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Author Topic: Bringing a motor up to speed Cody Martin Expert Film Handler Posts: 214 From: Edinburgh, IN, USA Registered: Jun 2004 posted 02-11-2005 03:49 PM                        Hey, I've been experimenting with my projector today. I got the reel arms set finally and they look good. I put some film on...threading up the 6000' reels and ran her. SNAP...right at the first roller. I tried a few times...always snap. It's not losing the loop or anything...it's like the motor is starting to fast. Is there an easy way to start a motor slower and work it up? Possibly a dimmer switch? Thanks, Cody  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-11-2005 04:09 PM                     This is a major pain in the ass with reel to reel on anything larger than 2000' shipping reels. First, you can use floating hub 6K reels with a 5 inch or larger hub. Often this is enough to solve the problem. Be warned, the clutch tension is very critical for this to work smoothly. Next you can put a resistor inline with the motor's AC feed (or put one on the start winding). Finally, I ended up using the resistor as well as making a tension arm to prevent the film from slacking during startup in my screening room. (Taking up on 24" split reels w/4 inch core.) In an ideal world the projector motor would be 3 phase an on an inverter. Then you could set your ramp-up speed to whatever you desired.  |  IP: Logged Dan Lyons Jedi Master Film Handler Posts: 698 From: Seal Beach, CA Registered: Sep 2002 posted 02-11-2005 05:55 PM                     I hope you're using junk film for all your testing and setup purposes. You need to get everything set and running properly with 2ks, and get your scratch testing done before you even consider running a 6k. What kind of equipment are you running? You need a spring scale like this for setting the takeup. here Get the Red one. For a 6k reel, 14 Newtons on a 5" hub is good and won't cause any perf damage. For the feed arm, you can set it much lower, below 8N. If you set the tension properly, and run with floating hubs on your 6k reels, you shouldn't have a problem.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 02-11-2005 06:19 PM                     make sure you take up any slack film between the spools and the projector before pressing the start button. Havng the back tension on the feed spool set too low can also cause problems. Are you getting slack flm, which is then snatching? Most projectors can start 6k spools ok, large tower spools can be a problem though. What projector are you using? I've run 6ks on 1950s Westar, recent Century, and various Philips/Kinotons, going back to early '60s  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 02-11-2005 06:37 PM                        If at all possible, try to get reels with 7" hubs. The 5" hubs are fine for 2000' reels, but I have a strong preference for 7" floating hubs when running 6000' reels. The 5" hubs are fine for feeding, but are less-than-ideal for use as takeups. If you can't get large-hub reels, put a few hundred feet of junk film around the hub of each reel and tape it there permanently (you may want to mark the edge of the reel so you can tell where the junk film begins in order to avoid missing changeovers). You can set the tension without the spring scale, using old, brittle, junky trailers on acetate base stock. Basically, you want to use the largest reel you have and set the tension so that the film takes up evenly without breaking at startup or tearing perfs. With a 6000' reel, you won't get perfectly even tension throughout the reel (unless you have motor-driven takeups), but you want to make sure that the film winds fairly tightly out to the edge. If it winds loosely, the film will cinch when you rewind it. Be sure to test with 2000' reels (with both 4" and 5" hubs to make sure that you can take up easily onto those sizes, too. The whole process is a bit of trial and error and is far more critical when running the larger reels. If you don't already have some junk film, you can order "picture sound fill" from an editing supply house (e.g. Christy's Editorial in Burbank, CA). This can usually be purchased quite cheaply.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 02-11-2005 07:12 PM                     Depending on the soundhead wire a 2 ohm 250watt resistor in serries with teh motor to slow down th start up  |  IP: Logged Thomas King Expert Film Handler Posts: 119 From: Sheffield, Yorkshire, England Registered: Oct 2004 posted 02-11-2005 07:54 PM                        With some projectors, you can configure certain parameters like ramp-up speed. Our Vic5 ramps up very slowly.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 02-11-2005 10:21 PM                     most projectors running with 3 phase motors now run on invertors that allow programabel ramps not an option on older single phase motors  |  IP: Logged Stan Gunn Expert Film Handler Posts: 176 From: Clematis, in the hills near Melbourne Australia Registered: Aug 2000 posted 02-11-2005 10:40 PM                        Another way is to have a fly wheel fitted to the moter as in simplex and rca. Regards Stan.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 02-12-2005 02:24 AM                     True, this is where Simplex has it over with the slow ramp speed, esp when using the old SH-1000 soundheads when using 6k reels, with the absoluted needed floating hubs for takeup. When doing this, just make sure that the tension is completely taught from lower holdback sprocket to reel when starting. Then when hitting the run switch, a practice that I did was to have my finger in the hole of the hub of the reel to make certain of the required taught, then when the motor took off, my finger would be assisting the rotation of the reel, thus preventing the inital slack that can happen when motor takes off and the takup belt and clutch having their delayed action before getting up to speed. I had to do this many-a-times with MotioGraphs AA's with Mirrophonic 7400's soundheads - and we know how the Motiograph took off with their snap starts. -Monte  |  IP: Logged Cody Martin Expert Film Handler Posts: 214 From: Edinburgh, IN, USA Registered: Jun 2004 posted 02-12-2005 06:52 AM                        Hi, The projector I'm using is a motiograph AA with sh-7500. I'll check about the hubs of the reels today. I may end up doing the resisor thing. I'll go back and do some more testing today. I've got her running with 2000 footers..but the 6000' are a killer. Thanks again, Cody  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 02-12-2005 10:49 AM                     I have 1.5 ohm in serries with my motiographs to control them  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 02-12-2005 02:16 PM                     quote: Cody Martin I've got her running with 2000 footers..but the 6000' are a killer. ..worked at a Drive-In with this Motiograph setup using the 6k reels - just assisted the takeup reel to keep from busting the acetate on startup. Never could figure out why Motiograph never put a big enough flywheel on the motor to have a more easier ramp speed. Yep, Gord's got a pretty nifty MotioGraph setup at his house - see it in the picture's forum. -Monte  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 02-15-2005 11:15 PM                        I could never figure out why Kelmar just doesn't steal the spring loaded tension roller as is found on every plater system and incorporate it into their take-up arms. It's passive, it's simple and it would solve the problem quite elegantly.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-16-2005 01:46 AM                     Because that's not just a spring loaded roller. That arm (or elevator) is what is directlycontrolling the speed of the takeup. There is no "clutch" of sorts on a platter, hence why it has such precise takeup ability without varying tensions unlike running reel to reel with a conventional clutch. (You've never ran a platter, have you? )  |  IP: Logged

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