8mm Forum: elmo st1200 take up reel

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Topic: elmo st1200 take up reel

Tassos Laudas
Expert Film Handler

Posts: 102
From: Viersen Germany
Registered: Mar 2006

posted April 12, 2006 10:35 AM

Another question which might have possibly been answered-if yes please let me know the respective topic please!
Especially during the 2-3 fist minutes of projecting the take up reel slows down periodically causing a listenable...hiccup as the last roller's movement isn't enough to counter-balance the sudden tension.With a slight push the reel won't stop and the hiccup is avoided. Bearing in mind that the reel itself isn't damaged or something as well as that the rear belt seems ok-although a bit loose but maybe that's normal-what would you suggest? Could i possibly increase the back reel torque somehow?
Thank you!

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Jan Bister
Darth 8mm

Posts: 2629
From: Ohio, USA
Registered: Jan 2005

posted April 12, 2006 10:46 PM

Hmm... if I understand you correctly, there is one reason I can think of. But it'll take some explaining so bear with me...

Behind the reel arm (in the back of the projector) there is a clutch mechanism including a cog wheel. It is driven by another cog wheel next to it, which in turn is driven by the take-up belt. The two cogs have slanted teeth and the cog on the reel arm shaft actually is free to move up and down on the shaft (by design). What happens is that when the take-up belt runs, the cog in question moves up against the clutch and engages it, thus driving the reel arm and the take-up reel. On the other hand, if you were to make the take-up reel spin faster than its idle speed by hand, the clutch would disengage and allow the reel to spin freely, until its speed drops down enough that the clutch will re-engage. This also allows the take-up reel to spin freely when in the 'stop' or 'reverse'/'rewind' position, rather than being braked by the whole take-up belt arrangement.

I did my best to explain it but probably ended up being complicated [Wink]

so I suggest you open up the back of your machine, plug it in, and switch to forward running mode to watch what happens. Play around with the take-up reel, make it spin really fast and watch how the clutch behaves, both in the 'forward' and 'stop'/'reverse' modes.

Now, the point of all this... and my idea of what could be going wrong... it's possible the cog wheel's range of motion is somehow impeded and it cannot (or can just barely but not securely) engage the clutch so that the take-up reel loses and then suddenly re-gains torque, causing the scenario you described. If that's the problem, some possible solutions are to apply a little grease to let the cog move on the shaft more easily, or loosen a couple worm screws and adjust its range of motion.

If it weren't so late at night and I didn't have to go to bed 5 minutes ago [Wink]

I would provide some screenshots... maybe I'll do that next time I visit the forum. [Wink]

Hope you get an idea of what I mean, though!

--------------------
Call me Phoenix. *dusts off the ashes*

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Tassos Laudas
Expert Film Handler

Posts: 102
From: Viersen Germany
Registered: Mar 2006

posted April 13, 2006 04:35 PM

Jan i'd like to thank you for your detailed answer,i feel oblidged realising how much time you've probably dedicated in order to help.
The reel rotation is stable when not carrying any film and, in fact, it seems that the low torque makes the reel slow down at the slightest obstacle.The question is how to increase it-could it be the belt eventually?!

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted April 13, 2006 05:27 PM

It sounds to me like insufficient take up torque. I have had to strip the clutch on these machines and clean the cork discs to enable them to be adjusted correctly. Was this machine bought second hand?

Over time what happens is that the grease on the cork discs goes hard giving too much torque. Some sellers then reduce the clutch tension to get it working again but thats then not enough for proper take up torque.

The clutch is my bet on this one.

Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Jan Bister
Darth 8mm

Posts: 2629
From: Ohio, USA
Registered: Jan 2005

posted April 13, 2006 10:37 PM

Seems I was off on this one, so I'll go with what Kevin said. [Smile]

You also mention that the take-up belt itself is "a bit loose" (just now actually noticed that in your post) so the question is, how loose exactly? It should really feel quite tight to the touch and be able to run the take-up mechanism against its own friction (tested by running the projector and stopping the take-up spindle with your hand, then observing the belt and pulleys).

--------------------
Call me Phoenix. *dusts off the ashes*

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Tom Photiou
Film God

Posts: 4837
From: Plymouth U.K
Registered: Dec 2003

posted April 14, 2006 08:08 AM

Of course if the belt is streched this also causes the problem, as Kevin said, a good clean up of the clutch but also go for a new belt, it makes a big difference when using 1200 foot take up, usually the problem is when they begin to get to around 900foot or more of film on them.

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted April 14, 2006 08:38 AM

The belt is worth checking especially if the machine hasnt been used for a long time. You get a belt which sits in one position and then end up being oval in shape. This can lead to this stop and start motion on take-up. Take the belt off and put it in near boiling water. This should help it go back to its normal shape and be a little more supple.
This trick woks very well on the belts in the GS 1200 and also works well on the GS's main motor belt which does exactly the same thing.
On the subject of the GS1200, I have stopped using the normal V belt on the GS and now use a rubber "O" ring type. This runs much quieter and is less fussy to set up for correct belt tension
It also seems to put less strain on the motor and should hopefully give the motor a longer life. The Elmo V Belt has no give in it and puts quite a bit of strain on the motor and its bearings.
I now have a few of these belts and can get more.
Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Tassos Laudas
Expert Film Handler

Posts: 102
From: Viersen Germany
Registered: Mar 2006

posted April 15, 2006 01:36 PM

Thank you all for the advice. I've followed your intructions but don't see any difference. Seriously, for how long should the belt be left in near boiled water, 24hours maybe?
Something that could possibly give you a clue about what is going wrong is the fact that when i prevent the reel from moving, both the 2 cog wheels -the reel's one and the other next to it carrying the belt- stop as well and the belt just slips over forced to rotate by the wheel on the left -which, of course, is still moving.
The belt seems ok but if nothing works i'll order a new one. I'll also try to send a couple of fotos as a last alternative!..
Thank you again.

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Tom Photiou
Film God

Posts: 4837
From: Plymouth U.K
Registered: Dec 2003

posted April 15, 2006 02:14 PM

That slipping of the belt is normal if you hold the reel, i do reckon a ne belt is in order as this is what cured mine, hen you remove the old belt but before fitting the new one ensure you clean the belt groove in the to plastic wheels really god, get all the old black oily belt residue off. If you dont the new belt may ell become soiled before much use.
Give it go . [Wink]

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Jan Bister
Darth 8mm

Posts: 2629
From: Ohio, USA
Registered: Jan 2005

posted April 15, 2006 04:03 PM

I have to disagree, the belt should NOT be slipping... it definitely should be replaced (and the pulleys cleaned as Tom suggests). The friction should be taking place between the pulley and the adjacent cog (by means of the cork disc sandwiched between the two), not between the belt and the pulley. The cork disc might have dried out or gotten stuck, and/or the friction is simply adjusted too strong.

--------------------
Call me Phoenix. *dusts off the ashes*

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Tassos Laudas
Expert Film Handler

Posts: 102
From: Viersen Germany
Registered: Mar 2006

posted April 15, 2006 04:18 PM

Jan, the dried out cork disc was exactly what i have suspected from the beginning ,but after cleaning it and even putting some oil over it it still refuses to move between the pulley and the cog, so, i thought it's not supposed to move at all and that both pulley and cog act as one.
And of course i've losen the outer torque spring as much as possible.
So, how can i make the pulley move independently?

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Jan Bister
Darth 8mm

Posts: 2629
From: Ohio, USA
Registered: Jan 2005

posted April 15, 2006 11:36 PM

That's weird.... Regardless of whether the belt is strong enough or tight enough to keep the pulley going, can YOU turn the pulley and cog wheel independently with your hands, against the cork disc friction? I can't really imagine why you wouldn't be able to. [Confused]

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Call me Phoenix. *dusts off the ashes*

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