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Author Topic: Flywheel problems on my Century Projector Mark Farr-Nash Film Handler Posts: 40 From: Vernon, TX, USA Registered: Mar 2007 posted 07-20-2007 09:43 PM                        Here's a doozy for you: I recently swapped my flywheels on my two century projectors (as part of a project involving replacing and then re-replacing my intermittent). The new flywheel didn't quite fit as well, making a little more noise while the projector was running. I'm in mid-run, so I decide to swap it out first thing in the morning. Heh. My bad. First, the screw unscrews itself and the flywheel falls off during the run. No problem. I stop the projector, replace the screw, tighten it down extra tight, and then start the movie. Voila. It even sounds quieter. At the end of the movie, my projectionist is threading the movie and I decide, just for grins, to check the screw again. Sure enough, it's come out. I retrieve it and notice that it's somehow shorter... The movement of the intermittent sheared the screw in two. Yep. In two. My brother-in-law is in the booth, right now, trying in vain to drill out the still-in-the-shaft piece so that I can hurry to the hardware store and pray to Jesus that they have a replacement screw in the narrow threads, same diameter, and length, so I can un-swap my flywheels and get both projectors up and running by 3 PM. Otherwise, I'm in a world of hurt. Mark  |  IP: Logged Eric Robinson Jedi Master Film Handler Posts: 538 From: Santa Rosa, CA Registered: Jan 2005 posted 07-21-2007 01:41 AM                     I had a loose flywheel which spit out every screw I put in. It sheared two of them, but luckily I was able to get the remainder out with a sharp tool and lots of patience. I didn't have any good luck until I installed a new properly fitting flywheel. It does make you wonder though how it is able to shear these screws ???  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 07-21-2007 03:30 AM                     NOW, I'm kinda wondering how an assembly flywheel can have so much rotational force to shear off the holding screws like that when it's not that big and heavy .. Only thing I can think of is that the rear cover plate got put back on backwards and was dragging on the flywheel...let alone a snap start from the motor.. And you'd think that the vertical driving gear that drives the assembly would be shredded out in the meantime .. .. just interesting questions like this..  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 07-21-2007 05:24 AM                     The later/latest flywheel screws have a terrible habit of doing this, we often have to drill out the screw hole and tap it for a larger size, I don't remember what off the top of my head. I suspect this is down to good old Strong manufacturing tolerances being a little wide of the mark. Never happens on older Centuries or Westrex machines. The fit between the flywheel and the shaft isn't great, so you tighten the screw up sufficiently to take out the movement, and it breaks. Personally I've never had one break but I've had them get to the stage of felling spongey through the allen key, and the flywheel is STILL slipping on the shaft fracionally.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-21-2007 08:01 AM                     Try getting your flywheel from LaVezzi or Wolk instead.... Mark  |  IP: Logged Mark Farr-Nash Film Handler Posts: 40 From: Vernon, TX, USA Registered: Mar 2007 posted 07-21-2007 08:47 AM                        My current plan is to hammer out the remaining bit of screw (carefully and gingerly) and then tap in the next size up of screw and hope that it'll hold through the rest of the weekend. Otherwise, my schedule will look really wonky. Thanks, Mark, for the alternate flywheel suggestion. I'll look into that. Mark  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 07-21-2007 10:26 AM                        The secret is to realize that the flywheel wants to rotate continuously while its shaft is rotating intermittently. The screw must be really really tight to CLAMP DOWN the flwheel onto the shaft. Soft screws are inappropriate. Use a 10-32 x 3/4" allen hex screw: Hollocrome or equivalent. The screw is not the device by which the mounting is made; it is the force for the clamping. Some people put the screw in backward; this is noisy and leads to broken screws. Louis  |  IP: Logged Mark Farr-Nash Film Handler Posts: 40 From: Vernon, TX, USA Registered: Mar 2007 posted 07-21-2007 12:10 PM                        Update: We tapped out the flywheel (10X32, thanks for the tip, Louis), fit the new screw in, and I tightened the bejeezus out of it. Also, re-switched the flywheels. I noticed that my OTHER screw on the other projector had the exact same wear as the screw that sheared off, so we tapped out THAT flywheel, too, and put a new screw in. Started it up; the projector is purring now, without that loud, plinky metallic sound. I'm gonna watch and tighten screws today as needed, but I think the problem is fixed. I love this website. I've told you that before, haven't I? I'm starting to feel like a projectionist. Mark  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 07-21-2007 04:44 PM                        FYI: same problem on the screw in the GR-207 (fibre shutter) gear. Same screw, too. We changed them out wholesale in the 70's. Louis  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 07-21-2007 06:21 PM                     Louis is giving out a trade secret on Century I have drawers of these screws.  |  IP: Logged Michael Moore Expert Film Handler Posts: 188 From: Dover, DE / USA Registered: Jun 2006 posted 07-21-2007 07:22 PM                        Holo krome good stuff is all I have to say. Mike  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 07-21-2007 10:12 PM                     Louis is on the money here...including the mode of failure. I don't recall having to go to larger threads but definately using hardend screws and that the collet of the flywheel MUST be clamping the shaft tight or you will have the flywheel constantly trying to chop the screw on each and every pull down. As for the GR-207...I couldn't imagine not using a hardened screw to make sure it is nice and snug on the shaft. A common mistake I see is when one throws up their hands and loads hex-cap screws in the Century to do away with the fillister slot head screws is that the GR-7 that drives the GR-207 MUST remain as a fillister head OR one must grind down the corners of the hex-cap or they will find themselves cutting up the GR-207. And...no complaints with Holo-Krome either. Steve  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-22-2007 12:10 PM                     quote: Louis Bornwasser The secret is to realize that the flywheel wants to rotate continuously while its shaft is rotating intermittently. I donno Louis.. All the cams shafts in the Mountain States rotate continously.... but with pull down placing a little back load on the cam itself. Perhaps it something to do with being East of the Mississippi... or you are using some really old Wolk gears . Really, I think that you meant that the kinetic motion stored in the flywheel helps to overcome the intermittent load that is placed on the continously rotating cam . Mark  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 07-22-2007 04:40 PM                     quote: Mark Gulbrandsen flywheel helps to overcome the intermittent load that is placed on the continously rotating cam . Now, this can bring un an interesting question with this statement above and on the issue of shearing flywheel screws: Would high gate tension cause excess work on the cam rotation and with the combining rotation force of the flywheel cause these screws then to strip if not tighten correctly? Now, we know that Century cams are quite a bit bigger than the Simplex variety, thus more mass that has to rotate, would this be a factor as well in the condition? Another thing on this issue is wondering if the intermittent sprocket shaft lock collar is too tight against the shaft boss where there is no allowable oil clearance between collar and the boss which could cause the 'chug-chug-chug' startup of a machine and putting excessive workload on the cam and going back to the flywheel issue as well .. ...just some observation questions to ask.. - thx Monte  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-22-2007 05:39 PM                     1. Yes 2. Yes and No 3. you'r drivin slow in the left lane again....  |  IP: Logged

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