Film-Tech Forum ARCHIVE: What Is Soooo Difficult About Platter Design?

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Posted by Will Kutler (Member # 770) on 01-08-2006, 05:25 PM:

This leave me scratching my head.I'm still wondering what is soooo difficult about designing a reliable platter that is easy to thread, maintains its timing and does not promote feed and roller problems?

Think about it...the platter is essentially a variable speed controlled dc motor. Gee whiz...I was playing around with LEDs and similar circuits with the Radio Shack Science Fair Electronics Kit that my folks bought me in 1977!

Brad and I disagree about platter rollers. Personally, I like roller bearings and have never seen them overspin and dump film on the floor as others have claimed. I also think that aluminum rollers are much easier to clean and maintain...especially in todays booths where idiots love to put Lubriplate on everything. Trying to clean Lubriplate off of plastic rollers is a time consuming pain in the WAHOO! I also think that many roller designs open the possibilities of film jumping rollers and riding on flanges...

Brushless DC Can Motors would solve many a problem!

Anyhow, I do understand manufacturers need to reduce costs, and that some of my suggestions, while increasing product cost, would also improve quality.

Enough rambling!

Posted by Louis Bornwasser (Member # 3063) on 01-08-2006, 05:35 PM:

Will: of course you are correct.

If you started with a Christie-style platter (easy threading) and used a disc that used a digital position sensor, you could program any possibility of motor actions. Wrap proof; self calibrating, etc.

The reason we don't already have this is: No demand and no way to pay back development cost. Louis

Posted by Don Hallmark (Member # 3450) on 01-08-2006, 06:00 PM:

What would be a reasonable price to upgrade a platter to work off of a motor controller with sensors? I have been working on a design that would be beneficial to the simple platter systems but might not make sense to do to a Christie. I am looking at it costing me about 1000 bucks to do a Potts 3 teir platter. Would that be reasonable in the market?

Posted by Mark Gulbrandsen (Member # 72) on 01-08-2006, 06:19 PM:

quote:
Trying to clean Lubriplate off of plastic rollers is a time consuming pain in the WAHOO!

Well said Will! Anyone out there that still actually uses that crap ought to be sentenced to 5 years....

As far as converting a platter I gree that today a brushless motor is the only way to go. Good servo or feedback capable drive systems are VERY expensive to buy... starting with the drives at around $2,000.00. I always liked the Imax-Kinoton platter... beautifully machined payout heads and such.... I'd model my 35/70 platter system after that platter system any day.

Mark

Posted by Michael Schaffer (Member # 1204) on 01-09-2006, 04:22 AM:

quote: Louis Bornwasser
Will: of course you are correct.

If you started with a Christie-style platter (easy threading) and used a disc that used a digital position sensor, you could program any possibility of motor actions. Wrap proof; self calibrating, etc.

The reason we don't already have this is: No demand and no way to pay back development cost. Louis

Your vision has come true some time ago with Kinoton platter systems (ST200E). They constantly recalibrate themselves and are basically wrap proof. You can even hold on to the platter and brainwrap it massively and then watch it recover and recalibrate within moments. They are built like a tank - literally: the platter decks run on the same bearings used for German tank tracks.
Some have made a big deal out of the fact that the threading path used to be different for the lowest deck. I hear that has been changed recently (although I haven't see it yet), but even without a change the difference is really only that when you come back from the projector, you use either a roller that directs the film onto the lowest deck, or another one that sends it up the tree. In any case, that takes even less brainjuice than moving a roller cluster or setting a payout/rewind switch like on some other platter models. No matter what personal preferences may be, the threading path is just much simpler than on any other platter. There is simply less rollers, less up and down and no go here and then come back at all.
The brain defines which platter deck is paying out and some don't like that, I have never understood why. Since the brain has a very broad but shallow base and connector, it comes out of the deck easily and never gets stuck or the connector damaged.
Since there are no moving parts on the brain, there is nothing to get stuck there or go out of alignment.
The platters have a threading and a run mode which is selected by whether the motor of the projector is running or not. During threading, the platter gives you some film and then stops for a moment so that there is no hectic pulling out miles of film and brainwrapping before the show even starts, and when the projector starts, the platter immediately starts up by itself before the brain takes over so it doesn't have to "catch up" with the projector.

The problem is that all that costs more money than other platter systems and that also answers the question why they aren't seen here more often. But they are extremely popular in Europe despite the costs because people know that they will rarely if ever lose a show because of platter problems.
There is a lower cost version now (FT3M) which is mechanically simpler and has a brain with a moving take up arm (and a hall sensor) but the steering routines are exactly the same and there is even a software tool to monitor the performance and correct functioning of the sensors.

Posted by Steve Guttag (Member # 268) on 01-11-2006, 10:49 PM:

quote: Michael Schaffer
The brain defines which platter deck is paying out and some don't like that, I have never understood why.

You've got to be kidding...it is one of most incredibly silly design flaws of the design!

If the take-up arm set the "Mode" of the platter deck between payout or take up, one would not need to move a payout module about. Less equipment handling leads to less wear and tear and less damaged equipment.

What does the method of moving the payout module from deck to deck bring to the design? Nothing.

The only reason I can see why Kinoton went with such a design is to determine which deck spins immediately when the projector starts. However, that means that the payout module can't tell that there is film threaded pass the IR sensors for if it could...then the deck with film threaded past the IR sensor is the one in payout mode. I would even take a set of switches to determine which is the payout platter over the present design.

This is just another case of getting something 95% there and has incredible engineering behind it...far more slick than the compitition but in the end, makes me scratch my head....Kinda like why they still have their soundhead LEDs turn on when the changeover opens rather than when the motor starts...thereby causing a reversion of the Dolby Digital track or a THUMP on each changeover.

Posted by Mark Gulbrandsen (Member # 72) on 01-11-2006, 10:54 PM:

quote: Steve Guttag
Kinda like why they still have their soundhead LEDs turn on when the changeover opens rather than when the motor starts...thereby causing a reversion of the Dolby Digital track or a THUMP on each changeover

Changover.... Whats that? They probably wired it that way because 95% of the Kinoton equipped booths around the world run off platters..... [Wink]

.

Mark

Posted by Will Kutler (Member # 770) on 01-12-2006, 09:58 PM:

If I remember correctly, Christie had two different styles of platter control cards for the AW-3. The earlier design tended to be a little problematic, but the later design seemed to be ok.

Bevan probably remembers a pain-in-the WAHOO theatre owner that we dealt with in repairing an AW-3 5 deck! [Big Grin]

Anyhow, there is one improvement that I think Christie should make to their platter decks. Many of todays popcorn/concession "projectionists" tend to be very abusive of exuipment, and I have seen many a platter deck and center hub banged-up from abuse and the payout heads being removed and installed anything but gently! Maybe a protective nylon or rubber insert would be a good way to protect those areas?

Cheers

K

Posted by Mark Gulbrandsen (Member # 72) on 01-12-2006, 11:10 PM:

The only AW-3 drive card that gave problems that I can think of was the version that was driven from a 555 timer IC, but those were quickly pulled back and replaced with the standard drive card.. It was never a stable card. All I generally see fail are the 1N5406 diodes, there are hundreds of them out in this area(thank god!).

Mark

Posted by Steve Guttag (Member # 268) on 01-13-2006, 05:11 AM:

Mark, I think you will find that Kinoton's LED logic is a throw back to their exciter-lamp based changeover! That is, when they made changeovers, they switched the exciter lamps on/off...the logic has stuck through today.

If you think about it..even if you are running a platter, you would want the digital LED lit up ahead of the changeover opening to avoid always starting in analog and then switching to digital a second or two later. It isn't really right for anybody.

Posted by Robert Throop (Member # 61) on 01-13-2006, 07:48 AM:

Years ago I worked in a drive in with FP20s. The exciter lamps were switched with the motor. It was a Ballantyne installation.
Bob

Posted by Mark Gulbrandsen (Member # 72) on 01-13-2006, 08:20 AM:

quote:
Mark, I think you will find that Kinoton's LED logic is a throw back to their exciter-lamp based changeover!

Steve,

I was just pillin yer leg.... you missed the winkie. I have no idea how many are on platters or c/o. What ever the reason can't it be easily re-wired the correct way?

Mark

Posted by Paer Hoegberg (Member # 3133) on 01-13-2006, 10:22 AM:

Our FP30:s and FP30E lights the LED:s when the motor starts, and the LED:s remains on until you power off the projector.

Posted by Steve Guttag (Member # 268) on 01-13-2006, 05:52 PM:

Mark,

I actually did see the wink...however I'm sure some will say that the LEDs are wired that way for platter operations...and it doesn't benefit them either...except maybe "loop" platters like the ST2000E...now I'm sure THEY are in the distinct minority.

Rewiring the LEDs for tracking with the motor is indeed doable on every machine I know. Most of the Kinotons we sell are multiformat though..FP38ES machines...as such it is trickier to have the LEDs turn on ONLY for the 35mm shows and track the motor...also doable but more difficult. The easiest thing would be for Kinoton to fix their firmware so that it works properly to begin with.

On mechanical projectors (D and A series) one doesn't have the 2nd format to contend with and often it is a matter of moving a pair of wires to another relay contacts that follow the motor (e.g. on the PK-60D, there are terminals on the relay board within the projector labeled "RES"...they will have the LEDs follow the motor). It is just annoying to have to "modify" 100% of the projectors for something that is so obviously wrong.

Posted by Mark Gulbrandsen (Member # 72) on 01-13-2006, 06:26 PM:

quote: Steve Guttag
It is just annoying to have to "modify" 100% of the projectors for something that is so obviously wrong.

I agree, perhaps they should have two version of firmware available Or just get yourself some of those small C.E. supplies and forget the built in ones..... easier interface!

Actually I can't remember a piece of large pro equipment in the last 30 years that didn't have to have something done to it to make it work right(CP-650's excepted!). Broadcast equipment is the worst of all. I'll never forget installing the brand new Chyron at one of the stations I was at. The thing didn't even function out of the crate at all. Ditto for many of the Sony 1" machines... there was always a bug or two left in them from the factory and almost always something in the edit mode that was a real pain to make right.

Mark