8mm Forum: How to measure the real speed ...

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Topic: How to measure the real speed ...

Flavio Stabile
Jedi Master Film Handler

Posts: 707
From: Roma, Italia
Registered: Feb 2005

posted June 01, 2008 01:05 PM

I think my 16mm ELMO doesn't run at 24fps but It seems to run slower ... Is there a simple method to measure the real speed in such a case?

Thanks
Flavio

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John Whittle
Jedi Master Film Handler

Posts: 791
From: Northridge, CA USA
Registered: Jun 2003

posted June 01, 2008 01:33 PM

What I do is cut a loop of leader exactly 18 feet long and mark an X on one frame. Then I run the loop and with a stop watch start it on the flash of the X on the screen and let it run for 10 passes. Since film runs at 36 feet per minutes, 18 feet run for 30 second and ten passes should be five minutes. Any error on the stop watch can be figured back to exact frames per second. You can use any size loop and count any number of passes. The longer you let it run, the more accurate your measurement will be. The projector should be warmed up to operating temp before you start (run a cartoon or other short first).

John

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Josef Grassmann
Expert Film Handler

Posts: 190
From: Hennef-Sieg, Germany
Registered: Apr 2005

posted June 03, 2008 07:08 AM

Optical, digital speed meters are nowadays resonable priced.
You hold them in front of lens, projection bulb turned
on, if bulb his provided with preheating, that works fine, too.
Price for speed meter ist appox. 28,-Eur/ 40,-US$

If you have a second 16mm projector and you are sure it´s running with correct speed, then you can put both machine in line. Now you feed film through 1st maschine (24f/sec.) with an acceptable loop into second machine (unknown speed). Start both projectors at same time and watch loop between both projectors.
If loop gets smaller, second projector ist running too fast. If it gets larger, second projector ist running too slow.
If you can adjust running speed of second projector, adjust until loop size stays constant.

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Flavio Stabile
Jedi Master Film Handler

Posts: 707
From: Roma, Italia
Registered: Feb 2005

posted June 04, 2008 03:01 PM

Thank you! I will try both methods, even if, when discovered that it runs slowly, I don't know what to do!!!

Flavio

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John Whittle
Jedi Master Film Handler

Posts: 791
From: Northridge, CA USA
Registered: Jun 2003

posted June 05, 2008 08:42 AM

If machine runs slow:
1. Check drive belt--slippage with an old worn belt common
2. Check dirt on drive pulley--dirt causes slippage
3. Check lubrication though out drive train. Often a bind in take up can work back to loading down projector
4. Bad or failing motor
5. Voltage problems. Most 16mm projectors have induction motors which operate over a wider voltage flucation but are very sensitive to hertz changes. If projector was set up for a 60hz country, then the pulleys either need to be changed or the belt needs to be moved to other pulley position. Projector would run fast with 50hz pulley in a 60hz country.

John

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