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Focus motors - typical speed and torque


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#1 Curt von Badinski

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Posted 25 February 2007 - 02:54 PM

Hi all, first time poster here. I was wondering if anyone could tell me what the typical speed and torque of an average focus motor is. I have looked all over and that data always seems to be omitted. Usually maximum torque is given but not nominal torque, I have yet to see any numbers for maximum speed.
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#2 Erwin Landau

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Posted 25 February 2007 - 06:17 PM

Hi Curt,

These questions would be more interesting for manufacturers then users. And as history teaches us it doesn't matter how good your motor is (SLD) if your whole system is not worth while (LC3/WRC4) than that is a mood point. For instance the M-1 motor is at some points out performing the Preston Digital Motor, like speed or torqueness , but at some point, every operator here in the US, when reaching a certain level, has or will buy/switch to the Preston system.

As long as the AC is happy, the motor drives any Lens at extreme circumstances like heat and cold, and the dailies are in focus... And the costumer service is outstanding, I couldn't care less what the nominal torque or the maximum speed is...

Thoughts?


Erwin
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#3 Curt von Badinski

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Posted 25 February 2007 - 06:59 PM

Erwin, Thanks for the reply. Actually I am making a motor... I agree that there is more to a system than those two points but from a mechanical point of view it is the most important to make sure I'm at least in the same ball park as the motors that are currently on the market.
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#4 RobVanGelder

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Posted 25 February 2007 - 10:43 PM

Hi Curt, Erwin is right, for us users, we have only one concern: can it drive that big and stiff lens in almost all conditions in a reasonable fast time from infinity to say 2-4 feet (depending on the focal length), as that is the test case; the fast focus pull to a close-up of a face.

With the smaller, older lenses that was not so much of a turn, but with the big barrel high speed lenses nowadays, like Cooke S4, Utraprimes, Masterprimes and the Highspeed Zoomlenses (Optimo) this becomes a big issue; the distance the motors have to cover is much bigger, but the allowable time is the same.

The best thing is to test and measure a proven set (Preston) and clock the time it takes for this set on a lens that i mentioned.

If you cannot get the same or preferably BETTER performance, don't even bother!
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#5 Curt von Badinski

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Posted 26 February 2007 - 01:30 AM

Thanks for the feedback. I'll check out a DM1 or DM2 and use that as my goal.
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#6 Dan Coplan

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Posted 26 February 2007 - 03:53 AM

but at some point, every operator here in the US, when reaching a certain level, has or will buy/switch to the Preston system.


I beg to differ. I know one operator who has regularly been shooting on a top network TV show for years who has a BFD. He could easily afford a Preston, but isn't getting one. I know another top operator who commented to me once about selling his Preston in favor of the BFD.

Granted, Preston, far and wide, is considered THE follow focus system and I would like to think that one of these days, for features, though more to avoid the rolling eyes of AC's who have to spend 20 secs. calibrating a lens instead of 5 secs., I'll get one myself - I just don't have a spare $20,000 lying around...

I'm playing a bit of Devil's Advocate here but it's not a given that every operator upon reaching a certain level will eventually get a Preston.

I would be interested to know the spread, though - what percentage of Preston vs. BFD/Other out there.

Dan "Hey Jim, Where's My 10 Bucks?" Coplan
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#7 JimBartell

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Posted 26 February 2007 - 12:45 PM

Dan "Hey Jim, Where's My 10 Bucks?" Coplan


Dan,

Your next BFD repair is free except for parts.

This is a very interesting question which I have no idea the answer to. We discussed doing this testing but it is time consuming and boring so we skipped it. Let's face it, no one is going to buy a motor based on the spec's, they're going to buy it after playing with it and seeing what it can do (or talking to someone who has).

Heden does list the torque for their motors on their website. The M28VP is about in the middle of the torque range, less than the M-One or DM1, more than the FMG-6 or M26T.

Jim "motor head" Bartell
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