Vintage Lighting Self Sustaining Carbon Arc

Thanks for the above and I will seek higher advise & meter what is advised.


I would wire the incoming hot wire to the terminal that goes to the resistor common. That will allow the resistor to act as a current limiter if the thing shorts someplace else. I would connect the resistor tap wire to the lower carbon arm. I would wire the incoming neutral to the solenoid coil, and the other side of the solenoid coil seems to go to the other carbon arm. (?)

Got it mostly in understanding and will get shop help that know more. What you specifiy agrees with fixture head markings.

And other side of solenoid coil goes to carbon arc.

W-Shaped solenoid, one arm shorts to frame in a way that somehow cancels the arch I think in adjustable shorting to frame.

Hot wire thru resistor coil than lower arm, neutral directly to solenoid than upper arm.

Still a question remaining of given the lower part of the coils are attached to hot... there is brackets or rings to adjustable tap the power from them above, but I still have like +6" of wiring at the top of the resistor coil that in my fault... I don't remember where or how such wiring above the brackets, they were terminated. Literally 6" now hot wires just hanging out. I doubt they connect to neutral, or get shoved to the underside between coil and ceramic. What do do with them given once a resistance of an arc is struck - those wires sticking out from the top of the coil springs - if touching something would easily be less resistance than the arc. I would hate to cut them given they are original length.
 
Still a question remaining of given the lower part of the coils are attached to hot... there is brackets or rings to adjustable tap the power from them above, but I still have like +6" of wiring at the top of the resistor coil that in my fault... I don't remember where or how such wiring above the brackets, they were terminated. Literally 6" now hot wires just hanging out. I doubt they connect to neutral, or get shoved to the underside between coil and ceramic. What do do with them given once a resistance of an arc is struck - those wires sticking out from the top of the coil springs - if touching something would easily be less resistance than the arc. I would hate to cut them given they are original length.

That's an interesting problem. There is no other terminal to land them on, so I only see two options. Wire them to the sliding taps, or wrap them tightly around the ceramic end so they can't touch any metal. Either way will work the same electrically. I would be hesitant to cut them shorter since nothing is certain.
 
Agreed and agreed in thinking about it more today the conclusion of sliding tap attachment. Big mistake on my part in having never worked on such a thing before, to not note and photo where those wires went.

I did note on the single resistor core tap, that there is three tapped holes, one to the pressure plate bracket, one to the output, and one un-used. And that the dual slider tap bolt was extra long for what was needed when removed. Twisting around the core doesn't make sense and is not in the photo, perhaps tucked in between coil and ceramic core, but given their over 6" length, that would not work. Given their over 6" length, that would leave lots of room for adjustment as long as these conductors were trained in a safe way that with adjustment - no shorting to frame. Were they just wrapped around the ceramic core - there would be no reason for them to be that long, they will have been cut off at the factory.

I'm fairly certain, that when it was re-wired for 12/3 type S cable it was before it fell over and broke the ceramic cores. Why re-wire it for 12/3 if your ceramic cores are busted. But on the other hand, I didn't note that until I took it apart given the steel rod thru the core of the ceramic, and the resistor coil spring supporting the broken ceramic parts. Doubt though someone was re-wiring the upper part of the resistor cores in some way though, the resistor top wire must have been wired back to the brackets for some unknown reason. My fail in this question but likely is re-terminated to the brackets.

Changes for safety... Ran out of bronze/brass nuts and washers tonight or will have gotten further - many were just steel especially for the upper dual tap threaded rod. Adding internal tooth bronze lock washers to the various assemblies so had to change some placements like the lower Z' angle iron stud, and won't bond the fixture with the ground thru the sponge. Before (when upgraded/downgraded to 12/3 - wrong wire gauge but grounded), the ground was done thru one of the bottom asbestos isolation strip mounting block screws = floating ground. I'll drill a new hole for a proper mechanical ground to frame. Some stuff in wiring I want a little more proper even if it's not a touring fixture I normally work with.

Interesting for me is the use of hex nuts on this fixture! I normally help date stuff of the hex nut to after WW1. Might have ground square nuts off the plumbers tape straps mounting the resistor core to the arm of the fixture, but no more. All other nuts seen, brass/bronze or (Non-Zinc coated) steel have been hex nuts. Often these hex nuts have been the "heavy hex" size in larger size, but in general the hex confounds my dating. Granted it's a "Hollywood" style fixture and perhaps they were just above the curve for what normal stage lights were using.

Thanks again for the advice, keep it coming... getting close now.
By the way on wiring, I'm using 10ga TGGT 250c wiring with a fairly tight braided asbestos looking (McMaster Carr #8798k31) fiberglass sleeving over it to simulate the asbestos. High temp ring terminals and 3M #69 fiberglass electrical tape. Works well and no worries about the heat. Not as flexible as SF-2, but limited flex internal fixture or ballast to head use - not a cord whip. This part I have lots of experience with as with connections.
 
Last edited:
That's why I suggested putting the test unit (the rebuilt arc) in series w/a 2 kW lamp. Will limit current in case of a short circuit anywhere in the test unit.. For testing I'd worry less about PPE, goggles, etc.--maybe with the exception of sun glasses. Put your off hand in your hip pocket. Just pit the unit on the concrete floor of your shop & don't look at the arc.

A little beyond sunglasses on my part - will test once there safely including a 30A in-line cord mounted fixture switch planned. So if understood the above correctly, there is one tied resistor core, and one not attached. Should first try with the single, than with the dual. Hot does now go thru the resistor coils as sensible as opposed to what I saw in later wiring possibly mis-wired in from the fixture and photos - hot was not going thru the resistor coil. This assuming hot to plug was going to proper non-NEMA plug. Very possibly mis-wired in the past for conductor 12/3 mis-wired cable attached.

In series with 2Kw lamp not a problem and will plan for but that than means a 60A breaker PSU... not a problem in 5KW Fresnel PSU's, but wondering about two different styles of testing between first coil and 2Kw in series. Can you and FM get on the same page of how to best try this light? Personally, I for a 25Amp fixture would prefer not to series wire it to a 2Kw lamp, but if that's the best way to do it will do. It is safe but doesn't tell which coil orientation is best given a say $45.00 lamp blows at each trial - not a real problem, but it would seem with FM's concept it could be connected directly.

Otherwise can I waste some of my overstock in Euro 240v 2Kw lamps I have no use for in testing? Again there is no budget for this, but would be a shame in profit sharing bonus to toast lamps if not necessary.

If the single coil does not strike an arc, switch to the dual coil. Both coil taps should be about where they were last used in the photo, though when this thing runs, it will be with new carbon rods. One antique carbon rod is intact and indeed being longer than the other indicates DC the last time it was used, the other (lower/hot) didn't survive removal.

Given re-wired at some point, broken porcelains etc.. possibly someone attempted a re-wiring repair and it didn't know porcelains were broken. This if still wired for DC in ballast connections especially, much less broken ceramics in shorting of conductors perhaps. Good to start small resistor core and if not working go to the larger dual. Serious complex math and technique question for variables in how it was wired for now in how to test. Thanks in a lot of help. Thanks again for advice, it's getting close, but still a puzzle.
 
Last edited:
In series with 2Kw lamp not a problem and will plan for but that than means a 60A breaker PSU..." Ship, if you have a (say) 2kW lamp in SERIES with your test device, the combination, even if the device under test (DUT) were a dead short, cannot draw more than the 2kW of the 2kW lamp. A 20A circuit would be fine. Assuming that the arc ((the DUT) was in series with the 2kW lamp, the arc might be difficult to sustain, but an arc could be struck. If it works, even sporadicly and with difficulty. with the series "safety" lamp in th circuit and nothing blows up, try it without the '"safety" lamp.
 
Still on the fence, sorry in not sure how well FM's single coil would work with the series concept and curious about what to do. FM's starting with one coil than going second coil seems sensible in if I get an arc, adjusting the coil collars to best sustain it makes sense. Good to know it cannot draw more than 20A in series though in scratching my head in how given a 25A listed and 16.66 amp combination in series for now 60v each works out well on a 20A breaker - I would be doing a 30A breaker (L21-30) for testing as I think sensible given I don't need the 60A breaker.... confused on my part on how to test - combination of Jon' and JD's or one of the two. Sorry Joh' leaning towards JD's concept in not a competition and thanks to both of you for advise. Will discuss with the head of our electronics repair - he is much smarter about stuff like this. In the mean time, I think I have the last of the parts I need coming in tomorrow, so in theory by this weekend it's done. After that... political and timing to actually get tested, much less "this rusty old thing" back to the shop. Photo's once done, but might be a while before it strikes an arc - at least a week before I buy the new carbons.
 
20 amps is what you get with the sliding tap all the way to the end of the resistor. Apparently, the sweet spot for the carbon rods was 25 amps, so the sliding tap could be moved to lower the resistance, which increases the current. That's why they used adjustable resistors. Hard to say whether modern carbon rods perform differently.
 
In past readings of old carbons, hopefully modern ones are more pure and spatter less = Iriquois fire. So for say 120VAC, this individual coil tap might be needed in getting say in the range of 1.5 ohms resistance?

Metered resistance, dual coil 3 ohm's, single coil 6 ohm's. Wow! how the heck did you know this?

Dual core resistor on assembly isn't really adjustable. The bracket is too tight for sliding and you would need to remove all conductor attachments before adjusting it. Photo in wiring direct to bracket or return resistor wires isn't me getting lazy, once the glued together ceramic cores were done, I had to clamp to install center rod retaining cotter pins. I didn't want to further stress the very old resistor core wires in perhaps wrapping back around the hard to install ceramic cores for attachment.

The other first (right) single coil is very adjustable especially without the return wire wrapped around the ceramic core in being neatly wrapped around the back of the coil. It will go down about 1/3 it's length.

Startup I think is try with the dual core resistor, than if there is a problem, bridge it to the single core adjustable one, and adjust it down as needed... correct?


Ignore my mis-wiring of the power in... brain fart in that I had it correct at first and reversed that. A bit more of correct color fiberglass sleeving over the conductors to cut or replace and new crimp terminals - simple fix. Getting really close. Thanks for the help. Properly grounded to frame now.
 

Attachments

  • IMG_20181018_231300885.jpg
    IMG_20181018_231300885.jpg
    314.3 KB · Views: 128
Two resistors set high will give you 3 ohms. Assuming 120 volts line in, and about 35 volts across the arc, would give you a run current of 28 amps / strike current of 40 amps. Using the rating of 110 volts, run current 25 amps / strike current of 37 amps. Both of these numbers DO NOT take into account the voltage drop across the solenoid. I have no way of knowing the inductive value of the coil, but let's assume it drops 10 volts. Now the current at 110 volts would be 22 amps run / 33 amps strike. For 120 volts, 25 amps run / 37 amps strike.
 
Assuming my voltage is about 125VAC line.. fixture is ready, just need to buy new carbons. I have a note from the welder that broke one of the rods research of Eisco Labos Carbon Rod Electrodes - as a source. At this point I only need two new ones in not trusting the original given all the chemicals and heat involved necessary to remove it. That much less say a 1900 carbon rod would no doubt have more impurities than a modern one. Almost ready.
 

Attachments

  • IMG_20181025_215733632.jpg
    IMG_20181025_215733632.jpg
    319.6 KB · Views: 114
Very nice looking restoration, Ship! I see now why it originally fell over & broke--very large "top structure" on a short-legged caster base. Doesn't look like it would take much of a push!

Have you fired it up, and how did it do?? (The world wonders.)
 
Thanks guys for the help. TBD burning down the building, or at least it's going to work, need adjustment or be brilliant. At the moment it has poplar flat black rods for the carbons... Also need to search my inventory for a female 30A stage I plugged it with so as to make an adaptor with to L21-30. Could just plug direct, but will see what I have in stock. Shame of the project was sand blasting almost everything was necessary due to shop management wants, think it because the clients don't see the original paint and patina - they see the rust and dings. At least that's what shop management wanted in sand blasting most all of it & re-painting. Did my best given that requirement & will see if management lets it back into the shop or sends it to a storage building to... Only good thing I can say about the total down to bare metal restoration is that I was able to learn a lot more about the light in finding stampings or cast iron verses cast bronze parts I will have never thought of, or stamped wiring designation. In the end, might work and probably better we did a complete tear down and start over. TBD the testing, not a rush for me but will post once done... think it's going to work.
 

Users who are viewing this thread

Back