Film-Tech Forum ARCHIVE: Strong Platter Wrapping Loosely

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Posted by Joe Redifer (Member # 3) on 04-11-2003, 01:52 AM:

Strong A3 platter. 6 of them. Two of them brand new. Well 5 or 6 months old anyway. The others are a few years old. The older platters always take up the prints so that they are pretty tight. The newer ones do not wrap as tightly for some reason, even though the motors and variacs on all 6 platter systems are 100% identical. However over the past week one of the new platters and one of the older ones have begun wrapping prints very loosely no matter what deck is used for take up.

Any ideas on what can cause this, and perhaps a remedy?

Posted by Pete Naples (Member # 761) on 04-11-2003, 03:36 AM:

'Electrical Zero' of the take-up variac? The procedure for adjusting it is in the book.

Posted by Bill Langfield (Member # 818) on 04-11-2003, 09:30 AM:

Fix of the Week - Pete wins. Bill wins next week (Exciter Problem - You'll love it)

Oh great, Pete, Im sure Joe is more informed now. After he reads the manual, should be an easy fix for him.

(Gezz, Joe read the damned book before posting here. What were you thinking?)

I look farward to hearing how Joe fixed the the problem after you gave him the solution.

(With Speco 270's hang a weight on the take up elevator - or clean & oil the dam shafts)
(With CNR-35's get three football players to tighten the spring)

Bill.

Posted by Joe Redifer (Member # 3) on 04-11-2003, 11:41 AM:

I don't need to read the book. I already know how to do that procedure. I'll do it today and see if that helps. If it doesn't I will be sure to rub it in. [Smile]

Posted by Pete Naples (Member # 761) on 04-11-2003, 01:27 PM:

Jeez sorry, I was only trying to help.
I won't bother in the future.

Posted by Paul G. Thompson (Member # 655) on 04-11-2003, 02:58 PM:

Personally, Joe, I don't think that will help. I have had this phenomenoa happen on Xetron XNR's, CFS, Potts, and Strong. I have seen it happen once in a while on the AW-3's, too.

I never did figure out why, although I suspected the booth enviroment.

Then, the next day or so it would be just fine.

BTW, what is your RH in the booth?

Posted by Brad Miller (Member # 2) on 04-11-2003, 04:00 PM:

I agree with Paul, this seems like a wasted effort. It's not like the elevator gets heavier the closer it is to the top or bottom end of it's travel.

Posted by Peter Schoell (Member # 919) on 04-11-2003, 07:31 PM:

It seems to me the problem has to be in the elevator. The elevator has a constant weight on the rewinding film, if the rollers bind a little, this will cause less force and looser film. You could add a little weight to the elevator to see if this corrects trhe problem. I've used wrenches or even an old trailer.

A few times I've noticed spongy films, and thought for sure somebody let it run crooked on the sprocets and added a little dent between each sprocet hole on the film. When I check the film all I find is the slightest raise on the edge of each sprocket hole. Then I look for a hooked sprocket. The last sprocket in the sound head is usally the culprit, since it takes all the weight of the elevator.
I've also noticed I will have a spongy film, then the next film will be fine.
I don't know if anything in the production can dent the film a little.
I also have all Potts/Strong platters, most atleast 20 years old.

Posted by Joe Redifer (Member # 3) on 04-11-2003, 08:25 PM:

Well I checked and re-adjusted (they were pretty much fine anyway). I'm not sure if it had any effect or not because I was too lazy to move the print from deck to deck today.

Posted by Bill Langfield (Member # 818) on 04-12-2003, 09:27 AM:

Sorry Pete, I was attempting to be FUNNY.

I should give that up. Always comes out wrong for me, even Joe missed the fact (I think. It's hard to tell with him) that I was trying to send you up; in a nice way.

I was simply having a go at the fact that you told Joe to read-the-book.
(aka Read-the-f***ing-manual) RTFM

THAT Said, I don't understand what you mean by 'Electrical Zero' Could tell me what that means?
(I dont have a strong platter manual to look it up)

Again Pete, sorry for another lame attempt at being funny. Perhaps I should have added some smilies to the post.

HEY Joe,

quote:
I don't need to read the book. I already know how to do that procedure. I'll do it today and see if that helps. If it doesn't I will be sure to rub it in.

Which procedure? How to read a book, or the Electrical Zero thing? [Smile]

Bill

Posted by Joe Redifer (Member # 3) on 04-12-2003, 03:54 PM:

Even if I had the Strong manual memorized, the thought of resetting the electrical zero on the variac would have never occured to me. Pete offered a suggestion and I figured it couldn't hurt.

Posted by Paul G. Thompson (Member # 655) on 04-12-2003, 07:48 PM:

Electrical zero to me is zilch! With the elevator fully lowered, the brush wiper on the variac will sit about 50% but the platter will go nowhere because of a switch. With the elevator fully raised, the brush wiper will be near the end of the variac.

If you fiddle with this and make a slip, you could very easily destroy the variac or bust the wiper brush if it reaches the end of the mechanical travel of the variac.

Remember the power of the take-up motor is determined by the position of the elevator. Also remember the take-up motor has a resistor that is switched into the motor circuit while the motor is in the take-up position.

Loose wind? Well, one cause could be feeble contact of the drive wheel to the platter dish. This would be evident by the elevator nulling at a lower level than normal. This condition will also cause a wilder-than-normal payout speed, such as fast over-shooting and under-shooting instead of a lazy over-shoot and under-shoot.

Be advised the variac adjustment very very rarely will become out of whack, unless someone abused the equipment or a couple of set screws came loose allowing the linkage to slip on the shaft.

Posted by Mike Perju (Member # 1482) on 04-12-2003, 08:11 PM:

Hi Joe, All you have to do to wind the film tight is miss the top right hand corner roller of the elevator assembly. Be careful when you start up, or the elevator might bottom out before the platter catches up, piling film on the floor. 9 out of 10 platters (especially the newer ones) will start ok, but it's a mixture of how fast your projector starts up and how fast your platter takes up. If you ever come across a 35/70 Potts with 6 rollers on the elevator assembly be aware that missing one roller will make the film a little untight on the ring (when moving) but missing both top right hand corner rollers will make the film waaaaay too tight (I've had to pend 5 mins trying to unlock the ring)! Give it a try. If you need more clarification, I'll try to send you a picture. This method will mean 99.9% safe clamp-less print moves in 30 seconds or less... just make sure you can trust the centre ring latch.

Posted by Dave Macaulay (Member # 813) on 04-13-2003, 04:59 PM:

Mike's idea will work, but it's not a great solution for a platter that's winding loose all the time. With microswitch or phase control platters it will confuse the payout and you'll get uneven speed there.
The problem almost has to be with the dancer unit or else you have film rollers that are turning with drag. Possibly the dancer's wheels are binding on the tracks... you can undo the top and bottom screws on the 2 rods and adjust their position a bit to make it run freely. The film tension is directly related to the weight of the dancer, and that's not adjustable... if some rollers are dragging then some of the tension will be lost turning them though.

Posted by Daryl C. W. O'Shea (Member # 1303) on 04-13-2003, 05:03 PM:

Wouldn't tension increase if you had rollers that weren't turning freely, since the film would have to pull harder to turn them?

Posted by Paul G. Thompson (Member # 655) on 04-13-2003, 05:30 PM:

Some of these comments are very interesting, and have great merit. I would like to find the answer, too.

However, I only experienced this problem on one disk during the take-up mode, while the other two disks presented no problem under the same basic circumstances. That eliminates the elevator as a possible problem since it is common to all three disks when they are being used as take-up disks.

Posted by Daryl C. W. O'Shea (Member # 1303) on 04-13-2003, 06:01 PM:

In that case Paul, I wonder if it has something to do with the drive wheels. Specifically, I wonder if the looser winding deck isn't contacting the deck 'as firmly' as the others.

Posted by Mark Gulbrandsen (Member # 72) on 04-13-2003, 07:08 PM:

Yea, the drive rings do get hardened and glazed up to the point that you will ultimnately have slip between them and the motor and platter. I replaced a plex worth of drive rings last Friday that were really, really bad. So bad that the timming was affected by it and the loss of grip caused some of the platters elevators to slam to the top on film startup. That problem disappeared with the new drive rings.
Mark

Posted by Mike Perju (Member # 1482) on 04-13-2003, 07:52 PM:

Daryl, I'm not proficient on the principles of pulleys, but that would happen on the payout of the platter, but not on the takeup.

Posted by Dave Macaulay (Member # 813) on 04-13-2003, 08:56 PM:

quote:
Wouldn't tension increase if you had rollers that weren't turning freely, since the film would have to pull harder to turn them?

Hmm. Sounds right. If I hold the film back, the tension increases.
Since the tension is set by gravity, which is probably reliable, I can only figure that the dancer is sticky. The motor needs the least torque at the beginning of a print because of the small pack radius. That torque is probably enough to keep the film taking up later on, and if the dancer fails to drop as the show progresses (as required to increase torque compensating for the radius increase) the film tension would go down but there wouldn't be an actual stoppage.

Posted by Paul G. Thompson (Member # 655) on 04-13-2003, 09:09 PM:

Daryl, I mentioned that in a previous post. There is that possibility......

Mark, some of the belts used on the CFS and Potts machines were very troublesome. They would simply fall apart to the point where the plastic roller edges would come in contact with the platter dish.

The orginal belts CFS and Potts used were the neoprene type, and those lasted practically forever. A newer rubber version came out and those were worthless. If there was any tracking error whatsoever, there would be a pile of rubber shavings laying on the disk beneath it.

I know I pissed CFS reps off at a Sho-West trade show years ago when they changed belt styles. I asked the "Big Boy" how the new belts were holding up. He said they worked beautiful. Then I asked him what the pile of rubber shavings were that gathered around the drive linkage and the rubber shavings laying on the platter beneath it. I received no answer....just a stare of daggers.... [Big Grin]

The Alpha-3 uses "0" rings. The vast failure I have seen is they just crack and deteriorate.

Posted by Mark Gulbrandsen (Member # 72) on 04-13-2003, 09:12 PM:

Paul, the O rings do crack and deteriorate, as well as glaze as was the bunch I replaced last Friday...the glazing caused alot of strange problems. Also, the motor shafts become glazed at the two points where the O rings ride as well.......
Mark

Posted by Paul G. Thompson (Member # 655) on 04-13-2003, 09:15 PM:

Mark, very true. Also seen them groove the shaft spindle, too.

The rubber belts used on the older Potts and CFS platters wore out those spindles, too. But if left running with the plastic roller flanges touching the spindle of the motor, the spindle would be severly damaged.

Posted by Joe Redifer (Member # 3) on 04-13-2003, 11:36 PM:

How long do the O rings last in a typical "5 shows per day" cinema Strong platter motor before they should be replaced?

Posted by Paul G. Thompson (Member # 655) on 04-13-2003, 11:41 PM:

Joe, a weekly or even a monthly inspection should indicate that. I have ran some of them in excess of 4 years before they started to go HS. How long they last depends on things such as enviromental conditions, adjustments of the linkages for proper tracking pressure and proper operation during the make-up and tear-down modes.