8mm Forum: Elmo ST1200HD belt change problem

This is topic Elmo ST1200HD belt change problem in forum 8mm Forum at 8mm Forum.

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Posted by Jim Bishop (Member # 81) on November 20, 2016, 08:07 AM:

Hi.
I've just changed the belts on my ST1200HD. Immediately afterwards I tested it and it ran fine, but a few hours later when I ran it, it began slowing down, eventually grinding to a halt.
Does anyone know what may be the cause?
Many thanks. Jim

Posted by Tom Photiou (Member # 130) on November 20, 2016, 08:38 AM:

Is the shutter edge rubber Ok Jim?
When this happened to mine years ago it was a breakdown of the rubber 24fps clutch rubber and the shutter's outer edge rubber.

Posted by Jim Bishop (Member # 81) on November 21, 2016, 05:45 AM:

Hi Tom. When I had it serviced years ago the decayed rubber was removed from the shutter edge, but it has still played ok ever since.

Because it was becoming obviously slower than 24 I decided to put new belts on. Ironic that it should stop the machine playing, I must've missed something out or made a booboo.

I've tried to decipher the service manual troubleshooting section without too much success; should certain components be aligned in a precise position, maybe?

Tx

Posted by Andrew Woodcock (Member # 3260) on November 21, 2016, 06:10 AM:

Jim, have you tried yet, slackening off the belt to see if the motor is able to turn freely up to full speed after warming?

These motors can over time lose some of their torque, especially if the rotor has ever been allowed to severely overheat due to extreme amounts of torque exerted upon it.

I would try and run the motor on no load for a while without the belt even fitted. Then refit it if all appears ok, but just gradually increasing the tension on the belt until the minimum tension can be found where it will drive the shutter wheel and the rest of the drive chain adequately.

If the motor shows resistance or a tendency to stall or will not reach full speed even on no load then either the motor or capacitor (if it has one) or both will be defunkt.

Of course it also goes without saying that you must ensure you fit the exact identical belt to that of the original ones on these.

Refer to this old thread, in particular Kevin's advice here!
http://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=002137# 000005

Another issue here could be if you completely removed the drive wheel clutch assembly to fit the new belt.

If this has not been placed back in exactly the same position as it was previously, there is a good probability that the friction pressure applied from the drive wheel to the shutter is either higher or lower than it previously was when working well.

Only you will know from tracing back in your memory from doing the work of fitting the belt, whether or not this may be the case.

[ November 21, 2016, 10:42 AM: Message edited by: Andrew Woodcock ]

Posted by Mathew James (Member # 4581) on November 21, 2016, 08:04 AM:

Hi Jim,
What i find with these machines is, if the belts are the 'good ones'(ie. OG Square Type) then it should run nice. If you are certain the belt is correct and fitting properly(ie. no rubbing spots) then I would start looking at friction plate cork.
Andrew knows how much i love cork- he hee - after working on mine for so long...but i find these corks get either greasy(from lube that seeps into them accidentally) or they just loose grip. We are currently testing different 'cork' solutions as replacements, such as leather and such...the trick will be to locate which cork may be doing this.
I know you didn't mention rewinding or whether this issue is only in forward, but regardless, check this link out just in case it may apply to you:
http://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=010888#000001

Posted by Andrew Woodcock (Member # 3260) on November 21, 2016, 08:55 AM:

Mathew the cork you refer to would only affect the machines performance in it's ability to rewind or take up the film.
This cannot effect the motor performance driving the shutter.

This problem here, all has to be related to early stages of the drive chain, not the later ones as you are describing.

Posted by Mathew James (Member # 4581) on November 21, 2016, 09:54 AM:

Could be Andrew.
Sorry, i don't see where Jim says this was related to the shutter. I just see his post saying the machine started to slow down after he replaced the belts.
I was troubleshooting based on that info. You may be correct that it is related to motor or shutter, but I didn't glean that from his posts as of yet. [Smile]

I agree with removing belts to see what happens first as you suggest.

Posted by Andrew Woodcock (Member # 3260) on November 21, 2016, 10:07 AM:

By Jim using the expression "grinding to a halt" I assume he means the entire machine Mathew, plus it is the main drive belt which has been changed which cannot directly effect the reel torque on either take up or rewind.

No doubt Jim will confirm which part of his machine is slowing down to a halt before any of us can point him in the right direction, for sure.

Posted by Mathew James (Member # 4581) on November 21, 2016, 02:56 PM:

You are probably right Andrew, at least I hope so, so we get another Elmo up and running [Smile]

Posted by Andrew Woodcock (Member # 3260) on November 21, 2016, 03:07 PM:

We'll see Mathew. We wait for Jim of course first??
Obviously he isn't looking for a quick fix! [Big Grin]

Posted by Jim Bishop (Member # 81) on November 22, 2016, 01:02 PM:

Gentlemen, thank you all for your thoroughly helpful suggestions here.

To cut to the chase, I have 'remedied' the problem as such by simply replacing the newer belts with the ones I originally had on there. It is therefore back to running a little slowly of course, but at least not at about 3fps!

But to reply to some of your comments where I can:- the belts I tried as replacements are of the squared variety, but are ever so slightly smaller - literally a couple of mm. From changing them in the past this seemed normal as I thought they slacked off with heavy use, but whatever the case these smaller ones caused the motor to slow down to almost nothing.

I think the new belts are going in the bin !

I really appreciate all your advice. I wish I could address the really in-depth pointers, but quite frankly at this point I've chickened out - I just need it to work!

All the best.
Jim

Posted by Steve Klare (Member # 12) on November 22, 2016, 01:15 PM:

Hi Jim,

I realize this is going transatlantic, but I've done new belts a number of times for a number of different machines from this seller and he's never done me wrong:

isellprojectorbelts

If you go for the deluxe belt set it even includes a new rubber surface for the shutter wheel. I've been running with this about a year and a half.

I've had the slowpoke ST-1200HD myself. It came down to two things. Number one was my lube was old and dirty. Number two was my motor pulley was worn: the valley the belt rests in was actually worn deeper so that the effective diameter of the pulley was reduced and the machine slowed down. The poor lube aggravated the pulley wear because the belt slipped.

My Great Worm-Glop Weekend!

Restoring the Rubber Shutter Wheel Surface on Elmo ST-1200 (and other tales!)

(-note that there's a learning curve between these two incidents.)

Posted by Mathew James (Member # 4581) on November 22, 2016, 02:45 PM:

I have to second Steve on the belt seller from ebay. I've used him a few times now, as following his advice, and they really are nice belts that fit exactly how they should. I believe even a couple mm's could tighten it enough to slow down, but if you ever get another go at it, i would give it a lube job too.
You can get superlube at home depot(at least in Canada) for dirt cheap. [Smile]

Good luck with it.
We love our elmo's as you can tell [Smile]

Posted by Jim Bishop (Member # 81) on November 25, 2016, 05:28 PM:

Thanks Steve, Matt, for the recommendation - I'll give that a try.

All the best
Jim

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