Got Lucky - Right Place at the Right Time

[larryk]

Yea that vest is unreal,it weighs about 23 pounds. Maybe it's a combo battery pack bullet proof vest if your shot in the back. I was thinking of making a removable battery box that could be attached to the base of the MR somehow. That would make it self contained and give a more stable base for it to stand on. It's quite tipsy the way it is now. I have a pair of 4s 5000ma Lipo batteries that I used in an RC boat. Running them in series would give about 30 minutes on high. The heat sink would need to be addressed though.

[BVH]

8S would probably over volt it if fully charged to 33.6. I've been searching and searching for a nice looking small box for the bottom and a nice, simple sliding and locking rail for ease of connect/disconnect but have not come up with anything I really like. I was going to use 2 each, 6S/4Amp in P for 6S/8Amp. Probably 25-30 minutes. I want it to look really good but have not found any boxes that do that. Nor any thin, simple sliding and locking rails. Please help!

[larryk]

I haven't looked for a battery box yet but I got a chance to test the light with the tube extended 1 inch. At first it looked very promising. At the short ranges (40 to 50 yards) I had available the beam was perfect. Much tighter and a perfect circle. But when I briefly shinned the light in the sky I could see that the beam about halfway up started to expand wider than normal.

[BVH]

I split the case on one of the MR's to replace a raspy sounding fan. Upon initial inspection, I noticed what looked to be a simple hold-down bracket for the ignitor (pic) had one of the two soldered attachment rods come unsoldered. Cleaned it up and re-soldered it. The fan coming out is a 12V, 2.5 Watt, 24 CFM unit. The fan going in is a 12V, 3.5 Watt, 29 CFM unit. I wanted to provide a little more cooling capacity over the 40 heat pipes. In earlier run tests with the front lens out, I noticed that a tiny bit of magic smoke was escaping after about 14 minutes of running. Despite a couple attempts to get it smoking and then quickly turn it off and ID the smoking culprit, I could not see anything. There is nothing flammable or smokeable in the bulb chamber except maybe the ring style Cathode electrical crimp connector insulation piece (red in the pic). So I removed it, as it serves no purpose. I also noticed a white residue coating both halves of the black body in the bulb chamber. (pic) I cleaned this off with some 95% alcohol. I also wanted to order a spare bulb and have been holding off to positively ID the bulb via a part number on the body of the bulb. It looks like the part number is covered by the yellow o-ring so I've sent pics to a bulb expert to see if he can tell me whether it's the Elliptical model or the parabolic model. I need the Elliptical, which is harder to find and more expensive. I won't know if I've fixed the magic smoke issue for a few days.


Note red crimp connector insulation piece. Suspected magic smoke source?







A little hard to see but the copper'ish looking rod on the right side has come unsoldered on the bottom half.




Repaired




Bulb mountig system front view




Bulb mounting system side view. Note the double concave lens about 3/4" in front of the bulb window




Heat pipes and fan (blurry, will fix later)




White residue in bulb chamber

[get-lit]

They really packed that circuit board. Being a military light, it should be weather proof, at least to some degree, and it should have an air filter. I can't make out enough from the pictures to see the source of the magic dust. Hope it works out.

[Lips]

Nice pics, thanks!


Did you wipe down the double concave lens for dust?


Is the cooling fan a typical computer fan?


No air filter system but it looks like it was designed that way... Blow it out with a little compressed air...

.

[BVH]

Yes, typical size - 60mm by 60mm by 25.4mm computer fan but none of them are really typical in the sense that the 60's on Digikey range from around 18 CFM to about 38 CFM, some with sleeve and some with ball bearings. The double concave was actually very clean but I did give it a wipe with a new eye glasses wipe. I agree that no air filter was designed into this light. The electronics and bulb chamber are 99.5% isolated from cooling chamber. The heat sensor wires and fan wires go thru a small grommet with a bit of space left over. I might just dab some silicone in there before I close it up. Then just blow and go. The only vulnerability is the fan bearing itself if it's not sealed. The two halves are mated tightly together but I would call it 99% water proof, not 100%.

Looking into the easiest way to try to get another 1/8" to 3/16" forward travel to see it the light will focus down tighter. My telescoping sleeve (which holds the flat rear/convex front secondary lens has two snap ring grooves. Normally, the lens seats all the way back in the bore against a thin bead of clear silicone and the snap ring goes in the second groove back, right against the lens. If I make a 3/16" spacer and insert it first, the lens will be moved out 3/16" and the snap ring can go right into the first groove and hold the lens snug. Just need to figure what to make the spacer out of. I have a lathe and could peel off a bit from the telescoping sleeve molded stop but I'd rather not make a permanent mod.

[larryk]

Was the bad solder joint causing the raspy noise ? I would be careful with that snap ring so close to the optic. My clip seems to be awfully stiff. I think it would be easier to temporally have the tube out a little past the stop to test the focus. That way you can easily test the focus between 0 and 1 inch forward. I had mine out about an inch past the stop and the short range beam was much tighter, but lost it at the farther ranges.
Maybe MR has it focused as good as it can be.

[BVH]

Larry, yes I'm very careful when using a tiny pick to catch the "right" end of the snap ring. Even though both ends look the same, I cannot begin to catch the left end to remove it but the right end is fairly easily caught and removed.

I don't believe the broken and separated solder joint was causing any noise. The two pieces were too far apart to vibrate together and the ignitor is well removed from where I was hearing the "fan" noise.

I see what you're saying about temporarily lighting the system up with the halves apart and the tube temporarily maneuvered back and forth. I may try that at the range because as you say, it looked good close up but not so good far away. I found that same thing when trying to optimally focus my Maxabeam at 50 feet. It was perfect until I went to the range with the same focus and it was no where near correct.

[larryk]

You only need to loosen the top screws to wiggle the tube out, then lightly retighten the screws. You my also want to mark you tube with a pencil when at the farthest factory setting. That way you can measure what length works best.

[BVH]

Did a down and dirty tube extension test tonight. I took the lens out and held it as close as I could to the front of the tube. That position is exactly 1" beyond normal, lens installed max tube extension. So I pushed the tube in precisely 1 inch so that I would be in the relative same max extension position by holding the lens as close as I could to the front. I turned it on, held the lens in front and the spot looked about the same as normal when the tube is fully extended. I then began to move the lens a little further out and immediately a slight doughnut hole developed. To confirm, I extended the tube by 1/8" and retried. This time I could not get rid of the doughnut hole by moving the lens as far back as I could. Test was done at about 400 Yrds.

[larryk]

I'm going to have to find an area where I can get some distance and see if mine does the same.

[Patriot]

So cool to have these kinds of pictures and description after so many years of wondering about this light. Thanks so much for the ongoing updates Bob!

[get-lit]

If you adjust focus for flood by moving the ellipsoidal reflector and lamp assembly, the virtual image of the light source moves to de-focus the beam, but since there's little variance in the lens reflection distances over the luminance angles, there will be a distinct doughnut hole. The method I'd use is to move the lamp light source in relation to the ellipsoidal reflector. This would make the virtual source larger without a doughnut hole in the beam. Of course this can't be done with a lamp that is coupled to the ellipsoidal reflector.

[Walterk]

Nice build, with the seal, grp-housing with inserts.
Great to see the inner workings, especially the lens.
So in effect, it is the elliptical reflector and double concave lens that is doing the tric ?

[BVH]

Actually, I'm 99% certain that the sealed beam lamp is the Parabolic version based on seeing the lamp close up, taking measurements of the length of the ceramic body and sending pics to a multi brand short arc bulb dealer. But still going to nab that extra 1% before I buy a spare lamp. Based on a little browsing yesterday, the collimated beam from the Parabolic lamp hits the double concave lens which diverges the light out to the convex lens which re-collimates it into a larger diameter beam.

[LuxLuthor]

BVH, you split it open!!!!!!!!!! You are my hero!

I won't ever have one of these, but it's so great how you are investigating, tweaking, fixing. This is what CPF is about.

[get-lit]

Ah I see. Interesting that the lamp is sealed.

[BVH]

I'm used to seeing small arc chamber short arcs so seeing the volume of space inside these lamps that must be filled with Xenon is interesting. I'd roughly say the space is equal to a cylinder with an ID of 1.062" x 1.250" long.

Lux, I just can't help myself! I just have to know what's inside. Even though I'm not very knowledgeable in electronics, I really enjoy seeing how the boards are populated. I know what most of the parts are but how they interact and function is still magic.

[ma_sha1]

Actually, I'm 99% certain that the sealed beam lamp is the Parabolic version based on seeing the lamp close up, taking measurements of the length of the ceramic body and sending pics to a multi brand short arc bulb dealer. But still going to nab that extra 1% before I buy a spare lamp. Based on a little browsing yesterday, the collimated beam from the Parabolic lamp hits the double concave lens which diverges the light out to the convex lens which re-collimates it into a larger diameter beam.

When I built my Mega Blaster, I looked into the Mega Ray info. quite a bit, I am pretty sure it's Elliptical, that's how I built my light.
http://www.candlepowerforums.com/vb/...-MegaRay-style

A parabola of that small is not going to have serious throw even with a short arc source. Expanding the beam will further reduce the throw.
There was a guy from Mega Ray commented in my Mega Blaster thread at the end, might worth contacting him & find out for sure.
You can't tell by the looks. I'd hate to see you waste money if it's the wrong lamp. Then, maybe not, you seems to have a pretty big budget .

[bshanahan14rulz]

Magic smoke was probably just dust. Looks like most of the residue from the smoke is in the optics chamber.

[BVH]

Unfortunately, the magic smoke is still leaking. So it wasn't the crimp fitting insulator nor the white residue on the body walls. Before I closed the cases, I noticed a tiny piece of thermal compound on the Anode band of the lamp. It's white. Hmmm, I thought, maybe this is the culprit. Cleaned it off hoping for positive results. But no. There are two possibilities I can see. A thermal paste is used on the entire Anode band/connector/backside of the lamp. Even though none shows, I'm thinking that some of it hidden just inside the heat pipe sink may be burning and smoking. I know of 3 MR's that are doing this so it seems to be common. The other possibility is a tiny patch of the exposed heavy foam ring that is used to help hold the heat pipe in the case halves. It helps suspend the lamp/heatpipe ass'y in the body. 99% of it is behind a bulkhead of body material just behind the lamp but there is a hole in that bulkhead about 1/8" by 1/4" where the foam is exposed to the lamp chamber heat. It looks as though it may have at one time, been a hole thru which to route the Cathode wire in an earlier version of the light. But the visible foam shows no sign of burning or distortion. Given all the white residue on the case halves in the lamp chamber, my 1st guess is on smoking thermal paste.

I've looked at the elliptical and parabolic lamp specs again and again. There is a full 1/2" difference in their lengths, the parabolic being the shorter. When comparing the dimensions of the Cathode band, ceramic body and Anode band parts of my lamp with the specs, they agree exactly with the parabolic. I've got one coming so we'll see. If it's not right, a simple 180 mile trip and I can exchange it.


Parabolic is 2nd from left and Elliptical is 3rd from left.

[Lips]

.
.
I think you have the lamp (not even close) figured out and the cause of the magic smoke (thermal paste). What! 14 min run-time with heat-smoke and on multiple units. I bet the original/designer engineer knows also! Nice diagnosing work...

I doubt the intended users would have notice anything array... Lighting up the battle-field for 14 min would probably mean incoming so...




cheers


.

[BVH]

I doubt the intended users would have notice anything array... Lighting up the battle-field for 14 min would probably mean incoming so... cheers
.

Hey! Here I am, shoot me!

Although, these were supposedly used in Afghanistan and at least 2 have white residue on the case halves in the lamp chamber so they probably did use them for more than 14 minutes.

[ma_sha1]

.
Lighting up the battle-field for 14 min would probably mean incoming so...
.

Something I've always wondered as well. Using log distance projection light to look for enemies, either get shot on the spot or expose your position for later, doesn't sound like a good idea...

[BVH]

Just an FYI, I just received my new Cermax PE175BF, Parabolic lamp and it is just like the one in the light. To further confirm, I just got an email response from Leon from MR, that it is, in fact, the Parabolic model. Leon was fantastic in answering some questions for me and I was very pleasantly surprised to get a response within 30 minute or so!

I think I may have describe the first lens in front of the bulb as double concave. It's actually a Plano Concave. Flat on the backside and concave on the front. It it still a diverging lens and expands the beam to meet the flat side of the Plano Convex lens in the front.

Evidently, Cermax supplied MR with the lamps with the yellow silicone donuts. It was not a MR add-on. They are no longer supplied this way so if I ever need to change out the bulb, I won't re-install it. Maybe it or the silicone adhesive is the cause of the smoking. Maybe I'll remove it and see what happens.

[ma_sha1]

Sounds like the lens system is like sending parallel lights through a monocular to expand spot size?
That would actually reduce the throw, would it? Unless it'll actually increase the throw based on the largest lens diameter?

I hope RA is around to put some logics in.

I wonder if it'll throw further with a smaller spot if all the lens are removed? But then, the parabola is so small, how would it throw?
I am kind of confused right now, would love to see some 100 meter lux measurements from MegaRay.

[BVH]

I'd really like to become knowledgable in optics and will attempt to do so. From the few diagrams I've seen online, the Plano Concave accepts the collimated Parabolic reflectorized light and expands it out its front at least to the 4" (104mm) flat/back side size of the Plano Convex. Then the PCx recollimates the light between 2 and 6 degrees depending on extension tube placement and sends it out the front. I'm going to try to work with the Edmond Optics folks to see if I can get a pair of lenses to reduce beam size down to 1.5 or 1 degree. I'm not real clear on something their videos say on the relationship of spot size and beam divergence. It sounds like what happens is backwards from what I think. Something like spot size growing as beam diameter is decreased and spot size getting smaller as beam size is increased. Can't quite grasp that yet. I'd love to hear from others who know a lot more than I.

[Walterk]

Could you describe the front assebly for us?
How many lenses, the plano, concave, convex surfaces as far as you can figure out?

BTW Edmunds and alike have projecting all written out in 'white papers'.

[BVH]

Cermax PE175BF light source. Approx .9mm gap. 1" Parabolic reflector. Focal point of reflector is approx 25mm behind flat surface of first 40mm diameter, single element, approx 7mm thick Plano Concave lens. Depth of center of Concave surface estimated to be 4.5mm. Have not estimated surface curve radius nor focal length. This lens has the concave surface pointing forward. The distance from the exterior of the bulb front window to the flat surface of the first lens is approx 8.5mm. Front Plano Convex lens is single element, 104mm diameter, approx 205mm radius surface curve, approx 105mm focal length (if I'm following Edmonds directions in finding this distance with a laser pointer), 3.5mm edge thickness, 6mm center thickness. Front lens is able to be placed from 7.5" to about 11" in front of first lens via sliding tube. Max extension results in smallest (2 degree) beam. The convex surface is pointing forward. I would imagine that the focal length and surface curve radius specs of the first Plano Concave lens are critical for any calcs to be done. I've just not wanted to remove the front lens bracket and end up changing the distance between lamp reflector focal point and back surface of first lens. But, that measurement may not be critical from what I understand?

Can you point me to a calculator where I can plug in these numbers to begin to calculate what I need to do to reduce beam diameter? Is it that simple?




By the way, I've found out that the yellow silicone donut and it's silicone adhesive are probably the cause of the magic smoke. I need to remove it and move the lens bracket about 1.5mm forward - even with the back edge of the front lamp metal band. The bracket band is too wide and in it current placement, shortens the distance between the front lamp band (which is the Cathode connection) and the lamp back band (which is the Anode connection). This reduced distance can cause flashover during ignition. Newer MR's do not have the yellow donut because the lens bracket width has been reduced thereby increasing the air gap between Cathode band and Anode band.