Film-Tech Forum ARCHIVE: What should a Century SA intermittent sound like?

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Posted by Tom Ostertag (Member # 8318) on 03-13-2015, 01:38 AM:

I've been working on getting this Century SA up to operational condition for my personal collection. This is the first I've dealt with 35mm gear (being a 16mm collector mostly), so I'm not sure how these intermittents should sound when working correctly.

This projector came out of a drive-in whose operators horribly neglected their equipment. They had apparently gotten this intermittent as a replacement (it's clearly from a later Century model), but when I got the machine the intermittent had nothing but a few drops of black sludge in it for oil. Who knows how long it had been operated like that.

Here's what it sounds like, with the proper amount of LaVezzi intermittent oil:
https://www.youtube.com/watch?v=XTaX_UlHwV8

How bad is that? My guess is pretty bad.

How quiet is an intermittent supposed to be without film? Should one hear noise on each frame advance without film, or should they be almost silent?

Posted by Monte L Fullmer (Member # 2797) on 03-13-2015, 03:47 AM:

They can be a bit ticky with no film running through it, but there's more tick than normal with this one.

Trick would be is to turn the motor by hand, hold on to the intermittent sprocket and feel how the cam pin is entering into the starwheel.

The pin should enter into the starwheel with very little resistance.

Also, the front collar that supports the front end of the shaft has that dimple on top where a drop of oil goes in to lubricate the front shaft.

I would have thrown some ATF in that unit - purposely overfill it - and spun the intermittent assembly by hand spinning the motor to allow the ATF to work out the sludge, drain, and then fill with new oil.

Posted by Scott Norwood (Member # 30) on 03-13-2015, 07:16 AM:

Is the intermittent flywheel installed tightly? If the screw is loose, the intermittent will sound like a machine gun. Check the screw and tighten it if necessary.

Posted by Dave Macaulay (Member # 813) on 03-13-2015, 07:30 AM:

That does sound loud - video sound is unreliable though. There's always some noise but a really good Century intermittent purrs more than clanks.
If lubrication was ignored for years the bushings may be worn out, that causes more noise and some vertical image shake when film is running... and a pin crash gets more likely.
However: I've seen noisy ones running grind for years without failing.
There is an adjustment for star/cam clearance that can quiet them but it's easy to cause a jam and pin snap if you don't know how. Plus a new gasket will be needed unless you're a wizard at saving the delicate old one (which will probably have become bonded to the case).
I agree a good cleaning is prescribed. I use diesel fuel (more aggressive cleaning than ATF). You can get a small amount at any self-serve diesel station.
After cleaning, check for play in the locked sprocket (set between pulldowns) - if you can feel any rotation the clearance should be adjusted.
Century oil was (eventually) C3 compressor oil but any light motor oil would do for occasional use.
Personally, I would disassemble and clean it thoroughly, inspect the star and cam for wear, measure the pin for wear (they go oval), and use a new gasket on assembly. Lucky you don't have the original - probably that has a thin star shaft and tiny tapered drive pins securing the sprocket. Most have been retired or converted to large shafts and screw-on sprockets but those were a bugger to service. I doubt if the sprockets, tapered pins, or tiny tapered reamers are available anywhere now for sprocket replacement. I could probably get my hands on them (Hi Chuck!) but wouldn't count on it.
Used intermittents should be common now - probably someone here has a box of them salvaged from a digital conversion.

Posted by Mark Gulbrandsen (Member # 72) on 03-13-2015, 10:55 AM:

What Scott said, and... The only reel way to gauge the sound of an intermittent is to operate it in a run-in stand. Then it is the only thing making any sound at all. That one sounds like the cam pin is flattened down but video's are unreliable. I have replaced cam pins right in the booth many times as part of normal service. You need to do this before the slot's in the star become wavy from being beat by the flat spot on the cam pin. If you don't catch it then the star is also trash. They haven't made oversize cam pins since the 1960's.

I had one site that they NEVER checked intermittent oil AND they were only on line for once a year service visit. We sent them from one to three intermittents a year! Literally they were that lazy... but the guy knew how to change them out. Digital is likely the only thing that kept this place from going out of business. Your intermittent sounds like most of theirs after lots of neglect.

Mark

Posted by Frank Bolkovac (Member # 6201) on 03-13-2015, 12:15 PM:

Exactly what Mark said....worn cam pin. I've done countless number of these and other models. On a good one, you should hardly hear anything. If you had a time machine, you could go back and order a Lavezzi kit..

Posted by Louis Bornwasser (Member # 3063) on 03-13-2015, 01:27 PM:

I'm with Dave on this one. If perfect, there is no sound at all. Noisy ones are either crying for help or it doesn't matter. No way to know without a tear down.

Am I the only guy with brand new LaVezzi kits and parts?

Posted by Pete Naples (Member # 761) on 03-13-2015, 01:43 PM:

Louis, nope you're not [Wink]

Posted by Buck Wilson (Member # 5885) on 03-13-2015, 03:47 PM:

Doesn't sound TOO much worse than ours did, but it also had a lot of neglect. It also had a lot of movement on screen.

Nice to hear that buzzy Century hum again [Smile]

Posted by Tom Ostertag (Member # 8318) on 03-13-2015, 07:08 PM:

Thanks for the info so far!

Unfortunately the sound in the video is pretty accurate here. It's a pretty sharp sounding tick, and closing the projector door doesn't do much to quiet it down. Turned quickly by hand, it's more of a "clack" sound than a tick (with the intermittent shoe open, so it's not that). With film, it's ridiculous.

I tried the little test Monte suggested, and the pin enters the starwheel with almost unnoticeable resistance, but about 1/3 of the way through a pulldown stroke it tends to grab a little. This happens more or less depending on which of the four slots is engaged on the starwheel, but it's present each time. If turned very slowly by hand, the drive shaft sticks, and requires a bit more force to make it continue to turn. Definitely sounds like cam pin damage to me. Maybe a distorted starwheel as well, by the inconsistent nature of the grabbing.

There's no play at all in the sprocket in its locked state (either rotational or end play), and the intermittent flywheel is tight.

At this point, I'm interested in finding a replacement intermittent before I'd go poking around inside the current one. While I'd love to have a freshly rebuilt one, it's hard to justify the cost for this project. At least I think. What's the going rate for rebuilt intermittents, or rebuild work?

I'm considering eBay item number 290957226241 at the moment, which seem like they're coming from a seller who at least knows a little. It's surely a gamble, but it's probably a lot better than what I have, if they were indeed kept maintained. Any thoughts on this?

I'd love to make a project out of the current intermittent someday, provided I had replacement parts and the necessary tools. At the very least, it would be informative to see what makes it tick! hehe

Posted by Rick Raskin (Member # 1561) on 03-13-2015, 07:22 PM:

I can get you an intermittent for the price of shipping if you are interested.

Posted by Tom Ostertag (Member # 8318) on 03-13-2015, 08:07 PM:

Thanks Rick, I think I might be! How's the condition? Smooth/quiet running and all that? And not that it matters, but is it the matching white SA one, or a newer variety? Same through-bolted intermittent sprocket mounting?

I won't be too picky for that price of course!

Will shoot you a PM with shipping info if all is good.

Posted by Mark Gulbrandsen (Member # 72) on 03-13-2015, 09:03 PM:

Tom,

Don't worry about the color so much as how well it runs AND that you get an A type movement. The C type movements have a much smaller cam and the outboard bushing block is not removable. Intermittents were typically completely repainted when a major overhaul was done. At least I did that to mine.

Mark

Posted by Tom Ostertag (Member # 8318) on 03-13-2015, 11:16 PM:

Ah, good point Mark. Noted.

As always, thanks for the info!

Posted by Robert Koch (Member # 3728) on 03-23-2015, 02:13 PM:

Not like that.