DIY McR-18 reflector shortening

After receiving PM's asking about McR-18 shortening, I took some pics to share while modding last night. Pretty much all you'll need are: A sheet of 220 grit abrasive (stay away from wetsanding), a flat working surface, canned computer duster and calipers for measuring. No worries if you don't have calipers handy, a good way for referencing reduction is to match up height with an IMS 17mm. When you're finished, the McR-18 will fit as a nice replacement for IMS SO17, NX-01, NX-05 and Fraen optics inside an ARC LS.

'Superfine' 220 aluminum oxide sandpaper works well and costs only 75 cents per sheet from any Canadian Tire or Home Depot, cut that into quarters and you'll have enough for modding several reflectors. Basically the technique is to work the upsidedown reflector in a circular motion, using even hand pressure. It's a good idea to spin the reflector 1/4 turn each time you measure or clean off the working surface, so that material comes off evenly. Measure often, at different points as well to make sure the reflector is straight. You'll get some aluminum dust as well, so please take precautions by wearing a dust mask. Avoid touching the reflector surface to remove dust contamination and use computer duster to blow off anything unwanted. If there are any small burrs around the rim, gently run a toothpick around to scrape off debris and repeat with computer duster until everything's gone.










You'll notice there's a small lip where the reflector material was removed, this lines up with the ARC LS bezel perfectly and is not visible (unlike the IMS SO17).




IMS SO17 vs. shortened McR-18



That's basically it, happy modding!

GOOD JOB

I assume this method could also be used to get a McR-18 reflector to fit in a 'classic' JIL-CR2 head (the new JIL JCR2 heads are designed to fit the McR-18, but the classic JIL's are not).

So, how much did you take off and what is the aperture size now ?
Nice job !

EDIT:
Went to the store, bought 220grit, started sanding, and within 3 minutes,
I got 1.5mm off the reflector.
Calculations from a friend of mine said that if I take 1.5mm off
the front, the aperture (front opening of the reflector) will be about 16.7mm,
which also happens to be the aperture of the Arc LS...

There was indeed some dust in the reflector, which I got rid of using
a can of compressed lungs :naughty: :naughty: :naughty: .

In the end, I won 1.5mm of Arc Landscape ! :rock:
Very nice ! (pics later)

Now to build myself FluPIC-engines for non-First Run Arcs.... :naughty: .

Cheers !!

Great that you were able to repeat these results Bombel, hope you didn't 'sputter' the reflector with your compressed lung technique

The McR-18 originally measured 12mm and the modded height is 10.75mm (IMS SO17 height), for a total reduction of 1.25mm. The aperature diameter will decrease and the rim's edge will grow as more material is removed. I didn't measure with calipers due to risk of scratching, but the reflector edge lines up perfectly with the 16.7mm ARC LS lens opening.

vortechs, don't know if the modded reflector will fit older JIL-CR2's since I don't own one. Maybe some of the JIL modders can chime in, but please let us know if you are able to make it fit!

HTH,

Great job.It's so satisfying when you do it yourself.
I am about to work on three McR-18 reflectors myself for a project.

i've done this mod over half a dozen times.. i use a lot harsher sandpaper on a bench sander.. i've never had a problem with the alm. dust.. i just ignore it as the first layer that builds up on the refl. protects it through the procedure and it all blows right off with one dust from the canned air.

I make the mod to fit them into the groovy. .and it really significantly improves the output both in quality and lux! (example.. 900 lux up to 1200).. that's a huge gain!

sanding the height down i just hold it against the belt sander a few seconds at a time, rotating as much as i can to keep it even.. and check every few passes with the dig. caliper to check the height.

I think i cut them down to 10.6 for groovy use.. IIRC.. the IMS17 needs to be sanded down just a touch to fit properly but maybe not any more with groovy vs CNC123.

I also have to sand down the sides if i ever want to remove it.. it can be press-fit ONCE into a groovy w/o sanding down the outside, but non-destructive removal.. i wouldn't bet $10 on it.

Thanks for sharing the detailed post.. i'm sure a lot of people can benefit from it, and i didn't have time to make a similar post, incl pictures etc.

-awr

mosport said:

The McR-18 originally measured 12mm and the modded height is 10.75mm (IMS SO17 height), for a total reduction of 1.25mm. ... the reflector edge lines up perfectly with the 16.7mm ARC LS lens opening.

Click to expand...

I wish I had written down your measurements when I did this mod. I had to go slow because I forgot to write down how much I was supossed to sand off. It took a while, but I also reduced ~1.7mm off the MrR18.

Edit to add:
I just re-measured the modified reflector - 10.24mm is where I stopped, but I could still shorten it a few fractions of a mm more and still match the opening of the LS. I'm not sure why I'd want to do this, though, since the gap between the body of the light and the tailcap is ~1mm.


This is what I got - beamwise, against an L2P (on the right):




The light is in my pocket as I type; I've kept forgetting to post and let you know how the mod went.

:thanks: for building that module for me! I compared it against my stock LSL-P last night and I as much as I like my trusty'ol LSL-P... I think it'll end up being modded at some point...