QTC **POLL** functionality

QTC (Quantum Tunneling Composite) technology seems to often generate a bit of debate .... I thought it might be of interest to set up a poll to see a variety of opinions on its use for adjusting flashlight output

Given the inherent limitations, it is great. Can't exactly repeat a setting. Need to be careful when twisting the head - if you press or squeeze, when you release, it loosens (if you know what I mean). And if you keep twisting because you are trying to get brighter, then you can damage your battery. But it is efficient and it does work. I like it on my 10180 Nichia 219 mule. But my long AAA with momentary swich and XP-G2 N large head is non-QTC. I voted great.

Edit
gravelmonke's mention of magnets reminded me that I forgot to mention my Quantum DD. I also like the QTC on this tiny 10180 light. The QTC is held by a magnet and this makes getting the battery out a little tricky. Not a big deal. The next generation upgraded to the XP-G2 and ditched the magnet.

I've used more than 10 lights employing QTC for output adjustment and only found it unsatisfactory in one light. I believe the problem was due to body length, because once i removed the pill and put it into a different body, the problem was resolved.

Thanks very much for the comments .... It is very helpful to hear the specifics of your experience(s) - the model of flashlight, duration & type of use, etc.

Quite honestly, I don't know how I feel about it, I have 2 Peak Logans, an 10180 Eiger and 10440 body (with a head on the way). When it works, it's brilliant- but I do seem to spend a lot of time faffing with it to make it work. Maybe I'll be happier when I get the momentary switch for one of my Logans. That all said, I haven't actually used my lights in serious anger yet (ie camping, power-cut, being chased by government forces through sewers etc) and they would probably be absolutly fine for those kind of duties, but when something's carried on my keychain/in pocket, the flaws are more apparent.

If Peak produced some sort of Gen.3 QTC pill then I think I would go on a buying spree. As it is, I've had mainly positive results (to a degree) with all sorts of tactics including packing the pill with aluminium/copper foil; magnets, spacers, lube, bigger bits of QTC, smaller bits of QTC..etcetc.. Current set-up in the Eiger I was having problems with is a 'doughnut' shaped spacer of paper to stop the two peices of metal in the pill coming into contact (and therefore stop the jump from medium to high).

Bottom line is, if you understand the limitations (ie- its not a magnetic variable control) then you shouldn't be disappointed.

I also only just realised that the Eiger Ultra X existed! How come there is so little written about this light!?

I find QTC to be an acceptable solution for a light in the, oh, $30-ish or less range. I don't expect world-class finish or performance at that price point and the QTC lights I have (several L3 Illumination L10's, a ThruNite T-21 and a Sunwayman R01A that I got free with another SWM purchase) all perform fairly well. I'd rate their reliability/performance a 7 or 8 out of 10. I carry an L10 Nicha in my front pocket 24/7 and use it regularly but it is only a "last chance" backup. I can't see using it or any of the other QTC lights I've tried as a primary light. And I'd never consider using one in a mission critical or "lives on the line" scenario.

QTC is one of the reasons I've stayed away from Peak lights. It's not that they don't work or aren't capable lights; there are plenty of posts here that bear that out. Rather, it's that I don't think QTC performance rates a price of $60, $80, or more. (Bear in mind, this is my own opinion based on my own experience and my own bank account.)

TL;DR - I feel that QTC is an acceptable solution for inexpensive backup or backup-backup lights only.

yoyoman said:

The L10 doesn't use QTC and I don't think the others do.

Click to expand...

You're absolutely right. I was confusing actual QTC material with the ring of foam used to distance the battery from the contact point in the head (as well as the overall function) of the twisty lights I mentioned above. Just goes to show, I should always read carefully, know what I'm talking about, AND have coffee before writing anything.

Funny thing is, I just received some QTC material this week and was planning on tinkering with it over the weekend. Perhaps I'll have a valid opinion in a few days. Until then, I'll just sit quietly over here in the corner...

The L10 doesn't use QTC and I don't think the others do. Because it doesn't involve a circuit to dim the light, it is reliable. Nothing to fail. The problem some people have is about usability. Not as simple as clicking or twisting to change modes.

I'm not gonna vote because I've never used a QTC light, but I'm not interested in them, I just don't like the idea of having that type of interface. I wanted a Peak light until I found out that was the interface they use.

I've had many qtc peaks (almost 10?). Sold most of them. Gen 1 qtc was poor and unreliable. Gen 2 is better but still degrades too fast and the pills often fall apart on me. I like the concept and how they work. I hate how the poor pill design causes the qtc to break down and become unreliable quickly.

I end up with a 2-3 level light that doesn't ramp well. I know the failure mode is full on, so you won't be left in the dark initially, but things will be dark 30 mins later when your battery is dead from running full blast.

I did not have good reliability with mine. It became frustrating to use. I had the gen one in a Peak.

Can NOT stand the stuff, 2 stage CC driver designs are obtainable by a careful web search . I would prefer a simple DIY, 2 stage light to QTC material. Not to say that the QTC technology could not advance. At it's present state I vote thumbs down.

archimedes said:

Thanks very much for the comments .... It is very helpful to hear the specifics of your experience(s) - the model of flashlight, duration & type of use, etc.

Click to expand...

I waited a while before adding my own vote & comments here ... to let the thread get started

Most of my experience with QTC has been in Peak torches, but I have also used these occasionally in others, like the Veleno Designs Quantums (Quanta?), and a couple of older-type "twisties" (McGizmo Sapphire, JiL-CR2, and others).

Beginning with "Gen0" (raw QTC) and continuing through the Gen1 and Gen2.0 Peak "pills", I have used these in EDC keyring lights, every day, for over two years now.

I like their simplicity of use and efficiency of design. Ramping is certainly not perfect or smooth, though the later versions do seem to have made incremental improvements.

I suspect that, over time, the added mechanical wear on the threads and/or breakdown of the compound may eventually degrade performance to some degree. For now, though, I have been very satisfied with their functional utility in providing an easy way to lower and adjust output in many of my single-mode twisties. I have not yet found the need to repair or replace any of these QTC, even in those without a protective disk.

Just to keep the discission going, I think that how you use the QTC impacts the useful life and reliability. I've seen threads showing damage to batteries. Clearly, if you are twisting so hard that you are damaging a battery, then you are also likely to be damaging the QTC material. QTC is not as simple as a click or twist to change modes. But it is efficient - more efficient than a 2 stage driver. Maybe your next poll should be cc vs. pwm (aka constant color by McGizmo).

yoyoman said:

....I've seen threads showing damage to batteries. Clearly, if you are twisting so hard that you are damaging a battery, then you are also likely to be damaging the QTC material....

Click to expand...

Excellent point!

I've seen those photos too .... My batteries aren't all dented and crushed, since I don't ever crank the output "up to eleven" :devil:

I've been thinking about this issue of crushed cells and reading other threads related to QTC and I've learned a lot and enjoyed the discussions. Peaks are not regulated. This means that as the cell drains, output drops. As a result, it is possible that you keep twisting to get to what you think is high. But you won't get the output you want because the cell is drained and if you keep twisting you'll damage the cell and the QTC.

I mainly use my Peak Eiger Nichia 219 mule for low light levels. This means I never (or almost never) fully twist it to get to H. I think this may be one reason why I haven't had any problem with the QTC - no flickering, no sudden jump in output.

The QTC is also more efficient than what I've experienced with magnetic ring control lights. The low levels on these lights don't deliver the runtime I expect because they are not efficient. You can dial down to a low level, but the runtime is not great. The QTC is efficient and I can have a low lumen light that is really small and has good runtime on a 10180.

I think if you want a sub-lumen or very low output light, the QTC is a really good option. If you want a light that has distinct modes and you'll use H frequently, there are other, better options. I also have a Peak Eiger SS AAA body with a large optic XP-G2 N. This is set up with a momentary switch and no QTC because I mainly use this on H. (Bonus: The Streamlight Stylus Pro clip is a perfect fit.)

gravelmonkey said:

Quite honestly, I don't know how I feel about it, I have 2 Peak Logans, an 10180 Eiger and 10440 body (with a head on the way). When it works, it's brilliant- but I do seem to spend a lot of time faffing with it to make it work. Maybe I'll be happier when I get the momentary switch for one of my Logans. That all said, I haven't actually used my lights in serious anger yet (ie camping, power-cut, being chased by government forces through sewers etc) and they would probably be absolutly fine for those kind of duties, but when something's carried on my keychain/in pocket, the flaws are more apparent.

If Peak produced some sort of Gen.3 QTC pill then I think I would go on a buying spree. As it is, I've had mainly positive results (to a degree) with all sorts of tactics including packing the pill with aluminium/copper foil; magnets, spacers, lube, bigger bits of QTC, smaller bits of QTC..etcetc.. Current set-up in the Eiger I was having problems with is a 'doughnut' shaped spacer of paper to stop the two peices of metal in the pill coming into contact (and therefore stop the jump from medium to high).

Bottom line is, if you understand the limitations (ie- its not a magnetic variable control) then you shouldn't be disappointed.

I also only just realised that the Eiger Ultra X existed! How come there is so little written about this light!?

Click to expand...

Update: Eiger sized lights get used and the logan sized lights are on the shelf (all gen.2 QTC)- I don't know if it's the threads/materials/bigger chunk of QTC but the Logans require a proper, two handed, crank to get upto ~70%+ output and the momentary switch makes my thumb joint crunch which I'm a bit tired of 2bh.

I'm hesitant to shell money out for the peaks with new generation QTC...

I've read that the newest Quantum and some modded Arc AAA lights put the QTC at the head rather than the tail and are more consistent.

I still like my Peak Eigers.

I haven't any stock QTC lights, but I got some bare pills and I've been experimenting with them for over a year now in many configurations. I modded many pocket sized lights such as Minimags AA and AAA with momentary plungers. In my opinion there are 2 key points to get it working reasonably well: precise body machining(especialy tight threads) and some kind of protection from tearing the pill. I used "CQG S1" and "CQG S2" bodies to make QTC based direct drive EDC lights, and they served me well without fail for a year now. Of course they aren't perfect, nowhere as smooth as potentiometer, but don't flicker and it's possible to get desired brightness, just takes a while to "tune" it. The higher brightness, the more consistently it will stay. Main drawback for me is its unreliability on low levels - any small bump can shut it off. When I finally manage to set it very low and leave it, brightness slowly increases. What appeals me to this technology is it's simplicity, it's fascinating that a piece of rubber can serve as both, switch and dimmer, with no moving parts and no electronics needed. Generally I prefer multi stage, electronically complicated lights because of their advanced features, but in my pocket I'll always have small QTC based unit as backup that unlikely fail. So for me QTC is great and have it's place in flashlight industry, you just have to know it's limitations and don't expect piece of rubber to function like microcontroller.

I have the eiger and el capitan with the qtc, and don't like using either one. The concept is fantastic, but changing brightness is a hit or miss. Drop the light and the mode will usually go much brighter then what it was set at.

I've had success using raw qtc no pill in a jil light. Never have torn the QTC. I get good smooth ramping. I've never crushed a battery. I have upgraded the circuit to put out 150 Mac lumens and a beautiful warm tint.

I think it's just the way the threads are on the old jil light. They are fine and precise. So that work well. I've tried other but no luck. I do like the concept
Of it. One day someone will perfect it.