Film-Tech Forum ARCHIVE: Using different diameter Carbon Rods, is it possible?

This is topic Using different diameter Carbon Rods, is it possible? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Ryan Plaisted (Member # 2409) on 05-11-2004, 11:39 AM:

This is my first post here, but there will be many, many more to come soon. I work at the Ioka Theater in Exeter, NH and recently the GM up and quit. And that leaves me all by myself. I've only worked there for a about two months and have had minimal training, so I'm going to have to be on a steep learning curve. Hopefully, you can help.

Okay, first question. We are using Ashcraft Suprex lamphouses which have a hole that fits 8mm positive rods (and nothing larger), which I am running out of. I have a case of 9mm rods that we have received by accident. The piece that holds the positive rod uses a bolt to hold it in and the bolt hole has been stripped (and retapped and then striped again, several times) and I was already thinking about just machining another piece (I talked to the people at Ed Wolk and they don't have the piece, but if anyone knows of a source for Suprex parts that would be useful, too.) If I was going to machine a part I would just make the hole fit 9mm rods as well.

So, my question is, Can Carbon Arc lamphouses burn any size carbon rods? Do the positive and negative rods have to be close in size (I have 7mm and 8mm negatives for some reason). What happens with larger rods: are they brighter or do they burn longer?

Okay, that's it for now.

Posted by Scott Norwood (Member # 30) on 05-11-2004, 12:00 PM:

Different diameters are for different amperages. You'll have to check the current rating for the 7mm negative and 9mm positive, as well as the capacity of your rectifiers.

New carbons (including 7mm/8mm, which is quite common) are available from Marble. You might be able to trade the 9mm carbons with another theatre, as the larger sizes are usually more expensive.

BTW, _please_ send in pictures. The Ioka is a great theatre.

Posted by Pete Lawrence (Member # 130) on 05-11-2004, 02:57 PM:

Here are a couple links with sizes and amperage ratings. I have no idea as to the quality of their products.
cinemacarbons.com
Marble Double Eagle

Posted by Steve Kraus (Member # 476) on 05-11-2004, 07:06 PM:

Bravo to anyone running carbon.

Posted by Jack Ondracek (Member # 1466) on 05-11-2004, 09:48 PM:

Even if you can do this physically, and assuming you can burn a proper crater into the positive with the amperage you use now, you'll have to readjust the negative feed to keep the trim in place. That may not be possible, if it's outside of the design parameters of the lamphouse.

I never had good luck with the Marble carbons, but that may have changed over the years. The best service I was able to get out of them was when I kept them in a broken-down refrigerator with a light bulb in it to burn off the moisture.

Posted by Ryan Plaisted (Member # 2409) on 05-12-2004, 11:48 AM:

Alright, in that case I'll forgo the experiment and get some 8mm.

Thanks for the supplier links. We have the Marble DE's now and I've never had a problem with the exception that if I keep rods "on deck" in the lamphouse for too long they get warped and won't fit.

I'll try to get pictures up in the next few weeks.

Posted by Randy Stankey (Member # 64) on 05-12-2004, 04:28 PM:

quote: Jack Ondracek

I kept them in a broken-down refrigerator with a light bulb in it to burn off the moisture.

Would something like a welding oven used to heat welding rods/electrodes before use be handy to have in a carbon house?

Yeah, at $800.00 it's not cheap but (A) it could save you at lot of trouble (less trouble = less money lost) and (B) I'm sure there are smaller, less expensive models out there that do the same thing.

...Just a thought.

Posted by Gordon McLeod (Member # 33) on 05-12-2004, 06:13 PM:

All one has to do is put a couple of trims inside the lamphouse a day ahead of time and they will be ready to go

Posted by Jack Ondracek (Member # 1466) on 05-12-2004, 06:44 PM:

yah... we did that, too... but we had to brute-force the early Marbles, and the refrigerator method did as much as anything.

None of that was required with Nationals [Frown]

Posted by Gordon McLeod (Member # 33) on 05-12-2004, 06:49 PM:

The only carbon I used to dislike was the Ibagwa line called Sunny Carbons also the Diamond carbons sorta sucked too