This is topic Velvet in film trap in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Matthew Taylor (Member # 2310) on 07-12-2005, 12:18 PM:
 
I want to try an experiment to improve steadiness when running certain films. I have obtained some velevet that Kinoton supply for film traps. My question is whether it's best to stick the velvet to the gate bands or the film runners?

My preference is the bands because at least if my experiment goes horribly wrong, I can get new bands rather than scrape off glue from the runners.
 

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Posted by Thomas Jonsson (Member # 1902) on 07-12-2005, 03:27 PM:
 
Hi Matthew,
I have Vic 5 with the new curved gates, and have velvet
on the tension bands. Works beautifully, and I need just an
absolute minimum of preassure on the bands.

I use very handy self-adhesive velvet bands - no messy
glue. Easy to apply, easy to pull off. If you would like
to try them, just give me your address and I´ll send you
a couple in an envelope.

Thomas
 

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Posted by Matthew Taylor (Member # 2310) on 07-12-2005, 04:57 PM:
 
Thanks Thomas. The only thing I'm concerned about is that sticking velvet to the gate bands will increase the pressure on the film too much, maybe causing excessive wear on the intermittent mech.
 

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Posted by Rick Long Jr (Member # 541) on 07-12-2005, 06:07 PM:
 
I've seen this done on oldstyle Vic-5 gates with not bad results, but the felt changes the position of the film in relation of the aperture, causing a wider fuzzy edge. This wouldnt be a problem on the newer curved gate or a Simplex curved gate type design - at least not to the same degree. I'd want to be sure that the addition of the felt to the pressure straps doesn't cause them to contact the aperture plate.

What kind of projector?
 

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Posted by Gilbert Travin (Member # 2138) on 07-13-2005, 01:38 AM:
 
Accurate focusing is sometime impossible with velvet !
 

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Posted by Thomas Jonsson (Member # 1902) on 07-13-2005, 04:58 PM:
 
The main reason I use velvet in my Vic 5 curved gate, is
to isolate the film from the very hot metal tension bands.
I have removed the stupid "pushers" above the gate, and
the preassure is next to none. The velvet bands have to
be changed after one or two months - being brushed and
cleaned daily ofcourse. They also make the machine run a
little smoother.

Another reason for using velvet, was dirt getting stuck
real hard on the tension bands because of the heat. Almost
impossible to remove. At the Cinema Expo in Amsterdam this
year, I spoke to very nice Mr Massimo Riva from Cinemeccanica
about it. He told me they have come up with a special tool
to clean the bands with. I haven´t seen it yet, but if it
works, perhaps I´ll say goodbye to the velvet...

Thomas
 

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Posted by Pete Naples (Member # 761) on 07-16-2005, 11:00 AM:
 
Erneman machines have velvet as standard, seems to work fine, but you do have to change it regularly.
 

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Posted by Stan Gunn (Member # 554) on 07-16-2005, 10:16 PM:
 
Felt pads have been used on many machines at differant times for many years, but is only succesful on new or clean film.

Stan.
 

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Posted by Dominic Espinosa (Member # 2122) on 07-17-2005, 04:31 AM:
 
I've never seen a machine (I'm sure they exist though) that you can't adjust the gate clearance.
Wouldn't this be an automatic requisite if you're adding thickness to the bands via the felt?
 

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Posted by Steve Scott (Member # 630) on 07-17-2005, 10:10 AM:
 
The Heights Theatre in Minneapolis has Velvet in their AAII's. I talked to TJ Hopland last week and he said the velvet bands run great in all aspects for them.
 

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Posted by Brad Miller (Member # 2) on 07-17-2005, 01:55 PM:
 

quote: Stan Gunn

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Felt pads have been used on many machines at differant times for many years, but is only succesful on new or clean film.

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Hallelujah! I tried velvet bands back when I had an AAII in my screening room and on a Christie projector. What a joke it was. If you were running anything but a lab new print, it made far more of a mess than anything else. Steadiness was NOT improved and print wear was greater as the velvet collected dust and dirt from the films.

Velvet on the bands is a stupid, stupid idea.

 

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Posted by John Pytlak (Member # 331) on 07-18-2005, 12:56 PM:
 
If the film contacting components of the projector gate are running really hot, it can aggravate buildup of hardened gelatin emulsion that will severely abrade the film. If you can't touch the metal parts of the gate after running a while without getting burned, it's likely much too hot.

Things that help:

1. Water cooled gates (duh!), especially for larger lamps.

2. Use heat filtration (dichroic coating on reflector, or auxillary filters that reflect infrared energy to a heat sink). Be sure the mirror and heat sinks are well cooled by sufficient air flow.

3. Be sure any heat sinks or shields are in proper position to protect metal components of gate from excessive radiant energy --- light should just slightly overfill the aperture

4. Be sure to clean the film-contacting components of the gate between shows, especially to remove any hardened buildups of gelatin emulsion. Scrape with your fingernail or a hard plastic pick (NEVER use metal tools that could cause a knick or burr on the gate components), and then use a stiff bristled toothbrush.

4. Between shows, apply a thin coating of a hard wax (carnauba or paraffin) to the film-contacting components of the gate.

5. Be careful not to let relative humidity get too high. Humidities above 65% can make the gelatin film emulsion softer and more likely to build up on a hot gate.
 

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Posted by Thomas Jonsson (Member # 1902) on 07-18-2005, 03:37 PM:
 
Mr Pytlak,
The build-up on the tension bands of the curved gates of my
Vic 5 was stuck so hard it couldn´t be removed, no matter how
I tried. I had to replace them. The water cooling of the curved gates doesn´t cool the gate, just the surrounding area. That´s
why I started to use velvet, to isolate the film from the heat.

In your opinion, is velvet a bad idea?

Thomas
 

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Posted by Gordon McLeod (Member # 33) on 07-18-2005, 06:23 PM:
 
I am a strong believer in using velvet bands in most projectors
 

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Posted by John Pytlak (Member # 331) on 07-19-2005, 10:37 AM:
 

quote: Thomas Jonsson

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The build-up on the tension bands of the curved gates of my Vic 5 was stuck so hard it couldn´t be removed, no matter how I tried. I had to replace them. The water cooling of the curved gates doesn´t cool the gate, just the surrounding area.

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quote:

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Curved seating is more important if your auditorium is fan shaped (with seats not directly in front of the screen). Many modern multiplexes are built with wall to wall screens and rectangular auditoria.

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That's quite an interesting idea -- a surface material that has a very low friction coefficient. It would seem that the non-stick properties would prevent that very type of emulsion build-up (and burn-on) that is so often seen on bands and gate rails. The one issue which might prevent this application, at least on the bands, would be whether or not Teflon is a flexible substance or is it rigid and can only be applied to a hard substrate?
 

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Posted by Randy Stankey (Member # 64) on 07-22-2005, 09:07 AM:
 
The main problem with Teflon coating film bands is getting the stuff to stick to them.

True, nothing likes to stick to Teflon but Teflon doesn't like to stick to anything else either. It's a long, difficult and expensive process to Teflon coat metal.

First, the metal has to be acid treated and bead blasted to make the surface rough. Then an ultra thin layer of Teflon is sprayed (or somehow coated) onto the part and baked. After that Teflon is repeatedly layered onto the part and baked until the desired thickness is reached.

When finished, the surface is not perfectly smooth, nor is it very durable. I can't imagine it would hold up very long as the film runs against it for hours on end.

I figure that the expense of Teflon coated parts plus the expense of replacing them when the coating wears off would be prohibitive to say the least.
 

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Posted by Gordon McLeod (Member # 33) on 07-22-2005, 09:23 AM:
 
Go like kinoton and make the entire band out of delrin
The only problem is if the film is cleaned with filmguard it will not produce a steady image no matter what you do (been there done it with dp75)
The velvet also improves stability because the hairs engage the perf and act like little registation pins
 

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Posted by Brad Miller (Member # 2) on 07-22-2005, 07:28 PM:
 
Bullshit Gordon. I am running a dozen Kinotons with delrin gates and each print is FilmGuarded on every show and they are producing images steadier than is possible from any other projector.

Get your facts straight.
 

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Posted by Steve Guttag (Member # 268) on 07-22-2005, 07:35 PM:
 
Film Guarding on a Kinoton delrin skate/runner system also seems to make them last nearly double as compared to non-Film Guarded theates.
 

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Posted by Gordon McLeod (Member # 33) on 07-23-2005, 08:35 AM:
 
"Bullshit Gordon. I am running a dozen Kinotons with delrin gates and each print is FilmGuarded on every show and they are producing images steadier than is possible from any other projector.

Get your facts straight. "
I have several DP75 in service and non will produce a steady picture if the print is treated yet are rock steady with out and you will notice i did specifie the DP75 THe FP 20's we use are all in post facilities so it has never been an issue
 

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Posted by Brad Miller (Member # 2) on 07-23-2005, 04:43 PM:
 
You implied all Kinoton and then mentioned your experience with an DP75. So what's different about the gate design on a DP75 than the rest of Kinoton's line to cause this problem no other projector (Kinoton or non-Kinoton) has?
 

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Posted by Gordon McLeod (Member # 33) on 07-23-2005, 06:03 PM:
 
I think but am not sure it is due to the multiple curves it has and the overshoot between them
 

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Posted by Steve Guttag (Member # 268) on 07-23-2005, 06:22 PM:
 
Oh...the DP75 gate is indeed a strange one! You will wonder what someone was thinking when you see the "path" the film must take.

It enters the gate like a Century SA on a "back flip" it is immediately guided by delrin but the curve is concave towards the lamphouse so the film starts traveling back toward the lamphouse as it moves down to the aperture (pretty aggressive radius). Tension is applied at this stage too.

As it enters into the aperture area, the runners remain delrin but the "skate" area transistion to metal (I don't know the material off hand). It the film moves almost straight down in this area, almost like a stright gate (this area is about an inch and a half long.

The film then starts heading back on an mirror image of its entrance with delrin on the rear with the runner once again concave towards the lamphouse (the skate just stops at this portion so you can see the film exiting the gate prior to entering the intermittent).

The film exits the gate via the intermittent with the film heading forward like on a AA2.

I'm guessing they were trying to design the gate/skate such that it naturally tensioned the film without the normal tension bands or merely pushing the film harder against the runners. There is a tension adjustment that applies more tension to the film at the top where it enters this contraption.

Sound strange? It is...I wish I had a good photo of it to show you.
 

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Posted by Richard Fowler (Member # 893) on 07-23-2005, 08:42 PM:
 
FP-75, my least favorite projector from generally a great manufacturer The last two I had to deal with where replaced with V-8/35-70 with SLH 5 kw lamphouses ( pair of ORC 4500 removed from service ). The result 250% increase in light output and rock steady image. Made the judgement call based on service records, parts cost and lack of some accessory upgrades for the existing machines.

Velvet for gate runners have their issues....outside of use in Ernemann products, we have used them in some laboratory and library archive screening room projects.

I was one of the intital users of the V-5 curved film gate and dirt sticking to the bands became an issue...I am glad they have a fix for this. The band material behaves as something between metal and plastic composition and is thin compared to a typical Century SA gate unit, the last time I played with them.
 

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Posted by Steve Guttag (Member # 268) on 07-23-2005, 09:09 PM:
 
I actually run a pair of DP75s on occasion...strange as it may sound...I like them and they put on a good picture. They are used very infrequently and are in a small screening room.
 

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Posted by Matthew Taylor (Member # 2310) on 07-24-2005, 05:41 PM:
 
Well, Just to let you know hoe I got on...

I have been testing a couple of different types of velvet bands. Clive Carmock kindly sent me some kinoton velvet, but that created focus issues. I next tested the velvet strips that Thomas Jonsson kindly sent me. They are thinner than the Kinoton velvet and worked better.

I got slightly better picture steadiness and a slight reduction in noise. I disdn't have to use much, if any, tension on the bands with the velvet.

The big drawback is that using velvet seems to make the aperture plate act like a dust magnet. Would this be to do with static? Anyway it doesn't take long for the aperture to get big buildups of dust at the bottom (top on screen).
 

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Posted by Miguel Garcia (Member # 2443) on 07-25-2005, 05:32 AM:
 
To Matthew Taylor,

Your projector has a very important problem with static load.

The velvet bands increases the referred problem still more.

The friction of the film on the velvet, behaves as a real magnetic generator, and that is why the particles adhere easier to the velvet.

If you allow me, I suggest you to increase the level of relative humidity of the air in your projection room.

Also, you must clean frequently, with an antistatic cleaner, all the metallic parts of your projector which are exposed to the film running; you can use for this purpose any of the products authorized for the cleaning of video heads. The isopropílico alcohol also can be used for cleaning and desmagnetization.

If you fulfill these instructions in a periodic form, verified that every time less particles were accumulated in your projector.

With my greatings,
Miguel Garcia
 

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Posted by Thomas Jonsson (Member # 1902) on 07-25-2005, 02:30 PM:
 
Matthew,
what projector do you have? Sounds strange that you get so much
dust in the aperture.

In my Vic 5 I get almost no dust at all with the velvet. I have
a lot less trouble with the velvet than without it.

Thomas
 

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Posted by Matthew Taylor (Member # 2310) on 07-25-2005, 05:03 PM:
 
Hi Thomas,

I've got a Prevost P70.
 

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Posted by Thomas Jonsson (Member # 1902) on 07-26-2005, 10:04 AM:
 
Nice machine. I used to run two of those some years ago.
I used velvet on the tension bands, with no trouble at all.
The wide ones for 70mm, too.

If you have problems with steadiness, and it´s not the print,
there might be other reasons. Worn intermittent sprocket or
even the geneva movement. Another thing is, the axis for the
intermittent is very long, and if you use too much force when
tightening the screw, there´s a risk the axis get slightly bent.

Thomas
 

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