Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

JP Labs

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Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

I have been truly impressed with the variety and performance of the searchlight builds here, so I have been watching for a quality reflector, cheap. As you all probably already know, this is not easy! Well, I finally found one that seems pretty great for less than $100, shipped. I am excited. Now, I need to decide what to do with it. I would like the community's help to select a lamp/power supply, and with various other build questions that will come up. I hope this thread will be interesting to you, as well.





Goals:
I want to be able to put an obvious spot on clouds as first priority, and maximize visibility of the beam as second priority. I want to minimize spill. I live a mile from a small city with all its outdoor lighting, so I am working with a fairly bright nighttime sky.

--
EDIT to add a constraint on power, per post 18:

Constraint:
Run from car 12V battery power for at least 5 minutes. Run from idling car power for as long as I want to. Big, clamp on inverter or 12V direct are both OK.


--

I would love to have 20k lumens or more! But the 8000 or so (?) lumens from a '100W' HID is very accessible and easy. Would fewer lumens with a smaller source like a projector short arc be better for my goals?

While I have studied many of your beautiful builds and learned what I can, this seems to be a unique project. I am leaning towards salvaging a lamp and ballast from a DLP projector. But not sure.

My budget for a lamp & ballast is hopefully <$250. I could go higher for significantly better value. Portability is not terribly important, as this will go on some kind of tripod/turret mount, so anything heavy can go on the stand. 12V is preferred over mains power, but I do have an inverter. Modified wave. 750/1500W. Vector VEC043.

From what I have learned here, I think the relatively large reflector means it can collimate a proportionally larger light source, so maximum surface brightness might not be so important for my goals. Maybe HID will be better for this, and short arc overkill that unnecessarily compromises beam power. I know it's a tradeoff, but for my goals, what do you think is the optimal lamp technology?

Here's what I know about the reflector:




From the markings, I think maybe it is an electroformed reflector from Phoenix, or similar. Can you help me ID it?


  • P/N P60-08
  • 16" Diameter
  • Focal length is about 2". You can see this in the pics - bulb is focused.
  • Rhodium plated from the RH marking.
  • Very smooth image, not a spun reflector, I think.
  • About 1mm thick at edge. Can measure if helpful
  • Outer surface looks to me like the ED reflectors. But I think they are Nickel, and a magnet will stick to mine. Are ED reflectors magnetic?

As soon as it arrived, 2 days ago, I had to play. I started on an adapter to house a spare 35W HID to test it. I found that an old Air Conditioning R/D I had was a perfect OD to fit the reflector ID, so I cut it down on my Smithy and pressed my lamp into it:


This fits nicely, and I use 2 o-rings to retain it while allowing adjust-ability.





Note the AA battery for scale:


The lamp is from a Harbor Freight Off Road HID that was on sale a while ago at 2 for $49. I think the outer glass tube is a UV filter. Is that correct?

Here are a couple of beamshots.

From about 100' away, not quite dark out yet:


From about 4' off-axis:


Zoomed in on cloud. Small spot already, so I am very encouraged! The spot is deformed here. If I hold the light by its base, the spot is round. But here, it is set into my sunroof opening, which slightly distorts the shape. Very sensitive!


This light throws very much better than the 9" Autozone spotlight I modded with the matching HID. And I think it looks rather well collimated. So, already it makes HID seem like it might have a small enough source to work well.

What do you think? What lamps should I consider for the final build? What would you do?

I'm off to try to source a tempered cover lens, and then to the shop to start fabricating a mounting system.
 
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BVH

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Just a quick reply on reflector Identification. Might be an Optiforms P60 here:

//www.optiforms.com/parabolic.htm

Find the P60 and go right to the VIEW button for different configs of the P60 and find the "-08" unit to get your specs.

RH means: Electro deposited Bright Rhodium. That's a nice reflector!
 
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FRITZHID

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Very nice! A short arc would look awesome in that. Nice laser like beam. Now for you to find a lens to protect it!

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JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

BVH - Thanks for that link! The dimensions match as closely as I can measure. I think you ID'd it. :twothumbs So, it's a 2.35" focal length and it catches an 85 degree band of light from the source.

Fritz - Thanks for the suggestion about short arc.

I did find a lens. The local lighting shop had an extra 17" Tempered Glass lens lying around. When I answered the inevitable 'what model light' with a brief description of the project, the guy thought that was neat, so he gave it to me. I threw $5 in the coffee fund.

I also started on the frame and mounting system. I'll get some pics up soon.
 
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JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Ok, pics. Here is the frame on the lens. Note this lens is just a flat piece of glass to protect it, not part of the optics. The lens has a gasket and a galvanized steel surround, with 3 spring clips. These clip over feet of the frame. Frame is 4130 tubing, overkill but on hand. Joining is silicon bronze, TIG brazed. I didn't clean the steel very meticulously, so the joints are a bit dirty, but it will be abrasive blasted and painted.



Reflector mounted. Center ring of frame is clamped under the threaded nut that retains the center tube to the reflector, with an o-ring under it, so there is no load to deform the shape. There is a gap to the glass, about 1/2", so I can have forced air cooling.


This is the horizontal orientation in which it will be mounted. Center leg up. Hopefully this will provide some protection for the reflector if something ever falls on it.


Detail of reflector mounting:


The 2 center tubes that the mounting ring are attached to will also support two pivots for mounting the whole thing to a yoke. That yoke will mount on a tripod.


Pivots will go here, at the end of the 'V'. This is near the balance point. The glass is heavy.
 
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BVH

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Looks like excellent quality construction! You're moving right along. In my humble opinion, you really should go with a 500 to 1,000 Watt Short Arc system. Of course, the problem will be finding a compatible power supply and lamp system for a price within your budget. The power supply will probably be somewhat heavy also at that power range. I don't know if your modified Sine Wave inverter will cause a problem with a Short Arc PS or not. I bought a used Oriel universal 400 - 1000 Watt, Xenon and Mercury-Xenon PS with its' associated lamp housing off Ebay for around $1,000 a while back. The lamp housing contains the ignitor so only low (relatively) voltage cables run between the PS and ignitor. You could mount the ignitor to your framework so that the final high KV run is very short. Search Ebay using oriel arc lamp or oriel arc supply or other similar combos. If you use a Mercury Xenon lamp and PS, then you will not suffer loss of Lumens versus regular Automotive HID. Lumens per Watt are much higher with Mercury Xenon vrs Xenon. If you go with something in the range of 200 to 500 Watts, the used supplies on Ebay are quite a bit cheaper than one that supplies up to 1000 Watts. For cooling, search Vaneaxial on Ebay for high-CFM, small size fans. I can do some research on the vaneaxial unit in my Spectrolab Starburst 500 Watt light to see what the CFM is if you decide to go with something of that power range. I don't see an open space around the lamp in its' mount for cooling air to blow over? (assuming you go with a short arc system) This will be fun to watch. Post lots of pics!
 
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Bill Idaho

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Yeah, I'm sittinhg her with a bag of popcorn, awaiting the outcome. I have a vested interest in this!!! My VSS-3 guts are looking compatible to this.
 

JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Thanks for the encouragement, guys!!

So, another (highly regarded!) vote for short arc, as big as possible. Re-reading some info from BVH, Ra, and Get-Lit last night, I now better understand that Mercury short arc is more efficient than Xenon, needs very precise adjustable mounting, and about the UV and explosion hazards. Nice guidance.

BVH, you are taunting me with the potential of a better lamp. Good! I will try to execute something in that direction, instead of a simple HID kit set up. Decision made:thumbsup:. Now, it is all about what I can find, and what is a good value. I will look into the Oriel lamps and universal power supplies you suggested. They are not out of the question. I will try to build this light to satisfy me the first time. (I can not ever allow myself to think about my relative with a movie theater, and my welder power supply).

It is funny how, the more I put into a project in build hours, the more easily I can justify nice parts. In my twisted logic, each hour of fab time is worth about $50 of my precious free time. So, that is a $500 frame I spent most of yesterday working on, with materials.:thinking: Seems a similar value is now justified for the heart of the beast. But, probably not 4 figures cost.

Good suggestion to consider a configuration which will allow me to keep the HV leads short.

I am more seriously considering the highest powered range of used video projectors for donors. These are rated up to 8000 ANSI Lumens OTF, so the lamps must provide more than that. But that approach is a gamble, relying on my ability to get the power supply to work once extracted. I think I could figure it out. I think there is a very significant benefit to using a projector. They have smart controls. I would try to keep the control system intact, using the temp sensor, fans, fan control, and airflow sensor to manage cooling and provide automatic shut down if something fails. Since a burst bulb could probably destroy my precious reflector, I think this is significant.

BVH, about your cooling suggestions, great info. I am a Thermal Systems Engineer by trade, so I have some grasp of what is needed, but never worked with lamps like this, and experienced suggestions are best, so thank you. I'll look into this more.

You are correct, there is currently no air path in my lamp mount. But it is hollow, and can easily be opened up on the end around the lamp to guide airflow over the lamp. A concentric aluminum tube could be welded on to better direct air at the lamp, or to mount a Pyrex tube that surrounds the lamp if necessary. While the test lamp (HID with bigger arc, so not as sensitive) is nicely centered because the current mount is a lathed part, I do not think it is good enough for a short arc source. The fit of my lamp mount in the reflector allows some wiggle, maybe 1 mm at the arc. If I go the short arc route, I think I would make a better lamp mount, with 3 axis adjustment. Maybe I can reuse this one, and add 'tilting screws' to turn the mechanical slop into a feature. I also have ideas about easily adjustable focal length.

I do have a couple of gasoline generators (easily carried 900W and heavy 4500W) which could be used if the modified sine inverter is insufficient. I think single-RPM analog generators are sine wave by nature. But the inverter is preferred, so I can run it from the car more easily for parties.

--
Possible lamp option:

I sent an email to my various friends asking for leads on big projectors. I learned of a working used commercial projector that uses a 330W Ushio NSHA Mercury Short Arc Lamp, which I might be able to buy. Service manual with schematics, too. I couldn't find specs for the lamp itself, so don't know lamp lumens. Anybody know?

Is it reasonable to assume that this type of lamp can run vertical, without dying in a very short time, if well cooled?

I am thinking of offering a couple hundred bucks for this projector, but maybe I should offer more. While that lamp is on the low end of what BVH recommends, it seems to be at the high end for single-lamp A/V projector power. It might be a very good value for short arc lumens/dollar, compared to buying a lab power supply and lamp separately. Maybe that used projector is worth a few hundred dollars to me in light power.

The most reasonable used Oriel power supply I saw today with 500W capacity is $550 (Oriel 68811 on the big auction site) without a lamp, so the projector is probably worth a few hundred easily, by comparison, if it is suitable. 1KW Oriels are going for 3x that much.

--

Bill, I am VERY jealous of your VSS-3!! I wish I had such nice hardware to work with. In fact, your old thread about acquiring it was one inspiration for my 2 year online search for anything with a good reflector. It showed such things are sometimes attainable. But VSS-3 bring big money, and I never found one that seemed reachable, so I am building from scratch. I hope that the info shared here will help you in your quest to find a suitable lamp system to finally bring it to life! It is very hard to find a 'plug and play' recommendation, and such lamps need careful operation, thus my tendency to start with a salvaged projector system so everything plays nice, electrically and thermally. On the other hand, there are some really well documented builds here that either of us could duplicate, if time and funds allow. But they tend to be seriously high end stuff. CPF attracts the big dogs of the DIY lighting world, doesn't it? Nice to have them to learn from.

--

I'm off to work on the mounting hardware. Should have a few more pics later today.
 
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BVH

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

When I machine lamp adapters to fit over a lamp base, I shoot for about .0005" clearance and end up somewhere between .0005" and .001". I assume you will build some sort of 3 to 4-leg spider to provide support for and an adjustment mechanism for the front of the lamp you settle on. As long as the front is supported, that up-to .001" adapter clearance in the back will not result in any significant focusing issues. As far as upward shinning of the light (which we all want to do), most SA searchlights I have and have seen place the Anode (the bigger, more massive electrode) in the rear of the reflector so that when the light is pointed down from an aircraft, boat, what-have-you, the brunt of the arc flame which naturally rises is against it. Reverse that scenairo and there is some amount of tendency for some of the effect of the flame heat to be directed back towards the small, thin Cathode which does some damage and results in less lamp life. That's the theoretical and now to the real-world for us enthusiasts. I've talked a few times with my contacts at Advanced Radiation Corp (my obsolete lamp supplier) about this issue and I have specifically asked them about pointing my Spectrolab lights (they make the OEM lamps) up as much as 60 degrees above the horizontal and the answer is pretty much what I just wrote - You will technically shorten the life of the lamp but if you're starting with a 1000 hour lamp, you might still get 300 - 500 hours of good life out of it if it's life is spent pointing up. They do caution to not run it for excessively long times when only pointing up. They say pointing horizontal won't shorten life by much. With Mercury Xenon, the amount of cooling is more critical as you may have read in Getlit's Nightsword thread. Too much and you won't get full Lumens output.

Are you after a Laser beam or a flood monster or something in-between?

If you end up with a 500 Watt system (closer to 650 Watts total) then you're not going to want to run it off your car battery for more than a minute or so. 650/12=54 Amps of current. That's why I ended up making a 9-Cell, 100 Ah LiFeP04 portable battery. With that battery, I can run the 1600 Watt (1800 Total) NightSun for three, 20 minute sessions before needing to re-charge it. I also bought a 1500 Watt, Full Sine Wave, 24VDC input (22V - 33V input range) inverter so that I can power some of the 120VAC SA power supplies out in the field from the same battery. I need if for my TrakkaBeam 800 Watt PS and my M134 minigun light PS. The battery system is also great because there is no generator noise. You should hold out for a 500 Watt system. That is a great compromise between the 150-300 Watt systems and the 1000 Watt systems.
 
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JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

I got the yoke built yesterday, and stuck it on a temporary tripod. Then I got invited to a buddies bonfire at his defunct 10 acre apple orchard in the country, where it is darker, so I just HAD to stop working and go play. I'll get a couple pics up soon, and more tonight or tomorrow.

His place was once overgrown, and now it is carved up into a maze like network of grassy trails. Several of us regularly race around these park-like trails on mopeds and small (250cc or less ) ATVs and motorcycles. It is easy to get lost or disoriented. I ran the 35W HID test bulb for about 3 hours vertical as a beacon, and it was great.

--

Wow BVH, you are really helping me, here. I truly appreciate your interest and suggestions. I feel like a little kid who showed up at a park, and an NFL pro dropped by to teach me how to toss a football.

When I machine lamp adapters to fit over a lamp base, I shoot for about .0005" clearance and end up somewhere between .0005" and .001".

I assume you will build some sort of 3 to 4-leg spider to provide support for and an adjustment mechanism for the front of the lamp you settle on.

I was not planning a spider. But I suppose a large lamp would require this for support. If I use a lamp with electrodes on both ends, I can do this.

As long as the front is supported, that up-to .001" adapter clearance in the back will not result in any significant focusing issues. As far as upward shinning of the light (which we all want to do), most SA searchlights I have and have seen place the Anode (the bigger, more massive electrode) in the rear of the reflector so that when the light is pointed down from an aircraft, boat, what-have-you, the brunt of the arc flame which naturally rises is against it. Reverse that scenairo and there is some amount of tendency for some of the effect of the flame heat to be directed back towards the small, thin Cathode which does some damage and results in less lamp life.

Can the lamp simply be installed with the large electrode, the Anode I believe, on the top? It seems that would help with the heat issue. Also, since the hot spot in the arc is formed at the Anode/big electrode, I think this would direct more light rearward towards the reflector. That is the way I envisioned setting it up.

That's the theoretical and now to the real-world for us enthusiasts. I've talked a few times with my contacts at Advanced Radiation Corp (my obsolete lamp supplier) about this issue and I have specifically asked them about pointing my Spectrolab lights (they make the OEM lamps) up as much as 60 degrees above the horizontal and the answer is pretty much what I just wrote - You will technically shorten the life of the lamp but if you're starting with a 1000 hour lamp, you might still get 300 - 500 hours of good life out of it if it's life is spent pointing up. They do caution to not run it for excessively long times when only pointing up.

After last night's fun, I really want to be able to run this completely vertical for extended times, as a beacon. With a quiet generator or idling car, I could do this. 30 degrees off vertical (the 60 you mention) could work but I would make trade-offs to be able to achieve vertical. If that is completely out of the question with short arc lamps, I could keep an HID lamp configured as a simple drop-in for beacon mode, with correspondingly lower power so it can run silently from a car for long times.


They say pointing horizontal won't shorten life by much. With Mercury Xenon, the amount of cooling is more critical as you may have read in Getlit's Nightsword thread. Too much and you won't get full Lumens output.

Yes, because the vapor pressure of the gasses inside will not climb high enough if the lamp is too cold, as I understood.

Are you after a Laser beam or a flood monster or something in-between?

Something in between. I don't really have any 'safe' targets more than a mile away, except maybe clouds above, so reach beyond that seems un-needed. From the discussions about 'Beam Power' (Get-Lit if I recall correctly), I think that is what I want to maximize. Highest beam power, with ability to put a nice spot at 1 mile, including on clouds above.

If you end up with a 500 Watt system (closer to 650 Watts total) then you're not going to want to run it off your car battery for more than a minute or so. 650/12=54 Amps of current. That's why I ended up making a 9-Cell, 100 Ah LiFeP04 portable battery. With that battery, I can run the 1600 Watt (1800 Total) NightSun for three, 20 minute sessions before needing to re-charge it. I also bought a 1500 Watt, Full Sine Wave, 24VDC input (22V - 33V input range) inverter so that I can power some of the 120VAC SA power supplies out in the field from the same battery. I need if for my TrakkaBeam 800 Watt PS and my M134 minigun light PS. The battery system is also great because there is no generator noise. You should hold out for a 500 Watt system. That is a great compromise between the 150-300 Watt systems and the 1000 Watt systems.

I have a 1920 hit or miss engine which needs a job. It's a 2 1/2 HP Stover. It makes nice noises, and could spin an alternator. This may wind up configured as an optional power source for parties. But I don't think it would have the oomph to power a 500W lamp. With a larger lamp, it could extend the runtime of a battery significantly, though. Generator or idling car would be acceptable to run big lamps.

The large battery packs intrigue me. I also want to build an electric bicycle in the next year or so. At that point, I would have a 15 AH 48V or so LiPo pack to share. But that would be a later mod, not designed into the initial light's features.

 

JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

OK, here are a few quick pics as promised. I am short on time, but will add a few more later.

Simple fixture to align the mounting pivots, which are simply bolts:


Pivots installed in yoke:



Temporary setup. Tripod is NOT robust enough - only temporary. Need a solid, wide one for safety! I purposely made the yoke extra tall, to leave room for electronics if needed. Can shorten easily if not needed.


Another beamshot. Again, this is the test lamp, just a 35W CHEAP HID. Seems to be AC, not DC.


The spot, from about 100 yards (EDIT - only 65 or 74 yards per Google Map, not sure which tree it was on the map):
 
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BVH

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Absolutely the lamp can be installed Anode up. The brightest light source is actually right off the tip of the Cathode and it gets dimmer as the arc progresses towards the Anode. Technically, the brightest light source would be pointing directly out the front instead of back to the reflector. But again, in real world use, it is probably not going to matter at all for your use. Getlit could give you a much better answer than I can.

The only SA I've seen without a spider is the marine ACR 150 and 300 Watt lights. They're mounted on boats/ships so very little vibration/shock potential. But if you were to remove the lamp for transport and reinstall it on-site and then not move the structure once it is running and hot, I think you'd be fine.
 
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JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Couple more.



The furthest I viewed from was about 296 yards, and the beam was BARELY visible when aimed straight up.
The furthest target (tree) I illuminated was about 435 yards, and the spot was still strong and bright. No pic, since it is on a neighboring property and I just touched it for a moment.

This one is from about 130 yards away. Below shot's camera settings.
F2.8
1/2 second
ISO1600
Focal Length 4 mm
Equivalent 35 mm Focal Length 25 mm




I am realizing that I don't have any suitable (read: certainty that I won't blind or annoy anybody) long distance objects to illuminate that are not on roads, or straight up. The one mile away tree I can hit from home is along a road, so not for regular use. This is why I think my goal should be beam power, more than throw. I am not in an aircraft pattern, nor are the places I camp. And when we camp in the woods, it can be hard for others to find us. A beacon would be fun for such times.
 

FRITZHID

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Have you considered a manual focusing mechanism? Shouldn't take much movement to go from full flood to tight laser like spot.

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JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Have you considered a manual focusing mechanism? Shouldn't take much movement to go from full flood to tight laser like spot.

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I was only going to have a screw and spring to set up the bulb, and to tweak it a little. Flood to spot would be a nice feature to add. I would want it to be mechanical, no focus motor. A lever or twist grip, maybe. Not sure how to do that.

Any ideas?
 

BVH

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

All you need to do is create a lamp holder/adapter movement mechanism that will give you roughly .250" of "Z" axis movement forward of the focal point to get flood. How does your lamp holder attach to the reflector? How can you make it slide forward and rearward? Secure it with a large ring nut? Can't tell from the first pics but it looks like you already have the capability. Is that a big ring nut I see and threads on the lamp holder?

EDIT: I re-read post and I see you're using two O-rings to hold the focus position (Z axis) of the lamp holder. Are the 6 holes in the reflector hub ring threaded? Maybe drill and tap two opposing holes in the side of the lamp holder and make some type of "L" brackets with slots that will bolt to the hub ring and sides of the LH. Slot the L brackets and use the bolts to lock it down in any focus position you want.
 
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JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

More Discussion About Goals:

Playing with the light and seeing what I can do with it has been 'illuminating' for me. My goals are adapting.

My own suburban home is not the best testing ground. Too close to the road.

I set it up again briefly last night, at another buddy's house in the country, for a ~5 minute run just to demonstrate. I am a lot more comfortable doing that, than using it in my own suburban yard on a fairly busy 2 lane road. Every car that drives by can tell where its coming from. Its awfully nice to be able to pull it out and plug in to the car. And to have a silent power source for short runs (Suburban's Optima Yellow Top in this case).

Certainly, grid power is ok for testing and home use, but my best opportunities to use this have been away from wall sockets at parties hosted by my friends. If I needed a heavy, noisy generator to run it, I could do that, but I don't think I would use the light very much. My light might become a 'once a year toy'.

I want to be welcomed, even encouraged, to bring this to social events without annoying the host and guests. My generator is annoying.

While it would certainly be more fun for me to build the biggest, most powerful setup I can, I have realized that I want 'grab and go' capability. Toss it in the car (well, Suburban) and bring it with me on short notice. It should not be a requirement to hook up the trailer and load my heavy 4500W generator. (It is too heavy for me to set in back of truck).

While my functional goal for the light hasn't really changed, I think this means I need to add a constraint. I think I should limit power draw to a level that an inverter will support so I can run it from battery clamps for a few minutes, or with a 180A alternator, idling, for an hour or more.

Having an HID lamp I can install for 'economy mode' would have achieved this for the smaller lamp, but I think most of my usage will be off grid, and I don't want to have to use the weaker lamp all the time. While I wrote above about it not being a problem to power a big lamp, I have realized that doing so would restrict my use quite a lot, and that generator noise would make me a lot more conspicuous and annoying to anybody nearby. I want to be as quiet as possible. So, my 'big lamp' choice should enable this.


Additional constraint: (added to original post 'Goals' statement for clarity).
Capability to run from clamp-on style inverter, or direct 12V, from alternator power.

I think this means an A/V projector is my upper limit for lamp power, not a 1kW monster.

Thoughts?
 
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JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

All you need to do is create a lamp holder/adapter movement mechanism that will give you roughly .250" of "Z" axis movement forward of the focal point to get flood.

1/4 inch should be do-able with the current mount. I think I read that de-focusing should always be done by moving the lamp rearward, so as not to cause the focal point to hit the lamp and overheat it. Glad you corrected my about that - defocus FORWARD from focal point, OK.

How does your lamp holder attach to the reflector?

It is a sliding fit, no threads or positive location, yet.

How can you make it slide forward and rearward? Secure it with a large ring nut? Can't tell from the first pics but it looks like you already have the capability. Is that a big ring nut I see and threads on the lamp holder?

EDIT: I re-read post and I see you're using two O-rings to hold the focus position (Z axis) of the lamp holder. Are the 6 holes in the reflector hub ring threaded? Maybe drill and tap two opposing holes in the side of the lamp holder and make some type of "L" brackets with slots that will bolt to the hub ring and sides of the LH. Slot the L brackets and use the bolts to lock it down in any focus position you want.

I used that ring to clamp my bracket to the REFLECTOR (edit correction, originally wrote LAMP), so it is not available for focusing. But, I could extend the frame rearward and put a plate behind the lamp, with one bolt in the center. Then I could use springs to pull the lamp against the bolt. Turning the bolt would push against the springs and push the lamp holder forward.

 
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JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

There is a problem with the way I built the glass cover into the light. The gap between my reflector and cover lens was added for airflow, but it causes 2 problems. Bugs get in, and light spill hits those who look towards the light, even if pointed almost straight away from the observers, because light bounces off the inside surface of the cover glass. I don't think this is safe. This is why I had the light set up to be above head level, so far. I will add a black baffle which blocks this, so all you see is the beam. It will probably just be a strip of aluminum flashing formed into a ring. positioned to cover this gap.
 

JP Labs

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Re: Scored a Nice 16" Parabolic Reflector. HID or Short Arc? Test Beamshots w/ HID.

Why defocus by moving lamp forward of focal point instead of rearward?

I thought about this more, and the way I am picturing the light path, if I move the lamp forward of the focal point for flood, then the angles to the reflector become more acute (smaller), and the light will cross over itself. It seems that this would possibly result in a hot spot of focused light landing on the bulb. Defocusing by moving the lamp rearward would make the light bounce angles get bigger, so the light would diverge into a spot pattern without crossing over itself and making a hot spot.

I don't claim to actually understand this, and may not be correct, above. But I have seen comments that support each technique for de-focusing. Can we discuss this more? I would like to understand.
 
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