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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » SH-1000 flutter woes (Page 1)

 
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Author Topic: SH-1000 flutter woes
Scott Norwood
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Posts: 7929
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99


 - posted 02-04-2007 07:07 AM      Profile for Scott Norwood   Author's Homepage   Email Scott Norwood   Send New Private Message       Edit/Delete Post 
What would cause flutter issues on an SH-1000 with a Century C on top of it? Dialogue isn't so bad, but music is very nearly unlistenable. The flutter doesn't seem to change from the beginning of a (2000') reel to the end of it.

Some history: the theatre had this problem a couple of years ago and it was supposedly "fixed" by replacing a gear in the projector head (I don't know which one, nor do I completely trust the individual who replaced it). For a variety of reasons not relevant here, I recently diassembled this projector (removed Century head, removed soundhead flywheel, removed motor, removed soundhead from base) and reassembled it. The flutter problem is back.

This suggests to me that there is something critical about the alignment of either the projector head or the motor, but I haven't been able to get rid of the flutter issue by making adjustments to either. Another possibility is that the previous "fix" wasn't done correctly and that the issue was never really fixed properly.

Has anyone had this issue before and, if so, what else should be checked/adjusted? Thanks.

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Louis Bornwasser
Film God

Posts: 4421
From: prospect ky usa
Registered: Mar 2005


 - posted 02-04-2007 07:59 AM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
Flat spots on impedance roller?

Bad bearings in impedance roller or sound drum? Can't be much else unless impedance flanges are very very worn. Louis

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Gordon McLeod
Film God

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From: Toronto Ontario Canada
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 - posted 02-04-2007 09:05 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
The other possibility is the flywheel
I have seen them dropped or leak and the inner floating flywheel starts to touch or bind against the outer shell
In the old WE books they reffered to this as whiskers

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Dave Macaulay
Film God

Posts: 2038
From: Toronto, Canada
Registered: Apr 2001


 - posted 02-04-2007 10:52 AM      Profile for Dave Macaulay   Email Dave Macaulay   Send New Private Message       Edit/Delete Post 
Since there's a slack loop between the projector and soundhead, the projector won't directly produce any flutter in the sound.
What speed is the flutter, and is it constant? A Dolby tone loop will give a fairly constant tone to listen to, just don't interpret the built-in warbles as flutter.
First thing to check is the lay-on roller, and then the impedance drum bearings. The lay-on roller usually causes a flutter or warble every turn. Bad bearings are easy to feel if you remove the "flywheel". You can test the impedance "flywheel" by turning it at about normal speed then suddenly stopping it, holding it still a moment, then releasing it. It should start turning again, not as fast as before.
The top sprocket in the soundhead pulls film through the impedance drum and if the sprocket rotation speed isn't constant it will cause flutter, you may be able to feel it with a finger touching the film betwen the drum and sprocket.
Projector drive problems: the driving gears being meshed too tightly can cause speed variations. The drive gear should be set "tight" and then loosened off enough to be free turning. There may be an eccentric screw in the projector mounting to adjust this, usually it's gone.
The motor may be misaligned enough to cause a speed variation but I doubt it, usually it just causes a lot of vibration in the whole unit. A bad flex coupling might be at fault too, but that would cause a flutter at motor shaft speed as far as I can imagine. If that's what you have, check the motor mount alignment.
End force on the gearbox shaft may be a problem too, the "motor" shaft should be driven against the motor end bearing by a spring in the opposite end. If you're pushing in on the shaft with the motor mount, the shaft may be floating axially and could rock back and forth with any load variations. That would give you some flutter.
Since apparently it was OK before you worked on it, I would check all the alignment issues with the soundhead/projector and soundhead/motor very carefully.

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Mark Gulbrandsen
Resident Trollmaster

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From: Bountiful, Utah
Registered: Jun 99


 - posted 02-04-2007 11:53 AM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Also check the SN171 upper lateral guide roller bracket to be sure it is not cracked. The cracking of this bracket is actually more common today than bad gears in the gear box. Crappy Simplex Die Castings! New brackets are cast alumnium alloy and much stronger. If this bracket cracks the roller can actually bend back taking alot of the comntact pressure off the film and scanning drum.

Mark

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Jack Ondracek
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From: Port Orchard, WA, USA
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 - posted 02-04-2007 04:02 PM      Profile for Jack Ondracek   Author's Homepage   Email Jack Ondracek   Send New Private Message       Edit/Delete Post 
quote: Dave Macaulay
Since there's a slack loop between the projector and soundhead, the projector won't directly produce any flutter in the sound.

But the projector is connected to the soundhead by its geartrain. Binding in the intermittent, for example, could travel back to the soundhead mechanics and that WOULD show up as flutter.

I've also seen situations where the main drive gear on a "C", which is sometimes missed when greasing the machine, can cause rough operation.

Not that any of this is obviously the problem, but since it worked before, it makes sense that it would be an alignment or assembly issue.

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Gordon McLeod
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From: Toronto Ontario Canada
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 - posted 02-04-2007 05:18 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
Since the SH1000 should have about 3 perf of slack film in the loop the projector and the gear box should be much of a non issue
I would suspect the roller or the assembly or the bearings of the scanner or the flywheel before anything else

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Bob Koch
Expert Film Handler

Posts: 183
From: williams ca
Registered: Nov 2001


 - posted 02-04-2007 06:57 PM      Profile for Bob Koch   Email Bob Koch   Send New Private Message       Edit/Delete Post 
Very seldom is the stabilizer at fault in this reproducer or others of RCA manufacture using a rotary stabilizer. Bearings, yes, and with SH1000 the lateral guide pressure roller is suspect,bad bearings,deformed roller or cracked pot metal casting on upper portion of lateral guide/pressure roller assembly. also defective spring and ball between the upper and lower castings which supplies snubbing pressure to the felt roller against the drum.

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Louis Bornwasser
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From: prospect ky usa
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 - posted 02-04-2007 07:11 PM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
I once found 38 of 50 pot metal upper lay on roller holders cracked. 50% fresh break and 50% old break with paint inside the crack from-the-factory. Estimate that these were from 1945 to 1954. Louis

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Gordon McLeod
Film God

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From: Toronto Ontario Canada
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 - posted 02-04-2007 07:36 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
I have found lots of stabalizer flywheels damaged due to being dropped when moved

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Monte L Fullmer
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From: Nampa, Idaho, USA
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 - posted 02-04-2007 10:23 PM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
Wonder, being an older SH-1000, would this have the fluid filled flywheel instead of the newer solid flywheel?

And something's not working too well with the fluid inside the flywheel causing slight variable rotation speed with the impedence drum shaft?

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Tim Reed
Better Projection Pays

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From: Northampton, PA
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 - posted 02-04-2007 10:32 PM      Profile for Tim Reed   Author's Homepage     Send New Private Message       Edit/Delete Post 
Scott, if it's flutter (as opposed to wowing) I'd certainly check first for flat spots on the sound drum roller felt (or rubber, as the case may be), like Louis, et.al. said.

Also look for cords/cable dragging against the flywheel itself.

Bad bearings, too, as others have mentioned.

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Dave Macaulay
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From: Toronto, Canada
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 - posted 02-05-2007 08:48 AM      Profile for Dave Macaulay   Email Dave Macaulay   Send New Private Message       Edit/Delete Post 
Gordon - one of the ones I rebuilt for Tom had the worm gear bearing loading spring missing and had a pretty nasty flutter. I figured it was from the shaft moving axially and speeding/slowing the sprocket gears while running. I could feel pulsing in the film between the gear and sound drum. After getting new bearings, the missing spring, and fresh oil... it was steady. I can't say for sure that the gearbox was at fault, the pressure roller assembly and drum bearings etc. were all redone at the same time.

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Scott Norwood
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From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99


 - posted 07-24-2007 11:56 PM      Profile for Scott Norwood   Author's Homepage   Email Scott Norwood   Send New Private Message       Edit/Delete Post 
Update: this appears to have been fixed.

On the advice of a technician who looked at this, I replaced the bearings, spring, and roller in the "dirt embedder" assembly in the soundhead (Brad's favorite piece of cinema equipment). This seems to have solved the problem. The lower feed sprocket in the projector head and the first sprocket in the soundhead were also swapped with modern VKF sprockets (the old ones were the small CinemaScope sprockets). I'm not sure which of these was (or were) the cause(s) of the issue, but the end result is that everything is fine now. Thanks for all the advice and suggestions above.

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System Notices
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It has been 3500 days since the last post.


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