"M4" question

[scout24]

I have a couple of questions for the incan gurus here: I just pieced together a pseudo M4. KT4 turbohead, FM M to C adapter, FM 2x18650 C body, and a C2 tailcap with AW 3 level softstart. At least to start with, I plan to run MN15 and MN20 bulbs as they are both listed as safe on two 18650's. ( AW 2900's) I understand the softstart will help prolong bulb life, but how much? I will use this as a high level only light most of the time, for 10-20 minute dog walks. Is this type of constant use better for incan bulbs than short bursts? Are there better choices for bulbs on 2x18650's? I realize "better" is subjective, but opinions are welcome. I like the MN15 and 20 since I can run both in my M6 as well, which was a consideration. All thoughts and input are welcome! Thanks for reading! :)

 

[archimedes]

I'm certain that fivemega could answer your technical lamp/battery questions much better (& in more detail) than I, but I do think the AW SoftStart is very helpful ... and I wouldn't mind having another :)

As long as the voltage and current are within appropriate range(s), I think there are at least two distinct issues - overall burn time and sudden failure.

Lamp burn time (eventually) results in loss of filament substance related to heat, as it "burns away", without significant relation to on/off cycles. Long burns on high will maximize this effect (but minimize sudden failures).

Sudden fail can be from many factors, such as physical shock, vibration, envelope gas leak, "current rush" into a cold filament, and similar insults to glass envelope and/or filament integrity. Frequent cycling and short burns will maximize this effect (but minimize filament consumption).

Here's a very interesting (older) thread that discussed some of the latter issues in detail ...

http://www.candlepowerforums.com/vb...ogen-process-filament-temp-and-envelope-glass

Hope that helps !

 

[scout24]

Archimedes- Fascinating thread on the hows and whys of bulb failure! Thank you for the link and the thoughts on competing forces of long burn vs. a lot of shorter use.

 

[Fusion_m8]

For 2x18650 use a LumensFactory HO-M3T lamp, it is brighter and more durable compared to the MN15 on rechargeables. Surefire incandescent lamps are not recommended for use with rechargeables and tends to either instantflash or have a significantly reduced bulb life.

 

[scout24]

Thanks! After some reading, that HO-M3T looks like it will run in the M6 on primaries as well, with a slightly reduced bulb life. This is good, I'm looking for maximum versatility as far as RCR/ primary compatability in both lights, with the MN-21 for M6, (primaries only) as an OMG bulb.

MN15: Both lights on 2xRCR18650, M6 on primaries or 2x18650 with adapter.
MN20: Same as above.
HO-M3T: "M4" or M6 with 2x18650, M6 with primaries.
MN21- OMG bulb for M6... :)

That may well cover my bases. Thanks for the help! :thumbsup:

 

[Flea Bag]

I would like to add that the MN20 is very conservatively driven by 2x18650 and may even be very slightly under-driven. I've got well over 30 hours on one of my first MN20s and even over-drove it a few times by accident and it still looks identical to a new MN20. I won't be surprised if I use it past the 40 or 50 hour mark and still not notice any performance degradation.

The MN20's beam is quite different. Its beam is warmer in CCT (more underdriven). Its spill is less bright but its hotspot is significantly larger and as a result does not throw as well. However, this makes it a better close-medium distace bulb than the HO-M3T as the hotspot-to-spill transition is not so sudden and more natural. That means your night vision doesn't get murdered as you would with the HO-M3T at those distances.

By comparion, the HO-M3T's hotspot-to-spill-transition is so sudden that it can sometimes look as though there's a dark ring around the hotspot. The MN20's hotspot however is much more oval, to the extent that outdoors, you'll easily notice when it's not how you want aligned. I like mine horizontal with the horizon in almost any situation. The HO-M3T's is much more round -not perfectly round, but round enough to not really be that noticable outdoors.

Technically, the HO-M3T is a better beam for its rounder hotspot, better throw, higher CCT and brighter spill. However, I still prefer the MN20 for its more natural and well-rounded behaviour. If you have an FM24 diffuser, then I would recommend the HO-M3T for better close to medium-close distances. Hope that helps!

BTW, an MN21 on any 2x18650 is over-driven to the extent that bulb may blow at any time and if not, bulb will go brown much faster as ageing advances much more rapidly.

Also, the LG 2600mAh versions of the 18650 were the best at holding their voltage under 1C or heavier loads, allowing higher CCT for incan bulbs -better than the 2900 or 3100 versions. However, the new 3400 cells are said to be level with the 2600 for those situations and better for most other situations.