LED Zeppelin
Flashlight Enthusiast
In brainstorming about a 2-stage upgrade for ARCmania's upcoming SuperFlashlight Mc38 (see TrueBlue's post in the B/S/T forum), TrueBlue gave me a spark that resulted in my following mod. My Arc LS was the guinea pig, and now sports a working 2-stage function. Please note that I have not searched the threads for this mod, and if it has been done before my apologies for the redundant post.
The basic principle is the same as the popular Fenix mod, the SPST Kroll on/off switch is shunted by a resistor and now functions as an on or resistored selector, while the on/off function is delegated to twisting of the tailcap.
This is a shot of the components: the disassembled Kroll with the spring and button cover removed, and two new parts - a 10 ohm resistor and an aluminum battery contact I fabricated to replace the spring and house the resistor.
The following shows just the switch mechanicals and the battery contact housing the resistor before soldering and shaping.
This shot shows the reassembled switch with the new components installed. The battery contact is sized to snap into the base of the Kroll where the spring used to seat. The free end of the resistor is bent to nest in the relief below the small silver spring, and tuck under that spring. The spring needs to be removed to accomplish this. Note that there is barely enough room to fit the resistor wire up the side of the housing. You need to make sure the wire is completely tucked in or reinstalling the switch assembly back into the tailcap will be difficult. If it feels like it's crossthreading, take it out and flatten the wire some more.
Here is another view of the finished switch.
And finally a shot of the installed switch and what it looks like from inside.
So far it works flawlessly in the Arc.
This modded switch will most likely work in a multitude of lights with a separate threaded tailcap. However, depending on the seal design, the light may or may not be sealed at the tailcap when untwisted. Try turning on the light, and see if you can use the tail as a twisty. Note that due to the original Kroll spring, the cap may come off before the spring looses contact with the battery.
You could do the same mod by shortening the spring and soldering the resistor directly to it, but due to flexing the resistor wires and/or solder joint may fail prematurely. Also make sure the resistor lead that goes up to the small spring doesn't touch the main spring or the resistor will be bypassed. That is the reason I strategically placed the body of the resistor in the side of my custom battery contact.
Depending on the host light and the internal clearances between the battery and the Kroll, the cutom battery contact may have to be longer in order to engage the battery before the tailcap bottoms out.
If there is sufficient interest I could look into having the battery contact reproduced by a shop. I'd specify a brass or copper material though for solderability. Also, a couple different lengths would make it adaptable to different lights, or a longer length that could be easily filed down. The shorter the better so the overall light length will be minimized and the seals engaged (as long as the tailcap doesn't bottom out). Appropriate resistor values would range from 5 - 60 ohms depending on the light and personal preferences. Or possibly there are members with lathes that could make these.
My design is by no means the final word. There are probably more elegant and more easily made alternate designs, but over a 12 hr timeframe from concept to prototype (with the distraction of my job thrown in) this is what I came up with.
The basic principle is the same as the popular Fenix mod, the SPST Kroll on/off switch is shunted by a resistor and now functions as an on or resistored selector, while the on/off function is delegated to twisting of the tailcap.
This is a shot of the components: the disassembled Kroll with the spring and button cover removed, and two new parts - a 10 ohm resistor and an aluminum battery contact I fabricated to replace the spring and house the resistor.
The following shows just the switch mechanicals and the battery contact housing the resistor before soldering and shaping.
This shot shows the reassembled switch with the new components installed. The battery contact is sized to snap into the base of the Kroll where the spring used to seat. The free end of the resistor is bent to nest in the relief below the small silver spring, and tuck under that spring. The spring needs to be removed to accomplish this. Note that there is barely enough room to fit the resistor wire up the side of the housing. You need to make sure the wire is completely tucked in or reinstalling the switch assembly back into the tailcap will be difficult. If it feels like it's crossthreading, take it out and flatten the wire some more.
Here is another view of the finished switch.
And finally a shot of the installed switch and what it looks like from inside.
So far it works flawlessly in the Arc.
This modded switch will most likely work in a multitude of lights with a separate threaded tailcap. However, depending on the seal design, the light may or may not be sealed at the tailcap when untwisted. Try turning on the light, and see if you can use the tail as a twisty. Note that due to the original Kroll spring, the cap may come off before the spring looses contact with the battery.
You could do the same mod by shortening the spring and soldering the resistor directly to it, but due to flexing the resistor wires and/or solder joint may fail prematurely. Also make sure the resistor lead that goes up to the small spring doesn't touch the main spring or the resistor will be bypassed. That is the reason I strategically placed the body of the resistor in the side of my custom battery contact.
Depending on the host light and the internal clearances between the battery and the Kroll, the cutom battery contact may have to be longer in order to engage the battery before the tailcap bottoms out.
If there is sufficient interest I could look into having the battery contact reproduced by a shop. I'd specify a brass or copper material though for solderability. Also, a couple different lengths would make it adaptable to different lights, or a longer length that could be easily filed down. The shorter the better so the overall light length will be minimized and the seals engaged (as long as the tailcap doesn't bottom out). Appropriate resistor values would range from 5 - 60 ohms depending on the light and personal preferences. Or possibly there are members with lathes that could make these.
My design is by no means the final word. There are probably more elegant and more easily made alternate designs, but over a 12 hr timeframe from concept to prototype (with the distraction of my job thrown in) this is what I came up with.
