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Author Topic: Century curved gate on Model CC Lindsay Morris Expert Film Handler Posts: 233 From: Darlington, WA, Australia Registered: Sep 2002 posted 12-16-2003 05:03 AM                     Before many of the older hands jump in and say "toss it out and get a straight one" it aint that simple. I am stuck with a curved gate and parts for these over here in sunny West Australia are a bit few and far between. The Century "blurb" somewhere I read extolled the virtues of the curved gates as being the best focus set up for any cinema projector... but I am beginning to wonder about all that. I have a random problem with the focus which pops in and out of focus most noticeably on scope and to a lesser degree on W/S. I initially found that the curved lateral guides had a small wear on the shoulder where they sat upon the gate runners and this appeared to cause the film to wedge in there and buckle. The wedging was purely random and the focus on the screen was all over the place like top LHS, bottom RHS a big spot in the middle. An even focus was almost impossible to maintain unlike the old Super Simplex's I had retired from service where I set it ONCE and vitrually never went back there again. This thing drove me nuts. I had the gate runners reground dead flat, the curved blocks also ground so all shoulders were dead square and the guy who did the grinding of these did a magic job on the curved face it is just like a factory set unit. Assembled all the bits and using a brand new bit of film realigned the guides so the film was just held snug with a little bit of clearance and put it all back into the machine. Ran a reel of scope film that I knew was normally good focus but RS on the Century previously.... result perfect focus I though problem solved but last week with a WS film the focus started to pop again and being a 2 feature weekend I watched the Sat night show closely (Chicago) and pin sharp focus edge to edge. On the Sunday put the Friday night show back on and focus uneven. A squirt or two of FilmGuard thru the holes in the MUT spool stopped it totally for the rest of the night. The Manual section here covers the CC but NOT with a curved gate. Has anybody got any tips for setting these brutes up correctly as when they are running well they are quite good. It seems strange that other machines from 8mm upwards all have at least one sprung side plate in the gate... the Simplex had none yet the Ballantyne has. I am almost to the point of just opening up the side runners so the film just runs through without touching them much at all and so can accomodate a slight variation in filmstock width as the print of Chicago was done in the Rome labs of Deluxe and the problem print (Mrs Caldicot) was done in the Deluxe labs UK at Uxbridge. It is obviously a lubrication or tightness in the gate problem as the slightest application of FilmGuard just to the edges of the film whilst it is feeding off the MUT stops it totally. In fact one scope film that was subtitled had the subtitles slowly going out of focus, apply a bit of FilmGuard and as the treated section went thru the focus of the titles just drifted back in crisp and clean as if you were adjusting the focus knob. Take the FilmGuard away and the focus slowly went back to bloody awful but that was prior to the clean up of the gate blocks and runners. So what is the trick to setting up these curved gates ?? The entire upgrade to Xenon lamp, stereo sound with an ACL laser reader and the longplay of the MUT has gone very smoothly it is just this focus shift that is driving me batty. Love the screen light. love the sound but hate the variable focus. Lindsay  |  IP: Logged Stan Gunn Expert Film Handler Posts: 176 From: Clematis, in the hills near Melbourne Australia Registered: Aug 2000 posted 12-16-2003 06:27 AM                        Hi Lindsay A possible problem is lateral guide roller to tight for poly film I have found this problem on various machines. I will send you my phone number direct should you wish to speak direct on this, easier than emails. Regards Stan Gunn.  |  IP: Logged Warren Smyth Expert Film Handler Posts: 158 From: Auckland ,New Zealand Registered: Aug 2003 posted 12-16-2003 06:48 AM                     Have you got excessive heat on the gate? Is there any sign of embossing of the film frame at the aperture edges? Water cooling may be required if you are using a high wattage lamps.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-16-2003 08:51 AM                     There are two alternatives other than fixing the problem at hand. One is the Kelmar trap assy which performs excellent to 3kw lamp size...its not available water cooled but could be adapted to be so. The second is to install an SA gate and trap with water cooled dovetail assy. Many dealers have lots of SA gates and taps laying around from doing Kelmar conversions and the parts can sometimes be obtained cheaply. The SA setup is hard to beat. Mark @ CLACO  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 12-16-2003 09:35 AM                     You won't find a manual for a C or CC with a Curved gate since they were not original equipment...you want to see an H or HH manual (the CC just means that it is a double shutter...likewise with the HH). As to the "Studio guides"...DONT have them touch the film at all. Let the lateral guide roller do all of that work and it will do a great job. Normally there is enough slop to open the studio guides up so they wont touch if not...grind them down so they won't. From what you describe, that will probably cure your problem. Putting an SA gate/trap assembly on can be a bit of a pain. In addition to the new trap dove-tail, you will need to modify your light guard...which is a big pain in the butt. However, the results when all complete are normally quite good. Mark may know off-hand if an SA light guard will fit onto a C frame. Steve  |  IP: Logged Lindsay Morris Expert Film Handler Posts: 233 From: Darlington, WA, Australia Registered: Sep 2002 posted 12-16-2003 04:51 PM                     Thanks Mark & Steve, I have water cooling running and the whole trap assembly runs very cool indeed... without it the aperture plate was so hot after 15mins I could be hold it long enough to do a lens/format change "on the run" (I splice in 12 secs worth of blue film and change lens on a blue screen rather than stop and go again). I suspect that this may have been a DI machine previously as the water jacket appears well used. Will open up the Studio Guides and as Steve suggested let the lateral roller do all the work. What I like about the Century is the ease at which bits come off.. just a couple of screws here and there and most parts are in your hands unlike the old Simplex that had bits that almost defied you to get them off. Century seem to have applied a rationale of improving access and maintenance unlike some others that never seemed to improve at all. Not running a very big lamp on this replacement setup.. a 2kw lamp in a Lumex "yellow" lamphouse and just under 70 amps and the light on screen is very good (never measured it though) but the beam heat is a lot hotter than the old carbons ever were. The lamp mirror is a goldish coloured metal unit and obviously NOT dichroic hence the heat but the water jacket controls that so no worries... worth the change for the improved screen image and no more reel changes. Will post results of some readjusting shortly, thanks for input fellas. Lindsay  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 12-16-2003 06:01 PM                     The rule on the Century is that it is easy to work on...because you will have to! Simplex is a more precise machine but as you say more difficult to work on...especially for the un-initiated (particulalry on the pre XL machines). I can't tell you the last time I needed to change a Simplex XL main drive gear, shutter drive gear or intermittent drive gear...on the Century...one of those happen about once a month in our service area...somewhere. Steve  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 12-16-2003 06:09 PM                        For whatever it's worth, I sent Brad a copy of the Century H manual and it will probably be available on this site soon.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-16-2003 11:31 PM                     All of the SA stuff will bolt right onto a C frame without any alignment or such, except fo the gate clearance adjustment. he light shield is also a bolt on thing. Only a small notch for the door clasp needs to be cut into the shield. A properly working solid curved gate and trap can work very well when everything is just right. It can also be hell to ge tit there !! The advantage on the SA trap is auto equalization(even pressure) of the trap bands. Works the same as on an X-L curved trap. Mark @ CLACO  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 12-17-2003 06:11 AM                     Mark, I seem to recall a clearence problem with the intermittent spocket when an SA trap is fitted to a C frame...that the sprocket can crash into the bottom of the tension bands if framed all of the way up. Steve  |  IP: Logged Lindsay Morris Expert Film Handler Posts: 233 From: Darlington, WA, Australia Registered: Sep 2002 posted 12-17-2003 06:51 AM                     Scott, Yes I can see that the Century HH manual is almost at the point of Public access so another couple of days and I will be able to download that and go over the gate bits and pieces. Thanks for supplying that manual. I am really curious of the rationale behind these fixed side blocks on the Century.. they do of course provide the curve to the bands but are they really supposed to be a lateral guide?? The old Simplex never had any side weave and probably had a slightly steadier picture than this CC but it will take me a while to get all the bugs out of things. Steve mentioned always having to pull them apart but of those that I have seen in operation the Century's have always seemed a solid reliable unit and made much more uncluttered than the old Simplex which is a product of evolution I guess. However it great to be able to just unbolt almost all the bits from the operating side and give things a really good clean and then get it all back in place with no problems as most bits are nicely dowled so they drop back in exactly where they should. Time will tell just how reliable it turns out to be but with only a summer season of around 80 odd sessions I reckon it will go a long long while between major surgery events. Will try the suggested setting of the blocks this weekend and see how it goes. Thanks for all the info. Lindsay  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-17-2003 07:48 AM                     Steve, You're right about that, the C has a bit more framing adjustmet available than the SA does. Its an easy to cure problem though by simply screwing a small spacer to the film side top of the intermittent carrage, or just a hardened steel stopper screw. Cinerama 35mm heads had an adjustable stopper screw at each end of the travel. Mark  |  IP: Logged Dick Prather Master Film Handler Posts: 259 From: Portland, OR, USA Registered: Feb 2002 posted 12-17-2003 10:47 PM                     Lindsay, The studio guides were designed to bring film side sway down to a gentle weave making it less objectionable. Simplex E-7 and X-L flat gates had them but in fixed locations. Century guides can be moved. Century C's had a shorter trap and unless they were set properly had some side sway. Steve is correct let the guide rollers do the job not the studio guides. Almost sounds like a buckling problem in the film trap. Suggestions: Make sure the guide roller lines the film properly to the intermittent sprocket. Make sure the studio guides are not grooved, or placed too close together causing the film to slightly buckle or catch in the guides. I believe the H guides were also reversible so 4 sides were available. Setting them wide should prevent this. Set film tension only tight enought to keep the film steady in the trap by moving the lens assembly back and forth. The C's were 2 film thicknesses from the guides to the gate when closed. I forget what the H spacing was. I did do a couple of rebuilds on Century C projectors with a SA trap & gate. Only problem I remember was I needed to make a gate stop. The normal gate closure caused way too much film tension. The framing carrage problem was already taken care of.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-18-2003 06:43 AM                     Dick is right about the studio gides. I normally remove them from both Century and Simplex machines and put them in the verticle file. Also makes cleaning the trap much easier. The picture is always far steadier too. Mark @ CLACO  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 12-18-2003 12:48 PM                        In a 35mm, lateral positioning should always be done by the lateral guide roller, with the "Reference Edge" of the print being gently pushed against the fixed guide roller by the spring-loaded one. The "Reference Edge" of a 35mm print is the edge along the analog soundtrack side of the film, and the lateral guide roller is usually at the top part of the gate assembly, just above the aperture. The idea is that when printing the film, the printer positions the printing negative and raw stock using the "Reference Edge", and then the processed print is positioned during projection using the same edge. This allows "cancelling out" any dimensional variation leading to a steadier image, otherwise known as the "principle of cancellation". See the paper "Challenges to the Concept of Cancellation" by Roland J. Zavada, published in the December 1981 SMPTE Journal, Volume 90, page 1173. "Pinching" or "skewing" the film, or having multiple contact points with the edges can lead to problems with steadiness or focus stability. Always be sure the lateral guide roller is turning freely, and that the spring loaded side is free-moving and just gently pushing on the non-reference edge of the print to position the reference edge on the fixed guide.  |  IP: Logged

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