Film-Tech Forum ARCHIVE: Vic 5 belts squealing

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Posted by Sally Burgess (Member # 1493) on 07-29-2006, 07:13 PM:

OK, its the inner belt...after taking it off and putting it back on I started the projector and the belt moved over to the far side where it rubs against the back and squeals away. Its giving off lots of brown dust. The top idler is at the right tension. Any ideas?

Posted by Gordon McLeod (Member # 33) on 07-29-2006, 07:37 PM:

Check the tensioning idler to ensure there is no build up
remeber that basic pulley theory a belt will always ride on the crown and that can trhough a belt off

Posted by William Phillips (Member # 1162) on 07-30-2006, 11:40 AM:

Ah, I have seen what happens when a belt gets throwen off the pulley, It can be not a very pretty sight.
Ok so this is good one to try and figure out what happened.
New belt in a VIC 5 about 6 months ago, correct tension and retensioned after a few days settiling in. No build up,every belt change all pulleys get cleaned. Started a show the other week, fine for about 1 min, join went through on ads, big bang from mech, ghosting on screen. Stopped, opened up the back nothing, Belt tension fine. Changed belt and carried on all well since. Nothing wrong with anything, all teeth on belt, no build up, cross box good and shutter drive. Im still trying to work out what it was. Anyone??

Posted by Tim Reed (Member # 137) on 07-30-2006, 01:53 PM:

The belt skipped a tooth? Were you seeing travel ghost from an out-of-time shutter, or just blurring from film that lost its loop?

If it was the belt, the little "keeper" rollers around the shutter and the intermittent gears are critical to preventing skippage - particularly on starts. Note, however, they are not designed to ride on the belt; rather, they prevent the thickness of one belt tooth from lifting off the gears. I set these rollers very close to the installed belt, and then give them only about 1-2mm clearance. Makes for a quieter-running machine, too, and requires less tensioning on the belt.

Posted by William Phillips (Member # 1162) on 07-30-2006, 03:14 PM:

It was an out of time shutter. When I put the new belt in the red dots were a good few teeth apart. The belt containment rollers on my machine are also about 1mm from the belt. Have never had these with a big gap.

Posted by Richard Fowler (Member # 893) on 07-30-2006, 04:01 PM:

If your belt is fairly new and favoring too far to one edge the tension idler may need in / out adjustment. This can be checked by hand pushing the threading knob after adjustment....NOT under power. The tension rollers are on eccentric studs to allow adjustment and they should be cleaned and lubricated occasionally so they don't freeze up. They are not touching the belt but if they don't roll when touched, they can become dirt traps which could affect the belt.

Posted by Gordon McLeod (Member # 33) on 07-30-2006, 07:58 PM:

Maybe it would be a good idea to check with the theatres engineering deptartment to find out where they want the operator to stop and the field service engineer take over

Posted by Sally Burgess (Member # 1493) on 07-31-2006, 12:38 AM:

Thanks guys. I am on tonight so will have another look.