Z41 as a reisistance "mod"?

[kramer5150]

I read somewhere on here that the Z41 twisty has a higher resistance than the other SF switches.

Can it be used as a resistance mod when using the P91 with 2xIMR18650 ?

thanks in advance.

 

[ampdude]

I wonder why that would be said. It just seems like a larger version of the Z52. Basically a spring and a chunk of aluminum.

 

[csshih]

yeah. I found it really odd that a *twisty* which is just a piece contacting the tube would have any sort of resistance that would affect things. odd......

 

[Black Rose]

I wonder why that would be said. It just seems like a larger version of the Z52. Basically a spring and a chunk of aluminum.

Here is a post by ElectronGuru, summarizing Moddoo's test results:
http://www.candlepowerforums.com/vb/showpost.php?p=3393046&postcount=37

 

[JCD]

I read somewhere on here that the Z41 twisty has a higher resistance than the other SF switches.

I tested ~5 Z41 tail caps, including the "guts" of a pre-lockout SF twisty, and got consistent readings of ~0.6 Ω. The leads of my DMM (Blue-Point EEDM503ASCH) by themselves show a resistance of ~0.4 Ω. The specs of my DMM show a measurement resolution of 0.1 Ω and an accuracy of ±0.5% reading ±1 digit.

 

[csshih]

wow, thanks for the information.

 

[JCD]

This thread has left me curious about the SureFire Z41 "twisty" tail cap. I went through bigchelis' thread containing actual lumen outputs for various lights, looking specifically for lights that were tested with both the Z41 tail cap and the McClicky tail cap. I found three such comparisons, in posts #573, #636, and #637, summarized in the table below.

In two of the comparisons, the Z41 and the McClicky perform very similarly, with the output of the McClicky equipped light being, on average, only about 1.5% higher than with the Z41 on the same light (σ ≈ 3.6%), with the Z41 outperforming the McClicky in 4 of 10 readings.

However, in one of the comparisons, the difference between the two tail caps is significant. Why is that? It seems strange that a switch comprised of a spring and a chunk of aluminum could perform so badly. What, exactly, caused the results?

Possibilities include:

Experimental error. Perhaps the readings were incorrect. The Z41 might not have been screwed down completely, making less than optimal contact with the flashlight body and/or cell. Maybe there was a small piece of debris preventing good contact. Perhaps the host and Z41 were significantly warmer when the Z41 was tested than when the McClicky was tested.

Battery length. The tests were done using a SureFire 6P, which, in conjunction with the Z41, was designed specifically for two times CR123A cells. These two cells combine for a 69 mm length. I was unable to find the length for an AW IMR18650 cell, but an AW P18650 has a length between 67.9 and 68.5 mm. Without a protection circuit, I would expect the IMR cell to be slightly shorter. The Z41 may simply not get as much contact with the IMR18650 as it does with the primaries it was designed for.

Damaged or faulty Z41. It could be that the tail cap used had a spring that had been shortened slightly from heat in high current applications, rendering it unable to get optimal contact between the spring and the cell.

Too much current. The highest current draws I was able to find in this post for a SureFire approved configuration on the Z41 was 3.7 A, but that was with 4x CR123A cells. While the Nailbender SST-90 drop-in was drawing a current of 4.91 A at the tail, it was from a single 3.6 V cell. Would the performance limits of the tail cap be dictated by current rather than power?

Obviously, multiple factors could have combined to cause the results shown by the test.

The sample size of the comparisons is too small and the results too inconsistent to draw any firm conclusions about the performance of the Z41. The results do, however, raise some interesting questions.

 

[MrGman]

I tested ~5 Z41 tail caps, including the "guts" of a pre-lockout SF twisty, and got consistent readings of ~0.6 Ω. The leads of my DMM (Blue-Point EEDM503ASCH) by themselves show a resistance of ~0.4 Ω. The specs of my DMM show a measurement resolution of 0.1 Ω and an accuracy of ±0.5% reading ±1 digit.

You cannot take accurate resistance readings in the less than 10 ohm range without using a 4 point (Kelvin) connection type meter. You may think that because you subtract out the resistance of the leads you get an accurate reading but you don't. You need to measure low resistances across a milliohmeter bridge using separate leads to provide current and measure the voltage drop. Regardless of what gauge wire your leads are, the contact points create a voltage drop on their own and it throws the readings off. The Z41 twisty is not anywhere near 0.2 ohms. There is no hand held two leaded multimeter that can accurately measure resistance below 10 ohms regardless of what they say, and definitely not something below 1 ohm. That is why expensive resistance bridges using 4 point leads are around. I will try and get around to measuring a Z41 twisty and get a real reading again. I did this a long time ago, it was very good compared to everything else because it is nothing more than a "chunk of metal and spring".

 

[JCD]

You cannot take accurate resistance readings in the less than 10 ohm range without using a 4 point (Kelvin) connection type meter. You may think that because you subtract out the resistance of the leads you get an accurate reading but you don't. You need to measure low resistances across a milliohmeter bridge using separate leads to provide current and measure the voltage drop. Regardless of what gauge wire your leads are, the contact points create a voltage drop on their own and it throws the readings off. The Z41 twisty is not anywhere near 0.2 ohms. There is no hand held two leaded multimeter that can accurately measure resistance below 10 ohms regardless of what they say, and definitely not something below 1 ohm. That is why expensive resistance bridges using 4 point leads are around. I will try and get around to measuring a Z41 twisty and get a real reading again. I did this a long time ago, it was very good compared to everything else because it is nothing more than a "chunk of metal and spring".

Thanks for the info. I knew that accuracy and precision would suffer on measurements of low resistance, but I didn't realize that there was no way to accurately take such measurements at all with a handheld DMM. I look forward to seeing the results of your measurements whenever you are able take them.

 

[Meterman]

Thanks for the info. I knew that accuracy and precision would suffer on measurements of low resistance, but I didn't realize that there was no way to accurately take such measurements at all with a handheld DMM. I look forward to seeing the results of your measurements whenever you are able take them.

Of course you can accurately take measurements with a handheld DMM even down to the resolution of 1μΩ if you choose the appropriate brand and model. To measure low resistances I use my MetraHit 27M (in a 4-wire rig as you may imagine).

Wulf

 

[JCD]

Of course you can accurately take measurements with a handheld DMM even down to the resolution of 1μΩ if you choose the appropriate brand and model. To measure low resistances I use my MetraHit 27M (in a 4-wire rig as you may imagine).

Wulf

Thanks for the correction.

 

[kengps]

....Just did some light meter testing with my 2.8 Amp SST-50 in a Z2 host. I tested McClicky vs two different Z41 tailcaps and got identical numbers with both Z41's.... A 35% loss vs the McClicky! Also I can see that there is no way the metal sleave can touch the neg terminal of the battery because it would hit the plastic case on the perimeter of the battery. So all the Amps flow thru the Z41 spring. I gotta wonder though if something else is going on, the springs don't look that much different. Maybe the Brass Mcclicky is making better contact with the Host tube? It's just too much.

Edit- Actually it matches the numbers for the SST-90 test above....893 lumens vs 688 is a 30% loss.

 

[JCD]

....Just did some light meter testing with my 2.8 Amp SST-50 in a Z2 host. I tested McClicky vs two different Z41 tailcaps and got identical numbers with both Z41's.... A 35% loss vs the McClicky! Also I can see that there is no way the metal sleave can touch the neg terminal of the battery because it would hit the plastic case on the perimeter of the battery. So all the Amps flow thru the Z41 spring. I gotta wonder though if something else is going on, the springs don't look that much different. Maybe the Brass Mcclicky is making better contact with the Host tube? It's just too much.

Edit- Actually it matches the numbers for the SST-90 test above....893 lumens vs 688 is a 30% loss.

Interesting.

I don't think the Z41 is designed to contact the negative terminal of the battery except through the spring.

It still seems odd that the Z41 would perform worse than the McClicky in some situations, but better in others. It's unfortunate that we don't have a larger data set, so we might be able to figure out exactly what is going on.

Edit to add: @kengps Is your Z2 bored to accept 18650? I wonder if/how that affects the contact area between the aluminum piston in the Z41 and the flashlight body.

 

[kengps]

It is bored, and you're right, there is very little contact area left for the Z41 to hit the edge of the tube. In fact a rough measurement shows the outer Dia of Z41 to be almost the same as ID of bored Z2 tube.
I do think the McClicky is subject to variation from the spring rotation. It changes the amount of spring in contact with the switch body. I soldered my spring to the body after rotating the spring to put maximum spring length in contact with the metal switch contact point.

BTW- My AW 18650's are 2mm longer than my AW IMR's. You mentioned that as a possible cause.

 

[kengps]

JCD...I think you found it. Most of these lights that sport Nailbender's are running bored tubes for 18650's. My tube is 18.6mm ID and a guess of the Z41 was 18.5mm - 18.7mm OD by my guesstimate. You wouldn't happen to have the measurement of a Z41 metal part OD would you? I haven't taken mine apart.

I just measured a second Z41 and it was a bit bigger. Maybe .70mm larger diameter. The smaller one was off a G2 Nitrolon.

 

[MrGman]

Of course you can accurately take measurements with a handheld DMM even down to the resolution of 1μΩ if you choose the appropriate brand and model. To measure low resistances I use my MetraHit 27M (in a 4-wire rig as you may imagine).

Wulf

I should have stated more specifically any 2 wire handheld meter. If you found some that have 4 terminal (Kelvin clip) connections as this appears to have then it should be able to measure into the milliohms range. I doubt very seriously the accuracy of a handheld meter measuring down to 1 micro ohm. We have lab standard units that have a hard time going below 5 u ohms accurately. Claimng it and actually doing it are 2 different things.

 

[JCD]

You wouldn't happen to have the measurement of a Z41 metal part OD would you? I haven't taken mine apart.

I have the metal part from a pre-Z41 twisty, but all of my actual Z41 tail caps are still assembled. The pre-Z41 part has an OD of about 20. mm, but I don't have calipers or micrometer to obtain a precise measurement. I have no idea if it has the same dimensions as a current Z41 or not.

 

[MrGman]

Now you guys aren't forgetting that the threads on the Z41 are anodized and not conductive right? The only conductive parts are the bare metal exposed ring that touches the back edge of the host tube and the central spring to touch the battery. When the tailcap button is pushed forward it allows the recessed metal ring to touch the very edge of the host tube. Most other "clicky" type switches have no anodization on the threads of the tail cap so they have a lot more contact surface area. Using a bored out tube to hold 18650's I have found makes for barely minimal contact to that ring. I had some Solarforce hosts that took 18650 batteries that either made only intermittent contact or none at all and could not use the Z41 tailswitch because of that. I had some of the older style Solarforce hosts that still only take the 17mm max width batteries and it works fine. You may be getting higher resistance and less output simply because you have reduced your contact area significantly to bored out tubes that take the 18650 batteries.

I found my Z41 tailcap and will try to remember to take it to work tomorrow to measure it (again). I know I did this a long time ago and its resistance was insignificantly small.

 

[JCD]

Using a bored out tube to hold 18650's I have found makes for barely minimal contact to that ring. I had some Solarforce hosts that took 18650 batteries that either made only intermittent contact or none at all and could not use the Z41 tailswitch because of that. I had some of the older style Solarforce hosts that still only take the 17mm max width batteries and it works fine. You may be getting higher resistance and less output simply because you have reduced your contact area significantly to bored out tubes that take the 18650 batteries.

That is exactly the possibility I was curious about when I wrote in post 13: "Is your Z2 bored to accept 18650? I wonder if/how that affects the contact area between the aluminum piston in the Z41 and the flashlight body."

You described the possible scenario I hinted at much better. Thanks!

 

[Moddoo]

Hello guys,

I would like to clear up a few things here.

First, to answer the OP, yes, you can use a Z41 to add resistance to a light that may be on the edge of insta-flash. Exactly how much resistance it adds, I do not know.
The higher current that you are dealing with, the more of a difference resistance in the circuit makes.

Second, A bored out Surefire tube does not have a smaller surface area for the Z41 to contact. Take a look at an un-bored light. The nicely machined section at the end of the tube, plus the tiny chamfer on the ID of the tube add up almost exactly to the diameter that the 18650 lights are bored to.

Third, The resistance problem with the Z41 lies in the long thin spring.


I have some "ZERO RESISTANCE" Z41 mods coming out for you guys in about a week.
These parts will allow you to run as much current as you like through the tail with no measurable losses.