Film-Tech Forum ARCHIVE: Strange wear point on Simplex Runners

This is topic Strange wear point on Simplex Runners in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mark Gulbrandsen (Member # 72) on 02-26-2003, 11:02 PM:

I've noticed recently that there seems to be a point on the Simplex curved runners that comes into contact with the picture area. Not sure if this is poor design or not, but the film does come into awful close proximity to the center section of the runners(even brand new runners!) and even has rubbed the center area at the top as you can see in the photo. The top photo shows runners that are just three years old. The second photo shows the area which I ground back with a bench grinder....very slowly so they didn't get too hot and warp. This completely eliminated some slight, very fine scractching scratching in the image area. Anyone else seeing this problem out there?
Mark @ CLACO

In the above photo notice the wear point at right of center. The obviously polished area.

In booth cure for this rubbing spot. Top of runners are actually at the bottom of photo.

Posted by Rick Long (Member # 213) on 02-26-2003, 11:35 PM:

Got exactly the same thing here. 12 out of 12 machines in the last complex I checked. Installed new runners a couple of months ago, and am watching them for the same problem.

Posted by Paul G. Thompson (Member # 655) on 02-26-2003, 11:37 PM:

The trap shoe guide rods are probably sprung or otherwise mis-aligned. Rotate the focus knob to see if the focus holds better on one side of the screen than it does on the other. That might give a clue.

Posted by Mark Gulbrandsen (Member # 72) on 02-27-2003, 12:00 AM:

Paul,
The strange thing was that everything in the trap was just peachy keen!! Nothing wrong there....at least visually, not even really excessive wear on the bands either. The film seems to run through without cupping or doing strange things. Its obviously doing something though on occasion. I tried large loops, small loops, and just the right size loops.....doesn't seem to affect rubbing at that point too much. Also, one machine seemed to have more of a wear spot than the other one did.

Rick,
I noticed very fine scratching on the prints that were running at this theatre....do you see the same thing?
Mark

Posted by Paul G. Thompson (Member # 655) on 02-27-2003, 12:46 AM:

Mark, get some Persion Blue (or something equivilant) and a new runner shoe, and see how the mating is between it and the bands. See if one side is contacting before the other.

Posted by John Pytlak (Member # 331) on 02-27-2003, 08:40 AM:

Seeing wear like this in supposedly non-contact areas, or any buildup of film debris, is usually a sign something needs to be modified or adjusted. Otherwise, scratching is likely. [Frown]

Posted by Gordon McLeod (Member # 33) on 02-27-2003, 09:28 AM:

Run a loop of fullcoat mag stock for a while to polish them up and show the contact area quickly

Posted by John Pytlak (Member # 331) on 02-27-2003, 09:34 AM:

Here's a link to the Kodak FPC catalog of magnetic film stock:

http://www.fpchollywood.com/magnetic-film-fullcoat-5-mil-.html

Posted by Bill Langfield (Member # 818) on 02-27-2003, 09:34 AM:

Mark, I don't want to change subject, But;

Can someone refresh me the difference between Simplex and Century.
(I got a refresher of the diff between Christie & Bauer a few years ago. Thanks David - Still lurking are we?)

We haved changed all the machines gate/trap to the Kelmar units (except the JJ's, Oh and that half 70/35 mess in C#2)

I don't fully understand your description
But I think, your problem might simply caused by making the loop TOO big on the feed spocket, thus causing the film to 'slap' against the top of the gate.

Bill.

Posted by Mark Gulbrandsen (Member # 72) on 02-27-2003, 02:17 PM:

Bill,
I know what you're thinking, but making the loop too large does not seem to make very much of a difference as to the possibility of the film rubbing there. And to boot, these folks are running CAT 701's on top. Making the loops too large would cause the sound to be noticibly out of sync with the pix, and they would definately notice that. Personally I think the runner is a poor design as there is basically no clearance at the top of the back plate and machined runner area. Grinding that away completely takes care of any possibility of the film rubbing in that area and it certainly has stopped any film scratching too.
I'm pretty surprised Pat Moore hasn't caught this one.....
Mark

Posted by Darryl Spicer (Member # 711) on 02-27-2003, 02:58 PM:

What model is this projector. I have ran the 1050's and the 1060's with no problems in that area. Have the rails been replaced at anytime from the original ones. there is an adjustment on the back of the gate trap that controles how far the gate moves in and out on the rails. Is it adjusted in to far.

Posted by Steve Kraus (Member # 476) on 02-27-2003, 06:32 PM:

I have a similar situation with the Simplex straight gate with the 1-piece H shaped runner. The prior management here put in the straight gates in preference to the curved ones the machines were built with and with the low wattage we run (this is a screening room) there's no problem with flutter and steadiness is fine (a new loop of 35PA/RP40 will look like a stationary slide). But the way the gate runner rails bevel away this is the remote possibility of misbaving film making contact.

I am sorely tempted just to machine away the top cm or so of the middle part of the runner piece. Does Strong even make this part anymore (not that a new one would be better unless it was redesigned).

Otherwise, since I'm happy with the straight gates I guess I will just have to round up a couple of these:

Posted by Mark Gulbrandsen (Member # 72) on 02-27-2003, 07:26 PM:

Darryl, I've never had this problem on a 1050 machine. The problem I'm experiencing is on the Mellinneium Projector. This uses what appears to be the same runner fomr the 1050 machine. The difference is in the gate opener which is a linear bearing slide type of arrangement which works out nicely. The depth of contact of the curved runner seems to be set properly too. No excessive, or uneven wear on the bands. Everything appears symmetrical. with even tension to both sides of the trap. The wear that was apparent on the solid curved runner is also even....just that darned wear area at the top center of the runner plate.
Mark

Posted by Rick Long (Member # 213) on 02-28-2003, 01:50 AM:

And the only thing that can cause this wear (with the attendant tiny scratches) is.....the film itself!

A year or so ago, a Strong rep. dropped into one of our theatres with two cures for this problem. (1060 heads)

(1) a newer set of runners with a much deeper "groove" between the rails at the top of the runner

(2) insertion of a C-clip into the centre of the latteral-guide rollers so as to provide less tension on the film. It was this excess tension (remember these springs were originally designed for cellulose-acitate film) that was causing the centre of the film to "bow" forward into the runnner-frame.

I also ran into this problem with a couple of 4-star soundheads. The film had a tendancy to work its way right out from the sound drum. This was solved by cutting a little bit off the end of the spring to lessen the tension here.