Film-Tech Forum ARCHIVE: film loosing sound cinemeccanica V8 (MI?)

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Posted by Patrick de Groot (Member # 858) on 03-04-2004, 10:13 AM:

This is a 35mm machine with also possibilities to play 70mm (not used).
When the film looses from the lower sprocket, it is making a irritating sound. It is equiped with a failsafe device under the lower sprocket.
Can I do something about it? I already tried to lower the tension on the take-up clutch (we work with spools). It makes a difference, however the knob is then vere loose...
It seems (when I slowly run the projector manually) like the perforations on the projector side are causing the problem.
We have 2 of these projectors, and both have this issue.

Posted by Pete Naples (Member # 761) on 03-04-2004, 05:07 PM:

Sprockets could be badly worn or the pad roller clearance could be maladjusted, or the holding spring/mechanism sticky?

Posted by Paul Carey (Member # 2241) on 03-04-2004, 05:51 PM:

It could be that the teeth on the lower sprocket are starting to hook. An easy way to test this, unless it has been done already, is to take the sprocket off and put it on the other way. This will allow the film to be pulled by the non hooked edge.

If that does make a difference then invest in a new set of sprockets. I've had this problem before and its easy to fix.

Paul Carey

Posted by Mark Gulbrandsen (Member # 72) on 03-04-2004, 10:23 PM:

The Italian sprockets have always been a big area of dislike for me as they are not case hardened as U.S. made sprockets are.

You may want to consider buying 35mm only sprockets as used on the V8R for your V-8. This will save you a ton of money over the combo 35/70 sprockets. HOWEVER! Carefully pack the worn combo 35/70 sprockets that you end up replacing away with the gate change parts in case of future need... its doubtful that the 70mm part has any wear on it at all.

Mark @ CLACO

Posted by Patrick de Groot (Member # 858) on 03-05-2004, 06:21 PM:

I have put the sprocket on it the other way. It was the solution. Thanks!

Posted by Gordon McLeod (Member # 33) on 03-06-2004, 08:00 PM:

"The Italian sprockets have always been a big area of dislike for me as they are not case hardened as U.S. made sprockets are"
Never really had an issue with the Italian sprockets and they are at least a hell of a lot harder than the aluminum ones in the DP70

Posted by Mark Gulbrandsen (Member # 72) on 03-06-2004, 08:31 PM:

Actually Gord you are dead wrong [Roll Eyes]

. The hard coating thats used on the Norelco Sprockets and many others for that matter is actually far harder than even stainless steel! Here are some of the real advantages that a conventional hard coat process provides you with....... This is taken right from the companys web page that we use to hard coat our Sony DFPR 2000 sprockets.

Hardness:
2nd hardest material to diamonds

Wear Resistance:
10x wear resistance of conventional anodizing

Uniformity:
Precision control of close tolerances

Thermal Properties:
Low thermal conductivity & minimized expansion

Heat Resistant:
To the melting point of aluminum 1221° F

Corrosion Resistant:
Excellent corrosion resistance

And I will add to this list less friction generated as these Hard Coated sprockets run far quieter than the bare Sony Sprocket. I have to chuckle that even Cinemecanica changed over to a LaVezzi made hardened stainless steel 70mm intermittent sprocket as their gold anodized alumnium sprocket rarely made it through one run of a 70mm film. The Italian sprockets are also quite expensive, far more than the DP-70's are.

IMHO, so far the only company that ever did any of this correctly was Bauer with their seperate 35 and 70mm sprockets which were also non magnetic stainless steel.

Mark

Posted by John Hawkinson (Member # 1135) on 03-07-2004, 12:20 AM:

What's the Rockwell hardness, Mark?

--jhawk

Posted by Mark Gulbrandsen (Member # 72) on 03-07-2004, 12:57 AM:

Hawkeye, you are so inquisitive...

Since hard coating is just below the hardness of diamond and diamonds are measured in Mohs of hardness not Rockwell it might be around a 9.5 on the Mohs scale. Mohs is a 1 to 10 scale but is lograthmic, not linear. Want to know more about Mohs just ask Larry or Curley! Nuk Nuk Nuk........ [Big Grin]

Mark

P.S. I looked up the hardness of steel in my Heat Treating book and it rates about a 5 on the Mohs scale so that makes Hard Coatng at least 4 times harder than steel.

Posted by Gordon McLeod (Member # 33) on 03-07-2004, 09:15 PM:

Mark we ran those gold anodized sprockets with no problems up here and usually they were in use a year
In fact we used them on the spanish wassmans and ran 8000 passes of 70mm prints typically per sprocket change (every 3 years)
I have had to replace a lot of the norelco sprockets (dp75's in particular) rarely a cinemecanica sprocket
Also at one point dolby switched to cinemecanica for the cat 701 sprocket because the Lavezi one sang too much

Posted by Mark Gulbrandsen (Member # 72) on 03-08-2004, 08:02 PM:

Common gord, I wore the 70mm teeth out at home when I had my V-10's! Replacing them with the later stainless steel sprocket proved very worthwhile plus a steadier image as the stainless sprocket didn't distort when you tightened down the end screw like the alumnium would. It was no surprise to Cinemacanica users that it was changed to stainless and LaVezzi!

Doesn't surprise me that the DP-75's wear out sprockets..... crappy trap assy on that machine. The DP-75 trap is right up there with the Cinemacanica alumnium intermittent sprocket.

I never heard a VKF sprocket sing a song before.... What was it singing [Big Grin]

?

Mark

Posted by Erick Akers (Member # 875) on 03-09-2004, 05:51 PM:

Mark,

Gordon never replied about the VKF's,
But....

I'm Guessing "Don't Be Cruel" by Elvis! [Big Grin]

Thank you very much!!!

The Arse Kicker has left the building!!!!

Posted by Mark Gulbrandsen (Member # 72) on 03-09-2004, 06:26 PM:

Actually Erik,
VKF's really can't sing due to the way the teeth are made. I would suspect there were pitch problems with the film or some other excess film tension problem going on. While the early CAT 699's may have used Italian sprockets all Dolby and the BACP reader now use LaVezzi VKF sprockets. Same sprocket as is on the upper and lower of the X-L Projector.

Mark

Posted by Gordon McLeod (Member # 33) on 03-10-2004, 09:32 AM:

The 699 and the 700 used VKF sprockets
The 701's5 have uses a cinemecanica sprocket
Th 700's typially sing