These washers may be in uxcell.com
This may be a size
http://www.uxcell.com/30mm-40mm-15mm-metric-ring-shape-copper-flat-washer-pcs-p-687105.html
This may be too big
OK OK sorry for asking (I’ll take a srk driver to the hardware store next time to find a disc for my RMM V2 drivers) didn’t mean to detail the thread 
Not sure on electrical performance, but Zinc-plated steel looks nice and is cheap and easy to find.
I did it to my SP03 Here
electrical conductivity of copper is 100,silver 106,iron 17.
Yikes :person_facepalming: Actually steel is listedd as “3-15”, even the zinc is only 27!
What material are the battery contacts though?
Pure nickel
I have 3-channel PWM working in the bistro-tripledown firmware, and the ramp calculator supports 3+ channels. However, the third channel runs at 31 kHz and I don’t know how to slow it down. And, as you noted, it would eat a pin currently being used for other purposes.
It can make the mid-high modes more efficient, but it’s a pretty big tradeoff due to the added driver cost and complexity, and probably eliminates the indicator light. It also tends to put a second elbow in the ramp and makes the driver even less friendly to changes in the number or type of emitters.
Usually get them at the Parker/Exotic store- we have one in our plant. But you can get them online too.They are actually copper hydraulic sealing rings (crush washers) - they come in various sizes and thickness. I use them for making driver adapters, 26650 battery tube spacers, heat sinking drivers and contact rings for SRK/M6 builds. Shouldn’t be a problem to get in China.
I started a new thread for a possible driver upgrade/option for the Q8 that would allow for a pretty easy 4S cell conversion and the use of XHP35’s in place of the XP-L’s.
There is the possibility of up to 10k lumens with XHP35’s based on the fact that Acebeam gets 2600 lumens out of an XHP35 HI in lower bins then we can get now in the K70.
If anyone is interested here is the new thread: The Texas Buck driver series, Q8 / Skyray King 2S/4S buck driver RELEASED!
Also got some discussion going on in this thread about a possible Q8 driver with 3 channels and a bank of 7135’s to allow for a regulated low and medium mode, which is honestly all you will need most of the time with a light like this IMHO. Would also net you more lumens and less heat in all but the highest modes as well.
Ooops, Yes - that's an old post of mine. Since then, learned much 
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The size of the copper washer in Roche M170 is 20mm x 29.9mm x 1.1mm
The most similar at Uxcell a14122500ux0519 (22mm x 30mm x 1mm)
Here are some links… https://www.amazon.com/uxcell®-30mmx38mmx1-5mm-Copper-Washer-Sealing/dp/B00W97KNTK/ref=sr_1_52?s=industrial&ie=UTF8&qid=1471302091&sr=1-52&keywords=copper+washers Amazon.com https://www.amazon.com/20pcs-Flat-Copper-Washer-22mmx27mmx1-5mm/dp/B00WW53JKY/ref=sr_1_14?s=industrial&ie=UTF8&qid=1471301898&sr=1-14&keywords=copper+washers
TA, NICE!
Say now that we are on the topic of a washer…BISMUTH!
This conducts heat 50 times worse then copper
Argh no it is has a high resistance
But bismuth bronze has a high conditivity, it loses the advantage of low heat conductivity
BUT the bismuth n the bronze acts as a libricant thus a disc made of this would have the advantage of not waring down.
I really enjoy this idea.
By the way we still havent see tail pcb shape/design. 4S convertion requires insulated tail pcb with battery pads connected in pairs.
Search thread tail PCB is spoken about and designs are posted.
The battery tube and tail are Thorfire design and our design is not emailed yet.
First we have the housing ledboard reflector and driver to tackle.
Here you go
Copper ‘rings’ are used as sealing washers (sometimes called crush washers or banjo washers) to attach hydraulic and oil lines, and come in a variety of sizes.
Copper oxidation shouldn’t be an issue. Wipe with steel wool and you’re good as new. Or tin the whole ring or disc with solder before installing. I doubt oxidation has a serious enough electrical effect to matter though it may be measurable in a lab. All houses have copper connecting to various metals through pressure-type connections with no problem except when connecting with aluminum. Would be an easy mod.
Phil