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Topic: Steel vs. fibre gears on Simplex 35

Christopher Seo
Jedi Master Film Handler

Posts: 530
From: Los Angeles, CA
Registered: Jun 99

posted 08-11-2002 04:19 PM

Hi all,

I'm wondering what the basic reasons are for pairs of gears to be steel and fibre. Some possible reasons I could think of are decreased wear, and the need for something to give way more easily in the event of problems (i.e. the fibre gear) rather than have two steel gears locking against each other.

Ideally then the fibre gear would be the easier one to replace. That seems to be the case with most gear pairs in the Simplex except for the shutter gears. I'm wondering why all the drive gears on the vertical shaft are steel except for the shutter gear, which seems much more difficult to replace than the gear on the shutter shaft. The same question applies to Century projectors as well, I suppose.

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Darryl Spicer
Film God

Posts: 3250
From: Lexington, KY, USA
Registered: Dec 2000

posted 08-11-2002 04:57 PM

one of the lovely gears to have to replace is on the oil pump. Not the hardest to replace but the stupidest. Stupid I say because on the older machines like the 1050's and earlier they are two pieces not one solid piece. The gear seperates it's self from the base causing loss of oil pumping. These are now one solid piece thank goodness.

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999

posted 08-11-2002 05:46 PM

Typically the metal/fibre or metal/plastic gear combo is used for two purposes: one being a mechanical fuse to prevent major gear damage in the event of a film pile-up and the other being to reduce operating noise level of the machine.

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Rick Sanjurjo
Film Handler

Posts: 26
From: Omaha, NE, USA
Registered: Jul 2002

posted 08-11-2002 06:31 PM

Ken is correct the two main reasons for having fiber gears are to prevent major damage in the case of a problem and secondly the machine produces less noise with a steel and fiber gear as opposed to two steel gears. The design of the gear on the shutter shaft is such that is has to be made of steel. If you take a close look at the gear you will see why it wouldn’t be wise to make it from phenolic, which is really what the fiber gears are made from.

Rick

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Dave Williams
Wet nipple scene

Posts: 1836
From: Salt Lake City, UT, USA
Registered: Jan 2000

posted 08-11-2002 07:10 PM

The one gear in the simplex box you are referring to is made of the fibrous material for one very good reason, and by example I will show you why...

Two years ago, I got called in to repair a simplex 35 that no longer ran, sripped its gears, according to the staff. What had happened, is that the entire staff stepped out back for over twenty minutes for a smoke break, the platter then wrapped the film. BUT... the film, that wonderful polyestar stock film, did not break. It just chewed up the gears to death, so the staff said. As it did not move anymore, they were right to feel really stupid.

HOWEVER.. that one little teeny tiny gear, replaced in about an hour, gives way in the case of this now very possible scenario. It prevents the stripping of every single gear. This one gear separates the drive shaft from the film sprockets to prevent the one odd scenario that the sprockets don't strip on the film, and instead it just holds.

Now I am sure it was designed for some other reason, but this reason is probably the best reason I have ever seen to have this thing.

There are a few of these fibre gears, all of them are between drive shaft and other gears, in the event of stoppage of the gears on the film end, to prevent the drive shaft or motor from toasting, with the rest of the gears.

Simplex machines are like tanks. Literally. You can drop a rag in one while it is running, and all that will happen most of the time is it will just eat the rag and keep running the film. BUT DONT TRY THIS JUST FOR KICKS.. NOT RECCOMMEENNDDEEDD...

Dave

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Richard Fowler
Film God

Posts: 2392
From: Ft. Lauderdale, FL, USA
Registered: Jun 2001

posted 08-11-2002 07:48 PM

In the new version of the Cinemeccanica V-5 shutter gear box it has been redesigned with two steel bevel spiral gears to increase service life.....but because of the metal to metal gearing they now encase the shutter box casting with a rubber boot to lower the noise level.
Richard Fowler
TVP-theatre & Video Products Inc. www.tvpmiami.com

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 08-11-2002 09:12 PM

Richard,
I'm surprised they went to mating two steel gears. Coulod it be a cast iron and a steel gear? Typically the use of steel on steel has never worked out too well. The Christie P35 gearbox is a good example of that. There are what appears to be steel to steel gearing in the DP-70 as well but on closer inspection the sprocket shaft gears appear to be cast iron. This combination is under constant oil spray, will also last a very long time. The other thing gained from fibre to steel pairing though is the wear factor. They typically last a long time if kept lubricated and clean. In a Century for example it is best to replace the steel and fibre gears as pairs. Several reasons for this....There have been alot of different manufacturers of these gears and slightly different pitch and tooth style can come into play and cause mucho problem, and secondly, for the input drive shaft, intermittent drive and shutter shaft if you inspect the steel gears with a 15 to 30 power magnifier you will find wear marks in the steel gear driving face from wear unless the machine has seen very little service. Upper and lower sprocket drive gears are less prone to wear though .
Mark

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Richard Fowler
Film God

Posts: 2392
From: Ft. Lauderdale, FL, USA
Registered: Jun 2001

posted 08-12-2002 01:12 AM

Mark,
both are steel.....the older nylon units where experiencing higher failures in the past few years....so this was the Italian solution. The shutter box is a part of the projector which most maintinance people forget to check the lube and the design is such that if the grease is not tightly packed, the gearing creates a greaseless void within the chamber and eventual failure. We rebuild the older units in house and for our shop tech ( Carlos ) is a quick job.
Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com

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Don Sneed
Master Film Handler

Posts: 451
From: Texas City, TX, USA
Registered: Aug 2001

posted 08-12-2002 01:32 AM

I had many of the 234 gears in a century strip out in a problem to protect the intermittent movement, I once had a Century made in 1960 loss a 234 vert. gear due to the operator put too much gear grease on the gears, the fiber gear came loose from the mounting...who would think that would ever happen....yes the fiber gears protect the machine in event of a major problem, they strip out before more damage can be done....an excellent idea....plus this keeps me in business !!!

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 08-12-2002 04:47 AM

Brenkert BX40, BX-80, and the BX-100 did that in the compensators, too. It was a fiber gear with a steel side plate. I never saw one stripped out.

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Frank Angel
Film God

Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999

posted 08-12-2002 12:52 PM

As Dave points out, when those fiber gears do what they are supposed to do in a catastrophic failure, they really save the rest of the gear train. I did have such a failure only recently and it became quite clear what life-savers those little guys really are. You look and see how neatly they broke away preventing tons of "colateral damage" to everything else, and you want to kiss them.

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Christopher Seo
Jedi Master Film Handler

Posts: 530
From: Los Angeles, CA
Registered: Jun 99

posted 08-12-2002 01:46 PM

Thanks for the responses, guys. I take it the Simplex 35 shutter shaft gear cannot be made of phenolic because of the hole in it needed for the pin to drive the flanged spline. So I guess it would not be possible to make, say, the inner portion of the gear steel, and only the very outer portion (the teeth, i.e.) phenolic?

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