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Author Topic: Damage when projector is left closed? Daryl C. W. O'Shea Film God Posts: 3977 From: Midland Ontario Canada (where Panavision & IMAX lenses come from) Registered: Jun 2002 posted 09-10-2005 09:17 AM                        My brain hurts just thinking about thinking about it. To give you an idea though... A freewheeling intermittent spins extremely easily. There's little force on the cam. Now add a few ounces or so of force due to the film. Since the intermittent cam exerts most of its force halfway into the slot you're going to see about 75-100% of that force (from the film), depending on the size of the intermittent, exerted on the cam. So... you've added a few ounces of drag force, up from almost nothing before. As the amazing John and Mark would say, that translates into a huge increase. Of course, if someone has access to MSC.ADAMS (or has $10,000 to renew my license) they could simulate it and find out the exact numbers. It might be cheaper to just buy Evans Criswell lunch though.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 09-10-2005 09:22 AM                     I don't think the equations would fill blackboards up (depending on your black board size). Using a bit o calculus and properly expressing the forces and such...but lets cut to the chase... Take a projector that has sat all night (particularly in the cold)...and try turning the flywheel. Spin the machine by hand for a few cycles of the intermittent. Now, run the machine for 5-10 minutes. After that, turn the flywheel again for a few cycles of the intermittent. You will (or should, since I always do) feel that the machine turns notably more free. Now, remember the motor on the projector is, more often than not, given a mechanical advantage in its gear ratios...any part of the projector that does not have a favorable gear ratio (in Century projectors, everything but the sprocket shafts) feel the differences more! Next day (or on a different projector within the complex)...thread the film before turning the machine on...take a feel of the flywheel with the machine cold with film...it will be turning more stiff than the non-film machine. I can' think of the time where the first thing I did in a theatre was to turn the machine over by hand FIRST...just to feel how it is doing and to listen for anything out of the ordinary. Then check the oil level and add oil/grease as necessary (machine dependent)...once all of that is satisfied...run the machine for at least 5-minutes without film (typically during this warm up time, I'll talk with the manager about anything to note about the day's events)...then thread up the projectors. Oh and reels never hurt anything  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-10-2005 11:38 AM                     quote: Steve Guttag Using a bit o calculus and properly expressing the forces and such Calculus wold undoubtdly play the key roll in determining the forces and such but you also have to come up with the forces at all angles of the cam pin and the forces of the film at all angles and place that into the rquation as well. Since this is a pin entering a variable revolving slot the angle constantly changes and is quite logarathmic as is evedenced by the wavey type wear of the slots in many movements..... Some place I have a book that shows the pull down cycle of star wheels with differing pin entry angles. I believe that recent Kodak Star Wheel patent also may show that, this book I have may also show one very similar to the Kodak design. Mark quote: Daryl C. W. O'Shea It might be cheaper to just buy Evans Criswell lunch though. Excellent idea !! Heyyyyyyyyy Evanssssss....... where you at dude...... Mark  |  IP: Logged Jeffry L. Johnson Jedi Master Film Handler Posts: 809 From: Cleveland, Ohio, USA Registered: Apr 2000 posted 04-07-2006 07:20 PM                        quote: Please help out our managers by threading up as many of the movies as you can at the end of the night. I know the concern about getting blamed for problems, but the projectors are checked over before they're started. Having all or most of them threaded just makes it easier for the people opening at the end of the night. [sic] I don't want to do this, but management wants it done. So it seems that I'll have to. It's their equipment and their managers running the opening shift the next day.  |  IP: Logged Eric Robinson Jedi Master Film Handler Posts: 538 From: Santa Rosa, CA Registered: Jan 2005 posted 04-08-2006 12:54 PM                     And of course in a perfect world the gate and trap closing distance would be set perfectly and the intermittent shoe pressure would be set perfectly. There are cases; however, when the gate and intermittent shoe adjustments are in error which produce extremely high pressure on the projector when it starts up.  |  IP: Logged Luci Reeve Film Handler Posts: 50 From: Telluride, CO, USA Registered: Feb 2006 posted 04-08-2006 03:43 PM                        1. Leave the gate and pad rollers closed at night. 2. Run the projectors 5 minutes before threading up. Are these the recommendations for a Century C projector?  |  IP: Logged

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