Film-Tech Forum ARCHIVE: Christie Projector Damping Fluid

This is topic Christie Projector Damping Fluid in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=008698

Posted by Richard May (Member # 2627) on 05-06-2007, 08:45 PM:

I can't find anywhere in the manual as to how much fluid to put into the dashpot. There is no line or any mark inside the cup. I'm assuming that you fill it up about 3/4 to leave room for the plunger. Sound good?

Posted by Brad Miller (Member # 2) on 05-06-2007, 09:19 PM:

It's an airpot, not a dashpot. Just make sure there is enough air in the booth and you will be fine.

Posted by Mark Gulbrandsen (Member # 72) on 05-06-2007, 09:35 PM:

Also make darn sure the travel is not too much on the down stroke... or it will eventualy brake off the hollow shaft [Eek!]

.

Mark

Posted by Jeremy Weigel (Member # 4208) on 05-06-2007, 09:42 PM:

No fluid needed. If you're having a problem with the damper roller moving too freely or not freely enough, there is an adjustable valve on the bottom of the air pot accessable thru a hole on the bottom plate. It is adjusted with a small flat bladed screw driver.

Also check to make sure the piston rod is not bent. I have seen these get bent causing them not to move freely if at all.

Posted by Richard May (Member # 2627) on 05-06-2007, 10:22 PM:

That's too funny. See what happens when you're used to century projectors. Thanks Brad. I'll make sure to open a window when I go there next...lol

Posted by Darryl Spicer (Member # 711) on 05-07-2007, 12:18 AM:

In that picture above it looks like the damping rollers are pulled to far apart. Shouldn't they be pulled apart just enough to have a slight bounce.

Posted by Jeremy Weigel (Member # 4208) on 05-07-2007, 01:32 AM:

Pull out slack, then back off 2 sproket teeth or about 1/4" gap between the roller and sound drum. Thats what my manual has as the correct tension. Been doing it that way for almost 15 years with no problems.

Posted by Darryl Spicer (Member # 711) on 05-07-2007, 02:12 AM:

We use the 35GPS model here and we pull the film forward a sprocket or two until the damper rollers have a slight bounce in it. Doing this eliminates the risk of damaging the airpot and there is no problems with the sound.

quote: Jeremy Weigel
Also check to make sure the piston rod is not bent. I have seen these get bent causing them not to move freely if at all.

Not had any problems in 15 years yet you have seen the piston rods become bent. Interesting......

Just looked at that manual here on film tech to see what the differance was between that model and the one we use. In that manual it states that you pull the film tight on the lower constant feed sprocket with out moving the idle rollers. Then you move the film forward on the sprocket two sprocket holes. That's the way it says to do it on ours and you do not have that big gap between the rollers and the drum.

Posted by Jim Bedford (Member # 4) on 05-07-2007, 02:25 AM:

At least some of the early models of the Christie P35C were supplied with oil pots. I know because one of mine went bad (probably due to running low on oil and abrading the cylinder wall which reduced the hydraulic effect to almost nothing) causing warbles. Bevan Wright got me an airpot to replace it and now I'm running on one of each. Both seem to work equally well, but the airpot is certainly cleaner.

And Darryl's right about the need to allow only the minimum bounce and tension as possible. In fact, the abrading of the cylinder walls in oil pots may be exacerbated by allowing too much bounce which will promote the rubbing of the piston on the cylinder wall.

Posted by Jeremy Weigel (Member # 4208) on 05-07-2007, 03:07 AM:

quote: Darryl Spicer
Not had any problems in 15 years yet you have seen the piston rods become bent. Interesting......

Back in our Regal days we had a sister theatre in OKC that was always having problems with the piston rod getting bent. It was usually due to someone getting a little too rough while cleaning the projector. Sometimes though it was due to someone getting curious and over adjusting the air valve so that the resistance was too great.

Posted by Brad Miller (Member # 2) on 05-07-2007, 10:35 AM:

I don't think Christie's current projectors have this problem, but on the older ones I've serviced (late 90s) my trick was to simply snip a tiny amount off of the end of the rod before I installed the airpot. That way it wasn't physically long enough to "crash" when the lower arm pulled tight.

Regarding tension. I pull only one perf of tension over zero tension. A Christie tech pointed that recommendation out to me years ago and I have achieved the best performance when threading in that fashion.

Posted by Ken Lackner (Member # 1002) on 05-07-2007, 03:12 PM:

quote: Brad Miller
...my trick was to simply snip a tiny amount off of the end of the rod before I installed the airpot. That way it wasn't physically long enough to "crash" when the lower arm pulled tight.

I don't know if Christie has changed the airpot that they supply, but I have always had to do that when replacing one, or else it would not fit properly. Seems like the airpot is generic and you have to cut the rod to the length desired for your application.