Problem with a Bored Surefire L1 Lumamax & Malkoff Head

[Glow_Worm]

I need some help with a project I'm working on. I want to use my Malkoff drop-ins in a VME head with a Surefire Lumamax so that I can get the nice Malkoff beam with the great Surefire two-stage UI. I've tried the Malkoff head on a new Surefire LX2, and everything works fine with no problems. However, I feel guilty about using an LX2 as a host (since it's such a great light in its own right), so I want to make this configuration work on an L1.

I picked up an early-generation L1 with the longer body, and completely removed the electronics and bored the body to fit a 17670. So the body of the L1 is now just a straight-through tube, exactly like the new LX2. The only difference is that the L1 is 0.27" shorter than the LX2, which makes for an even nicer fit in the hand IMO. When I put the battery in the L1, it sticks farther out toward the rear of the body than in the LX2, but the tailcap still screws on all the way. Fig. 1 shows the two lights side by side for a size comparison, and Fig 2 shows them with a 17670 battery in each (the LX2 actually has two CR123s in it since I haven't bored it yet, but the length is the same as a 17670). Fig. 3 shows a closeup of the L1 and how far the 17670 sits inside it.

Fig. 1 LX2 & L1

Fig. 2 With 17670 batteries

Fig. 3 L1 battery closeup

The problem is that I can't get constant Hi to work. Momentary Low & Hi, and constant Low work fine, but even with the tailcap screwed fully in, I can't get Hi to stay on. There is still a tiny bit of travel in the button that allows me to get momentary Hi, but it won't stay on Hi via the twisty.

From reading posts from Milkyspit and McGizmo regarding their experiences in modding the L1, I think the problem is that the battery is preventing the tailcap switch from getting full travel in order to give me Hi when fully tightened. I don't know how to disassemble the L1 tailcap to shorten its travel, so if anyone has some suggestions on that, I'd appreciate any pointers.

But before I start mucking with the tailcap, I figured I'd try effectively shortening the battery in the L1 until it was the same distance from the end of the body as the LX2. This seemed like it should work, so I used a 14500 battery along with a spacer made of aluminum foil inside some shrink-wrap to test this out. Fig 4 shows some of the spacers I've tried, and Fig 5 shows the L1 with the spacer giving the same inset inside the tube as in the LX2 (a working configuration).

Fig. 4 Spacers

Fig. 5 L1 w/ spacer

To my big disappointment, this still didn't work. I just can't get constant Hi to work. It seems like everything is totally equivalent to the LX2 configuration (which works great), but I can't get Hi to stay on. I've tried varying the lengths of the spacer from much longer to much shorter, but I can't get any combination to work properly.

If I can get this to work, I think it'll be a great configuration, as it'll let me use a 17670, or a CR123 or RCR123 or a 14500 or even a regular AA with a spacer, along with a Malkoff M30 or M31. I also bored and gutted an L2 in the same way so that I can use 2xAA, 2x17500, 2x14500, or single-cell configurations in it with spacers (using a M60 or M61 for the higher-voltage combos). Unfortunately it has the exact same problem as the L1, i.e., no constant Hi, so hopefully if I can fix the problem in the L1 it'll apply to the L2 as well.

I love the L1 form factor and prefer the grippier knurling of the older style L1/L2 versus the LX2. Surefire's wonderful two-stage tailcap UI adds a very usable low level to the Malkoff drop-in, and the M30W provides my favorite combination of flood, throw, and tint of any of my smaller lights. So although I have a workable configuration with the LX2, I'd really like to get this to work with the L1 body.

If anyone has ideas on something else to try, I'd greatly appreciate any suggestions.

 

[Gene43]

Shorten the spring on the Malkoff?

 

[Glow_Worm]

I could do that, but it'd be a pretty permanent mod to the Malkoff, and I'm not sure it'll help. With the head on the body, I can push the rear of the battery to the full extent of its travel against the Malkoff spring pretty easily. Do you think that last little bit of travel is preventing the tailcap switch from going to Hi in the fully tightened position? I'd think that my tests with a shorter battery spacer should do the same thing as a shortened Malkoff spring.

But at this point I'll consider anything, so I'll definitely keep it in mind. Since you don't sell the M30W anymore , I'm a bit hesitant to mod it unless I know for sure it'll solve the problem. I'd be more inclined to shorten the travel within the tailcap somehow if I could figure out how, since I do have a spare L1 tailcap.

Thanks very much for your reply Gene; I love your products, have two M30Ws, one each M60 & M61W, one MD2, and three VME heads.

 

[Gene43]

Ah, I see your point about shortening the spring. The M30W's are quite hard to find now. Shortening the spring in the tailcap may be a better option.

 

[alantch]

Your battery may still be sitting too high. Have you tried swapping tail caps? Maybe use a RCR123 and work you way up with varying heights for the spacer until it works? HTH.

 

[sabre7]

My Surefire L1 was bored so I bought another one to keep it company :nana: ... sorry couldn't resist that one I'll leave now...

 

[Glow_Worm]

You're right, I think the battery is definitely sitting higher in the head when compared to the height of the positive contact in the unmodified L1 body. In the stock L1 the positive contact is fixed in place by the body & the driver electronics, whereas the battery is "free-floating" in mine. And then the length of the battery determines where the black plastic collar inside the tailcap contacts the negative end of the battery, and whether it'll have enough travel to engage Hi when fully tightened.

I tried adding a spring to the Malkoff to force the battery to sit lower in the tube, and then used a shorter spacer with a RCR123 battery, but I still couldn't get Hi to lock on. Maybe my spacers are just too crude and I haven't stumbled onto the sweet spot of the proper total length. But I'm surprised that it should be so sensitive, particularly when the configuration simply works flawlessly on the LX2 tube without any of this jury-rigging. Oh, and I have tried two additional tailcaps with the same results.

I definitely don't understand the exact mechanism of how the two-stage tailcap switch works with respect to how far it's screwed in versus any additional button travel, and where it is supposed to first engage the battery.

 

[Glow_Worm]

Ha, it actually took me a minute to get that! Thanks for the laugh, I needed it...

My Surefire L1 was bored so I bought another one to keep it company :nana: ... sorry couldn't resist that one I'll leave now...

 

[Kestrel]

Hello GW,

Thanks for linking off to this thread yesterday - I missed this the first time around. I have one idea and a few questions, the idea first:

The L-series bodies have a plated steel ring insert at the tail end of the body. I cannot ascertain if that insert is still in your bored L1 body. If it has come out or was removed during boring, you probably will have tailcap issues - you will loose critical overall length and ID, just where you need it the most - the specific electrical contact surface.

I'd highly recommend PMing AaronM on this, he provided some insight about this possible situation to me in a PM a while ago. If he could post in this thread, it might be a help to myself and others as well who need to watch out for this condition.


Questions:

• What is the overall length of your L1 body - I'm curious how its length might be somewhat different than the next generation aspheric L1 bodies.
• What is the exact bored ID of your L1 body? Excessive ID might make the electrical contact issue worse.
• What about trying your L1 with an unprotected 17670 to regain a bit of interior length?
• What about gently prying the three 'tines' inside your L1 tailcap to bring them closer to the L1 body?

To summarize, my thoughts are not about overall cell length being the problem, but the precise condition of the electrical contact area at the tail end of the body. It might be too short - measure the exact distance between [the electrical contact surface at the tail end of the body] to [the shoulder where the outer flange of the tailcap will bottom out on the L1 body] - compare this measurement with your LX2. I can also compare your measurement with my L2 and my L1. It also might have too large of an ID - this would contribute to that problem. The condition of the three electrical contacts in the tailcap might make that issue worse - make sure they aren't flattened compared to the ones on your LX2 tailcap.

 

[Glow_Worm]

Kestrel,

Thanks for resurrecting this thread; I'd run out of ideas to try and had set this project aside for a later time, so this is a good opportunity to bring it back out.

I *think* the insert at the end of the tube is still there, but it has definitely been touched by the lathe (or whatever my machine shop used to bore the tube). It's now a duller copper-color rather than the shiny chrome color it originally had, but I believe that the overall length of the tube is the same. There is still a small lip where the ring of material at the end meets the rest of the tube further in, hopefully you can see it on the pictures below.

Oh wait; the ring area is a copper-color on the bored LX2, but a dull silver-aluminum color on the bored L1. Let me look a little closer…

Damn!! I think that's it!

The ring is still there in the bored LX2 (which works fine), although scuffed up a bit by the lathe. But the ring appears to be missing from the bored L1 (which doesn't work right). Same with the bored L2 (which also doesn't work). Pics below:

Holy cow, I guess I just got lucky that the machine shop didn't knock the ring out of the LX2 as well. Maybe because they bored it last, and had a bit more practice after apparently munging the first two (the L1 & L2).

I think you may have solved the mystery.

Here's the dimensions you asked about for my different models:

​

What about trying your L1 with an unprotected 17670 to regain a bit of interior length?

Unfortunately I have no unprotected 17670 cells.

What about gently prying the three 'tines' inside your L1 tailcap to bring them closer to the L1 body?

That's a really interesting suggestion. Do you know how to take the tailcap apart so I can get access to them a bit easier? There's not much room for prying with the big plastic cylinder in the center being in the way. I'll be happy to try that if I can figure a way to reach those little metal thingy's somehow.

To summarize, my thoughts are not about overall cell length being the problem, but the precise condition of the electrical contact area at the tail end of the body. It might be too short - measure the exact distance between [the electrical contact surface at the tail end of the body] to [the shoulder where the outer flange of the tailcap will bottom out on the L1 body] - compare this measurement with your LX2.

Do you mean this distance?

If so, that's shown in the table above as well, though I don't think it's relevant between my two L1's since they're of two different generations (my L1 listed as "stock" is the current short-body version).

But I think that the missing ring do-hickey may be the key here. I'm guessing that extra thickness it adds might have something to do with the light not being able to lock in the Hi position even when fully tightened.

There's probably nothing I can do about this at this point; the rings are long gone, either destroyed in the boring process or discarded as scrap. But at least this can be a cautionary tale for other folks attempting to bore these tubes. Probably would be best to leave the tail end completely alone, and just insert the batteries from the head end exclusively.

Thanks very much for this Kestrel, I bet this is entirely the problem. I'll go ahead and PM AaronM as well to see if he might have any additional thoughts, or perhaps a solution for my tubes, although I suspect they're beyond repair at this point.

At least I know one thing not to do in the future!

 

[Kestrel]

You really should have come to me first. I don't know everything about the L-series, but I try to read everything about them & I think about them a lot.

The 'prying the electrical contacts up' suggestion was from AaronM IIRC, but I have another idea. Place some sandpaper on a flat surface (such as a tabletop) and grind down the outer flange of your L1 tailcap just enough so it won't bottom out on the exterior shoulder of the L1 body. That insert ring adds about 0.020" of an inch to the total length of the light body, and that distance must be pretty important (plus the width of the electrical contact surface - you've lost maybe half of it by now asking the slimmer aluminum edge to be the electrical contact, so the electrical contacts on the tailcap have a smaller 'target' to hit and have less of an chance of making secure contact with their respective 'anvils' inside the tailcap itself when tightened down).

If you remove ~0.020" from the tailcap flange, this should permit the tailcap to go down farther on the body, depressing the electrical contact 'tines' enough so that they should make contact with the 'high output' circuit path in the tailcap.

If that helps only marginally, try removing the o-ring from the body to make sure nothing is stopping that tailcap from going as far down on the body (& your 'new' deeper electrical contact surface).

See how much length is lost when the insert isn't present? That's critical IMO, and losing ID from your electrical contact surface at the same time won't help at all either.

I think the best way to avoid this is to shoot for a smaller bore ID, that way less material is lost from this ring, lessening the chance that it is removed during the boring process. Furthermore, a very slow feed rate on the lathe will exert less stress on this important component.

Glad I could help

 

[Brasso]

A bit too late, but I was thinking that this is probably the problem as well. Try putting a small ring of foil in the bottom of the tail cap and see if it will make contact for high when you tighten it. This might let you know if this is really the problem.

You might also be able to put a couple drops of solder at the bottom of the tailcap to solve the length issue without having to permanently mod the tailcap.

 

[Glow_Worm]

Kestrel, that seems easy enough. If that doesn't work though, it will probably also prevent that tailcap from being used properly on other unmodified tubes later right? (Or would it only cause the travel to be shortened a bit on other L1's?)

Brasso, I'll give your suggestions a shot first, since they're more reversible. If that improves things, maybe I'll try shortening the tailcap as Kestrel suggested.

Thanks very much for the tips guys, at least I've learned a lot more than I knew before!

 

[Glow_Worm]

Woohoo, success!!!

Brasso, your foil ring suggestion worked! I may futz around a little bit more with different thicknesses of foil, but rolling a strip into a ring shape and shoving it around the bottom of the tailcap makes all modes work now.

I even celebrated by adding a LX2 clip to the guy. Here's a pic of it next to my former LX2 host to show the slightly shorter size.

Thanks for figuring this out guys!

lovecpf

 

[Brasso]

Cool. Glad I could help.