[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: core:key fit causing occasional problems



>I sometimes load reels of film on one of our Ranks that seem to have
>more play in their cores than others, causing the Rank to 'lurch' a
>bit when play is engaged.  This same Rank has had a mysterious history
>of breaking film, always in the following scenario: reel is fully rewound
>from take up to supply side, play is pressed, some sort of wild
>oscillation occurs, and the film snaps

Sorry for the late reply...I was out of town for the weekend. The problem
you describe is certainly not unique or isolated. I encounter this problem
all the time, and the solutions are simple. I am assuming that you are using
the standard rank platters, and that perhaps, the film is being cleaned
before use. I am also assuming that you are not using splits.  The problem
is most noticeable with film packs greater than 1000 feet. Less that that,
the problem is greatly reduced.

Assuming the film is cleaned or at least "tight wound" on a core, your
problem is the film pack shifting on the platter when the play forward
button has been pressed because the core is sloppy on the spindle. If left
in this condition, the film will eventually "throw a loop" causing the servo
to reverse snapping the film. With this condition, you can actually hear the
pack shift (kinda' of short  whooshing sound) as the servo starts and stops.
I highly recommend that you go no further, and take the film out of ready.

First, check the backside of the platter to see if any rubber residue has
built up on the core support center column. Clean this, and the rubber puck
on the Rank's reel shaft with what ever solution has been approved by your
telecine engineering department. Check this several times a day, if necessary.

Second, remount the film on the Rank's platter, and check the play between
the core shaft and the core itself. If you can move it back and forth at
all, it is too loose, and the film will be at risk. What you must do to
tighten the core is to place a shim between the core and its shaft. I keep a
supply of 16mm leader handy for this purpose. Break off a small piece, and
fold it over once or twice. Work it down between the shaft and the core
until it is tight. Check the pack in play, and if you can still hear it
shift, stop and do it again.

Some platters have tighter tolerances that others, and not everyone might
have this problem. The problem is most critical on the supply side, so one
might try changing platters with the take up side. I am not satisfied until
the film does not shift at all when I press play. One word of caution...if
you rewind the film to heads, be very careful removing the film pack as you
might wind up with a coreless pack. I hear some third party platters are
much better at securing the core...something you might want to look into.

The second cause of this problem is rewinding the film too fast on the Rank.
It causes a loose pack, and that is problematic regardless of how tight the
core is attached to the platter.  If you tend to place the transport in
"Full Tilt" when rewinding, you are just asking for trouble. I know it takes
longer, but I do not go faster than 40% of full at any time. I have set this
value into the DaVinci's setup, so the 40% value becomes automatic - but
only if you rewind the film using the DaVinci's cue feature. A word of
caution, remember the Rank's local controls will permit full tilt shuttling
regardless of the DaVinci setting.

Acetate film stock is more forgiving than Estar. If your are sure that you
will never see Estar based film stock, then a higher shuttle speed can be
safer (50%). However, since Estar based interpositive stock is not all that
uncommon, I would be very careful if you do any feature work at all -
especially newer titles. The subject of Estar based films is a another
matter of itself. Estar based film requires special handling in threading
and cleaning. Email me if you want further amplification.

All of this might just sound like overkill...but I have not had customer
film broken on a Rank (other than from film defects like splices or torn
sprocketts) in many years. Something must be right.

On the matter of residue, Film conditioning (durafilm), black and white
stock, old film stocks, Nitrate film stock,  and sometimes film cleaning
solutions - all can cause white power residue on the film gate and transport
- especially the sticky rollers. No other solution other than cleaning the
transport after EVERY REEL.

Tom Nottingham
Complete Post Telecine
Tom Nottingham

"You pays your money...and you takes your choice."
S. T. Nottingham Jr.