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Author Topic: Striking an arc Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 05-15-2003 11:10 PM                        Unless you had a lamp (like the one Strong made) that used some form of automatic alignment mechanism, how could any automatic form of striker give you a consistent trim?  |  IP: Logged John Stewart Film Handler Posts: 67 From: Austin, TX, USA Registered: Sep 2001 posted 05-15-2003 11:20 PM                     For a lack of better terms, I think we called them strikers. Ours were not made of copper but were the same material as the rods themselves. Carbon maybe. The ones we used were pointed on one end and the other had a "v" shape that allowed you to position that end on the edge of the crater. I positioned them at the same angle that the carbon rotated and they were kicked out as they struck. Didn't have any problems with them other than small fragments on the bottom of the housing. They were fairly reliable as I recall. Of course, I'd rather be on hand for change overs but it wasn't always possible. We were making automated change overs on 5k reels in that booth and 6k in the other with a lobby between the two. It was the Mann's Fox in Austin. We were running Norelco AA in that house with Strong lamps. The other house was Xenon. John  |  IP: Logged Rick Long Jedi Master Film Handler Posts: 759 From: Toronto, Ontario, Canada Registered: Nov 1999 posted 05-15-2003 11:24 PM                     Back in the 70's Barry Blackburn and I (both working for General Sound and Theatre Equipment in those days) worked out a way for a Kneisley ignitor to strike a carbon 7 & 8 trim in a Peerless Magnarc. Worked every time. If failing memory serves, it seems we had to use a relay to disconnect the arc-feed motor while striking though.  |  IP: Logged James Robertson Film Handler Posts: 40 From: Sydney, Australia Registered: May 2001 posted 05-16-2003 05:39 AM                     Bernard "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." I worked the original Projectomatic in the late 50's using the slugs to strike Peerless Magnarcs. The problem was that the automation struck the arc on the motor cue which only gave 7secs for the arc to stabilise before changeover. Not even a Magnarc is that good so often the light was unsatisfactory on changeover. We solved the problem by striking manually about a minute before changeover which sort of defeats the purpose of automation! Jim James  |  IP: Logged Jim Spohn Film Handler Posts: 95 From: Bakersfield, CA, USA Registered: Jan 2003 posted 05-16-2003 09:15 AM                     Paul... You're right about Ashcraft making lamps for RCA. My lamps have an RCA emblem on them but were clearly made by Ashcraft. RCA called these lamps "BRITE ARC" they are 120 amp high intensity, water cooled and rotating carbon. The unit that rotates the carbon is a ratchet affair and makes a click - click - click sound that takes a while to get used to. Give up my carbon arc lamps??? NEVER!! (I do have a couple of Super Lumex just in case I can't get carbons any longer.)....Jim  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 05-16-2003 10:51 AM                       Wide-Arc and Dyn-Arc were RCA "versions" of Ashcraft Cinex, and Super Cinex, respectively. There were other models, too. The Brite-Arc may be an Ashcraft Hydro-Arc.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-16-2003 02:31 PM                     Union Carbide made the pellets to autostrike Raven Labd made a rotary solidoid tht mounted onto the back of the slip clutch for the negative feed of the magnarc with a current sensing relay to auto strike them. It worked every time Morganite also built the auto arc that had a solinoid striker in it  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 05-16-2003 03:18 PM                     Jim, I am surprised you can find carbons for that thing. I had some 11mm black stick lamps I ran for years, and near the closing of that theatre (Drive-in) we found that carbons were getting extremely expensive... My lamps were (if I recall corectly-been over 25 years now) were called the Hi-Arc. It didn't have the ratchet assy to rotate the positive carbon. It was just a chain drive to the collett.  |  IP: Logged Robert Throop Master Film Handler Posts: 412 From: Vernon, NY USA Registered: Jun 99 posted 05-16-2003 03:21 PM                     The RCA Brite Arc sounds like the Ashcraft Super High. I don't believe the Hydro Arc rotated the positive carbon.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 05-16-2003 03:31 PM                     If the neg carbon was off-set, the positive carbon had to rotate. Without rotating, one helluva toenail would develope on the positive carbon. If it were a head-on feed, rotation of the positive carbon was not reqired unless there was a reason I don't know about.  |  IP: Logged Robert Throop Master Film Handler Posts: 412 From: Vernon, NY USA Registered: Jun 99 posted 05-17-2003 01:17 PM                     The carbons in a Hydro Arc were coaxial like in a suprex lamp.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 05-17-2003 06:06 PM                        Paul mentions that a "toenail" would develope on the negative carbon if it didn't rotate, but on occasion I have seen such a lip develop on the neg carbon in a Magnarc lamphouse (non-rotating carbons). Anyone know exactly why this happens? I haven't been able to pinpoint what conditions cause it, but when it does happen, it can drop light output to almost nothing and cause the drive motor to go wild. There is a tell-tail hissing sound the arc makes when this gets going. If you don't hear it and are not paying attention, your screen can go nearly black. You can get rid of the lip by smashing the two rods together for a moment and that will break it off, but that solution causes a momentary near-blackout on the screen. I found that using a thick screwdriver and reaching into the lamphouse and giving the tip a good whack with it will break it off and not be quite as disruptive to the screen image. It also gives you a nice sunburn on your forearm. Frank  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-17-2003 06:23 PM                     Two common problems To short an arc causes mushrooming and too high of current will cause spindling where the neg gains a long slender point Also there can be a problem with formation of a carbide tip on the negative that will make it hard to strike  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 05-18-2003 12:57 AM                     I have seen spindling as Gordon has described, mut never a toenail on a negative rod. However, I have seen a "ball" form on the tip that drives the arc nuts. Getting rid of it was easy to do if you smash the negative carbon into the positive. Of course, a couple of times I got a little too hefty the negative feed knob....and broke the positive carbon off slicker than snot on a brass doorknob.  |  IP: Logged

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