quality glass lenses.

 

[js]

Good replies here already, so not much for me to say, but I did want to add this much:

There is absolutely no reason that a SI bezel wouldn't have a sealed lens. You can seal a lens all around, thus not only sealing it, but helping isolate the lens from shocks to the head of the light. If the lens is plastic there is no need to isolate the lens all around, and an o-ring or two is all that is needed. If the lens is glass, you really don't want it to directly touch the metal of the head/bezel. Thus, if you use a straight glass lens in a TigerLight, for example, you will eventually chip the edges of it. This is why FLL.com's shock isolated UCL is best for the TL. And, I find it is best to remove the bezel o-ring entirely, and just let the SI gasket handle the sealing job instead of the o-ring. Gives you a better fit.

If you want to know more about the design of the TL, see my thread The complete guide to the TigerLight

The M6 has a better shock isolation design, but the TigerLight's pretty good too, with the plastic lens. Add the glass lens, even a SI UCL, and you have a problem because the reflector rests DIRECTLY against the lens, and can transfer shocks to it (and vice versa), breaking it. Not easy to do, but not unheard of.

 

[Robocop]

I have to say that the video I saw of that Tiger Light taking a beating was one of the most incredible ones I have ever seen. The light was even turned on while it was thrown and beaten without even so much as a flicker in the beam....amazing actually.

I am getting by for now with the use of a plastic material clear lens however heat may become an issue during extended usage.

JS by sealing the lens I am talking about the lens being glued to the bezel with the owner unable to replace it. I have a Raider D36 bezel that has been common to breaks and it does appear thet the lens rests directly on the bezel without need of an o-ring due to the sealed design. Now that I have the original lens out I would like to maybe continue with a glass lens however as you mention simply sealing it directly to the bezel would allow easier breakage.

I have not ever really noticed however does the Tiger Light indeed use a plastic lens? Here lately I have developed a bad taste towards any glass lens but honestly a glass lens does seem to provide a little more light out the front to me.

 

[js]

I have to say that the video I saw of that Tiger Light taking a beating was one of the most incredible ones I have ever seen. The light was even turned on while it was thrown and beaten without even so much as a flicker in the beam....amazing actually.

The TL is pretty rugged. That's for sure. But the M6 is even more so.

I am getting by for now with the use of a plastic material clear lens however heat may become an issue during extended usage.

You have to get into some pretty high power beams to starting melting lexan. Just take a "try it and see" approach. If you melt it, so what? Plastic lenses are usually pretty cheap.

JS by sealing the lens I am talking about the lens being glued to the bezel with the owner unable to replace it

Ah! I see. Got it.

I have a Raider D36 bezel that has been common to breaks and it does appear thet the lens rests directly on the bezel without need of an o-ring due to the sealed design. Now that I have the original lens out I would like to maybe continue with a glass lens however as you mention simply sealing it directly to the bezel would allow easier breakage.

I have not ever really noticed however does the Tiger Light indeed use a plastic lens? Here lately I have developed a bad taste towards any glass lens but honestly a glass lens does seem to provide a little more light out the front to me.

Yes. The stock TigerLight lens is indeed lexan. However, the lens provided with the 375 lumen lamp modules are borofloat, IIRC (pretty much the same as pyrex).

But the best lens to use is the shock isolated UCL, because the gasket that surrounds the lens, SURROUNDS the lens: edges, and a bit of the top and bottom outer radius. So it's "sealed" in a way, AND user replaceable.

As far as lenses and user replaceablity, if it were my company, I'd seal it up just like SureFire does. More often than not, when someone opens up the lens, the light ends up in worse shape than when it started. If a lens gets broken, SF will repair or replace the whole head for you.

You can, however, open the bezels up on most SF lights, if you know how. And thus you could replace a broken lens yourself, provided you had an OEM replacement from FLL.com or something.