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Author Topic: Roundthane question Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-07-2003 09:35 AM                     First off...roundthane and all its similar like belting is not my favorite. It is too elastic. As a result, take up tension is uneven and often adhesion to the various pullies is less than desired. If you have a roundthane belt system, take a tension guage and measure the take up tension on a reel (by stalling the reel with the tension gauge)...you'll see the tension gauge bouncing around and often seen the clutch speeding up and slowing down. My favorite mechanical clutch drive is direct (Noreclo DP-70) and a close second is chain-drive. After those comes the beloved V-belt. With a V-belt you will get a good long life and next to zero problems. Sure it isn't as easy as roundthane but rarely are better things easier to install. Back to roundthane... For lack of a better description...they will dry-rot over time and some batches of the stuff (we obtain it wholesale from industrial supply houses) are better than others. We have had to pitch entire rolls of the stuff due to premature splitting. It can be too hard (dry rots) and will split just with your finger nail or it can be too soft and will split due to the connector barb. Some tricks of the trade: Desharpen the barb a bit...it doesn't need to be so sharp. If your old barbs worked well...keep them, the new ones may be too sharp. Bur the barb....that is put some nicks in the barb so it can not rotate within the roundthane. One of the problems is that as the belt moves about, it will have some slight twisting action which will allow the barb to cut the roundthane like a knife...putting the nicks in will keep the barb from rotating within the belt. I have not been able to positively prove that heating the connection (to melt the belt around the barb) makes a better join. You can, however, overheat the connection and destroy the belt. Don't over tension a roundthane belt! The thing already has too much "spring" in it...over tensioning it only stresses it out, not improve adhesion. While you are at it, keep your clutches in good repair...having the belt put up with a jerky operation isn't good for the belt nor your entire gear-train. Clutch tension should be uniform. Check them often (weekly). Grab the lower reel and turn on the projector. You shouldn't feel a jerky motion from the reel while it is stalled. If you do, cleaning and possible clutch pad replacement may be in order. Some clutches need oil impregnation while others do not. If yours needs oil, then make sure you apply it evenly. After relubrication, you will find that after a weeks worth of shows, you will need to retension your clutch as the oil is squeezed out. Make sure your clutch is set properly...you only need enough tension to turn your largest reel to the point of no bouncing with a full reel. If you are snapping film or stretching perfs at start off, get floating hub reels, don't turn the tension up to get the reel to come up to speed faster. Lastly, Scott...you were just at the Kimball Screening room in Williamsburg, VA...where it is a manual changeover system with not one but TWO failsafes on each projector (one entering the upper feed sprocket, one after the lower feed sprocket). So you have indeed seen a manual changeover system with a failsafe...your life is now complete Steve  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 06-07-2003 01:33 PM                        Steve--good point...I didn't notice the failsafes when I visited. Really nice installation, BTW! Actually, the Columbus Theatre (see the pic gallery) has a failsafe on one machine, too, but it's only useful when running off the platter. Why didn't chain-drive takeups become more popular? The Western Electric bases at the Avon Cinema (also has pics in the gallery) are chain driven and I've never had a problem with them. It seems that this would avoid the problem of having the belt slide off the pulley on the takeup clutch, which I have seen happen elsewhere.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 06-07-2003 02:59 PM                        All good points, guys -- and Steve G., master of the reel-to-reel transport, thanks for the tips. You are right -- the "slip as you go" clutch is very susceptible to the variations of oil and dirt, the condition of the pad, etc., and IMHO, the slippage operation is pretty primative in terms of maintaining constant pull force without any feedback control mechanism. Adding even a tensioning arm would be helpful. I do check it periodically. And am always listening for the sound coming from the holdback sprockets. I almost always run 2000ft reels which are not as demanding on the clutch system as are 6000fters. Anyone remember the clutch arrangement on the old 300 series 16mm B&H takeup arms? The spindle pully was driven by a wide cloth slip belt -- as the reel filled with film, the weight put more pressure on the slip belt and more force was applied to the spindle, yet the belt slipped more. It seemed like a very elegant idea that could especially be applied to 6000ft 35mm reels where there is such a wide range of difference between the force needed with an empty reel and with a full one. The belt design seems like it self-adjusts better than the slipping clutch idea. As for a failsafe, well, I suppose it would be useful, but as Steve points out, this problem comes around so infrequently, I don't think the danger of it is worth the risk of a failsafe malefunction. Whatever I put in now, the clear stuff or even if I go back to leather as Gordon points out is the best, it will certainly last way past my retirement. And just for your information, as scary as a pile of film on the floor looks, rewinding it is quite easy if you careful. The film doesn't knot up and tangle like it looks like it would the first time you see such a thing; it simply reverses its "fall pattern" back onto the reel. Because it unfolds gently as it is fed out of the soundhead, no scratching occurs. The only film at risk of picking up dirt are the first few layers on the floor; the rest piles gently on top of it. If you are lucky, the failure happens toward the end of a reel and not the very beginning (mine happend near the end of the reel). I have seen some guys try to wind the film back on to the takeup reel as the film is running. THAT is very dangerous as you have to pull film from the bottom of the pile with great risk of scratching. Unfortunately some projectionists will do anything to keep from stopping a show. Letting the film pile up on itself is much safer because as I said, you can reverse the process quite easily, rewinding back onto the supply reel. I don't know what you would do with a 6000ft reel other than stop the show. Even as remote a possibility of a takeup failure like this happening, having one happen to you only once will keep you of a very good mind to always keep the area around the projectors especially clean. And with Simplex, the machine world's equivelent of hitting a Texas oil load, the need to be very vigilant about cleaning that oil drip pan. Naturally I thoroughly cleaned the reel before it went back (wanna make sure those prints are spiffy-clean when they're put on the bandsaw table!). Notice: no film was injured in the screening this print! Frank  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 06-07-2003 05:35 PM                     Simplex did have a takeup arm which worked on a weight compensated clutch set-up which I have not seen in a long time. The clutch was cone shaped which allowed the spindle to bear more weight as the reel loaded up. Some Kinoton models are happily using chain drives on the take up end Richard Fowler Kinoton America Inc. Miami  |  IP: Logged Robert Throop Master Film Handler Posts: 412 From: Vernon, NY USA Registered: Jun 99 posted 06-07-2003 06:13 PM                     The Clayton takeup was an example of both chain drive and weight compensated tension. The US Army and Air Force theatres still use the XL takeups Richard was referring to.  |  IP: Logged Dick Prather Master Film Handler Posts: 259 From: Portland, OR, USA Registered: Feb 2002 posted 06-07-2003 07:05 PM                     I have XL take up's in my screening room with 2000' magazines. Also in other private rooms I service. They are a cone and clutch type not a disk. For me it is the best belt take up there is. Would not use anything else. Self adjusting based on the weight of the reel and film. It is also supposed to run oiled. The manuals never had any instructions but I turned up the Simplex service bulletins and found the care and feeding of the XL take up. They work just as well with 6000' reels.  |  IP: Logged Christopher Seo Jedi Master Film Handler Posts: 530 From: Los Angeles, CA Registered: Jun 99 posted 06-08-2003 01:19 AM                     Frank, Good point about not trying to manually spin the takeup reel to take up a pile of film. Are you saying you would let the rest of the reel run out onto the pile, leave the feed reel mounted, and wind it all back onto the feed reel?  |  IP: Logged Daryl C. W. O'Shea Film God Posts: 3977 From: Midland Ontario Canada (where Panavision & IMAX lenses come from) Registered: Jun 2002 posted 06-08-2003 01:48 AM                        That'd be the way to do it... wind it back up onto the feed reel. Now whether or not you should knowingly let the last 500 feet spool out on the floor, well that's a whole different topic that I don't want to touch with a ten foot pole! Only once have I been surprised with a thousand feet of film on the floor as I walked into the booth just before the beginning of the credits (wish I could be in two booths at the same time). Since there was maybe 15 seconds before the credits hit the screen I let the extra 22 feet spool out, but the second the titles hit the screen I stopped it and spooled it all up to the feed reel. All was good... thank goodness for on-line film cleaners. Luckily my other few run ins with failed takeup belts (of all kinds) have been when I've been in the booth near the machine. You can easily spool ~25 feet back onto the takeup reel while the machine is still running... then sit there for the next 30 minutes winding the takeup by hand... yippee! In case anybody (lurking) doesn't know... the yellow belt pictured is Roundthane. Now if you're ever in this theatre, don't go and wipe the oil off of the belts, you'll mess the takeup right up. The adjustment springs are so tight on these machines that the takeup clutch doesn't turn at all. Instead the belt just slips. Incredibly, it gives the most even takeup tension I've ever seen.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 06-08-2003 09:04 AM                     Ballantyne Model6 soundheads I am suprised that the pinion can handle the 6K reel load  |  IP: Logged Stan Gunn Expert Film Handler Posts: 176 From: Clematis, in the hills near Melbourne Australia Registered: Aug 2000 posted 06-09-2003 01:58 AM                        Roundthane in OZ is orange, I have seen it in use on drive belts and take up over ten years old and no sign of failing.  |  IP: Logged Barry Floyd Phenomenal Film Handler Posts: 1079 From: Lebanon, Tennessee, USA Registered: Mar 2000 posted 06-09-2003 09:08 AM                        quote: Ballantyne Model6 soundheads I've got a pair of those bolted to some BX-60 heads. I'll never use them, except maybe as a door stop. If anybody wants them.. come get them. (The Ballantyne's - not the BX-60's)  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 06-09-2003 09:27 AM                     Steve, I am using Josh's laptop computer sitting on Brad's kitchen table, and since I get along with laptops like cats and dogs, I have not completely scanned this thread for the answer I might be looking for. So......what is the normal take-up tension of a 2,000 foot reel, and where should the measurement be taken? Thanks - Paul  |  IP: Logged

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