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Author Topic: Strong Platter Wrapping Loosely Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 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.  |  IP: Logged Daryl C. W. O'Shea Film God Posts: 3977 From: Midland Ontario Canada (where Panavision & IMAX lenses come from) Registered: Jun 2002 posted 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.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 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  |  IP: Logged Mike Perju Film Handler Posts: 90 From: Toronto, Canada Registered: Nov 2002 posted 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.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 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.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 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.... The Alpha-3 uses "0" rings. The vast failure I have seen is they just crack and deteriorate.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 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  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 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.  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 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?  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 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.  |  IP: Logged

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