Any interest in a potted BLF light?

Virisenox · 2019-04-28T16:55:20.000Z

Related to previously asked questions, but what kills a flashlight when it’s dropped? I assume it’s just components coming loose from the impact, right? I think I read somewhere that linear 7135 based drivers tend to be more durable for that reason, because all of the components are fairly low profile.

Paradise · 2019-04-28T19:19:15.000Z

My S2+ lights get dropped all the time, like all-year-round. So far, nothing has ever happened to them? The cells look a bit dented, but that will buff out
Lights are fine.

So what would potting bring in addition to the regular protection? Higher drops? break-resistant lens? different solder?

DBs post was excellent and gave me details I needed.

KawiBoy1428 · 2019-04-28T20:05:16.000Z

You need to restrict the movement of the battery from impacting the driver spring, which when bottomed out (coil bind) impacts the driver, Potting also aids in thermal transfer if you use the right stuff.

Agro · 2019-04-28T20:11:38.000Z

A related question:
In the future BLF projects…what can we do to make sure the lights are tough?

Agro · 2019-04-28T20:24:13.000Z

KawiBoy1428:

You need to restrict the movement of the battery from impacting the driver spring, which when bottomed out (coil bind) impacts the driver, Potting also aids in thermal transfer if you use the right stuff.

Do you mean that the spring should be long and stiff or that it should be short and not move much (like Emisar…or even more - DQG)?

KawiBoy1428 · 2019-04-28T20:36:27.000Z

Agro:

KawiBoy1428:

You need to restrict the movement of the battery from impacting the driver spring, which when bottomed out (coil bind) impacts the driver, Potting also aids in thermal transfer if you use the right stuff.

Do you mean that the spring should be long and stiff or that it should be short and not move much (like Emisar…or even more - DQG)?

Not really…. battery/cell stops in the battery tube, a shoulder restricting the cell from going too far forward on impact/recoil…usually a shoulder with an o-ring to eliminate abrasions to the cell wrapper.

.

. Even a bumper on the tail cap….limits movement allowing the spring(s) to maintain contact

.

Agro · 2019-04-28T20:45:21.000Z

Smart.

BlueSwordM · 2019-04-28T20:49:09.000Z

Or just use dual BeCu springs.

They resist deformation against shocks extremely well, even in heavy lights.

One example of this was when I threw my Q8 on concrete. By accident of course.

Didn’t turn off at all during the bump.

Even hitting it on a wooden table with all my might couldn’t shut the light off.

KawiBoy1428 · 2019-04-28T21:14:48.000Z

Agro:

Smart.

It is easy to do with the Surefire lights because they are all mostly CR123 powered and have to be bored for the 18650/350 cells, even my 6P mods can be weapon mounted, I machined a battery stop into the battery tube on the head end.

.

. Then polish the battery tube for a tight slip fit for certain cells like the VTC5A’s I use.

. Came up with a quick change module system fully potted driver, copper sink and reflector, the whole head is thermally potted and can be changed out from 2 different battery tubes depending on what emitter head I want to run.

.

KawiBoy1428 · 2019-04-28T21:23:29.000Z

BlueSwordM:

Or just use dual BeCu springs.

They resist deformation against shocks extremely well, even in heavy lights.

One example of this was when I threw my Q8 on concrete. By accident of course.

Didn’t turn off at all during the bump.

Even hitting it on a wooden table with all my might couldn’t shut the light off.

Usually the batteries will get damaged. I have a few batteries with dents from lights falling hard enough to break the lens and smash the flat top in from the spring bottoming out. Restrict the battery movement = less damage.

BlueSwordM · 2019-04-28T21:29:06.000Z

That’s why it’s so nice.

Your idea is better though.

The problem with springs is that not all of them are made equal.

Steel wire springs are good springs, but they don’t absorb a lot of energy on impact, meaning the cell has to absorb a lot of kinectic energy from impact.

BeCu springs are different since they take much more force to compress, depending on wire thickness and the number of coils, along with top diameter to bottom diameter ratio.

A large thick 1mm BeCu wire spring will take beating like a champ. A smaller 0,5-0,7mm BeCu spring will protect the cell, but might collapse.

ValuseekeR · 2019-04-28T22:05:42.000Z

Really appreciate ALL of the replies so far, very interesting and informative.

CREEXHP70LED · 2019-04-29T01:50:42.000Z

KawiBoy1428:

BlueSwordM:

Or just use dual BeCu springs.

They resist deformation against shocks extremely well, even in heavy lights.

One example of this was when I threw my Q8 on concrete. By accident of course.

Didn’t turn off at all during the bump.

Even hitting it on a wooden table with all my might couldn’t shut the light off.

Usually the batteries will get damaged. I have a few batteries with dents from lights falling hard enough to break the lens and smash the flat top in from the spring bottoming out. Restrict the battery movement = less damage.

I agree with what you have said. I have my first 2 Malkoff lights arriving tomorrow, and I ordered the battery bumper kits for both lights, and of course they are potted. I understand these are not budget lights, but it isn’t expensive to add a couple o rings to the front and back of the light. Then if you have a solid built light and you pot it, your good to go. Just as long as your not looking to mod it.

KawiBoy1428 · 2019-04-29T02:50:20.000Z

Malkoff’s are double thermally potted and done very well, a copper shelf, potting, driver with brass battery contact/sink, potting, spring. Heavy duty to say the least.

Agro · 2019-04-29T06:00:38.000Z

I view it like that:

1. Battery stop
Initially the spring compresses, transferring some impact energy to MCPCB. Then there’s stop which quickly transfers the rest of impact energy directly to the body.
2. Stiff battery
All the energy is transferred to MCPCB but unless the spring bottoms out - the transfer is much smoother and peak forces much lower.
BlueSwordM, did you try to bottom out with protected cells? That should be easier to do.

Big force on the driver will make it crack. A little smaller - will make it bend. Repeated bending will make it crack eventually.
Intuition tells me that both long stiff battery and a stop should work well enough. Note at the tail cap there’s a similar issue. Though I think it’s easier to support the tail PCB with the tailcap wall, at least in lights that don’t have tail switches.

But that’s not all of it.
F.e. this light died due to a sideways impact. Managing battery impact wouldn’t help.

This may be related to

Virisenox\_:

Related to previously asked questions, but what kills a flashlight when it’s dropped? I assume it’s just components coming loose from the impact, right? I think I read somewhere that linear 7135 based drivers tend to be more durable for that reason, because all of the components are fairly low profile.

But there’s also another thing making me think this is not a full picture. DB Custom’s EE X6 experiments. A spring collapsed there so it was not very stiff and there was nothing that would prevent it bottoming out. Yet the driver (as well as the tailcap) survived despite being directly hit with a cell multiple times.

Agro · 2019-04-29T14:20:59.000Z

I did a bit of learning on solder joint failure in drop shock. It happens to be a rather well studied topic and there’s even a standard way of measuring resistance (JEDEC JESD22-B111). In the era of everyone carrying one and often more electronic devices with them, drop resistance is a common requirement.

It is often said that SAC305 is not great for shock resistance. Though in most studies that I’ve seen it’s actually a great performer. There’s a number of specialized alloys that target high shock resistance, typically proprietary with undisclosed composition. I’ve seen indication that these are low-silver products.
F.e. Indium’s SACM is Sn0.5Ag1.0Cu0.03Mn

PCB finish matters.

Overall…the disconnect between common recommendations and study results that I found makes me feel that I don’t have any idea of what’s going on.

Interesting read:

circuitinsight.com

reliability_comparison_lead_free_smta.pdf

1559.86 KB

http://www.techni-tool.com/site/ARTICLE_LIBRARY/Indium%20-%20Choosing%20a%20Low-Cost%20Alternative%20to%20Sac%20Alloys%20for%20PCB%20Assembly.pdf
https://alphaassembly.com/-/media/Files/CooksonElectronics/Drop-Shock-Reliability-of-Lead-Free-Alloys—-Effect-of-Micro-Additives—-ECTC-2007.pdf

circuitinsight.com

Effect_Solder_Composition_PCB_Surface_Finish_Solder_Joint_Volume_drop_Shock_Reliability_smta.pdf

1340.99 KB

DB_Custom · 2019-04-29T15:51:54.000Z

Well, I probably forgot what actually happened in the X6 road test… the cell compressed the cell to it’s max and then dented in the top of the lap pull cell. This made it too short to reach the spring, so between some spring collapse and the dented cell the light wouldn’t work. I still have that cell and that light, both still work. But at the scene, under an extreme duress, the light did actually fail.

My thought to do the test was remembering those times something got left on top of the car, or on the toolbox on the truck, even on the bumper of the truck after looking underneath. So the 60 mph test was an extreme real world possibility. The light survived, took very little to resume working condition. Again though, had it been potted it might not have been repairable.

The Type III ano actually survived sliding on asphalt quite well, the major damage came when a pebble in the surface started the light flipping and it rebounded into the air then impacted very hard at landing. Comparatively minor damage even then, but the sliding action that could be heard in the video did virtually nothing to the light.

DB_Custom · 2019-04-29T16:08:26.000Z

I found the two video’s relevant to this conversation, uploading them to YouTube… it was September 06, 2014.

Agro · 2019-04-29T16:55:10.000Z

Spring collapse may be fixable - get stronger springs or go springless.
Performance of the rest of the light is remarkable and it would be good if future BLF lights could match it. Or exceed it.
[ADDED]
I mean: it doesn’t feature Elzetta-like wall thickness. It’s not made from high-end alloy. It doesn’t use potting. It doesn’t use any exotic construction. It’s not expensive. There seems nothing special about it but nevertheless it performed incredibly well. Maybe they just did something right…and I’d really like to know what it is.
Though seeing that was a single test of a single specimen makes me wonder if the result was not a pure luck. I guess we won’t be able to do tests at scale though…
[/ADDED]

I’m looking at X6 disassembly pics now.

Looks like there’s a generously sized ring for the driver to sit on. The driver doesn’t seem to be supported from the centre of its back which surprises me slightly. I wonder what’s the driver PCB thickness…

At the tail it looks like the spring presses on PCB which presses on the switch which presses on alu ring which presses on tailcap. So it’s complex but there is some support directly behind the spring.

BTW it just occurred to me that Zebralight or similar light engines are inherently safe against the batery damaging the driver - because it’s easy to make positive contact supported directly by the shelf.
Combine this with DQG style springless construction you have fat contacts at each end (which means relatively small chance of denting the cell) and the result seems very robust.

DB_Custom · 2019-04-29T16:54:33.000Z