Film-Tech Forum ARCHIVE: Jing Gang projector and westrex tower

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Posted by Mat Fleming (Member # 1685) on 12-05-2006, 08:30 AM:

I am struggling to teach myself how to operate this set-up which we have because sadly, in our volunteer run cinema, we cannot afford any other kit yet. If you can give any pointers I'd really apreciate it. I am seeking local tech help too but I'd love any advice I can get in the meantime.

The projector is a horrible Jing Gang Shan portable thing which starts up at full speed and this causes really terrible problems with the tension off, and to, the tower, which results in losing the top loop and tearing the film (often after the gate). And I'm not sure how to set the tensions. It is like there is so much carnage happening so quickly when I turn on the motor that I can't decide where to look for it!

Where I have seen towers being used the film comes off the top of the pay off but the spool turns the other way. I assume it needs to turn against the projector's pull to provide tension, which leaves me coming off the bottom of the pay off and on to the top of the take up.

as you can tell I need a lot of help. Please be nice to me [Smile]

Mat

PS I am only running scrap film right now - don't fret.

Posted by Richard Fowler (Member # 893) on 12-05-2006, 10:05 AM:

I have the same portables on reel tower systems with no problems. The back tension on the feed reel may be too great; film guidance with some shock type dancer would help. The main tower is a microprocessor type which controls tension on feed and take up; our other tower is a more simple type with a torque take up and a clutch dampen feed reel. The projector cloth motor drive belt may need replacement and a little wax to keep it supple and sould allow you to "ramp" up to speed. There are some models of this projector with a timing belt motor drive which, I feel, gives lower service life at the expense of a slow start up.

Posted by Mat Fleming (Member # 1685) on 12-05-2006, 01:06 PM:

Thanks.

Where would I find the cloth drive belt? the only visible belt is rubber with teeth. The dampenend roller sounds good. Anything that could provide some "ramping" would be marvelous. The projector model is 104-X2.

Posted by Richard Fowler (Member # 893) on 12-05-2006, 03:44 PM:

Generally the motor shaft wheel to the mechanism drive wheel uses a heavy cloth belt which slips and ramps up when the motor lever under the framing knob is engaged. If your unit has a timing (toothed ) belt drive you are out of luck. The system thou operating 208 - 240 VAC the projector motor is actually a 110VAC unit and not easy to convert to a Slo-start situation due to the small size and output.

Posted by Michael Brown (Member # 890) on 12-28-2006, 04:01 PM:

A few miles down south from you down in Bradford we were using a Westrex projector with a Westrex tower. To combat the tension problems we used an 'inertia reel' on the take up. Basically it's a reel where both the sides and hub can rotate freely against each other (I don't know the exact physics of how it worked) but that worked fine and we could switch the projector on and the film would run fine.

After the inertia reel broke we used a normal reel and a technique where as the projector started you would take hold of the sides of the film near to where it runs from the bottom of the projector towards the tower take-up and pull it upwards with your hand, then start slowly lowering your hand (and the film) downwards after it has started up. That pretty much worked ok.

Posted by Richard Fowler (Member # 893) on 12-28-2006, 04:58 PM:

Slip hub reels lower the mass at start up by slipping and allowing the outside of the reel to catch up. This type of reel or a reel edge to hub ratio if less than 5 to 1 work well on these "brute force" type of transports. Newer servo / A.C. frequency drive transports are more foregiving.

Posted by Hugh McCullough (Member # 1542) on 12-28-2006, 05:05 PM:

Michael

I run both a Westar, and Monee projector with Westrex towers, and do not have the problems that you seem to have starting the show.
Holding the film back by hand seems rather a dangerous way to keep start up tension.

I set the pay off tension to 120, and the take up to 160.
At these settings I find both the take up, and pay off is very smooth.

Start the projector, and when up to speed, I alter the take off to 80, and the take up to 150/160, depending what machine I am using.
This works well for me, and does not need any alteration during the running time of the films.

Posted by Ben Wales (Member # 92) on 12-29-2006, 04:34 AM:

Looks that you will need to have a slower start up on the Portable Projector, Westrex advise a 5/6 sec start up speed.

One option (if standard 1/4hp 1440 240v motor installed) is wire in a 150w 8 - 10ohm resistor to slow the ramp up speed of the projector.

If a Resistor or Autotransformer/Varic can not be used, try the the Jim Schultz's "Film Attenuator" design.

It consists of three guide rollers on the Take-Up side of the Tower mounted on a bracket with the Centre roller on a Bungie cord, this would absorb the slack when starting.

Posted by Richard Fowler (Member # 893) on 12-29-2006, 09:00 AM:

The Chinese motor is actually 110 VAC powered via a tap off from the power supply.

Posted by Ben Wales (Member # 92) on 12-29-2006, 05:37 PM:

Here is the Westrex Drawing for connecting a 110v supply through a AutoTransformer for a Projector soft start when in use with the Westrex Tower.

Posted by Mat Fleming (Member # 1685) on 01-04-2007, 10:30 AM:

Thanks,

I have worked out how to set the tension and use my fingers on the film's edge now to be reasonably alright, I've also bought lots of leader to go in front of everything while the tension settles. I'm going to look into these suggestions for a permanent solution.

It's ironic to read these posts today. I also found out that the large arts institution who loaned us the projector want it back now. Not to use - i doubt that they will ever use it again - it's their spare and film shows are rare enough there already. They just want it to audit their assets. it's frustrating though; we have 2 months of films booked, no cash to buy equipment and have only just proudly opened. such is life.

Mat