Century JJ (Occasional "knocking" sound)

[Ryan Gallagher]

I feel like this is a new sound on this JJ, or was more pronounced with this 40 year old print (Archive Print 2 of Ladies and Gentlemen The Fabulous Stains, But 16B on the paper loops).

It is a bit hard to make out in this video, but there is an occasional "knock knock" sound coming from somewhere other than the gate/loops. I think the most audible ones in the video are right at the beginning, but if you listen closely you can hear them. More obvious in person. Any guesses? Slop somewhere in gear meshing... not enough lube somewhere? Or a worn part? Intermittent has plenty of oil but this is also the unit that needs an oil change, it doesn't leak at all and therefore the oil it has hung onto has darkened in color. Grease has been refreshed recently on the drive side, but maybe it needs a re-application.

On that front, do you recommend pulling the intermittent for draining/flushing. Or try to do it in place?

YT Unlisted Link: https://www.youtube.com/watch?v=vEjji-u5vms

[Ryan Gallagher]

Amusing aside, the projected image appears red because it WAS. They opted to show a VERY red/magenta print. Was Austin Film Society's call, not us, and they show lower quality prints all the time at their space.

That print also had sprocket teeth tracks through the frame for like 12 feet in two places on R2, only 30 splices (excluding heads/tails), but the prior repairs held. We went back and forth a lot about whether to risk more damage on this one as we had a perfectly good blu-ray backup. Programmers went for it, described the print itself as a little "punk rock" during the intro. LOL

[Brad Miller]

That click doesn't sound quite like I was expecting to hear. The camera microphone may be making it sound a little different, not sure.

Does it make those clicking noises if you run the projector without film?

Also those loops are too darn big. 35mm is somewhat forgiving, but when you run 70mm you need to make them WAY smaller. Also you MUST remove the 35mm pad roller from the upper loop when running 70mm so you don't put "train track" (aka: "JJ scratches") on the print.

[Ryan Gallagher]

I’ll try without film tomorrow. Cheers on the loop size, we had a guest projectionist that night and that is his normal JJ mode.

This unit has a sweet spot where it “purrs” depending on loop size. He might have been outside of that but it does seem to prefer larger loops from an acoustic standpoint,

[Ryan Gallagher]

Can confirm, the noise does occur without film running.
Brushed some grease on the drive side, gearing. Re-oiled the starwheel and upper and lower drive shafts. Noise is still present. Not as pronounced without film though.

Listening closely without all the fans and projectors running in the booth it appears to originate at the intermittent. Will upload another video/audio tonight.

Seems like flushing and putting fresh oil in that intermittent would be next thing to try. Definitely overdue but lube may not be a solution. My only sign of encouragement on that front is initially it does not do it, only after it's been running for 30 seconds or so does it start.

[Mark Gulbrandsen]

Sometimes, on Century's, the knocking noise can be caused by the long shutter shaft bobbing back and forth on occasion. It's almost always caused by another gear, bearing, or both failing. If not tended too, then a new shutter shaft will also be needed. That long shaft is spring loaded to allow a slight lateral movement on start up of the projector, to relieve stress on the shutter gear. So keep an eye on it!!

[Ryan Gallagher]

Sometimes, on Century's, the knocking noise can be caused by the long shutter shaft bobbing back and forth on occasion. It's almost always caused by another gear, bearing, or both failing. If not tended too, then a new shutter shaft will also be needed. That long shaft is spring loaded to allow a slight lateral movement on start up of the projector, to relieve stress on the shutter gear. So keep an eye on it!!

Thanks Mark & Brad. I did an oil change on the intermittent too finally (in place). What came out did not look as dirty/dark as I was expecting, I think it is just the window/casing on that one that makes it seem darker. I did not have anything to flush with handy so will do that another day. But it does sound improved now. Maybe slightly perceptible without film, but with a loop running you can't detect it over the projector noise anymore (or at least couldn't in my short tests).

I did check that the intermittent does not have play in any of the lock positions. And it feels reasonably smooth by hand, though I'm sure i've never felt a perfect one. Will definitely keep an eye on it. Found some older videos in the archive and it definitely doesn't sound that awful yet. I was listening with the back covers off too, it didn't sound like it was shutter shaft side but will definitely stay vigilant.

[Jim Cassedy]

<edited> Also those loops are too darn big.. Also you MUST remove the 35mm
pad roller from the upper loop when running 70mm so you don't put "train track"
(aka: "JJ scratches") on the print.

Earlier this week I ran a 35mm print of a repertory title that was pretty much in "like new"
condition. (ie:never been platterized, zero splices in all 5 reels) EXCEPT all of Reel 4 had
these intermittent light 'scuff marks' on the emulsion side, which look like somebody made a
loop a little too big (or small) at some point. Since they didn't gouge the emulsion, they were
invisible on screen, unless you were really looking for them. But it could have been worse!


LoopScratch.jpg

Brad, as always, gives good advice about removing the 35mm upper loop pad rollers for 70mm.
I didn't always do that, until one time I got a print that had been scratched by somebody not doing
that, and I didn't want to be responsible for causing that type of damage to any print I handled.
Fortunately, in our spare parts bin, we had some extra 70mm rollers, so now I take the 35mm rollers
out and put in the 70mm ones. Brad told me there is a slight difference in size in some of the 70mm
rollers (he can elaborate more on that) but I guess I got lucky because I didn't have the problem
with the spare rollers we had in the booth.

[Tony Bandiera Jr]

Thanks Mark & Brad. I did an oil change on the intermittent too finally (in place). What came out did not look as dirty/dark as I was expecting, I think it is just the window/casing on that one that makes it seem darker. I did not have anything to flush with handy so will do that another day. But it does sound improved now. Maybe slightly perceptible without film, but with a loop running you can't detect it over the projector noise anymore (or at least couldn't in my short tests).

I did check that the intermittent does not have play in any of the lock positions. And it feels reasonably smooth by hand, though I'm sure i've never felt a perfect one. Will definitely keep an eye on it. Found some older videos in the archive and it definitely doesn't sound that awful yet. I was listening with the back covers off too, it didn't sound like it was shutter shaft side but will definitely stay vigilant.

Never flush an intermittent with anything other than clean oil!!

Be aware that with Century movements, if you see bronze or rust colors in that window rebuild or replace that movement immediately. At a theater I used to work at, our JJ started leaking oil. Then the leak got worse and the noise got a bit louder. We used to have to refill the oil TWICE daily! But the cheap (and stupid) manager refused to order up a replacement...until after it locked up, Saturday night, full house (around 600 people). The carnage was considerable: two stripped gears, about 500 feet of the print shredded, a burned up motor, 600 refunds, five lost shows....and the tech and replacement had to be flown in on a charter jet flight. My best guess is that $2,000 intermittent ended up costing the theatre well over $12,000 to replace! (i was not the projectionist on shift when it happened (I had moved on to another job)..the asst. manager (a friend) called me in delight. I called that former manager to rub his nose in it..when he hung up on me, I went to the theatre, bought a ticket to a movie and badgered him in person. I left when he threatened to call Paul Blart the mall cop on me. Best "I told you so!" EVER!

[Mark Gulbrandsen]

Tony, I never had anything like that happen to a Century, but I have seen other strange stuff happen that is no fault of the projector. If you had rust in an intermittent, you obviously had contaminated oil that got put in the intermittent. I used to service a theater in Chicago where a disgruntled projectionist put battery acid on the gear train. That also caused a big orange, rusty mess, and everything had to be replaced on the gear side. Even the intermittent drive gear and cam had to be replaced. I installed a loaner SA and did the rebuild in my shop.

[Ryan Gallagher]

For clarity on the 70 conversion. It is possible to remove the upper 35mm pad roller without putting a 70mm one in it’s place?

70mm is a month away still but we do not have spare 70mm pad rollers that I have seen.

[Ryan Gallagher]

Never flush an intermittent with anything other than clean oil!!

Tony, just wanted to ask here. I've read plenty of places about flushing them with diesel. But are you saying that if there was no evidence of non-oil or other problems in them, that it's best to just flush/refill with new oil instead and skip the solvents?

I can understand this from a mechanical perspective. Cause good oil creates that protective film, and a solvent flush would be starting over. Only for worst case scenarios?

[Brad Miller]

For clarity on the 70 conversion. It is possible to remove the upper 35mm pad roller without putting a 70mm one in it’s place?

Yes that is absolutely fine to do. In fact that's how I always do it.

On the systems that were cannibalized together for Hateful 8 they put two 70mm pad rollers so no matter which way you twisted that upper pad roller arm, you had a 70mm pad roller in position. That sounds like a great idea, but I actually do not prefer it as I've come across too many shafts that are slightly bent such that you can get one of them perfectly aligned for even clearance on both edges of the film, but when you twist it to the other position you can end up with a scenario where one side's clearance is fine and the other side is digging into the film or not holding the film onto the sprocket teeth at all...but that slightly bent shaft is often within spec for running a 35mm pad roller on.

For that reason, I prefer to run 70mm with just the one 70mm pad roller in place and the 35mm pad roller lives in the mag penthouse during 70mm projection. It will be obnoxiously obvious the moment you flip the pad roller if you engaged the shaft without a pad roller, so I don't see how anyone could possibly make the mistake.

I also keep a specific allen wrench needed for removing the "35/70" cap in the mag penthouse at all tims as well so it's always handy. It takes less than 30 seconds to pull the 35mm pad roller off for a 70mm show and the same for re-installing when switching back to 35mm. There is really no excuse for any JJ theater to ever run with the 35mm pad roller in place with it being so simple to prevent the dreaded "JJ scratches".

(Similarly I keep the Kelmar arm allen wrench needed on each electrical wireway along with the "not in use" size shaft at all times. It's no fun to be searching for tools when it comes time to make a switch.)

[Ryan Gallagher]

Yes that is absolutely fine to do. In fact that's how I always do it.

Thanks for the clarification. Yeah in my head I wasn't thinking about the shaft still being there... but now it makes sense, just remove the roller so the risky flanges aren't there. I located the tools just now for each projector (of course the grub screws are different), and in the process learned that one of the 35/70 flippers was never tightened last time anyone did it. Checked em all! I didn't try it but it almost seems like two 70mm rollers would risk contacting each other at the flanges.

Not worried about the added 2min step when it's the right thing to do, now that we are not having to remove reel arms it's actually a pretty quick/tidy conversion at the projector as far as physical parts swappage goes.

Other than taking em off and wiping down, is there a recommended method for cleaning/lubricating the pad roller shafts/rollers? Noticed our mag head ones are a touch more resistant to spinning.
ISO to clean and a tiny bit of century oil on shaft? Or a thinner oil? Or is any oil there just going to creep and get all over film.

[Tony Bandiera Jr]

Tony, just wanted to ask here. I've read plenty of places about flushing them with diesel. But are you saying that if there was no evidence of non-oil or other problems in them, that it's best to just flush/refill with new oil instead and skip the solvents?

I can understand this from a mechanical perspective. Cause good oil creates that protective film, and a solvent flush would be starting over. Only for worst case scenarios?

Correct on all of your statements. If the "worst case scenario" arose, it was either a full rebuild or replacement. If you flush with anything other than oil without taking the movement fully apart, you WILL have solvent residue that will contaminate the oil. In worst case scenario you'd be beyond the scope of flushing with oil anyways. That said, diesel does make a great solvent for cleaning the parts during a teardown or rebuild, but you'd still have to use a suitable cleaner to remove all residue of the diesel before reassembly.

As for pad roller oiling, I always cleaned the shafts and roller bore with alcohol, then used my finger to wipe a thin film of oil on the shaft. Install roller, turn it several times, and repeat with another thin film of oil. Never had a ny issues with oil getting on the film. NEVER just apply even a single drop of oil with the roller installed! That will just run all over onto the flanges and it won't penetrate the full length of the shaft anyways. I have used Century oil on our JJ with the method I described and it worked well. (But lighter oil like Simplex oil works a bit better.)