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Author Topic: Striking an arc Jim Spohn Film Handler Posts: 95 From: Bakersfield, CA, USA Registered: Jan 2003 posted 05-15-2003 09:48 AM                     The method of striking an arc with a zenon bulb is of course a high voltage spike across the electrodes to ionize the space between them and therefore create a path of conduction. Does anyone know if that same technique would work with striking a arc in a carbon-arc lamp, assuming that the correct trim distance, (or closer)is between the carbons, then let the feed motors adjust the trim ?....Jim  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-15-2003 10:11 AM                     It will work but the odds are against the arc staying lit as it will probably blow the core out of the postive carbon when it lights  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 05-15-2003 10:44 AM                        I remember trying little ignitor links that were sold in the late 1960's to try to automate lighting a carbon arc lamp. The link was placed between the negative and positive carbons, and when the lamp was energized, the link would vaporize and SOMETIMES light the arc. Does anyone remember what these were called, and who sold them?  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 05-15-2003 11:38 AM                     There was a type of arc lamp known as a Jablochkoff Candle, which had two parallel carbon rods a few millimetres apart, with the gap between them filled with an insulating material {magnesia?) The tops of the rods were joined by a small carbon bridging piece, and the burning away of this, when the current was applied struck the arc. The insulating material just crumbled away as the rods burned down. Sometimes several 'candles' were mounted together, each one striking automatically when the previous one burned out. They had to be operated on a.c. to ensure an equal rate of consumption of the two electrodes. The idea was to avoid the complexity of an automatic feed system, but I've seen one operating, and they didn't give a very good light. Also, if the arc went out for any reason, it would not re-srrike. They were used briefly for street lighting, I believe that the Victoria Embankment, in London, was lit by them for a while.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 05-15-2003 01:25 PM                     John, I used them, too. But I also forgot what they are called. I made my own. Real simple. Just take a used carbon rod, smash it with a hammer and use a small fragment that contains part of the core. They had (the ones I made) had about a 66% hit, but they were not worth the hassle.  |  IP: Logged Jim Spohn Film Handler Posts: 95 From: Bakersfield, CA, USA Registered: Jan 2003 posted 05-15-2003 02:18 PM                     I knew that the very clever guys on Film Tech would have the answers!! Thank you gentelmen......You have given me many ideas to play with......Jim  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 05-15-2003 02:46 PM                     Those pellets were still around in the 80's and early 90's. Evil things, they showered the innards of the lamphouse with crud when they vaporised. If you didn't have automatic rear dowsers (a la Magnarc), or you hand't closed the mirror dowser the life of the shiny bowl shaped part became somewhat reduced. I seem to recall them being marketed for use with Cinemation, and something to do with the Fedi 'monster' is ringing a bell in my grey matter too.  |  IP: Logged Bernard Tonks Jedi Master Film Handler Posts: 619 From: Cranleigh, Surrey, England Registered: Apr 2001 posted 05-15-2003 03:05 PM                     They were called copper slugs, supplied to cinemas with Projectomatic automation with the drum. Later models were Cinemation, the first types with a drum, then matrix boards. I worked at one cinema that had Projectomatic ‘0’ model which only did changeovers. I found the copper slugs very reliable. The BTH SUPA carbon arcs struck automatically when switching on manual or automatic, the negative carbon kissed the positive carbon with the aid of a solenoid.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 05-15-2003 03:55 PM                     Bernard said: quote: ...the negative carbon kissed the positive carbon with the aid of a solenoid. That was a great idea. Many moons ago a thought like that went through my mind but I never tried it because I was not that lazy to get off my butt and strike tha arc like a normal projectionist.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 05-15-2003 04:20 PM                       quote: Does anyone remember what these were called, and who sold them? I have a box of these somewhere. Mine are Nationals.  |  IP: Logged Jim Spohn Film Handler Posts: 95 From: Bakersfield, CA, USA Registered: Jan 2003 posted 05-15-2003 04:58 PM                     Paul...The reason that I want to strike the arcs automaticly is that every thing in my theatre is remote control from both stationary and hand-held remotes, house-lights, curtains, stage lights and booth etc. There are times when I have to play the pipe organ myself then run to the booth and start the movie (10 minute silent) then run back down and play for the movie. When the film is over I can shut down the projector via remote. It seems like a good idea to be able to start the film from remote also. There is nothing here to say that I'm not a lazy-ass because I am, but I just don't want to be a track star!! I know that a projectionst is the real answer, but that is'nt always feasable....Jim  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 05-15-2003 05:02 PM                     John, sadly I must say that it is probably time to retire the arc lamps since you are in that predicament  |  IP: Logged Robert Throop Master Film Handler Posts: 412 From: Vernon, NY USA Registered: Jun 99 posted 05-15-2003 07:11 PM                     The Peerless Hi Lo made in the late twenties also had a solenoid operated striker.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 05-15-2003 08:26 PM                     If one was to home-brew a modification of a carbon arc lamp to use a solenoid for arc striking, the Simplex High and the Enarc would be the easiest to do, as they have striking triggers that are not ganged with the feed motors either directly or indirectly. The rest that I know of requires the operator to rotate a crank or a knob (as an example, Ashcan's, Peerless, Strong, RCA Hi-Arc, Wide Arc, etc.) to kiss the carbons. Robert, isn't that an old "Ashcan" you have there that uses the "Black Stick?" I am confused, because it looks like an RCA emblem on it. I could be wrong, but didn't Ashcraft build some for RCA?  |  IP: Logged Robert Throop Master Film Handler Posts: 412 From: Vernon, NY USA Registered: Jun 99 posted 05-15-2003 10:19 PM                     Paul, That's a Brenkert Supertensity condenser arc. It burned 13.6mm carbons at currents up to 180 amps. It was Brenert's answer to the Peerless HyCandescent.  |  IP: Logged

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