Film-Tech Forum ARCHIVE: Top feed loop issue on an RK 60...

This is topic Top feed loop issue on an RK 60... in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Glen Rich (Member # 1150) on 03-26-2012, 06:50 AM:

I was called away from the comfortable chair on my front verandah to repair a faulty RK 60. After about three hours of checking, dismantling, rebuilding and still having the same issues here I am.
Top feed loop on an RK 60, (Cinemeccanica Vic 8 knock off), disappears in a poofteenth, (Australian technical term), of a second as soon as the Motor starts, (bottom loop is OK). Plus the oil pump isn’t working…
Opened the head up; no damaged or stripped gears, no gears lose on their shafts, no missing teeth, everything appeared OK.
Replaced the main drive belt as it was an oily mess, but the above issue remained.
Does anyone have an idea of the problem and how to rectify it?

Posted by Dave Macaulay (Member # 813) on 03-26-2012, 10:38 AM:

If the geartrain is good and the sprocket is secure on the shaft... tough call. Is there enough slop somewhere allowing the upper shaft gear to disengage under load?
Is this a reel-to-reel setup? Startup drag on the top sprocket is pretty hefty when accelerating a full reel. The trap roller spacing might be excessive allowing the film to skip, I've had this happen many times. "Just dragging on two film thicknesses" is the usual prescription.
Also, the film path should allow about a half-turn film wrap on the top sprocket. I've had to change the upper arm angle on several machines with platters to get this. You should have an idler roller at the film entrance to get a good wrap on the top sprocket, otherwise the film enters from way in front from a full reel with over-over rewinding: changing to over-under with the top reel feeding off the back helps that and is supposed to give better image stability as well.
You should have the oil pump working too!!

Posted by Pete Naples (Member # 761) on 03-26-2012, 11:32 AM:

Change the belt.... No, wait, that's the other Cinemecannica!

I've never actually had to delve inside a Vic8/RK60. However, something I've seen on a Century springs to mind.

Are the gears fibre, with a metal inner?

I had a similar thing once on a Century, it would continually go out of phase and ghost. You'd reset it cock on, start it up, and it was out.
Only by really loading the shutter and turning the mech by hand could you just see the fibre gear teeth section slipping with respect to the metal inner.

Posted by Glen Rich (Member # 1150) on 03-27-2012, 12:21 AM:

Problem fixed... it was staring me in the face, incredibly obvious but I didn't pick it. They replaced the main power board in the building the night before and the electrician wired the power phases back to front for that cinema; the bleeping motor was running backwards.

Managed to run it long enough whilst trying to find the problem that the motor needs to be re-wound and the bushes replaced. Boss happy that problem solved, and unhappy the cinema is still down cause the motor is off being fixed... the moral is- I should have ignored the bloody phone call and kept reading my book while sitting in the comfy chair on the verandah yesterday!

Posted by Damien Taylor (Member # 4255) on 04-15-2012, 03:37 AM:

Hi Glen, out of curiosity are you able to disclose the name of the cinema?

Posted by Glen Rich (Member # 1150) on 04-21-2012, 03:28 AM:

Sorry Damien, not on a public forum. I send most of the companies younger operators here to glean as much info as possible, and tongues will wag if I'm indiscreet. However I live and work in the same suburb, (subtle hint), if you really want to know just call up or in for a chat.

Glen