Film-Tech Forum ARCHIVE: Interlocking strong and monee

This is topic Interlocking strong and monee in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Peter John Anthony. C (Member # 2500) on 11-24-2004, 04:21 AM:

Hi!
We are having a 4screens Plex, where screen1 has Strong projector & Screen2,3 & 4 has Monee projectors.

I would like to use one print & show movie on Screen 1 & 2 (Strong has Synchronize motor & Monee has Inductance motor.)

I would like to take your suggestion before going ahead.

Thanks in advance.
regards,
Peter

Posted by John Pytlak (Member # 331) on 11-24-2004, 08:10 AM:

It's unlikely that projectors with inductance motors will run at exactly the same speed. Even a 1 percent speed difference is a significant difference in the length of film over a two hour feature. (Even more so with very long Indian "Bollywood" movies [Wink]

)

Posted by Leo Enticknap (Member # 534) on 11-24-2004, 08:56 AM:

108 feet in the case of a 2 hour 35mm feature (120 minutes = 10,800 feet at 24fps). That would need a very long loop absorber between the two machines to be able to start with that much slack if the second machine is running faster or to absorb the extra footage if the first machine is running faster. Selsyn motors are a must, I'd have thought.

Posted by Gordon McLeod (Member # 33) on 11-24-2004, 08:58 AM:

Replace the induction motor, and the rive pulleys and belts with a sync motor and correct timing belt and pulleys

Posted by Peter John Anthony. C (Member # 2500) on 11-24-2004, 09:44 AM:

Thanks Gordon,if you have any details specs for pulley, sync motor & belt to easy my experiments please let me know.
Thanks once again.

Posted by Gordon McLeod (Member # 33) on 11-24-2004, 09:48 AM:

I would contact monee or there local rep to get the correct pulleys for to match the gear train of your machines also ensure that the motor is the correct line frequency and voltage for you location

Posted by Peter John Anthony. C (Member # 2500) on 11-24-2004, 10:02 AM:

Do we need to install Ups to give a steady supply to the projector motor. At present we are not using any & every thing is fine?

Thanks once again.

Posted by Steve Kraus (Member # 476) on 11-24-2004, 10:12 AM:

That should not be necessary if the power is good enough to run what you have now. Motors are not bothered by the sort of voltage spikes and electrical "noise" that might cause problems with delicate electronics. Slight variations in frequency will cause slight variations in motor speed but this will affect all the motors in an interlock arrangement so everything will remain in step.

You need an accumulator between projectors to give out slack film or absorb it only as the machines come up to speed as they may differ slightly. Once the synchronous motors are at speed they lock to the power line frequency and from that point on the slack between projectors will not change.

Posted by Peter John Anthony. C (Member # 2500) on 11-24-2004, 11:15 AM:

Steve one of my friends told me that some of his friend has done interlocking between three projector (Monee, Strong & Monee), they had a problem.
With Monee & Strong no prob, Monee & Monee no prob, but sometimes Monee, Strong & Monee the film moving between Monee to Strong dangles down towards floor & film moving from Strong to Monee moves upward & gets tight or vice-verse. Due to which they have to stop the show & leave about 3 to 6ft of film loop between the two projector & run the show. This happens twice or thrice a week when they did not have ups installed. But after installing ups worth 543$ they had no such problems.
Please advice. Thanks.

Posted by John Pytlak (Member # 331) on 11-24-2004, 04:56 PM:

The UPS may just have changed the voltage somewhat, which could affect the speed of the induction motor. Syncronous motors "lock" to the line frequency when up to speed.

Posted by Peter John Anthony. C (Member # 2500) on 11-25-2004, 07:41 AM:

Yes John I completely agree with you. But these guys have installed the UPS for Strong Synchronize motor which confuses me & they say after installing the UPS everything works fine.
Anyways thanks to all, for your kind advice. I will go ahead to interlock between Monee & Strong without UPS & if I face any problem I will get back for your advice.
Thanks once again. Cheers.

Posted by John Pytlak (Member # 331) on 11-25-2004, 11:11 AM:

Maybe the UPS output was slightly off line frequency? [Confused]

Posted by Steve Kraus (Member # 476) on 11-25-2004, 01:22 PM:

If it's the type of DC-linked UPS is that is working at all times (rectifier->inverter) as opposed to just a backup supply that kicks in when mains power fails then there could be problems unless one UPS can run all motors. I'd stick with utility power for all so if there is variation they will vary together.

Posted by Mark Gulbrandsen (Member # 72) on 11-25-2004, 01:46 PM:

We have several customers that run interlock without sync motors. These folks all have two loop accumulators and when things start to creep up they slow down the faster projector to put the trombone back in the middle with their hand in very heavy leather glove..... by slight friction on the flywheel. Dangerous.... a bit... but it works and is cheap. They claim they generally have to do this once in a 2 hour film and sometimes not at all. Using two loop accumulators gives one quite a bit of leeway between projectors.

A DC invertor generating AC will not guarantee you perffect speed as induction motors inherently have alot of slip.

Mark

Posted by Rick Long Jr (Member # 541) on 11-25-2004, 03:18 PM:

There used to be a theatre here that ran interlock on a couple of Prevosts without sync motors. They had a large six-foot loop accumulator with micro-switches positioned near the top and bottom that would throw a resistor in series with the projector motor. Didn't work very well though. One machine was always slightly faster than the other, and as a result, the accumulator would ride up and toggle the switch on and off throughout the show, causing sound instability issues.

Posted by Steve Kraus (Member # 476) on 11-25-2004, 03:38 PM:

That's crazy. First of all cutting voltage is not the ideal way to speed regulate an induction motor (even non sync motors follow the frequency...they just don't catch up to it like a sync motor does). But to go to that much trouble rather than just getting the proper motors is/was a waste.

Posted by Rick Long Jr (Member # 541) on 11-25-2004, 06:48 PM:

I didn't install it, and in no way was recommending this method. Just thought I'd mention it as another example of theatres that run interlock without sync motors.

The method Mark mentioned reminds me of an incident where a theatre was running interlock WITH sync motors, but the operator didn't pay enough attention to what he was doing, and ended up with too much slack. He said "no problem" and proceeded to try to slow down a Vic 5 sync motor with a rag on the motors inching knob. The rag got twisted up, almost breaking the guys fingers, and stayed there flipping around for the rest of the show. All I could do was shake my head.

Posted by Gordon McLeod (Member # 33) on 11-26-2004, 09:16 AM:

Actually those resistors were in the capacitor part of the circuit that ran the 3 phase motor from single phase.
The resistors changed the RC constant and caused the motor to slow down
Carl had done several prevost installations that way since originally prevost didn't offer a sync motor for that model and it was a direct gear coupled motor as well