my profile | my password | search | faq & rules | forum home

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » What can cause a missing tooth on a sprocket? (Page 1)

This topic comprises 3 pages: 1  2  3

Author Topic: What can cause a missing tooth on a sprocket? Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 02-05-2010 08:10 PM                        Twice in as many weeks, an employee has informed me of missing teeth on a sprocket. For now I will just assume that he notices such things and is not somehow the cause. But the rest of the sprocket seems to be in good condition, no hooked teeth or anything. I have noticed no damaged leader or film. So what could cause a random tooth to go missing? Both sprockets came from the same vintage machine, Simplex XL circa late 60's or so. One of them was the lower constant feed sprocket (which is very kind to film, by the way) and the other was the feed-out sprocket in the 5-star soundhead (which is impartial to downright rude to film).  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 02-05-2010 10:18 PM                     #1 cause is the use of a toothbrush on a running machine. Which in my theatres has resulted in loss of employment when the perp is found. Or any contact with a tool or object other than film.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 02-06-2010 01:24 AM                     ? Which sprocket, the intermittent sprocket - caused by the shoes hitting the teeth if closed while running ?  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 02-06-2010 06:40 AM                        Must be a "foreign object." You would know if there was something internal to the machine because of a unique sound. Notice, also, that the tooth missing is ALWAYS on the sound track side of the sprocket. Louis  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 02-06-2010 11:30 AM                        Actually no. The missing tooth on the lower constant feed was on the soundtrack, but the one on the feedout sprocket in the 5-star soundhead was on the inside. We don't have any toothbrushes lying around. Not sure what could have come into contact with a moving sprocket or why.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 02-06-2010 12:04 PM                     They don't wear anything like a pendant or a cross around their neck do they, or even something like a security pass in a plastic holder?  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 02-06-2010 12:46 PM                     quote: Joe Redifer We don't have any toothbrushes lying around. Then how do you clean any crud off the sprocket teeth when it gets there? (Of course, religious use of Film Guard will prevent any buildup on sprocket teeth, but even during the first pass of a non-Film Guard(ed) print enough crud can still build up... ) In any event Joe, there is really no way the teeth "just fell off"....someone contacted those sprockets with something other than film!  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 02-06-2010 03:38 PM                        It doesn't get there! When it does a simple wipe with a shop rag is enough. And I know they don't fall off, that's why I am asking what the common causes are. More investigation is in order.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 02-06-2010 04:29 PM                        I would first suspect PEOPLE (or what passes for people these days.) Louis  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 02-06-2010 07:24 PM                     That is bizarre! Those sporockets are hardened to nearly Rockwell 60! Thats some dam hard metal there Joe. They almost have to be ground off. Mark  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 02-06-2010 09:34 PM                     A jammed toothbrush would damage gears but I can't see a plastic toothbrush breaking a sprocket tooth, just too hard and small. Edit.....After the above post I took an old sprocket from the junk box and tried to break a tooth using pliers, very difficult to get a grip and couldn't break one. Then using a screwdriver as a chisel, tried to chop a tooth off whacking the screwdriver with a hammer, no luck with that either.  |  IP: Logged Ian Parfrey Phenomenal Film Handler Posts: 1049 From: Imbil Australia 26 deg 27' 42.66" S 152 deg 42' 23.40" E Registered: Feb 2009 posted 02-06-2010 10:07 PM                     Joe. Grab a jeweller's loupe or a lens of some sort and take a real close look at the missing tooth position under a bright light. What does the site look like? Is it a clean break? Is there a jaggered appearance to the tooth remains? If the missing tooth is due to metal fatigue, you will see a very thin dense line around the perimeter of the tooth base and a dull metal interior with some sort of crystallisation. The dark line is the case hardening of the metal. If the missing tooth is due to trauma, you will find a rolling over of the edge of the tooth remains where it was impacted. It looks much like a bar of sheared steel does where the shear deforms the metal before it fractures.  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 02-07-2010 05:31 PM                        quote: Ian Parfrey What does the site look like? Is it a clean break? Is there a jaggered appearance to the tooth remains? See for yourself:  |  IP: Logged Damien Taylor Master Film Handler Posts: 493 From: Perth, Western Australia Registered: Apr 2007 posted 02-07-2010 08:16 PM                     WOW that's amazing!  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 02-07-2010 08:47 PM                     It looks like the tooth was a separate piece attached over the black band around the center which is intact except at the edges where the tooth was secured.  |  IP: Logged

All times are Central (GMT -6:00)

This topic comprises 3 pages: 1  2  3

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.