Film-Tech Forum ARCHIVE: Century SAW latteral shake

This is topic Century SAW latteral shake 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=007057

Posted by Dominic Espinosa (Member # 2122) on 03-26-2005, 01:32 PM:

Howdy.
After some poking and prodding I've come to the conclusion that the only real problem with the projected image in our big house is the slight latteral image instability.
It seems to shift only slightly side to side randomly.
I'm probably the only one that notices it, but it bothers the hell out of me.

I've looked at the sprockets, the teeth all seem to be in good shape, pad rollers are properly adjusted, preassure straps are comfy at 12 o'clock, gate is properly adjusted, latteral guide rollers are clean, no high spots that I can see, and have no unnecessary play.
I did notice though that the intermittant shoe has a small amount of latteral play, whereas, the other centuries I've looked at with rock solid images either have much less or no play at all.
Could this be the cause of the instabillity and what causes it to shift like that?

Posted by Mark Gulbrandsen (Member # 72) on 03-26-2005, 01:38 PM:

Check the lens mount to see if its loose at the top where the eccentric rotates to shift the lens mount laterally. This is a common thng to happen on SA's. There are two set screws that adjust the clearance between the ecentric and where it passes through the top of that mount casting. Tigntening up these screws will get rid of any slop in there but be careful not to over-tighten them ir you won't be able to adjust it if needed. remember that half a thou. of play there could translate into inches on the screen depending on your magnifacation factor.

Mark @ CLACO

Posted by Dominic Espinosa (Member # 2122) on 03-26-2005, 01:52 PM:

It seems to me I did tighten that a while back, back in the days of severe shake in that house.
I'll look into it.

Posted by Louis Bornwasser (Member # 3063) on 03-26-2005, 01:58 PM:

Adding to Marks response:
Also look at: 1. end play on lateral guide roller. The needle bearings sometimes wear allowing a little bit of slop. 2. If the "studio guides" actually touch the film, then variations in film width could show as a jump. Just like curved gate XL's. Centurys do not require any lateral guidance except that provided by the sprocket & lateral guide system. 3. Check to see if the entire sprocket and star shaft have excessive end-play.

BTW: Glad you are so attentive.

Posted by Dominic Espinosa (Member # 2122) on 03-26-2005, 02:23 PM:

I did manage to check those.
Basically, I refuse to be the "ghetto theater" as the staff generally refers to it, so I do everything I can to make the presentation as perfect as possible on every run, even if the auditorium is empty.
No ghetto theater does that!

Posted by Darryl Spicer (Member # 711) on 03-26-2005, 02:29 PM:

quote:
latteral image instability It seems to shift only slightly side to side randoml

So you are saying the picture is weaving horizontaly or jumping verticaly?

Posted by Mark Gulbrandsen (Member # 72) on 03-26-2005, 03:50 PM:

quote: Louis Bornwasser
If the "studio guides" actually touch the film, then variations in film width could show as a jump.

As a matter of habbit I always remove the studio guides and throw them in the nearest trash can. An SA will actually run steadier without them than with as there is too much film width variance in booths. They actually do nothing at all to improve the lateral streadiness on any projector and usually cause more trouble than they're worth!! A lateral guide roller in good shape and set properly,plus a good quality sprocket are the key items to dead steady lateral positioning.

Mark

Posted by Louis Bornwasser (Member # 3063) on 03-26-2005, 08:50 PM:

Agreed! they have no business near film. I leave them in since they guide in the aperture plate in a manual machine. I do , however, move them as far away from the film as I can get them.

Looking at machines we overhaul, many are severely worn, which shows that they touched the film edge. Also, I have quite a problem trying not to sell replacement guides to customers who believe they need them.

Posted by Dominic Espinosa (Member # 2122) on 03-27-2005, 03:10 AM:

Daryl, it's horizontal.
Mark, I checked the locking screws and it seems one of them was just a hair looser than it should be. Must've worked itself loose, that took care of it for the most part but I'm still seeing a little unsteadiness in the image overall, though it is much better.
I don't recall seeing any wearing on the studio guides which are adjusted as far out as possible on all our machines.
Just for the sake of testing I'll pull them off next week and see what happens.

Posted by Mark Gulbrandsen (Member # 72) on 03-27-2005, 07:55 AM:

quote: Dominic Espinosa
Just for the sake of testing I'll pull them off next week and see what happens.

If they are as far out as possible taking them off shouldn't matter much as far as steadiness goes but it makes cleaning the trap ALOT easier. As Louis mentioned it takes a bit of getting used to for inserting the aperature plates without at least then outer one in there, but its still not really difficult.... Again just takes gtting used to.

Mark