Film-Tech Forum ARCHIVE: Kelmar cue detector with ball bearing ground rollers.

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Posted by Philip Wittlief (Member # 1724) on 06-14-2004, 08:58 PM:

I've got two kelmar cue detector/failsafes I need to try to get working and installed. However, I can't find where the cues are supposed to make contact with ground. It seems that one of two rollers are supposed to make the ground contact, but the entire shaft is grounded except the rollers where the film (and cues) make contact. Are these supposed to be grounded or am I wrong in thinking how this is supposed to work. Here are pictures of the cue detectors I'm talking about to hopefully make it more clear.

phil

Posted by Mark Gulbrandsen (Member # 72) on 06-14-2004, 09:04 PM:

Phil,
The entire metal frame is actually ground with the green wire being the electrical ground that you connect to your automation. That particuluar detector was an attempt by Kelmar to actually make the contact type detector more reliable which they were not at the time. It was an improvement but nothing beats an Eprad FP-350 no contact detector for reliability.

Kelmar made and may still make a proximity upgrade kit with a cue stretcher that will fit onto your detector. No matter what automation you have don't expect 100% reliabilty from any type of contact cue detector, especially in a fairly humid area as where you live.

Mark @ CLACO

Posted by Rick Long Jr (Member # 541) on 06-14-2004, 09:22 PM:

The two rollers with the wires are not supposed to be grounded. What happens is, when a cue on either edge comes by, it electrically joins these rollers to groung via the other two roller assemblies right next to it. You have to thread through them, and the cue needs to be at least 2 frames in length (your automation may vary), and carefully folded over the edge so as to contact all the rollers. There are essentialy two separate cue detectors with reference to ground. The film travels too fast for any kind of "cross-cue application. These work best when kept spotlessly clean and free rolling.

Posted by Philip Wittlief (Member # 1724) on 06-15-2004, 03:28 PM:

quote: Rick Long Jr
The two rollers with the wires are not supposed to be grounded. What happens is, when a cue on either edge comes by, it electrically joins these rollers to groung via the other two roller assemblies right next to it.

I know that the two rollers with the wires aren't supposed to be connected to ground, what I'm saying is the other two roller assemblies next to it, give me a ground on everything except for the actual part that the film runs on when I test continuity with a DMM.

As far as getting better cue detectors, I know these aren't very good. The story is I work at an indepedent twin and we haven't run with automation since I've been here. Last fall I got my boss to get me two FM-35's, but due to having DP70's didn't install them immediately as I tried to figure out a mounting technique. In the meantime we opened up another theater and the FM-35's got taken down there 'temporarily' until some could be ordered for that theater. Now that theater is not being successful and it never got its own cue detectors, and doesn't have money to get any. We have these Kelmars laying around so they're going to go down there and I will get our FM-35's back.

phil

Posted by John Walsh (Member # 168) on 06-15-2004, 03:45 PM:

I think this type of detector not only sensed inboard or outboard edge foil cues, but also if a cue was placed directly across from edge to edge. So it could do "three" functions.

Posted by Tim Reed (Member # 137) on 06-17-2004, 01:10 AM:

That's right, the big rollers at the left/rear of the picture are the cross-cue. Place a foil straight across the film (on whichever side of the film contacts it - I think the base side). It does run past very fast, and Kelmar had pulse-stretchers in their Deluxe Automations for the cross-cue. The larger roller diameter also helped lengthen the time the foil was in contact with it.

Unless I am mistaken, the inboard cross cue bearing is the isolated one, and grounds against its outboard mate. Consequently, if you make inboard cues longer than 4-6 frames, it will also trip the cross cue by grounding it to the front ground roller.

Of course, the big problem with this pickoff is that you can't get the proper bearings for them anymore. When it was designed, the bearings from Kelmar were conductive, and (I was told) specially-made for the application. Off the shelf replacements, however, lose conductivity after just a few weeks and you end up missing cues.

Posted by Philip Wittlief (Member # 1724) on 06-17-2004, 03:32 PM:

quote: Tim Reed
Of course, the big problem with this pickoff is that you can't get the proper bearings for them anymore. When it was designed, the bearings from Kelmar were conductive, and (I was told) specially-made for the application. Off the shelf replacements, however, lose conductivity after just a few weeks and you end up missing cues.

Alright that must be the problem. Is it possible that the original bearings are no longer conductive. I have not idea whether they've been replaced or not. Either way it appears the bearings are not conductive anymore and that is my problem. So since they are no longer made anymore, is there any use for these detectors anymore, or should they just be thrown out? (yes I know if they were working they're still crappy and probably should be thrown out.)

phil

Posted by Tim Reed (Member # 137) on 06-17-2004, 10:41 PM:

No, they were okay when they worked - but just okay, nothing spectacular. But since you can't get reliable cues out of them anymore, they're really not much use, other than as a holder for a failsafe microswitch. Kelmar made a two-cue pickoff that had larger bearings and it was a lot more-reliable, even though it had the conductive bearing problem in later years, too.

quote: Philip Wittlief
Is it possible that the original bearings are no longer conductive.

I doubt they've survived this long. Normally, they'd wear out in a year or so anyway, and with off-the-shelf replacements now... you're lucky to get a few weeks out of them. And believe me, we tried everything... soaking bearings in solvent, lubricant, going wet/dry, you name it. Nothing worked for long.

You might get them to work if you had pulse stretchers on all the cues, but by the time you go through that trouble, you could just as well put prox's on them.

Posted by Tim Reed (Member # 137) on 11-21-2004, 12:42 AM:

Hey, gang. Bringing this back up because I'm in a situation where I could use a couple of Kelmar cue detectors with mounting plates to go on Simplex reproducers. I used to have a box full of them (which I had to pitch when I moved a few years ago), and of course, I went for years carrying the danged things around in a box and never needed one...

Don't need anything fancy, just two units, and they don't even have to read cues; as long as they roll and have microswitches on them. Just using the failsafe alone.

Preferably cheap or free (Philip, did you go with proxs after all?). We'll take care of the shipping, naturally. Please PM me or reply here if you can help. Thanks!

Posted by Mark Gulbrandsen (Member # 72) on 11-21-2004, 08:37 AM:

Tim, Cue detectors on a 16 wheeler [Eek!]

?????

Mark

Posted by Steve Kraus (Member # 476) on 11-21-2004, 11:21 AM:

Once again it's worth mentioning that if money is tight a highly reliable proximity cue detector can be made by purchasing a generic proximity sensor (it looks like a threaded rod with a plastic tip at one end and a wire coming out the other) and using it with a simple relay and any convenient source of low voltage DC (a wall adaptor will do). It won't give you fancy combination cues and you'll still need a failsafe. But it beats anything requiring actual electrical contact such as the one above. Just need to create a bracket of some sort to place the tip of the sensor a few mm from the film edge that will carry the cue.

For those who don't know what we mean by "proximity" it is basically like a metal detector circuit. It senses the foil going by without any direct contact. It's wired to a relay which in turn connects to the automation.

Posted by Tim Reed (Member # 137) on 11-21-2004, 11:39 AM:

Mark: I'm runnin' on all 18. [Smile]

Sorry, no. It's for Justin's drive-in. He was getting ready to run both screens manually, and I said that should be avoided if at all possible - let me see if we can at least come up with a quick and dirty failsafe. Any help is much appreciated!

Steve: Thanks. It's really bare-bones... no automation, no c/o.. at least not until he can get the theatre open and some cash flow. I just wanted to cobble together a rudimentary failsafe for him, to protect the equipment more than anything.

Posted by Mark Gulbrandsen (Member # 72) on 11-21-2004, 11:41 AM:

Tim, I was just a kidd'n

Most proximity detectors are actually based around an FM oscillator in which its frequency is upset by a passing piece of metal foil. This upset is in turn detected by a circuit thats built into the thing and then activates either a common collector or common emmitter transistor. This transistor in turn can be used to switch a somewhat high impedance relay.

Mark

Posted by Tim Reed (Member # 137) on 11-21-2004, 01:01 PM:

[Smile]

Posted by Tim Reed (Member # 137) on 11-25-2004, 03:09 PM:

*bump* Can anyone help us with a couple of these? If you have some old units just lying around in the way, we'll sure take 'em off your hands. Thanks.

Posted by Brent Neal Jones (Member # 1048) on 11-26-2004, 07:42 AM:

Those ball-bearing types work even less reliably when left in a bucket of water for two years. They shine up, but the rust on the balls can actually be detected with a volt meter even after multiple treatments of pb blaster. pisses me off...they're not supposed to go bad! Think we're going to upgrade... [Big Grin]

Posted by Tim Reed (Member # 137) on 11-26-2004, 01:21 PM:

Brent... anytime soon? We could sure use the failsafes.

Posted by Tony Bandiera Jr (Member # 2365) on 11-26-2004, 01:33 PM:

Tim: If they don't have to be exactly the same, I can send you two, email me with your addy so I can send 'em to ya!

Posted by Tim Reed (Member # 137) on 11-26-2004, 02:50 PM:

Cool, Tony! Thanks, bro! Email forthcoming...