MN15 vs. N2

[Ray_of_Light]

I recently acquired a SF M3T, that I love for size and balance. It is my intention now to buy a Turbohead for all my Z3s.
I have read that the 3-cell Turbohead kit comes with the N2 bulb, which has the same output rating of the MN15 bulb in the M3T, and is physically interchangeable with it.

Does somebody know of any other difference between the MN15 and the N2? I know the MN15 is an high-pressure Xenon with no halogen cycle, like the MN02 and the MA02, to provide a very white light trough the one-hour runtime.
This type of bulb usually develops tungsten deposits inside the bulb envelope, at the end of its useful life (usually 20 hrs), when the lumen output falls below the declared value.
Is the N2 an halogen type bulb?

TIA

Anthony

 

[Size15's]

You know that those lamps are not filled with a high pressure Xenon Halogen mix?

The MN15 produces more light compared to the N2 (125lu vs. 105lu)
These ratings are not 'peak' output.

I've not yet experienced an N2 or MN15 die of old age although one N2 that was used more than 30 battery sets died when the M3T was dropped repeatedly in an attempt to see whether it would break.
In fact, the rate of 'discolouration' is surprisingly minimal and comparing one that is slightly yellowed to a fresh lamp shows no difference in the light quality.

I believe the unofficial lifespan for SureFire bulbs is 25 hours but that is a big understatement in my experience. I've had no bulbs die of old age before 25 hours use and those that have been longer longer than that are still working fine. (I had an N62 lamp die of old age. One night it just quit working - didn't discolour or anything. It's hard to tell quite how many hours life it had had but I wasn't disappointed)

I find the MN15's to be more brilliant for longer. However, just like the MN10 (it's the same bulb after all) I find the beam shape to be 'squashed' such that it bugs me. I use the MN11/MN16 lamps mostly in the M3/M3T but also use the N2 because it's beam is round.

The N2 should not be used in WeaponLights because the spring contacts are different to the "MN" type lamp assemblies.

Al

 

[Ray_of_Light]

Al,

thank you for your reply.
Long time ago I was making gas mix for bulbs.
High pressure xenon reduces the rate of evaporation of the tungsten filament. Higher is the pressure, lower is the rate of evaporation.
So, you can increase the operating temperature of the filament by increasing the pressure of the Xenon gas. There is a limit and that is the pressure differential that the bulb envelope can manage.
The tungsten that has evaporated will show deposited inside the bulb in specific (cold) spots.
On the contrary, a vacuum bulb produces an uniform deposit all inside the envelope, because the lack of convective gas currents.

If the bulb is made of quartz, and adding some iodine to the mixture, the "halogen cycle" will be established. The tungsten evaporated from the filament is "collected" from the inside of the bulb envelope, and redeposited on the filament. An halogen bulb is designed so that the temperature of the filament is high, so the evaporation rate, so the redeposition rate. An halogen bulb will hardly have any deposit inside the bulb, even at life end.

It is possible to create a xenon-halogen bulb, and have the combined benefits of the high pressure and the halogen cycle, but only to a certain extent. The quantity of the halogen must be tiny, because at the required pressure and the temperature (more than 20 atm at 250 °C) the halogen would "attack" the filament itself. This type of bulb may show minimal deposit inside the envelope at life end.

Based on my experience, the bulbs created from SureFire for the Millenium series (except the M2) exploits the possibility of new materials and technology, by increasing the pressure and the purity of Xenon gas, and reducing to the minimum the halogen cycle.

The benefits of this approach is to have a bulb with a very predictable lifespan and a whiter light emission over the life of the battery.

Of course, this is pure speculation on my part, based only on experience with bulbs and observation of the SF bulbs.

Thank you again for your reply. I am going to buy soon a KT2-BK for the Z3, and I plan to use MN15 in it. I do not like the squashed beam, but I like the bulb.

Anthony

 

[Size15's]

I do not like the squashed beam, but I like the bulb.

Anthony

Yep!

SureFire worked extremely hard designing them.
My understanding is that SureFire do use high pressure Xenon Halogen mix for the majority of their lamps.

Enjoy your KT2. I have to say that the SRTH with N2 lamp on the Z3 is a kill combination. It's also one of the best looking flashlights ever (imho)

Al

 

[Topper]

I had a Surefire N2 fail just two days ago (had lots of hours on it It died well and quitely)..rummaged through my "stuff" and found a Surefire MN15 brand new slapped that baby in and best I could think was "Why in the heck did I buy this when I should have got a second Surefire N2" I figured it out dumb as I am.. I got a Surefire K2 HA III comes with a N2 I bought a Surefire K2 Black comes with a N2
MN15 came with a Surefire M3T. See I did not buy the squishy MN15 it was FREE just like the 2 N2's FREE man I saved a bunch by getting stuff FREE. I do not mount any lights to any guns so the N2 is the best for me as in Turbo 3 cell lights made by Surefire. Roy, I tried and it is wearing me out already, perhaps that was your game plan.
Topper.

 

[oldgrandpajack]

Hi Anthony:

I'll second what Al said about the SRTH for the Z3.

The SRTH is much lighter weight, than the KT2. This is important, if you plan to use the "cigar grip", with the Z3.

oldgrandpajack

 

[Kiessling]

It might be lighter, more practical and all you want :nana: ... but it's FUGLY IMHO. The KT2 is a work of art, is HA and has a nice Pyrex window. Big toys for big boys 😀
bernie

 

[KevinL]

Anthony, thanks for sharing your insights.. nothing beats hearing it from the guy who's been there and done it!

From what I've read, SF said something similar to what you've mentioned - they use a nearly 100% Xenon gas atmosphere, with a tiny bit of halogens added where necessary. I think this is in one of their catalogs.


KT2? Naah! SRTH has better beam collimation 😀

 

[Schuey2002]

>>"KT2? Naah! SRTH has better beam collimation"<<

While that may be true (Ok, it is true!), it's still thee ugly duckling of the SF Turbo Head litter.. :laughing:

 

[js]

Al,

thank you for your reply.
Long time ago I was making gas mix for bulbs.
High pressure xenon reduces the rate of evaporation of the tungsten filament. Higher is the pressure, lower is the rate of evaporation.
So, you can increase the operating temperature of the filament by increasing the pressure of the Xenon gas. There is a limit and that is the pressure differential that the bulb envelope can manage.
The tungsten that has evaporated will show deposited inside the bulb in specific (cold) spots.
On the contrary, a vacuum bulb produces an uniform deposit all inside the envelope, because the lack of convective gas currents.

If the bulb is made of quartz, and adding some iodine to the mixture, the "halogen cycle" will be established. The tungsten evaporated from the filament is "collected" from the inside of the bulb envelope, and redeposited on the filament. An halogen bulb is designed so that the temperature of the filament is high, so the evaporation rate, so the redeposition rate. An halogen bulb will hardly have any deposit inside the bulb, even at life end.

It is possible to create a xenon-halogen bulb, and have the combined benefits of the high pressure and the halogen cycle, but only to a certain extent. The quantity of the halogen must be tiny, because at the required pressure and the temperature (more than 20 atm at 250 °C) the halogen would "attack" the filament itself. This type of bulb may show minimal deposit inside the envelope at life end.

Based on my experience, the bulbs created from SureFire for the Millenium series (except the M2) exploits the possibility of new materials and technology, by increasing the pressure and the purity of Xenon gas, and reducing to the minimum the halogen cycle.

The benefits of this approach is to have a bulb with a very predictable lifespan and a whiter light emission over the life of the battery.

Of course, this is pure speculation on my part, based only on experience with bulbs and observation of the SF bulbs.

Thank you again for your reply. I am going to buy soon a KT2-BK for the Z3, and I plan to use MN15 in it. I do not like the squashed beam, but I like the bulb.

Anthony

Anthony,

Wow! Finally! An authoritative answer to this unresolved issue!

I knew about the xenon and about the halogen cycle, but I could never figure out why a manufacturer would NOT add a trace amount of a halogen to a xenon lamp. As long as you are going to that amount of trouble and expense, why NOT have a lamp which doesn't blacken over its life?

And here, I think, is the answer. Let me see if I got this right:

You can make a higher-pressure xenon-only lamp, and thus a brighter, whiter lamp, than you can with a xenon-halogen lamp because you must reduce the pressure somewhat in order to prevent the halogen from attacking the filament itself.

Correct?

And this explains why my A2 lamp is slightly blackened. It didn't burn out, and it ran for longer than its rated life--so I'm not complaining or anything. But I was surprised when I noticed the blackening on the glass because I thought SF used xenon-halogen lamps.

Now I know. The use xenon-with-just-a-little-halogen lamps.

Right?

Awesome. Awesome. Awesome. You don't know how long I have been wondering this.

Any chance you can tell me how I can get my hands on some of the technical manuals or books that detail the lamp laws and composition mixtures and all the chewy head-ache-inducing details? I really want to know more, but a search on Amazon yields nothing useful. I was planning on calling my contact at Welch Allyn and having her arrange for me to speak with one of the scientist/engineers there, and I probably will still try to do that at some point, but just buying a book or technical manual is easier to pull off and arrange.

 

[Ray_of_Light]

Jim,

sorry for the late reply. To design and build an high-efficiency incandescent bulb is more a black art rather than a precise science. For this reason, you will not find much information published on the Internet.
Other than the mixture of gases in the bulb, the other primary factor is the purity of the elements used. Any impurity will only detract to the bulb life.
This not only referred to the gases, but also to the pedestal, the tungsten wire, the quartz envelope.

The tungsten wire is not a "wire" so to speak, but is obtained from a very fine dust of tungsten, which is pressed under high temperature and pressure. We say it is "sinterized". The details of this process are all very critical for an high performance bulb. It's of utmost importance for DC powered bulbs, to contrast the process of "ionic migration" that can shorten significantly the life of a DC powered bulb.

In general, the "art" of designing a high performance bulb requires a lot of resource and experience. The situation is even more crytical with miniature HID bulbs, that requires a lot of science to be used in their production.
This is why, when it comes to miniature high-power light source like Incandescent and HID, I stick to professional manufacturers like SureFire, WA or Philips.

If you want see an example of durable but inefficient high halogen bulb, take a close look the the Pila 3.7 V 2 A bulb that we use to replace the P60, when using the 168S battery in the 2 cells SureFire.
Normally, an high temperature halogen bulb is designed so that the quartz envelope has the same axis of the tungsten filament. This criteria is used to make the redepositation of the tungsten on the filament evenly. This is not the case of the Pila bulb; they used the ancient design criteria of redepositation by convective flow; this is why the envelope is so long.
While this make a long life bulb (30 hrs+), the efficiency in lumen/watt is about 50% less than a P60.
This is because much of the heat produced by the filament is wasted from the excessive surface of the bulb envelope, and because of the overall lower temperature of the filament.

The most spectacular bulb that SF makes in terms of efficiency is the MN60, the long-run bulb for the M4. Roughly, is 100% more efficient than the P60.

Regards

Anthony