Film-Tech Forum ARCHIVE: Threading up Simplex 35s - Proper Frameline Position on Holdback Sprocket

This is topic Threading up Simplex 35s - Proper Frameline Position on Holdback Sprocket in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=008968

Posted by Matt Hollis (Member # 2954) on 10-31-2007, 05:06 PM:

Tonight at work I think I'm gonna give it a shot "threading up" by Simplex 35s. What is the correct frameline position on the holdback sprocket to ensure my movies are in frame. I have 5 Stars by the way, and this assumes I thread by the book by pulling the arm all the way to the stop and backing it off one perf. I also feel the best way to deal with the platters is to bypass the platter's take-up arm until I'm finished threading the machine. If anyone has a better suggestion on how to do that please mention it. (Potts A-3s by the way)

Posted by Mike Blakesley (Member # 26) on 10-31-2007, 05:49 PM:

Your post is confusing. At first it sounds like you're talking about threading in frame, but by the end it sounds like you're talking about having the sound in sync with the picture. Which is it?

Don't you have a framing light? If you can see the frame lines in the lit "box" then you're out of frame.

I'm not sure what you mean by holdback sprocket...the intermittent sprocket?

Posted by Robert E. Allen (Member # 1351) on 10-31-2007, 06:42 PM:

All projectors have a "framing port" with a light behind it which is used for properly framing the picture. The hold-back sprocket (which is at the bottom of your sound head) has nothing to do with framing.

Posted by Monte L Fullmer (Member # 2797) on 10-31-2007, 06:46 PM:

Yea, you pull that lower snub roller tight while pulling on the film across that lower holdback sprocket, then back it off one sprockethole then close the pad roller assembly over the sprocket on the 5-Star soundhead unit.

You turn the motor flywheel, watch the intermittent sprocket to make a quarter turn, then when the sprocket stops, you stop turning the flywheel and frame the film to the framebox accordingly before closing the gate and trap assembly.

Posted by Ken Lackner (Member # 1002) on 10-31-2007, 07:07 PM:

I could be completely wrong here, but I think what Matt is talking about here is threading the projector from the bottom up, the way Brad describes in this tip. Literally, "threading up." Since the holdback sprocket -- and not the framing aperture -- is the first thing you will thread after you pull the film up out of the failsafe, he wants to know where the frameline should land so that the film in the gate will be in frame.

Off the top of my head, I don't know. You will have to experiment a little to see what works best.

Posted by Brad Miller (Member # 2) on 10-31-2007, 07:24 PM:

Thread it with perfect loops and in frame any way you want to achieve that goal. THEN once you have a piece of film in the projector threaded exactly as you want it, advance the motor until the pulldown just stops and take a look at the holdback sprocket. There lies your answer.

Posted by Ron Curran (Member # 3631) on 10-31-2007, 08:25 PM:

Brad, I'm terrified to add this, but we hand advance, not motor advance.

Posted by Mike Blakesley (Member # 26) on 10-31-2007, 08:31 PM:

I think Brad meant to hand-advance, because he said "until it just stops." But Brad's suggestion will only work if the projectionist can remember EXACTLY the size of the loops every time. Bottom line, you need to use the framing light or the lightbox or whatever it's called in your part of the world.

I never heard that soundhead sprocket referred to as the holdback sprocket until today. To me it's always just been the soundhead sprocket. Learning something new every day is good.

Posted by Blaine Young (Member # 3992) on 10-31-2007, 08:59 PM:

I've always threaded everything from the top down - until I started working on the Apogee heads from Strong. The thread on these is just so stupid, I can't make my fingers do all the right things to thread the gate correctly. So I thread from the 'idle' sprocket down through the sound head and then go back and thread the intermittent and gate, and finally the top sprocket.

These heads are the dumbest design I've ever seen.

Posted by Monte L Fullmer (Member # 2797) on 10-31-2007, 09:50 PM:

quote: Mike Blakesley
I never heard that soundhead sprocket referred to as the holdback sprocket until today..

That term comes from the lower sprocket in the 4-star (SH-1000) soundhead being the "holdback" sprocket-holding back the film before entering into the takeup magazine. The upper sprocket is called the "sound" sprocket. Yet, I've always called them, "the upper and lower" holdback sprockets.

quote: Blaine Young
These heads are the dumbest design I've ever seen.

Why Christie is the better projector. (whoops, did I say that too loud??) [Big Grin]

Posted by Matt Hollis (Member # 2954) on 11-01-2007, 04:45 PM:

Yeah, Ken hit the nail on the head. I guess I wasn't specific enough. I guess I'll just take a scrap loop and thread it like Brad said. I just didn't know if anyone had a quick answer since I was short on time.

Posted by Monte L Fullmer (Member # 2797) on 11-01-2007, 10:18 PM:

True Matt, if you try this on those Apogees, in as much where I can do that reverse threading on my older Simplexes, it really does work the first time.

Thing is - you're going to have to think backwards for a while to get the hang of it. But after you do, then it'll come naturally.

Posted by Scott McGuire (Member # 4508) on 11-02-2007, 01:49 AM:

We have Simplex XL projectors and learned from that start from our tech guy to "thread-up" or backwards. He never mentioned anything about the framing port to us during training, but my father who was a projectionist for 25ish years pointed it out to me one day while he was checking out the booth. What i do is thread all the way making sure i am in frame when i close the gate and then adjust my second loop to the proper size after that i adjust the film on the holdback sprocket.

Posted by Michael Cunningham (Member # 210) on 11-02-2007, 02:34 AM:

As to the term Holdback Sprocket, if I'm not mis-remembering, I think I've seen the lower feed sprocket (last sprocket in the actual projector mechinism) listed as such in older manuals. Perhaps this is a hold-over from the pre-sound days when this would have been the sprocket "holding back" against the take-up reel?

Posted by Monte L Fullmer (Member # 2797) on 11-02-2007, 01:04 PM:

The term "Holdback" sprocket came out with the SH-1000 and with the RCA's version of the same head. For the projector, that lower sprocket was called thus: "lower sprocket".

That sprocket also "held back" the film to keep that loop created inbetween the upper sound sprocket and the holdback sprocket for these heads in check during operation.

For the "5-Star" heads, that lower sprocket was never given this name, offically, as a holdback sprocket. It's just simply called a "sprocket".

Just that some of us still call that sprocket by this "Holdback" name since it's basically doing the same job as the sprocket in those "4-Star" (SH-1000) soundheads-"holding" back the film inbetween the lower sprocket of the projector and that sprocket since the snubber roller is doing what the sound sprocket did in that older head.

that "4-star" head design was the "gem" of the industry in the way it handled the film and with that fluid filled flywheel for the inpedence drum, really kept wow and flutter down to a minimum..

Posted by Frank Angel (Member # 248) on 11-02-2007, 01:33 PM:

Hmmmm.....stuff does pass from one generation to the next, but one never knows exactly if it is true or just the older generation's misinformation.

When I was being shown how to thread -- YEARS ago, I might add --I actually asked the old timer who, like many at the time, called it a "holdback" sprocket and like Michael, I asked why it is called the "holdback" sprocket. He told me because it dampens or "holds back" any irregularlities/vibrations/torque from the takeup reel from transfering back into the soundhead. If it and the small film loop it forms between it and the first sprocket drive weren't there, those takeup reel vibrations would be impacted on the film at the cell and heard on the soundtrack.

Fact or fiction? I have no idea. I haven't ever heard anyone else explain that as the reason or if it actually functions that way, but and have never had any reason to question it....until now. It sounds passably logical, but that doesn't make it so or that the old timer was right or just pulling it out of his ass. Alas, now I am the old timer. Do I pass this on or not?

Posted by Steve Guttag (Member # 268) on 11-02-2007, 04:25 PM:

Actually,

The "holdback" sprocket is the last sprocket in any film projector/soundead. It does what its name implies...it holds the film back from the force of that which is pulling the film. That is true wether it be a take up reel trying to pull the film faster than the projector is allowing it to come out or a platter trying to do the same thing. The first sprocket is the feed sprocket because it is feeding the projector. It is all rather simple really and those names have been in use a long long time. I'll have to look at some of our old silent-era manuals and see if they use the holdback term on the last sprocket in the projector...particularly on the ones that had reels. Those that had "bags" may not have used the holdback term...since they were not holding anything back.

Note too, the pitch on the holdback sprocket was traditionally shorter to deal with the tension better...or so the idea goes. You can find that the original part numbers for Century, Norelco and I believe Simplex were different for the Holdback sprocket versus a feed sprocket. What I do know from experience is that on a Norelco, even a new holdback sprocket with an "H" on its face was more likely to "sing" than a feed sprocket when used in the holdback position so I'm not to sure on the facts backing up the theory. As most know, LaVezzi and other suppliers now only have the one type of sprocket (feed) for both positions on Century projectors and likewise for Norelco projectors....so it wasn't such a good idea that it has continued. It also never existed in the VKF variety of sprockets.

Steve

Posted by Robert E. Allen (Member # 1351) on 11-02-2007, 10:43 PM:

You're absolutely right Steve. I started as a projectionist in 1950 and that was the name and stated purpose of the hold-back sprocket. The feed sprocket was also called the pull-down sprocket.

Posted by Monte L Fullmer (Member # 2797) on 11-03-2007, 02:03 AM:

..then you have Christie's "upper constant speed, middle constant speed", and "lower constant speed" sprocket terms.. being the belt driven assemblies in an all-in-one frame..

Posted by Louis Bornwasser (Member # 3063) on 11-03-2007, 07:54 AM:

....and given the wow/flutter..."constant speed" is only just a name on the Christie. Louis

Posted by Robert E. Allen (Member # 1351) on 11-03-2007, 09:15 AM:

Hey Louis!

The last house I worked (a CineMark 15 screener) our booth tech put rubber bands around the sound drum rollers to stop the wow and flutter. He said the company wouldn't put out the $2,000 per machine to correct the problem. But the rubber bands worked. He said the problem was caused by the fact the rollers worked against each other. Can you believe it? A modern 15 screen multiplex and the sound is assisted by rubber bands?

Posted by Mark Gulbrandsen (Member # 72) on 11-04-2007, 09:16 AM:

quote: Robert E. Allen
Can you believe it? A modern 15 screen multiplex and the sound is assisted by rubber bands?

Kinoton and Ernemann both do the same thing... rubber bands on the sound drum!

quote: Steve Guttag
Note too, the pitch on the holdback sprocket was traditionally shorter to deal with the tension better...or so the idea goes. You can find that the original part numbers for Century, Norelco and I believe Simplex were different for the Holdback sprocket versus a feed sprocket. What I do know from experience is that on a Norelco, even a new holdback sprocket with an "H" on its face was more likely to "sing" than a feed sprocket when used in the holdback position so I'm not to sure on the facts backing up the theory. As most know, LaVezzi and other suppliers now only have the one type of sprocket (feed) for both positions on Century projectors and likewise for Norelco projectors....so it wasn't such a good idea that it has continued. It also never existed in the VKF variety of sprockets.

Thats because the VKF sprocket inherently generates LESS sprocket tooth ripple on its own. So holdback sprockets are not required. The rounded teth do make a huge difference. When we had the VKF's produced ffor the DP-70 we asked about having seperate holdback versions made up and their reply was that "it didn't matter any more, the VKF tooth design negates the need".

Mark

Posted by Steve Guttag (Member # 268) on 11-04-2007, 03:50 PM:

Well, in all fairness, the Kinoton and Ernemann both use a loose-loop type soundhead. The use of O-rings allow one to decrease the amount of pressure the pinch roller must apply to prevent slippage. Kinoton, for the longest time did not use O-rings and I find it a welcomed change. One was often needing to increase pinch roller tension to the point that the film almost wanted to slip out in order to have flutter free sound at changeover. In fact, that is how I set the tension...not by any tensino gauge but by when the flutter was gone...it had to be gone in less than 7-seconds. With the O-rings, the tension dramatically reduced. Kinoton has also augmented their later soundheads with a damped roller too to minimize flutter.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 11-05-2007, 08:02 AM:

I think its easier to filter a loose loop sound reproducer than one with a tight loop for sure. The rubber "O" rings are fine till they wear or crack... a cheap replacement too. I'm surprised that Kinoton and Phillips before them didn't always have the extra damper in there as the FP-5 version of the Phillips sound head had the damper roller and its much lower in wow than all the others without it... FP7 and up.

Mark