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Author Topic: Intermissions, planning and longevity of carbons Robert Harris Film Handler Posts: 95 From: Bedford Hills, NY, USA Registered: May 2003 posted 08-11-2003 08:43 PM                     I was about to post to HTF in a thread regarding intermissions and thier necessity. I'm certain that someone (or several) here can tell me how long the average carbon lasts for arc projection, ie., how often do the rods needs to be replaced? RAH  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 08-11-2003 09:16 PM                     It is very dependent on the lamp type carbon trim and current A superex trim say 7mm neg and 8mm postive will burn 40 min at 65amps before the but needs to be moved forward in say a magnarc to get one more reel but at 60 amps it will do 1hour A futura with joinable carbons acan typically do 61-65min on a trim at 135amps  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 08-11-2003 09:36 PM                    I remember running hour reels on Futuras with no problem. In fact IIRC the positives (uncoated, rotated and moved forward by knurled rollers, current entering the rod close to the business end via water cooled silver contacts) could probably have gone 2 hrs. The negative (copper coated) was long enough as well but the negative mechanism which was a screw feed only had a bit over an hour of travel at whatever current we were running at. You clamped a new negative near the middle and after an hour reel cranked the mechanism back down and clamped it at the end for another one hour run. An adventurous machinist could have created modified components for a 2 hour Futura.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 08-11-2003 10:50 PM                        The National Carbon Bulletins (December 1957, Issue 3) published burn rates for various trims: http://www.film-tech.com/manuals/CARBONBULLETINS.pdf  |  IP: Logged William Hooper Phenomenal Film Handler Posts: 1879 From: Mobile, AL USA Registered: Jun 99 posted 08-12-2003 12:40 AM                        About two reels is a very gross, general, sight unseen mental measure.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 08-12-2003 07:26 AM                       Joinable carbons are no longer available.  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 08-12-2003 07:44 AM                        I'm pretty sure that we could do 60 minutes with Enarc lamps and 7mm x 9" and 8mm x 14" carbons. For a full 20-minute reel, we burn about 4 1/2" of positive and 1 1/2" of negative, so the carbons are long enough. I don't remember offhand how long the "carriage" (or whatever the proper term is) is for the positive, though, so it might not be possible without stopping and re-setting the positive carbon. I haven't run Peerless lamps lately, but I think that the situation is pretty much the same. On the other hand, I've seen some Ashcraft lamps which won't burn more than about 30 minutes per trim. I guess that the answer, then, is "it depends."  |  IP: Logged Mitchell Dvoskin Phenomenal Film Handler Posts: 1869 From: West Milford, NJ, USA Registered: Jan 2001 posted 08-12-2003 08:08 AM                     My experience has been 40 minutes in most theatres I worked in that ran carbons back in the 1970's. You could get another 20 minutes out of a set of carbons, but you needed to stop and re-seat them in the jaws after 2 reels. There were some theatres that were exceptions to this, but in general, 2 reels uninterupted was maximum. Before my time, but it is my understanding that when 3D was introduced (Polarized duel projector), the power to the lamphouse was reduced to allow for the 60 minute burn time. The lower light output was compensated for by the fact that you had 2 projectors (and 2 lamp houses) lighting the screen. Other than 3D where both projectors were being used at the same time, I do not believe carbon burn time had anything to do with intermissions. Theatres projected directly from of 20 minute reels, switching between the 2 projectors. In non 3D films, the only reason there would be an intermission was so that people could go to the bathroom and buy more popcorn. There was no technological reason for it. /Mitchell  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 08-12-2003 11:31 AM                     Morganite used to make 16 inch versions of the superex carbons and their lamphouse the autoarc would run 69min on a full trim at max amperage with the longer carbons Also some of the Kalee lamphouses allowed the full 14" stick to burn in one pass  |  IP: Logged John Spooner Expert Film Handler Posts: 186 From: South Australia, Australia Registered: Jan 2003 posted 08-12-2003 11:44 AM                     With this fellow here, we get 65 mins maximum from a full trim of 7x9 negative and 8x14 positive carbons. Currently using the Indian Schutz carbons.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 08-12-2003 03:00 PM                     President arc, mech looks like a 20 or 21. Nice condition, but it looks a bit odd without the spoolboxes. It looks like new, and it must be at least forty five years old now. I take it those are 6000 foot spools you are running there. Kalee did make 6000 foot spool boxes, they weren't common, but a pair of machines installed in the National Film Theatre at one time had them, for running two strip 3-D, as did the Kalee Vistavision projectors, of which I believe four were built. Do you only have one machine? There obviously isn't one behind the port in the foreground, is there another one behind the camera? If you only have one, how are you managing with a 65 minute run time? Is it an application where you only need to run shorts? What do think of the Schutz carbons? I've heard varying reports of them.  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 08-12-2003 03:25 PM                        Those spools look like the Cinemeccanica plastic ones. They'll hold 75 minutes of polyester easily.  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 08-14-2003 07:44 AM                        I took a closer look at the Enarcs last night; it looks like the positive feed mechanism can only feed about 10" without stopping and re-setting the carbons, so for us that would be about 45 minutes' worth of continuous running time.  |  IP: Logged Robert Harris Film Handler Posts: 95 From: Bedford Hills, NY, USA Registered: May 2003 posted 08-14-2003 09:13 AM                     How did I know that this group would have the answsers? Thank you to all. RAH  |  IP: Logged Frank Aston Film Handler Posts: 54 From: Albrighton, Shropshire, UK Registered: May 2000 posted 08-14-2003 05:00 PM                     Hi Robert, Given the fantastic resoration work with which you've been involved, can I ask what precipitated the question? Kind regards, Frank.  |  IP: Logged

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