Film-Tech Forum ARCHIVE: Loop problems?????

This is topic Loop problems????? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by David Favel (Member # 1125) on 12-06-2003, 04:04 AM:

My Vic 5 is not maintaining a full loop at the intermittent.
Even when I set up the loop as big as my thumb, still the film slack is distributed between the intermittent & the sound drum.

Any suggestions?

Posted by Pete Naples (Member # 761) on 12-06-2003, 06:07 AM:

Check pad roller clearances.

Change the dreaded timing belt. You'd be amazed............

Posted by Darren Briggs (Member # 1071) on 12-06-2003, 06:28 AM:

Tension on the sound drum to little?
Does the loop get smaller and smaller or is there slack film/loop between the rollers before the sound drum?
If you loose the loop totally, have you had any of the drive pulleys off in the back?
Put on wrong, and the bottom sprocket will go to fast and loose your loop in about 20 seconds.

Posted by John Walsh (Member # 168) on 12-06-2003, 09:12 AM:

Agree with Pete; Check the intermittent pad roller clearance. Other things could be a too-loose spring that holds the intermittent pad roller (10-754)

Could the "shear" device (0025) on the intermittent sprocket be sheared?

Do you have one of the newer V5's with a driving sprocket between the intermittent and the hold back sprocket?

This can happen if the operators leave on multiple layers of splicing tape, and made the intermittent loop too small. The splice becomes stiff and can push open the pad roller as it passes... but this doesn't seem like the problem you're having.

Posted by Daryl C. W. O'Shea (Member # 1303) on 12-06-2003, 09:47 PM:

Just for clarification, not that it matters too much, we are talking about the loop after the intermittent sprocket, not the feed loop above it, right?

Anyway, like Pete said, change the belts. A nicked belt can cause the belt to jump a tooth every time the gear rotates, causing everything after that gear to run faster.

Also check for build-up of belt rubber goo in the gear teeth. Although not as common, it will have the same effect as a nicked belt.

Posted by Paul G. Thompson (Member # 655) on 12-07-2003, 12:12 AM:

Change the belts, or at least make sure they are at the proper tension if they are otherwise in good condition.

Posted by Jeff Skallan (Member # 891) on 12-07-2003, 01:41 AM:

I agree with John. It could be a possible loose spring that holds the intermittent pad roller. I've had pretty good luck adjusting the spring end to the 5 - 6 O'clock position shown in the photo below.

Posted by Daryl C. W. O'Shea (Member # 1303) on 12-07-2003, 02:22 AM:

Well if that's the case it's easy to check for. Hold the pad roller up during startup, if you don't lose your loop you've found your problem.

Posted by David Favel (Member # 1125) on 12-07-2003, 10:10 PM:

It's not the spring.
First step to replace the belt.

Posted by David Favel (Member # 1125) on 04-13-2004, 04:44 AM:

Problem was, the drive motor was faulty.
basically was slipping somehow. New sync motor & away with no loop problems.

Posted by Peter Hall (Member # 695) on 04-13-2004, 04:54 AM:

Kia Ora David - how is godzone ?

Curious - how does the drive motor cause a problem only on one sprocket ? Surely if it is fast, slow or gyrating then this will follow thru on all ? Or is the loop transferring to the other side of the sound drum ?

Best one I ever had was looking at a V8 which a guy had purchased blind. Kept losing bottom loop, then snapping film "but the machine has been running well". Turned out that he had an 8 frame rather than a 6 frame sprocket on the bottom

Posted by Ken McFall (Member # 845) on 04-13-2004, 09:46 AM:

David, there is no way changing the motor would have cured the problem. The Motor belt goes to one side of the top pulley and the projector is driven from there by the inner belt and pulley. There is no way that was the cuase of the problem as the motor drive is at one point only.

I suspect that while changing the motor the belt tension was corrected which cured the problem. Did you have to change the top pully with the new motor? if so then you may have adjusted the tensions then.

However....

having just read your post again I'm a little confused.

You say "the film slack is distributed between the intermittent & the sound drum."

What this suggests is that you were not actually losing the loop, it was being distributed between the sound drum and intermittent rather than remaining at the intermittent as normal. If that is the case then a faulty motor could cause that to happen. If the motor slowed down or slipped on its belt the sound drum would continue to turn and pull the loop downwards.

But for this to happen you would certainly be able to see the machine shudder and be able to hear it.

Either way it all points to belt tension or wear. So a new motor with new belt and pulley would have resolved the problem in this case.

Glad to hear your problems been resolved anyway.

Posted by Peter Hall (Member # 695) on 04-14-2004, 06:19 AM:

Sorry Ken - first time in ages but I have to disagree. What happens to a V5 when you turn the motor off quickly (can't remember if your site has inverters or not).. ? The motor stops dead, but the sound drum maintains momentum, making it look like the intermittent loop has gone (indeed it has transferred to a S shape just before the holdback sprocket). My guess is that the motor was giving "intermittent" (adjective not noun !) power and acting like the motor was quickly going on and off.

By the way, nice BIG orange sign - how's things ? Lots of changes at you-know-where... Drop us a line....