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Arri S motor


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#1 Keneu Luca

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Posted 03 November 2005 - 12:36 PM

My arri S has been converted to 12 volts, which then allows for a more powerful motor. For example, my VARIABLE speed motor before the 12 volt conversion would run 24fps at the 3 1/2 setting, but now after the conversion runs 24fps at the 2 setting.

How does the 12 volt conversion affect a CONSTANT speed motor?
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#2 Patrick Neary

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Posted 03 November 2005 - 01:52 PM

Hi-

I ran an Arri M with a 12v into constant speed motor for several years worth of shooting, despite warnings that it would burn the motor out, with no problems. It ran constant at 24fps. In fact, very constant.

that being said, don't blame me if your motor starts smoking :)
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#3 Keneu Luca

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Posted 03 November 2005 - 02:05 PM

Thanks.

Did the 12 volts alter the frame rate in away way, like it does with a variable speed motor?
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#4 Clive Tobin

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Posted 03 November 2005 - 02:58 PM

How does the 12 volt conversion affect a CONSTANT speed motor?


There have been several versions of these. On some without the transistor, there is a resistor that will overheat and crack open. On others, the field winding will have too much current and burn out.

If the takes are short, before parts have time to overheat, any motor will work.
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#5 Keneu Luca

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Posted 03 November 2005 - 04:41 PM

There have been several versions of these. On some without the transistor, there is a resistor that will overheat and crack open. On others, the field winding will have too much current and burn out.

If the takes are short, before parts have time to overheat, any motor will work.


Is this only a problem with 12 volts to a constant speed motor, or will it also have the same potential for damage with a variable speed motor?

Short takes? How short? Or perhaps a better question, how long is too long?

Edited by Keneu, 03 November 2005 - 04:48 PM.

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#6 Clive Tobin

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Posted 03 November 2005 - 08:28 PM

Is this only a problem with 12 volts to a constant speed motor, or will it also have the same potential for damage with a variable speed motor?
Short takes? How short? Or perhaps a better question, how long is too long?


The variable speed motors seem to do okay on 12 volts, you just turn the rheostat to a lower number for a given speed and expect it to get a bit warmer. The rheostat appears to be a dual section type which changes both the field and armature current separately.

I have never run tests to see how long the parts take to actually burn out, sorry. I might wildly guess that 20 seconds might be okay, with a minute in between to cool down??? This number has no express or implied warranty. :-)
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#7 Sam Wells

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Posted 03 November 2005 - 09:32 PM

I had an S with a (pre transistor) Constant speed motor, some I knew had a VS, I wanted his for a shoot, we traded.

He ran my CS motor off 12v on his shoot - I got it back and it ran fine - at 21 fps....

I say "don't"

-Sam (who later switched to a VS motor made by this guy named Clive.....)
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