Building a short arc searclight

So I've finally started to collect the parts for a custom searchlight. I found a guy here who had a custom 9.6in silicon dioxide overcoated aluminium (AQ) reflector built by Opti-Forms. He also had a custom made anti-reflective polycarbonate lens made with high temp anti-reflective glass center piece. I bought both from him for $260. The reflector alone, when new from Opti-Forms, was $700 so I think I got a great deal! He glued his own mounting mechanism to the reflector using high temp putty. I think this will come in handy for my build.

A pic of the gorgeous reflector.


Side profile also showing mounting mechanism.


And some pics of the lens. A few minor scratches but nothing I can't deal with.


High temp AR glass mounted to the center of the polycarbonate lens.


After I had the lens and reflector I had to find a housing to mate all this too. Turns out Walmart had a cooking pot that will work just perfect as a housing for this beast.


Couldn't have asked for a better fit!!




Even the lens fits the little lip around the edge of the pot just perfectly.




So now that I have the reflector and the housing out of the way, I need to get to the heart of it all: the bulb. I still have not decided exactly what kind of bulb I'm going to use. I had seriously thought about buying some of member D1S's remaining stock of DL50 Fat Boys and overdriving them to 100watts. That should give me close to 10000lumens of light output which is plenty. But I took the reflector outside the other night and fired up a Osram 66240 bulb in the reflector and the results weren't as impressive as I had hoped. I'm looking for maximum throw and intensity. While the beam produced by the Osram bulb was tighter than most flashlights it lacked the intensity to be a seriously impressive light. I haven't found any specs for the DL50 bulb but I was under the impression that the arc dimensions are the same as a regular automotive HID bulb so the beam shape would be very similar, albeit 3X brighter with a 100watt ballast. I don't think being 3 times brighter would yield much more impressive results. So sadly I think I have eliminated the DL50 bulb as a possible candidate for this project.

That brings us to where I am currently. I have decided that the only way I'm going to get the results I'm looking for, and to utilize this reflector to its full potential, is to go with a short arc bulb. Automotive HID's are AC (two hotspots in the arc) while Short Arc bulbs are DC ( a single hotspot in the arc). Most of the light from Arc bulbs arc concentrated in that single hotspot which, depending on the bulb, may only be 1/4mm long. This should produce a super tight and extremely intense beam like I'm looking for!

Xenon short arc bulbs are much less efficient than automotive HID's. The bulb I think Im going to go with is a 450watt Xenon short arc bulb. According to Osram it produces about 13000 lumens. ( Thats only 28lumens/watt) but the electrode gap is only 3mm long. Considering the hotspot is possible only a 1/4 or 1/8 of this length I think it will produce the results I'm looking for....

And finally since I have not completely decided on the bulb I also don't know which ballast, ignitor, and power supply I'll need to finally fire the bulb up. One thing that is for sure is that all of this will cost quite a pretty penny so the project will move quite slowly. I'll continue to update thread as I figure out what parts I'm going to need next! Stay tuned!!

Awesome project. Looking forward to beamshots.

If you haven’t already, try searching on posts from ma_sha1 (sadly retired, but occasionally pops in) and FlashPilot. They’ve probably forgotten more about short arc than I’ll ever know.

Ma-sha is the guy I bought the reflector from.

Oh my, this is going to be great. I know nothing about short arc's other than hearing about a couple beasts out there. Looking forward to seeing what you create and, hopefully, how you create it.

Your setup seems very impressive. Looking forward to the outcome.

It’s freaking ingenious that you found a cooking pot to use as a host!! H)

I'm sorry to hear your project has gone to the pot so quickly. Seriously though looking forward to what you can cook up with these items, something amazing no doubt.

Fixed it for you. Had to keep the theme going. :stuck_out_tongue:

what an amazing project you have going. Loving all of it so far and can't wait to see what other ingenious ideas you have in store to complete it. I don't think I'd have thought of using a SS pot for a host. :D

Following with interest! A 700 dollar reflector in a cooking pot, what is more to desire for a flashoholic? :-)

Lol thanks for all the comments guys. I can't take credit for the cooking pot housing idea though. Got that from someone else on another forum.

I guess that was me? Cause I happen to have a 14” short arc in a huge stock pot :bigsmile:
I wish you good luck with the project!

Hi Polari! Glad to see you on Budgetlight forum! And yes I did get the idea from you. Don't think anything could have worked better

BTW my lights gonna be a baby compared to yours. Been doing a lot of research on short arc bulbs and ballast recently and its looking like I'm gonna have to go with a 300watt XSA. Finding ballast and power supply with a higher wattage is incredibly difficult and extremely costly.

I didn’t find any info on the XSA, is that Xenon?
Unfortunately short arc is never gonna be cheap. But speaking of Xenon, you can get new 500-1000 watt Xenon power supplies for less than $200-250 from China, and you can often find good lamp deals on Ebay. Just make sure the lamp can operate horizontal for a reflector like this. Also take into account that most of the bigger lamps needs a front support. Another option is metal halide lamps. These are AC, but has arc gaps from 3 mm (MSR 400 SA) and spit out a lot of lumens. But they will quickly set you back some $400-500 for a lamp and ballast. But lamp is more compact and normally easier to install than Xenon. The third option is of course UHP lamps like the one ma_sha1 had in this reflector (And I’m gonna try out in my newest project) These have extremely high luminance, but the lamp needs to be seperated from it’s reflector and can have a tricky ballast and power supply setup.
I guess it all boils down to a very long list of pros and cons, so research is definitely key here.

Yeah I was using XSA as an abbreviation for Xenon Short Arc.

I hadn't thought about looking for some Chinese made ballast because in the automotive world I know the Chinese HID ballast just about never produce the wattages they are rated at. Do you have any suggestions on a brand that you have experience with that may be of good quality? TIA!

And what kind of metal halide lamps are you referring too? Are they like automotive HIDs?

Aha, 300 watt xenon, that make sense.
When it comes to these xenon power supplies from China, they seem to be in a very different class than the million different automotive “HID kits” online. I have no reason to believe the PSU itself don’t deliver what they are rated for (or very close to it) Not sure if it’s ok to post links here, so I sent you an PM with some links.
The metal halide lamps are entertainment/touring/stage/film lamps. Similar to automotive HID, just way more power.

Kudos for your ambitious/expensive project, but I think youre probably going to find it very difficult to focus the beam. Especially if you would like to have a variable/adjustable beam width (which makes these light far more useful). Also, the depth of your reflector in comparison to its diameter is far deeper than what I have ever seen in any proper HID/short arc searchlight, so I wonder if it would be capable of focusing such a light source.

If this doesnt work out, maybe you could sell your project for an astonishing profit at CPF and reinvest in a 1kW AN/VSS-3A searchlight. If you are diligent in your search, you can still find them with 0-3 hours run time on the envelope (they have an hour meter that records run time). Many come with the proprietary cables, control head and remote controller. Ive paid from $350-1000 for the several I have owned. Due to their superior optical systems and design, these completely trounce a 1.6kW Nightsun Ive compared mine to. They are also extremely rugged becasue they were designed to survive at the base of a tank barrel in battle.

Thanks for the info Polari. I'll check everything out when I get a chance. And it's okay to post links here. BLF is no where near as strict as the other forum which I'm banned from.

FlashPilot the reflector I have is very deep as you say. I wondered about how it would focus the beam myself but the previous owner managed to get 40million candlepower from his setup so I would think its capable of focusing a short arc light source. From the research I've done a deeper reflector is more effective at gathering all the photons and focusing them into a tighter beam than a shallower reflector. I'm not sure why many of the larger short arc lights use rather shallow reflectors but my reflector's depth to diameter ratio is similar to that of the maxabeam which has an extremely long throw for a rather dim light source.

And if I found a vss-3 in the price range you say I would definitely snag it. At the same time I would like to conquer building my own light and work out all the kinks as it something I can be proud of having built myself. For a flashaholic having a rediculously bright light is rewarding but having built one yourself adds another level to the reward that can't be had by simply buying a light.

Have you contacted Opti-Forms to find your reflector application and associated parts list? If they dont have that information on hand, perhaps they could provide the vendor they were manufactured for and other data. You might be able to copy or approximate the intended light source parts with stunning guaranteed results. The maxabeam reflector depth to width ratio appears to be a good deal less deep than yours. I had 10 of them for a project that I had abandoned before stepping up to the VS3 while saving a ton of cash. Maybe this mechanical drawing of a maxabeam can give you a few clues that might assist in your build.

I think the larger short arc searchlights use a large flat reflector because they utilize a comparatively larger gap between the anode and cathode, which would scatter the beam in a deeper reflector. Comparing your example of the 450 watt short arc with 3 mm gap (0.118”) with the 1000 watt VS3 gap of 0.132”, I wonder if your reflector would scatter the light with the bulb you mentioned. The VS3 uses a 14” relatively flat reflector. But then, maybe it wont matter; as long as you can culminate the hotspot. Any scattered light should result in a brighter spill beam, which can be far more useful in the wild than a sheer intense long range hot spot with no spill beam. I never run a VS3 in max spot while moving, and usually in full flood mode or somewhere in-between… max beam range far exceeds what naked human eyes can view in any detail, and the police wouldnt enjoy my attempts in spotlighting high altitude aircraft in transit. :smiley: Beyond that, its proven completely useless in the max setting.

  • If you havent researched the potentially lethal explosive hazards of xenon short arc tubes, you might want to take a good hard look before committing. The VS3 has an internal cradle mounted on elastomer pads to isolate and absorb vibration and shock, and they are still very dangerous. The housing case is thick hardened aluminum, so if (and often when) the envelope explodes, all the shrapnel will destroy the internal components and send them through the front of the lens. I treat mine like an unsafe loaded gun and store face down away from people when not in use. If you search, there are incidents of short arc tubes exploding while sitting unattended on a shelf… scary stuff without the correct equippement (bulb changer/protective housing) and safety protocols for handling and storage. PM me with your email address if you’d like the VS3 manuals and warnings.

Have fun! :bigsmile:

As an aside, Ive been running a pair of 100 watt HID’s in my pickup truck driving lights (Hella Ralley 4000 with 9” reflectors) for nearly 4 years without incident. They have many hours of sustained use in a high vibration environment, which would kill most Chinese HID systems. This particular design is highly touted on 4x4 forums and has given others good results as well. Your thread reminded me of another pair of Hella 4000’s I picked up and forgot about, so I just ordered another 100W HID kit to convert them as well. They provide around 9000 lumens each, have ceramic mounting bases and very high quality ballasts that dont flicker and always ignite. Ive tested mine down to –4 F. Im told that the ceramic base 70 watt HID bulb can be used with the 100 watt ballast for higher surface brightness in a smaller envelope. This should translate to a more concentrated beam in your deep reflector for longer range but with less total lumens. Perhaps the best part is that the kit is only $70 for a pair of them (with free shipping). You could use your spare HID and convert a Coleman spotlight like the one I did a while back. Then you could have a killer thrower with your project and a cheap medium thrower for your car that would still slaughter anything LED. I went with 4300k (appears to be about 1A Cree tint) for max lumens and H1 bases to match the Hella 4000’s and the Coleman spotlight. 100 watt HID sales link (only 2 days left) Id stay away from the other Chinese 100 watt versions because they have been notorious to failure and being underpowered. The link does a good job of explaining the differences in the electronics. You might also ask about higher wattage ballasts and 70 watt blubs… if you’re interested.

I think ma-sha1 had this reflector custom made so I'm not sure how to explain to Opti-forms which reflector it is so that they can give me its specs. I'll see if I can get in contact with ma-sha and see if he still has them available somewhere. He hasn't been on this forum is 6 week though...

That cut away of the maxabeam is a very useful pic. THanks for that! Maybe I can steal some of Peak Beams trade secrets. I have figured out in my mind how I intend to mount the lamp. Should be easy. It's figuring out how to hold the reflector and the front lens to the pot securely without damaging either one, while also keeping it pretty that's got me stomped at the moment. Can't seem to find the type material I need in the stores no where.

And yes I'm aware of the danger of short arc lamps. I had highly considered using a mercury short arc lamp because of its higher efficiency than Xenon but the massive amounts of UV rays it produces is what led me to ditch that idea. The center glass in the window I'm using, I'm sure, blocks UV rays as it was removed from a UHP lamp. But the outer polycarbonate is what I'm not sure about. It may allow free passage of all the UV rays, and if so, it would be quite a bad idea to use a Mercury lamp. Also apart from not knowing exactly which bulb I want to go with, one of the reason why I haven't ordered the bulb just yet is that I don't have all the required safety gear to handle a one of these lamps, let alone bench test it.

I would love to run some auxillary lights on my car but I don't really have a great way of mounting them. My HID projector retrofit also puts out a ton of light as it is so I'm pretty much satisfied with my headlights ATM. I do intend to mod a flashlight but this project is gonna suck up all my money for now LOL. My FF4 and TN32 will have to do for the time being.