[Konvas] torque power of Arri ...

Thu Mar 11 17:34:44 CST 2010

Hi Olivier,

Yes, I think your main concern is measuring the friction torque? I used to make these measurements when I was rebuilding car differentials, I bought a bar type torque wrench that measures in inch/pounds (the American equivalent of Newton-meters) for that purpose. I would attach the wrench to the input shaft I was measuring with a socket, spin the handle of the wrench at a constant rate with my finger and read the position of the needle on the scale-- the friction torque. You can do it the way Patrick suggests, it requires a very small pull-type scale and string or fishing line, you wrap the line around the shaft, attach the free end to the scale and then tie another string on the other end of the scale and pull it. As the shaft rotates you measure the "weight" on the scale. That is the friction torque.

If I can find my wrench you are welcome to borrow it.

Bruce Taylor

--- On Thu, 3/11/10, olivier auverlau <firefly at uio.satnet.net> wrote:

From: olivier auverlau <firefly at uio.satnet.net>
Subject: [Konvas] torque power of Arri ...
To: "Konvas Discussion List" <cinema at konvas.org>
Date: Thursday, March 11, 2010, 1:48 PM

HI guys, i finnaly find a motor i hope it will work ...
BUT in other way i ask to motors company who make very weell good motors , info , but they ask me this : and i don t understand well what the want ... or how to do it ... anybody know the answer : ?

Hello Mr. Auverlau,

To suggest a gearmotor, I would need to understand the torque required.  I believe the gearmotor will need to overcome mostly friction torque.  As you have existing mechanics, the easy way to determine the friction torque is to use fishing line and a spring scale used to weigh fish.  Wrapping the fishing line around the drive axis, you can pull the line with a spring scale to measure torque.  The key is to keep the scale moving at a constant velocity or if you care to think of it as a constant force.  The force times the distance from the tangential point to the center of the axis (the radius) gives torque in units of say Newton-meters (Nm).  In this case, it will likely be mNm.  If you could, please send me the dimensions of the film spool and weight.  I would like to check the moment of inertia.

The following would also be helpful.

Dimensional constraints (length/width/height)

Duty cycle (on and off time in seconds)

Life expectancy (in cumulative hours of running)

Power supply (voltage and amperage) 12V  and ?A

Environment (relative humidity and operating temperature range)

Thanks,

Patrick Dell, Application Engineer

MICROMO

14881 Evergreen Avenue

Clearwater, FL  33762-3008  USA

Tel:  (727) 572-0131 Ext. 192 | (800) 807-9166

Fax:  (727) 572-7763

patrick.dell at micromo.com

www.micromo.com

----- Original Message ----- From: <colcam at aim.com>
To: <cinema at konvas.org>
Sent: Thursday, March 11, 2010 4:28 PM
Subject: Re: [Konvas] color correction in post (was: first test time lapse ... with 7D)

> 
> I was treated to a three day "this is what we are going to" class, and what sounds strange is that the best 4k projection is based on "printed" standards because the image is a mirror reflection image, and that's where the "positive versus negative" factors start to play.  When you go to creating an image that is then reflected and projected "how bright" is the first factor for an RGB color, while there is no "brightness" to the CMYK color-- it is defined as a color.
> 
> The next generation is based on an S image, one where only the pixels changed are changed, not a progressive redefined picture, but, like the new flat panel computer screens, it refreshes the whole thing 600hz and only changes the pixels that need to be changed.  That may be none, that might be all of them.
> 
> As you noted in your followup, the way the colors are defined makes things interesting.  The RGB has a block of "one color" that is shaded by brightness to take the place of ten steps or a hundred steps, and both the capture and display limit it, while the CMYK version has no brightness--  every color is defined as a color, and that is what it reflects.
> 
> Mix equal amounts of R G and B and you get white, so no R, no G, no B, you get black.  CMYK mixes colors to create the R, for example, but has to add black to create black, because it has to overprint the colors or replace the CMY factors.
> 
> In a nutshell, one starts by beating your head against the wall and crying.
> 
> 
> 
> 
> 
> 
> 
> 
> -----Original Message-----
> From: Adam Frey <thefirstrule at chainsawlinux.com>
> 
> 
> On Mar 11, 2010, at 1:29 PM, colcam at aim.com wrote:
>> One of the "quiet revolutions" being made is the way color is > handled--  it was "amount based RGB" with about 4000 colors-- it is > going to indexed CMYK with over sixteen million colors.
> 
> I recently ran into an issue for a client's project, importing a TIFF into a PPro timeline. It had apparently been converted to CMYK. After messing with it for too long (and trying to export Jpeg's that were a negative of the original file), one of the graphic designers came by and figured it out in about 5 seconds (she sent me a new TIFF in RGB a few minutes later that worked just fine). So I decided to learn a little about CMYK from that whole process.
> 
> I know CMYK and RGB are completely different - and to convert from one to the other, you're probably going to have some form of generation loss. But isn't CMYK for printing? Partially so the printer can save it's pricier colored ink over the less expensive black ink, but also because it's being printed onto a paper that absorbs inks vs projected with light?
> 
> While we're on the topic, talking about RGB bits is a pain, since 24-bit is really just 8-bit multiplied by the 3 color channels, and 48-bit is 16-bit also multiplied by the 3 color channels. But even those numbers don't even remotely add up to the 16 million colors your talking about (8-bit is 2^8 = 256. 16-bit is 2^16 = 65536).
> 
> Adam Frey
> 
> 
> Your donations will keep Konvas.org running:
> http://konvas.org/how-to/help-konvas.org-donate.html
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