Film-Tech Forum ARCHIVE: Lamp burned a hole in the dowser?

This is topic Lamp burned a hole in the dowser? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Thomas Jonsson (Member # 1902) on 07-14-2004, 02:42 PM:

I have Victoria 5 with 4 kW lamp. I don´t know what
metal is used for the manual dowser in the lamphouse,
but the heat makes it bend. The same thing with the
change-over dowser. Sometimes it bend so much it get
stuck and I have to straighten it out.

Between the commercials/trailers and the main film I
have a short intermission (about 20 seconds) with the
dowser down. Tonight there was a big flick and the film
melted - there was an inch big hole in the dowser!

Is it really possible the lamp heat is so intense it
can actually burn a hole in the metal, even if it seems
to be somewhat thin? Or could there be some other
explanation?

There is no hot spot, the light is even on the screen, and
it doesn´t get hotter than usual in the front of the
lamphouse.

I didn´t beleive this could happen. In my opinion the
dowser should be made to resist the heat of the lamp at
least for a couple of minutes.

Thomas

Posted by Dominic Espinosa (Member # 2122) on 07-14-2004, 03:22 PM:

It is entirely possible. Now I assume your intermission is with the motor off? Otherwise, yowsa that things way out of kilter.

Anywho, I've seen it happen on 3k and 4k houses in simplex 35's...Those dousers are paper thin aluminum or something. The douser in a lot of lamphouses is just as thin unfortunately. I'd recommend looking for a replacement douser much thicker than the previous.
G'luck.

Posted by Robert Throop (Member # 61) on 07-14-2004, 04:01 PM:

Back in the carbon arc/changeover days one of the guys I worked with was always forgetting to close the lamphouse douser. He burned holes in many Century and older Simplex (Super, Regular and E7) shutters. The crews used to hang burned shutters on the wall with chalk arrows pointing to the holes whenever he was scheduled to work a relief trick.

Posted by Steve Kraus (Member # 476) on 07-14-2004, 04:22 PM:

This picture I posted last April shows a hole burned in a Norelco AAII shutter by a 4K xenon (actual measured power of about 3700 Watts).

(Film Yak Forum, Upload Your Forum Pics, Page 50)

Posted by Ken Layton (Member # 133) on 07-14-2004, 06:16 PM:

It's possible you need a heat filter in your lamphouse. Also, always be sure to close the hand dowser on the lamphouse when the projector motor is not running.

Posted by Adam Martin (Member # 641) on 07-14-2004, 10:15 PM:

I've seen Christie, Ballantyne and Cinemeccanica changeover dowsers all warped or burned through by lamps as weak as 2K. This can often happen when someone turns the lamp on manually and forgets about it at the end of the show.

Changeover dowsers are designed for brief use. Always use the hand dowser for when the lamp needs to be on for more than a minute or two.

Posted by Peter Mork (Member # 1336) on 07-14-2004, 11:28 PM:

I used to spell it "dowser" too. But in fact, a dowser is someone who uses a divining rod to look for water. A douser is something that extinguishes a light, which is what we do around here.

Posted by Jack Ondracek (Member # 1466) on 07-15-2004, 12:24 AM:

quote: Peter Mork
A douser is something that extinguishes a light, which is what we do around here.

ooops! Mea culpa!

As for the plates themselves, I guess that's one area I'd hand to the Pro35. The DOUSER plate... and the shutter for that matter, are both pretty thick, and don't seem to be negatively affected by brief missteps like leaving a lamphouse in manual.

... of course, I wouldn't know directly...having never done anything like that myself! [Roll Eyes]

Posted by Dan Lyons (Member # 1454) on 07-15-2004, 01:09 AM:

quote: Jack Ondracek
As for the plates themselves, I guess that's one area I'd hand to the Pro35. The DOUSER plate... and the shutter for that matter, are both pretty thick, and don't seem to be negatively affected by brief missteps like leaving a lamphouse in manual.

It would take one hell of lamp to mess those things up! 1/4" thick!

Posted by Joe Redifer (Member # 3) on 07-15-2004, 01:25 AM:

[av=n]

Posted by Dan Lyons (Member # 1454) on 07-15-2004, 01:45 AM:

Damn!!!! [uhoh]

Is there a gun hiding in your lamphouse?!

Posted by Adam Martin (Member # 641) on 07-15-2004, 01:48 AM:

quote: Peter Mork
a dowser is someone who uses a divining rod to look for water. A douser is something that extinguishes a light

We've beat that to death in a thread not worth searching for. We all know what's being discussed here.

Posted by Chris Hipp (Member # 1788) on 07-15-2004, 02:12 AM:

I've had dousers look like Joe's picture on 2k houses. Strong is making a newer type that is much more resistant. By the look of it I would say it is stainless steel instead of aluminum, but im not a metal expert.

Posted by Jeremy Fuentes (Member # 2135) on 07-15-2004, 07:03 AM:

quote: Dan Lyons was the last to post
As for the plates themselves, I guess that's one area I'd hand to the Pro35. The DOUSER plate... and the shutter for that matter, are both pretty thick, and don't seem to be negatively affected by brief missteps like leaving a lamphouse in manual.

This is true. I havent seen any kind of damage done on ours when the lamp was left on manual for extended periods of time.