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arri 2b ...hopefully not a problem


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#1 rob spence

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Posted 28 July 2010 - 11:21 AM

Hi
I'm just checking my arri 2b over as I need to use it in the summer.
I've noticed when I use the inching knob I meet a resistance just after when the claw goes into the claw recess...ie just when it would be starting to pull the film down .
Is this normal.. Or should there be no resistance at all throughout the cycle ?

best
rob
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#2 John Sprung

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Posted 28 July 2010 - 03:20 PM

It's hard to know how much resistance you're feeling. There should be very little if any. Because the lubricants dry out over time, these cameras should be serviced every couple years. This resistance could be grease that has hardened on the gears. It's likely not to be a big problem, but you should get the camera tuned up before putting it back in use.





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#3 rob spence

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Posted 29 July 2010 - 07:21 AM

Hi John
thanks for the reply...I've found the problem.
I took the gate out of the camera and hey presto no stiffness in the claw mechanism on its rotations at all.

It seems the cardioid cam has been slightly hitting the gate semi circular cut out that is for cardioid cam clearance on the right hand side of the gate.
Now the cause of this seems to be that the gate mechanism has a little play from side to side within the camera
... apparent when the gate retaining clip is removed ( held in by 2 screws ) . If I ease the gate towards the door side of the camera there is just enough clearance for the claw assembly to work fine, but when I replace the retaining clip the problem comes back.
Any ideas on how to keep the gate fully to the door side of the camera?
Or should I take a dremmel and ease the clearence on the cardioid semi circular cut out?
By the way this camera has hardly ever been used and none of the parts are worn.
best
rob
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#4 John Sprung

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Posted 29 July 2010 - 01:36 PM

Are the gate hinges at all loose? That would allow the latch spring to shove the gate inward. Especially on a pristine camera like this, don't use the dremmel. Take it to someone who knows what they're doing. Perhaps the service department of a rental company could do it, or could recommend someone. Or, post a question here to find an Arri tech in the U.K.





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#5 Dom Jaeger

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Posted 29 July 2010 - 09:14 PM

The gate should be a reasonably snug fit in the gap created by the machined surfaces of the camera body. But even with a bit of play, when the gate is up hard against the movement side of this gap the cutout should still allow the cam to clear. I'm only guessing, but if I had to explain it I'd say either the gate is from a different camera model with slightly different tolerances, or the movement has been assembled such that the cam sits out too far.
As John said, don't take to it with a Dremmel. You could probably get away with just glueing some small shims on the movement side of the gap to push the gate towards the door. Just be careful not to get anything on the machined seats perpendicularly adjacent, which control the flange depth and flatness.
Or best bet take it to an Arri tech.
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#6 rob spence

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Posted 01 August 2010 - 08:30 AM

Thanks for the responses...the shimming route should work so I'll try that...I'm wondering why the gate has so much play in the camera, as a matter of interest are the gates customised to the camera from new. Or are arri 2b and c gates different...could I have a 2c gate?
cheers
rob
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#7 Dom Jaeger

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Posted 01 August 2010 - 11:24 PM

According to people I've talked to who are much more familiar with these cameras than I am, gates were often swapped over for different aspect formats, so within a model they should have identical specs. (A variation of just a few hundredths of a mm in gate thickness would throw the film plane out though, so I assume they did a flange depth check each time.)

In theory 2B and 2C gates should be interchangeable, just the doorside cutout for the viewfinder is larger on the 2C (the ground glass height was extended from Academy to accommodate Cinemascope), and there is a channel for the clapper light. However the 2A (really just the 2) went through a few incarnations including originally a different movement and a bakelite gate, the specs were probably less rigid, some bodies would have been hand machined with gates made to match, so there could be some variation there.

As I said, this is mainly second hand information, so I'm happy to stand corrected if if anyone knows different.

The two Arri 2B gates I have both measure 44 mm (plus or minus 0.1) in width.

A quick way to shed some light on your problem would be to get hold of another 2B and fit its gate to your camera: if the problem remains you know it is the camera body not the gate that is out of tolerance.
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#8 rob spence

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Posted 02 August 2010 - 12:19 PM

Thanks Dom
I've checked the gate width and it is 44mm...I'm sure the shimming will work. I'll let you know after a film test
best
rob
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