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Questions about the spring motor


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#1 jim blair

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Posted 09 December 2011 - 09:51 PM

Is it safe to keep the camera wound when not in use? If not, is there a way to wind it down without using film. I do not have a rewind crank.

Also, do cold temperatures (5 degrees Celsius and less) affect the spring? I was filming and as the motor was at the end of its wind it sounded as it it was running slower. Is this normal? Is the speed still constant despite what I was hearing?

Thanks
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#2 Dom Jaeger

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Posted 10 December 2011 - 08:26 AM

There's no problem storing the camera with the spring wound up for short periods, when there's film loaded for instance. The advice to run down the spring motor is really only pertinent if the camera is to be stored away for months or years. It just helps to prolong the potentially very long life of the spring motor.

Bolexes are remarkably tolerant to temperature extremes - they've documented Everest climbs - but they need to be serviced to operate at their best. Most of the ones I've worked on slow down a little towards the end of the spring run, but if they're in decent condition it's no more than by 1 fps or so, and only in the last few seconds.

If you remember to rewind before each take it rarely becomes an issue.
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#3 jim blair

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Posted 10 December 2011 - 02:42 PM

Thanks for the info. Puts my mind at ease! :)
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#4 jim blair

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Posted 29 December 2011 - 07:52 PM

I have another question.

My spring motor only gives me 24 seconds (24 clicks of the audible signal).
Is this normal?
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#5 Dom Jaeger

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Posted 03 January 2012 - 10:20 PM

24 clicks is normal.

The clicks relate to the amount of film transported - 28 frames per click or 7 feet per 10 clicks. The clicks are caused by 3 protrusions spaced around the circumference of the spring motor, which rotates 8 times before coming to a stop. At 24 fps you'll get a click each 1 1/6 seconds. Kinda weird, but that's just how the gearing is.

So a full wind of the spring motor should transport around 670 frames, a bit under 17 feet. At 24 fps you should get about 28 seconds. If it's less, the camera is probably running a little fast.
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#6 jim blair

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Posted 04 January 2012 - 02:00 PM

Thanks again.
So it must be my frame counter that is off. It only indicates 612 frames per wind.
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#7 jim blair

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Posted 04 January 2012 - 06:13 PM

I mean 662 frames
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#8 Dom Jaeger

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Posted 04 January 2012 - 06:42 PM

Sounds perfect. The mechanism that limits the motor's run duration lets it spin slightly under 8 rotations, so yeah it's probably closer to 660 frames.
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