Film-Tech Forum ARCHIVE: Vic 5 Bottom loop growing

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Posted by Phil Blake (Member # 2012) on 01-10-2005, 06:54 AM:

Have an issue whith the bottom loop i.e the one between the intermittent and the sound drum slowing getting larger through the show.

Set the loop so index finger can fit into it , by the end of the show the loop is touching the lens turret !

any ideas anyone ?

Posted by Pete Naples (Member # 761) on 01-10-2005, 08:59 AM:

Change the timing belt. Don't ask me what happens but somethign does and in my experience changing the belt sorts it.

Failing that, either the film sprocket or the belt sprocket for the hold back is loose and slippign on the shaft, or the pad roller is so out of adjustment the film is slipping over it, could be agravated by poor joins, perfs not cleared properly?

Posted by Gordon McLeod (Member # 33) on 01-10-2005, 10:33 PM:

Is the output sprocket possibly loose on its shaft or the timing pulley slipping on the shaft as that is a large amount of change to occur

Posted by Stephen Jones (Member # 16) on 01-10-2005, 10:58 PM:

Hi Phil,

Yeah I'd go with what Pete and Gord have already said.I always had problems with Vic 5's if it wasn't the shutter gear box it was those bloody belts no matter how much time and effort I put into them they still caused problems same you are discribing here.They always did this before the belt broke even though they were replaced as according to the manual at the recomended intervals.Check all your pulleys and make sure they are clean and free of any of that black crap that they tend to leave behind as it can cause the belts to slip slighty and also make sure no oil has gotten on the belt etc as well.In my time with the Vic 5's I found the keeping the drive side clean as possible helped prolong the life of the belts only by a small amount.Another thing that has come to mind is make sure they have the correct tension on them as well.Just some things I picked up when using these projectors.

Give me a Kinoton or a Kalee 21 anytime

Cheers Steve [beer]

Posted by Phil Blake (Member # 2012) on 01-11-2005, 01:49 AM:

thanks everyone, I changed the timing belt as Pete suggested and all is ok now .

Can't agree with you more Stephen ,Kalee 21 or even Centrex V.I.C 5 ( very irrational contraption mk5)
[thumbsdown]

Posted by Leo Enticknap (Member # 534) on 01-11-2005, 02:15 AM:

Agreed with all. Vic 5s aren't known as 'the rubber band machine' for nothing!

quote: Pete Naples
Don't ask me what happens but somethign does and in my experience changing the belt sorts it.

To hazard a pure guess - the secondary belt jumping over a tooth every now and again as the result of stretching over time?

Personally I had no problem with belts just as long as they were replaced regularly and, as Stephen points out, giving the drive side a thorough clean when doing it and making sure the belts aren't overtensioned. At the last place I worked we did them every three months which if I remember correctly was more often than the official spec; but £6 each or thereabouts is well worth paying to prevent any of these problems from ever getting started.

I can't remember ever having had one snap or cause a visible on-screen problem. Over the course of my 12 years or so in various booths I can remember having at least three shutter gearboxes go, though.

One thing I would say in the V5's defence is that routine maintenance and mechanical repairs are relatively straightforward to do. You could pretty much strip and rebuild one with a set of Allen keys. While other mechanisms out there will, in perfect condition, give you a more stable picture, the tradeoff is often in more complex maintenance and expensive parts. So there might be something to be said for them in remote locations and/or where technical support isn't easy.

Posted by Pete Naples (Member # 761) on 01-11-2005, 03:05 AM:

I thought that too Leo, but surely if it jumped a tooth it'd go out of phase and start to ghost?

Posted by Darren Briggs (Member # 1071) on 01-11-2005, 05:15 AM:

Im a big fan of the Vic 5 as you can get any projectioninst to carry out most tasks in an emergency over a phone.

It has to be the belt is slipping on the bottom drive pulley, i.e bottom sprocket slows as the belt jumps. Has this once at a cinema a friend was involved in, this was due to the projector not being looked after, old belt and projector was not running on a inverter, and it had no soft start. I ended up going to help out at the site and found the belt strectched and teeth missing.

Currently cinemeccanica advise belt replacement at 15000 hours, but i feel this is way to long, we change them every 6 months. For the small cost of the belts, it ensures you never loose shows. Also give you chance to strip and clean the rear mech when belts are changed.
A vic 5 maintained well and film path kept spotless can give a super stready picture.

Darren

Posted by Michael Schaffer (Member # 1204) on 01-11-2005, 05:31 AM:

I once had a related problem with a Century R3 (standard drive) soundhead: it pulled down the lower loop so that it disappeared within 2-3 seconds. The problem was immediately obvious: the projector drive pulley was loose and slipping on the soundhead sprocket shaft, so the soundhead would "outrun" the projector.

Posted by Gordon McLeod (Member # 33) on 01-11-2005, 02:14 PM:

I recomend that the belt get chan ged when the lamp is changed so for a 2000 watt system that would be 2000 hours
the belts are cheap and take no time to replace

Posted by John Pytlak (Member # 331) on 01-11-2005, 03:08 PM:

quote: Gordon McLeod
I recomend that the belt get changed when the lamp is changed so for a 2000 watt system that would be 2000 hours
the belts are cheap and take no time to replace

Wouldn't belt life be more likely to decrease with increasing lamp power (more heat)? [Confused]

Your formula replaces the belt more frequently on a cooler running machine.

Posted by Michael Schaffer (Member # 1204) on 01-11-2005, 03:36 PM:

I don't think Gordon meant to establish a formula xenon lamp wattage=operation hours for the belt here. I think he simply meant, whenever you change the lamp, change the belt too while you are working at the machine anyway. That appears a simple and effective way of organizing and keeping track of the belt changing intervals, although simply changing all the belts in all machines every 6 months like Darren suggested is just as easy.
I would doubt that increasing lamp size decreases belt life, but in any case, the bigger ones get changed more often, and so would the belts.

Posted by John Pytlak (Member # 331) on 01-11-2005, 04:03 PM:

Now I see the logic: larger lamps are replaced more frequently, so the hotter projector gets the belt changed more frequently too. Makes good sense. [thumbsup]

Posted by Stephen Jones (Member # 16) on 01-11-2005, 07:26 PM:

Phil,
How could I forget the solid, built like brick dunny Centrex projector.They were the very first projector I ever used all those years ago.They were a good reliable projector and there are still a few out there earning $ for thier owners.One of the few Aussie made projectors well one of three anyway,C@W,Centrex and Benbow i think it was called oh and one more the good old super standard.

Steve

Posted by Leo Enticknap (Member # 534) on 01-12-2005, 02:03 AM:

quote: Michael Schaffer
I don't think Gordon meant to establish a formula xenon lamp wattage=operation hours for the belt here.

Though one would probably establish itself by default since the hour meter measure lamp hours, not motor running hours. So if you're going to use the number of hours elapsed to determine the belt change interval rather than a set period of time (e.g. six months), that'll end up being the number of lamp hours. In a platter or long-play spool situation the two will probably be very similar (give or take, say, a couple of percent if you strike the lamp a few minutes before the start of each day's shows), but in a 2k changeover installation where both lamps are left on for the duration, the lamp hours will end up being double the motor hours for each projector.

But on a Vic 5 the belts are so cheap and so easy to change that it just makes no sense to leave them any longer than you have the slightest doubt over. After all, if you relied on your car for your livelihood you wouldn't leave it an extra few thousand miles before getting it serviced - the money involved just isn't worth the risk, just as it isn't worth trying to save £6 on a belt by risking it failing during a show and having to hand out 300 refunds.