# Tail Cap Spring Substitution Solution!



## Northern Lights (Dec 3, 2006)

I found I needed to replace OEM tail cap springs with some modifications done to lights. Many times the new power supply was not the same length as the original. 

For power packs a simple fix was to stuff the end with high-density foam as is found in packing material for electronic equipment shipping containers.

With any end cap jumping the spring with copper wire can lower the internal resistance. Copper is a better conductor of electricity than spring steel.

Longer spaces can be easily resolved with longer springs. With reduced end cap space due to longer battery systems it is difficult to obtain a wide short spring with sufficient tension to stabilize the batteries. 

As in the Nuwai TM-800-X3, a 3 D cell light converted to 4 C cells this system works well. In these cases I do the following.

Find reinforced hose as in wash machine supply hoses or automotive fuel and oil line hoses, use and appropriate diameter. Cut to a length that when it is place in the tail cap it will apply sufficient pressure to snub and stabilize the batteries. To find the length you can use a simple ruler or make a small ball or cylinder shape in modeling clay and put that in the cap and screw it onto the batteries, remove it and it will be the thickness of the compressed insert. Cut the insert appropriately.

I then wrapped the section of hose in with one piece of copper braid, a piece of de-soldering braid, for three wraps and solder the ends together. I glue them into the center of the cap with silicone glue or any version of the Goop brand that is tougher but elastic glue. The glue must be elastic to absorb the compression. Put the glue into the center of the ring of braid. Do not insulate the braid from the tail cap by gluing the braid that runs over the end of the hose. You could also use some sort of friction retention like the above mentioned high density foam cut into pieces that hold the insert from the outer surface of the end cap. In the case of shorter inserts I use small enough diameter hose so that if I choose to revert to the original length batteries I can just place the old spring over it without removing it.


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## Waffle (Dec 3, 2006)

Great idea..


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## missionaryman (Dec 20, 2006)

yeah really - great idea!


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## KillingTime (Dec 20, 2006)

innovative.


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## LuxLuthor (Aug 6, 2007)

Worthy of recognition even a year later!


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## jimjones3630 (Sep 25, 2007)

Recently applied this fix to two different lights. 

Tungsram 56580, the 64430 substitute in 4C with 3xA123s. after swithing hosts notices a yellowish tint not present before. switched tailcap mods, first was 10g jumper wire on tailspring, then applying NL,s method using thick wide old auto batt. braided copper the light shinned white white brights. What a difference.

Second light 5761 in 3C with 2xA123 NL,s fix inceased 0.12vbulb upto 6.4vbulb. Visiably brighter. read somewhere every 0.1v makes about 100 lumen difference. Sure looks like it.

Thanks NL


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## RichS (Feb 1, 2008)

I just used this solution it for a ROP and Mag85 I just built using 18650s. I originally modded the tailcap spring like many do, but due to the stiffness and hardness of the spring, it was scraping the bottom of the batteries pretty badly. I also wanted to reduce some of the resistance to get better output.

I used a slightly varied approach to this solution, and bought two different sizes of hose, where one would fit snug inside of the other. This allowed me to wrap the smaller hose on the inside, stuff it inside the other which secured the wrapped de-soldering braid without having to solder it together. I then used magic wrap (a roll of rubber stripping that "sticks" to itself) to wrap around the outer tube to create the perfect diameter for a snug fit for the spring replacement so it would fit in the tailcap and not fall out. I didn't want to glue it in, because I may want to take it out occasionally and use Deoxit to clean deoxodize the contact surfaces to get better connectivity.

So....I screwed everything back together and WOW! It absolutely did increase the brightness/whiteness of the light. In my estimation it was an improvement of around 25-30% to my eyes. Thank you for the ingenious idea Northern Lights!!

Here's some pics of the mod:


high-temp auto hoses





Magic wrap and de-soldering copper wick





New connector for tailcap


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## Northern Lights (Feb 1, 2008)

That looks good! Thank you for your gracious PM. I have on several used in lieu of an outside tubing just plain shrink wrap to hold the braid down. When I put an NTC in it for soft start,now I always use fuses in there too, I put one leg of braid up and one leg down with the electronics in the middle and the shrink around the outside to hold the loose end of braid. Those only have one braid contact to the battery so I usually use 3mm wide braid for those.
To keep them from falling out I have used a top cover of shrink or a wrap of bicycle inner tube rubber. On some of my LED conversions I have put a few lumps of silicone rubber glue in the center donut to hold it in place. The glue gives with compression so there is a good ground contact.


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## cat (Feb 1, 2008)

Excellent. Thanks for showing us. 
That's also the cleanest job of de-anodising I've seen. What did you do it with? I can see some buffing swirls on the left one, I think.


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## RichS (Feb 1, 2008)

cat said:


> Excellent. Thanks for showing us.
> That's also the cleanest job of de-anodising I've seen. What did you do it with? I can see some buffing swirls on the left one, I think.


Thanks Cat. Well, It's probably because I poured straight lye into each cap and let it sit for about a minute before pouring it out. I did this a couple of times with each cap. One of them looked a little cloudy after this, so I tried to polish it up a little with my dremmel to make sure it had a good contact surface. After doing that, I read something about 1 part lye to 10 parts water, but...too late. It worked out fine though. I finally charged my batteries for my Mag85 and switched it on for the first time...:huh: That's probably the whitest incandescent light I've seen yet! I still haven't gotten my Kai reflector in yet, so short bursts only. The stock reflector has already started to melt near the bulb...

This moddin' stuff is fun!


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## Northern Lights (Feb 1, 2008)

RichS said:


> This moddin' stuff is fun!


YEP! Sho' 'Nuff!:twothumbs​


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## jimjones3630 (Feb 2, 2008)

hose in a hose, I like that. looks secure and won't fall out.


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## Roland (Aug 26, 2008)

I see low resistance switch fixes and low resistance tailspring fixes but I see noone connect the top of the tailcap spring to the switch directly. 

Is there no significant gain to be made by soldering the tailcap spring with a copper wire directly to the switch?


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## lctorana (Aug 27, 2008)

I'e done exactly that, but not in a Maglite.

When you do this, you need to put an opposite twist in the long wire before you screw the tailcap on to avoid brealing the wire.

Also, it only works if the batteries are loose in the barrel; the wire must be free to move, er, freely. (Unless the spring can rotate freely in the tailcap, of course, which is rather hard to arrange.


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## Northern Lights (Aug 27, 2008)

lctorana said:


> I'e done exactly that, but not in a Maglite.
> 
> When you do this, you need to put an opposite twist in the long wire before you screw the tailcap on to avoid brealing the wire.
> 
> Also, it only works if the batteries are loose in the barrel; the wire must be free to move, er, freely. (Unless the spring can rotate freely in the tailcap, of course, which is rather hard to arrange.


In the arrangements I have used and published here the batteries are not loose. The braid is soldered into a loop aroung the tubing which is neoprene. Bumper is glued into place, the center holds silicone seal or glue but care is taken that the contact between the copper braid at the junction of the tube and tail cap is not infringed. The amount of snubbing is just enough to prevent the batteries from moving; since there is very little compression available in the neoprene the tension is quite high but that also means within two turns, usually one, the tension is released on the batteries. The copper braid slips easily accross the back of the batteries for that few turns. This is one example, I have used the method many times. I can understand if you put too much tension on the fit the system could twist the snubber and braid up.

I even put fuses into it and never had a twisting problem but if you do try a little silicone lubricant, even heat sink grease would work.

This one is fused and an additional wrap of shrink is put around the outside of the tubing to hold in place. In D cell mods the fuse can go inside the tubing. The above light is not a mag, it is a D cell Shyguang Nuwai TM-800X3, tri-Lux III converted to Cree P4 with C cells 

There are no absolutes in modding, there always is a solution. You just need to design it and find it.


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## SafetyBob (Aug 27, 2008)

Thanks for posting the pictures Northern, this is exactly what I need to see. Been thinking about how to do this very thing and always coming up with very difficults solutions. 

This seems to be as easy a solution as could possibly be thought of. 

Again, thanks, this just saved me ALOT of time. I can do this.

Bob E.


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## lctorana (Aug 27, 2008)

Perhaps I should have explained more clearly.

I was referring to the question immediately above my post, asking about whether anyone had ever wired the spring to the switch directly with a long wire.


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## Northern Lights (Aug 27, 2008)

lctorana said:


> Perhaps I should have explained more clearly.
> 
> I was referring to the question immediately above my post, asking about whether anyone had ever wired the spring to the switch directly with a long wire.


 
Oh well, more good info on a useful thread, it keeps the thread alive! CPF is to share ideas; isn't it a great, good place to meet like minds so keep adding to the thread it is young and needs to grow.


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## SafetyBob (Aug 27, 2008)

lctorana, I have not done it yet because I have not built a flashlight up yet that has built in charging jack on the outside. When I do, I will run a wire up from the bottom to (and through) the switch. 

However, makes just as much or more sense to have Lux build me some packs using Eneloops for my LED lights and put charging jacks on those too. Then I can run dedicated wires around and never move them again. 

Sometimes for ease of use for family members it just makes sense to use regular batteries in flashlights so they understand the concept......

My Triton2 unfortunately seems very intimidating for them to use. 

Bob E.


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## Northern Lights (Aug 28, 2008)

I put the jacks on the left at 60 degrees as I am right handed and when I pick it up this conficuration is not in the way and can still have the lead attached. I am now using only de-solder braid in the jack assembly now as is folds better. I clip off the connectors on the bottom of the jack and after it is wired cover it in shrink to help insure that no positive lead or connection is shorted. I am tempted to use a liquid insulation dip next time I do this as it would be easier to insulate it that way.


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## SafetyBob (Aug 28, 2008)

OK, got it. I am right handed also. I just tried visualizing this with one of my [email protected] and it seems really handy. 

Thanks for the tip on using the braid. Please let us know how the liquid dip stuff works. If it does, please tell me brand name and the works please....

Bob E.


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## Northern Lights (Aug 28, 2008)

SafetyBob said:


> OK, got it. I am right handed also. I just tried visualizing this with one of my [email protected] and it seems really handy.
> 
> Thanks for the tip on using the braid. Please let us know how the liquid dip stuff works. If it does, please tell me brand name and the works please....
> 
> Bob E.


You can find this in Home Depot, Radio Shack, ACE, etc.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=36821http://search.harborfreight.com/cpisearch/web/search.do?keyword=LIQUID+INSULATION

I have used it before in other applications, I really do not see any surprises for the jack.


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## SafetyBob (Aug 30, 2008)

Thank you, thank you, thank you!! That will be perfect for my boarding projects. At this early stage of my electronic component building it is UGLY. This will save some shorts against little things that get in the way. 

Will get some tomorrow. 

Bob E.


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