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This topic comprises 2 pages: 1 2
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Author
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Topic: Carbon Arcs and Health
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 09-20-1999 08:03 AM
I worked my way through college as a projectionist at the Grandview Drive-In theatre in Angola, NY. (It's still in operation, even without me  ). On cold nights, we would turn off the lamphouse blower system to keep the booth warm. When you came in from the outside, it would have a very strange odor. I really disliked the messy annual job of using a shop vac to clean out the carbon ash from the vent system. Last time I checked, I'm still in good health at age 51 (cough, cough, hack, hack,...).The other operator used to heat his pizzas and other food in the Ashcraft Super Cinex lamphouse. Lost track of "Carl", but not sure all those "rare-earth compounds that provide the special qualities of the light" (quote from National Carbon Technical Bulletin) were very good for his health. This was before OSHA (1967-1970), and before I knew any better. Does anyone else have carbon arc "war stories"? ------------------
John Pytlak, Senior Technical Specialist
Worldwide Technical Services, Professional Motion Imaging
Research Labs, Building 69, Room 7419
Eastman Kodak Company
Rochester, NY 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
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Rick Long
Jedi Master Film Handler
Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999
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posted 09-22-1999 10:46 PM
Me again. Sorry to hog the post, John, but you've hit upon one of my favourite topics.
I apprenticed with my Dad in a carbon-arc booth. The company who owned the theatre switched carbon brands from National (the best) to a cheaper brand, subject to core "blow-outs", often extinguishing the arc in the middle of a reel.
While lecturing me, with his back to the lamp, my Dad would abruptly about-turn and re-strike the arc before I even knew it had gone out. I began to wonder (as I often suspected as a youth) if he indeed had eyes in the back of his head.
It was not until I became a projectionist that I realized that he had reacted to the sound of the Peerless arc-feed motor suddenly speeding up, and how important the sense of hearing is to a projectionist. Spending enough time in a booth, one gets used to the natural sound of the equipment. This sense often acts as an early-warning system; detecting film not riding properly on a sprocket, unusual bearing or belt noise, ect.
When I go on a service call, and the projectionist reports that his equipment doesn't "sound quite right", I pay attention.
In all too many new multiples, this warning system is impeaded by craming exhaust fans and H.V.A.C. elements into the projection booth.
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Randy Stankey
Film God
Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99
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posted 09-22-1999 11:19 PM
Yeah, I hear you!When my friend taught me how to work arclamps, he showed me how the sound of the arc can tell you it's out of trim. First it starts to whistle a bit then it sounds like somebody letting the air out of a balloon. (Unless you have an AC arclamp. They whine continuously, but they are almost never found in projectors. Mostly old theatre follow spots and stuff.) Anybody ever light a cigarette off one?
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Scott Norwood
Film God
Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99
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posted 09-23-1999 07:55 PM
Are carbon-arc setups really all that bad for one's health? Most of the carbon-arc installations that I've seen are extremely well ventilated (as are the xenon setups that were installed in former carbon booths).
I started working as a projectionist (part-time) about a year and a half ago, running 2000' and 6000' reels and xenons. I did some carbon-arc work over this summer, though. For theatre use, my personal preference is for carbons, but I realize that it would be pretty foolish to install this sort of setup in a newly built theatre or as part of a renovation. Still, I really like the color temperature of carbons, and I like the convenience of being able to strike the arc for, say, a single trailer, without feeling guilty about taking a lot of time off of the useful life of the lamp.
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John Wilson
Film God
Posts: 5438
From: Sydney, Australia.
Registered: Dec 1999
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posted 09-24-1999 03:40 AM
I remember well as my Dad was training me as a 9 year old 'apprentice' at the drive in, going down to the cafe just before intermission and buying two ultra 'freshly' made hot dogs and throwing them into the carbon arc lamphouse while we showed the manditory 20 mins of advertising slides. At the end of the intermission and as the 2nd feature was cranked up and running away happily, we opened the lamphouse and ate our still hot (perhaps even hotter) fresh hot dogs. MMMMMMMMMMMMMMmmmmmmmmmmmmmmmm
hot dogs........................... ------------------
John
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Rick Long
Jedi Master Film Handler
Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999
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posted 09-25-1999 10:55 PM
I promise that this is probably the last post I shall make on this subject. It can then, like carbon-arcs should be, forever laid to rest for once and for all.
For the newbies, let me briefly describe the proceedure of a reel projectionist in striking a generator-powered carbon arc.
On the rear of the projection base was a two-bladed knife switch. To strike the arc, you "threw in' the knife switch, brought the negative carbon into the positive carbon, then quickly seperated the them to form a gap of about 1/2 inch to establish and arc. This was a proceedure you followed at least every 20 minutes of your working day. It was an autonomic response to the reel-end alarm - you didn't have to think about it - you just did it.
The arcs at Paramount, Peterborough were powered by a Transverter double-ended generator (basically a big three-phase motor with a D.C. generator on each end - one for each 70-amp arc.) Dual field controls practically negated the need for power-robbing ballast resistors.
One night, the generator for RIGHT arc began to exhibit an unusually strong "ring of fire" around the commutator. Ohmeter checks showed a couple of windings to be open. Due to the prohibitive cost of repair, it was decided to switch to rectifiers - but they wouldn't be available for three days. We were left with the problem of providing a continuous performance with only power for one arc.
We elected to use a series-arc configuration. WIRING: GEN+ to LEFT ARC +; LEFT ARC - to RIGHT ARC +; RIGHT ARC - to GEN -. Both knife switches were jumped so that when "thrown in" they would short-circuit their respective arcs.
To start the show (typically on LEFT projector), you threw in the RIGHT switch (providing full power to LEFT projector. You struck the arc, and started the show.
The tricky part was the change-over. You brought the LEFT (operating) arc to 3\8 inch,
at RIGHT arc you used the tounge-and-finger method to "wet" the negative carbon and then jam it into the positive carbon. You then "threw out" the RIGHT shorting switch and GENTLY brought the now-glowing carbons apart;
being careful not to go to fast less you extinguish both arcs, and cause a performace interuption. With both arcs burning (at about 40 amps) you made the change-over. You then proceeded quickly to LEFT arc to throw in the shorting switch. Just as quickly, you proceeded to RIGHT arc to separate the gap to 1/2 inch before it covered your reflector with soot from those wonderful rare-earth compunds.
You had to be be damn careful not to lose concentration and let your mind wander. Throwing both switches in would have resulted in welding the switches "in" and shorting the last available generator.
As you can imagne, we were somewhat releived to see the arrival of the new rectifiers.
So, maybe there are some advantages to xenon after all, but I sure felt more like a "projectionist" in those days.As you can probably imagine, we were somewhat releived to see the arrival of the new rectifiers.
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