Film-Tech Forum ARCHIVE: Strong Arc lamps

This is topic Strong Arc lamps in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Phil Krikau (Member # 1501) on 06-07-2004, 04:34 PM:

Does anyone know of where I can locate the glass reflectors for the Strong rotating positive arc lamps. I'm also looking for the 11mm contacts. Please email Phil-K@webtv.net

Posted by Paul G. Thompson (Member # 655) on 06-07-2004, 08:04 PM:

Phil, I think it is time to convert to Xenon. The reason I suggest this is because the jaws are made of silver - and the last time I changed them in a Strong (or any other rotater) the client was billed 600 bucks for the jaws. That was 20 years ago...

Posted by Paul G. Thompson (Member # 655) on 06-08-2004, 05:54 AM:

Besides, I might have a mirror to fit it. If it is the right mirror, you can have the damn thing if you pay the postage. If I recall correctly, it was from a Strong Futura II. I thought it was a 13.6mm black stick that mine used. Can't be sure of that though. I bought them as junk. The mirror I have is a cold mirror, and is in almost perfect condition. BUT ONLY IF IT IS WHAT YOU NEED!!! I will take your word of honor. [Smile]

If not, I want to keep it for someone else that might need it.

Is this what you need?

Email me if you need more specifics. The monitors in the background are 21 inches so that will give you a rough size of the mirror. Please provide me with the diameter of your mirror, and the depth of the curvature.

Posted by Stephen Furley (Member # 1277) on 06-08-2004, 06:36 AM:

You might be able to find somebody who has converted, and still has their old lamps in store, who may let you have some old jaws that still have some life in them. A lot of old cinema equipment seems to be left in store when it is taken out of service, behind screens, in rectifier rooms, etc.

Posted by Mark Gulbrandsen (Member # 72) on 06-08-2004, 07:26 AM:

Wolk might still have some silver jaws left around. Give Juan a call there. I can remember the ole days when Charlie kept the silver ingots for making the jaws for Strong and Ashcrafts in a big safe cause some employee of his walked off with the stash of them once [Eek!]

.

Mark @ CLACO

Posted by Steve Guttag (Member # 268) on 06-08-2004, 08:33 AM:

The Futura II took either 13.6mm or 11mm positive carbons. The positive drive determined which you could use and were stamped on the face of each drive roller.

Steve

Posted by Sam D. Chavez (Member # 1841) on 06-08-2004, 09:31 AM:

There were jaws for 10mm as well. They had air cooled jaws as well, which made burning carbon butts a real adventure.

Posted by Steve Kraus (Member # 476) on 06-08-2004, 11:45 AM:

What if you machined some jaws out of copper? Would it melt (assume water cooling)? How about some other high melt metal and just deal with the greater resistance...maybe increase the contact area proportionally? Or perhaps something akin to motor brushes to take some of the job of getting the current into the rod.

Posted by Stephen Furley (Member # 1277) on 06-08-2004, 12:31 PM:

Pure copper melts at 1098°C if I remember correctly. That's fairly high; brass melts at something like 850°C, depending on its exact composition. I don't know the melting point of silver, but I have a feeling it is lower than copper.

http://www.webelements.com/webelements/elements/text/Ag/heat.html tells me that the melting point of silver is 961.78°C

I don't know how much additional heating you would get due to the increased resistance, but copper is a pretty cood conductor.

The Loew's Jersey managed to get new silver jaws for their Ashcraft lamps, but I don't know where from.

Posted by Martin Risher (Member # 2453) on 06-08-2004, 01:03 PM:

Hey, by the way!
Whats the best way to get those reflectors clean? Alche-ma-hole? Windex? A guy i know say he uses lens cleaner, but im a little unsure...

Posted by John Pytlak (Member # 331) on 06-08-2004, 01:19 PM:

My guess would be that the corrosion characteristics of copper would be an issue for good electrical contact with the carbon, or it would have been used.

Posted by Sam D. Chavez (Member # 1841) on 06-08-2004, 07:02 PM:

I believe Silver oxide is actually a better conductor than the Silver itself, or so I've heard. You don't see any copper contacts in relays for a reason.

Any silver cleaner will work if you want them to look pretty, certain Anal operators in my past lihe in the booth used to get them to shine like well, Silver.

Bon Ami was also used at the time to clean them

Posted by Steve Kraus (Member # 476) on 06-08-2004, 09:07 PM:

Yeah but Bon Ami wouldn't get the bloodstains off the ivory in The Ghost and Mr. Chicken. Amazing the useless things one retains. Atta-boy, Luther!

I think copper relay or switch contacts would weld themselves or otherwise erode from the arcing that occurs as they part under load. That wouldn't be the case with carbon contacts. I'm sure there's a reason they didn't resort to such a cheaper alternative but then it wouldn't be difficult for someone make up a set out of copper and give it a shot and let us know.

Posted by Paul G. Thompson (Member # 655) on 06-08-2004, 10:33 PM:

Deleted by me.

[ 06-09-2004, 02:22 AM: Message edited by: Paul G. Thompson ]