my profile | my password | search | faq & rules | forum home

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » Cinemeccanica V4 speed problem

Author Topic: Cinemeccanica V4 speed problem Jeff Joseph Expert Film Handler Posts: 131 From: Palmdale, CA, USA Registered: Jun 2000 posted 07-05-2003 01:39 AM                        Help! One of my motors burned out. I ordered a new one from Cinemeccanica. It arrived; we installed it. And it's too fast. Further inspection reveals the following facts: The old motor was 1760 RPM; the new one is 1800 (so now I have one projector with an old motor and one with a new one). They no longer make the 1760 motor, and since I have to have identical motors (we are running 3-D), I ordered another 1800 RPM motor, which we will install tomorrow. Today, I made a roll of exactly 900 feet (10 minutes). On the projector with the old motor, it lasts 9:47 And on the new one, around 9:39. So this shows that I was running too fast in the first place, and now with the new motors, I'm running still faster. We are running 110 VAC, using big capacitors to simulate 3-phase (the projectors came to me this way 10 years ago). The motors are designed to be run that way, OR by running 3-phase at 208 volts. So: The way I look at it... I've always been running a little fast and didn't realize it. Why would Cinemeccanica make a machine that ran too fast in the first place? And... how do I slow the projectors down? Cinemeccanica says I can add a resistor in series with the motor power supply and this will slow them properly... but should I be changing the drive gear or am I missing something or ?? I'm puzzled as to why it was fast in the first place, and now that I have a faster motor, what is the correct thing to do? Thanks, Jeff Joseph SabuCat Productions  |  IP: Logged Daryl C. W. O'Shea Film God Posts: 3977 From: Midland Ontario Canada (where Panavision & IMAX lenses come from) Registered: Jun 2002 posted 07-05-2003 01:56 AM                        At 9:47 you're running at 24.53 frames per second (2.2% fast). At 9:39 you're running at 24.87 frames per second (3.6% fast). I normally see 24.5 to 24.7 frames per second using my V5's three phase sync motors. I wouldn't worry too much about running at 24.87 fps, that's only 2 minutes fast per hour. quote: Why would Cinemeccanica make a machine that ran too fast in the first place? I bet the drive gear sized for 50Hz runs dead on at 24fps (when running on a 50Hz supply). They probably made the 60Hz drive gear a little too small. If the V4 is anything like the V5, there's not too much room for the 60Hz drive gear as it is. Of course, I've never actually counted each tooth on both 50 & 60 Hz drive gears, so they might actually be sized to match the motors operating frequency identically. quote: I'm puzzled as to why it was fast in the first place Since adding a resistor would slow it down, it's obviously not a sync motor... which leads me to believe you probably have something closer to 118VAC on your mains, not 110VAC (only about a 1% difference, but could significantly add to your projector running ~2-3% fast).  |  IP: Logged Mike Pennell Expert Film Handler Posts: 150 From: Tucson, AZ, USA Registered: Apr 2003 posted 07-05-2003 04:17 AM                     Get the old the motor to a rewind shop and have it repaired. Those v4 motors are expensive.  |  IP: Logged Ken McFall Jedi Master Film Handler Posts: 615 From: Haringey, London. Registered: Apr 2001 posted 07-05-2003 05:16 AM                     Been a while since I worked on a Vic 4 but if the motors are three phase, then why not run them off inverters. That way you simplify the wiring and get rid of everything else, resistors, capacitors and switch gear. The inverter control line is a single normally open contact.... nice and simple. You can run the projector at any speed you like, selectable by a rotary switch if you need to. So you can effectivly match the projector speeds if your gearing is different. Just run a loop between them and tweak until they run exactly in sync. After that provided you have the same run up and run down settings they will stay in sync. More importantly as have full control over run up and run down speeds, which is much easier on the projector, you will extend the life of your ageing Vic's. There is better motor protection within the inverter as well so less chance of a motor burning out on you. I'm sure someone will be able to give you more information than I can on what is available to you locally.  |  IP: Logged Jeff Joseph Expert Film Handler Posts: 131 From: Palmdale, CA, USA Registered: Jun 2000 posted 07-05-2003 10:03 AM                        It is my understanding that these motors can be run either synchronous OR non-synchronous. We are running NON, so the resistor idea should work. I think. Jeff  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-05-2003 10:15 AM                     Under no load all motors are synconus and run at 1800 RPM (3600) or a multiple of the numkber of poles A true sync motor doesn't slow down under its rated load where as a asynconus motor does and that is where the 1725 RPM that most motor are listed at come from Almost all of the contenental european projectors used 3 phase motors (with a bank of caps for single phase operation) and current limiting starting resistors to slow them down on start up In north america there are many different brands of speed controlers (in europe they refer to them as inverters because they rectifier the single phase input and then generate high power 3 phase at the desired frequency) Allen Bradely Reliance Bodine all make good speed controlers and one advantage of them is you can actually program usually 3 speeds into them (at the labs it is usually 24 25 and 30fps) or in rep houses 18 24 25 fps and program the rampup to full speed to remove gear stress and stop snatching of take ups A solution would possibly be get a machine shop to make a adapter plate to hold one of the endmounting serries motors onto the machine with a shaft adaper to hold the drive gear One other advantage of speed controlers is they can be interlocked to have a master/slave sync that is frame to frame accurate  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 07-05-2003 11:03 AM                     Some observations; not all necessarily so relevent to Jeff. 1. Motors are not always what the nameplate says they are. Since the fps:rpm ratio in your case looks about the same, you're probably good. General-purpose motors may vary up to 5% from the nameplate, motors purchased from a projector vendor should be far better. Though our Bauer U4s have motors that claim 1700rpm on the nameplate and actually run at 1783rpm (I think this is a bizarre anomaly). 2. You can definitely hear the difference at 24.9fps, and people can also see it. Generally only either people familiar with the material, or those with perfect pitch. But correcting the speed down to 24.0fps is worth doing. 3. Gordon's explanation of motors is a bit misleading. For single-phase non-synchronous motors (which is most of what you'll find in the US, though not what Jeff has), motors have a characteristic called "slip", which is the difference (usually as a percentage) between the magnetic field rotation and the physical rotation of the motor, and it is generally a few percent. For instance, a 4% slip motor might run at 1728rpm (1725rpm) instead of 1800rpm. The slip is what makes the motor run... 4. I would be a little skeptical that simply adding a resistance is sufficient to slow down the motor, but maybe I'm missing something important about running 3-phase motors off of single-phase power... --jhawk  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-05-2003 01:02 PM                     The construction of sync motors are different than sync motors fairly substanially. The slip is the percent between full load and no load RPM and nameplate RPM are at full load True sync motors are very expensive and in single phase versions typically don't have a long life span and they run much hoter than a asynconous motor for the same RPM Also I mentioned only 2 speeds there are also 1440 and 1400 and 1200 RPM 60Hz motors As for starting resistors until the advent of inverter based motor controllers all 3 phase motors in projectors started through a set of switch 3 resistors (often 40 ohms)  |  IP: Logged Jeff Joseph Expert Film Handler Posts: 131 From: Palmdale, CA, USA Registered: Jun 2000 posted 07-05-2003 01:15 PM                        Well, I have to start with both projectors "on", then turn on the interlock, then turn "on" the motors, so they start at the same time. I'm going to be calling Cinemeccanica on Monday to discuss this further. Jeff  |  IP: Logged Ken McFall Jedi Master Film Handler Posts: 615 From: Haringey, London. Registered: Apr 2001 posted 07-05-2003 03:31 PM                     One of the big advantages of inverters is for running interlock as the projector wiring is so simple. In your case all you need is a double pole normally open switch to start both projectors. You can mount push buttons at each projector to allow you to inch the remote projector to assist lacing up etc. It really is very simple. I've run three screen interlock on Vic 8's with no problems at all. Stopping and starting many times on a test show was not a problem. The loop absorber's never moved! For the cost it's well worth considering installing them as they will extend the life of your projectors and reduce maintenance of the control gear. Hope you get it all sorted out. Regards Ken.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-05-2003 04:31 PM                     I assume you are using selsyns to keep the 3d sync be carefull that at no time do the selsyns attempt to actually run the machine as they are designed in this application as a govenor not a driver You may want to get Phil Hill to do a invertor control for you then it would be as simple as push one button and they will be frame locked  |  IP: Logged Ken McFall Jedi Master Film Handler Posts: 615 From: Haringey, London. Registered: Apr 2001 posted 07-05-2003 04:33 PM                     Gordon... who was your last post intended for...?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-05-2003 06:32 PM                     For jeff re his start up procedure to do 3d often selsyn motors are placed on each machine to control the sped of each projector keeping them in rotational sync  |  IP: Logged Ken McFall Jedi Master Film Handler Posts: 615 From: Haringey, London. Registered: Apr 2001 posted 07-05-2003 06:39 PM                     Sorry Gordon, I was commenting on running interlock where the need to retain exact frame sync is not important. I've never run two projector 3D so have no experience of the mechanics of it all. Wish I'd been able to see an original system where the projectors were locked by a rod between the two projectors, 3000' reels and carbon arc's. Today it all seems so easy with Xenon lamps, and electronic interlocking.... takes the fun out of it. I still remember the feeling of doing a change over where your fingers rubbed the palm of your hands whilst waiting of the motor cue.... the tension of the moment is missing today. BUT there is still a lot of job satisfaction to be had if you are so minded.  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 07-06-2003 04:47 AM                     Ken, there was an original set up like that in what's now a bingo hall here. The machines were standard, but the chuffing big, un guarded drive shaft running between them was not, and was a terrifying looking thing, imagine it catching your clothing! Follow this link to some pictures of a 3D system that I did for Warner Brothers at the Movie World Theme Park near Madrid, Spain. The equipment is Balantyne Pro35, driven by stepper motors, all controlled by Strongs SVA automation, and synced to the rest of the show with timecode.  |  IP: Logged

All times are Central (GMT -6:00)

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.