Stiff Calumet revolving back

[tonyowen]

I’ve recently acquired a Calumet monorail 4x5 camera s/n 14288, which I think is a CC401 long focus model.
The rotating back is very stiff to move. With the locking level in the up position CCW movement from vertical to horizontal (portrait to landscape mode) is smooth once friction is overcome. Whereas CW movement is much stiffer.
There is no (noise or swalf/debris) indication of metal to metal erosion or damage.
I’d like to know how the back can be removed so I can see what is causing the stiffness of movement. Also what lubricant, if any, should be used to ensure a smooth and easy rotation?
An image of the in-situ rotatable back is attached.
Regards
Tony

135364

[LabRat]

I have worked on a few of these years back... They do get "bindy" there... Let's see what I can remember...

I think the hold down screws are on the inside of camera... They are holding little plates that are over the rim... Unscrew, but be careful not to loose screws or washers, and note the order of any spacers removed... Screws might be stuck, so use a good matching screwdriver...

RB plate will lift off, but make sure no little spacer falls off locking lever shaft...

Usual issue is old grease gets sticky, but can be removed with a q-tip with lighter fluid... Clean it up, and try with the RB and see if it is still binding... If so, take a little toothpaste and apply to the mating faces, and rotate the RB for a few minutes, then remove toothpaste with a q-tip dabbed with 91% alcohol and see if it's better... If OK, get some silicone or lithium grease (in a little tube) from the hardware or auto store and wipe a little on the mating surfaces with a q-tip, then reassemble...

That should do it!!!

Steve K

[tonyowen]

Thank you
I recognize your description from when I was getting familiar with the camera and removed the lens plate.
I assume magnet and magnetic screwdriver would be useful to recover those bits that fall into the internal folds of the bellows.
I'll follow your advise when I get a bit braver!!!
regards
Tony

[Liquid Artist]

I would lay it on its back so you will hopefully not have anything falling into the folds. It could be hard to find, besides there is a tiny chance that some parts are non metallic.
The magnet and magnetic screwdriver are good ideas.

[Harold_4074]

A sometimes-useful trick when doing tasks like this (small, irreplaceable parts in unknown configurations) is to cover the work surface with something like a large terrycloth towel. Depending on the expected color of the parts, white, black or an intermediate shade would be appropriate. The rough surface will tend to trap things that would otherwise be able to bounce, roll and escape.

If something does appear to be missing afterwards, darkening the room and shining a flashlight at a low angle across surfaces and corners will sometimes reveal the fugitive, either by reflection or shadow.

(I learned this when handling glass spheres ~ 1mm diameter glass spheres; it worked like a charm.)

[Captain_joe6]

Removing the back, as I recall, is quite easy. The rotating mechanism isn't greased, but it is such a tight fit that little bits of dust and crap get in there and bind the whole thing up. Get the two halves apart and then go over all the bearing surfaces with some fine steel wool and a razor blade to scrape everything down to flat, smooth, bare metal. Should be good to go.

[tonyowen]

Many thanks for information.
Attached are two images of the ‘rear of the rotating back’ from inside the bellows.
One image shows a ‘gear wheel’ with a pin between two of the ‘gear teeth’
Opening and closing the (rotating back’s) external locking lever moves the ‘gear’ from being in contact with one side of the pin to contact on the pin’s opposite side – I doubt if the total movement is more than 1mm (1/32nd inch).
As an engineer I find this a most complex clamp mechanism – if that is what it is..
The second image shows the top left section of the rotating back. At the 12:00 o’clock position is a horseshoes shaped lug the right side of which has one of the 4 – securing tabs fastened to it.
Does anyone have any explanation for what is shown in the images and how these features affect removal of the back.
Regards
Tony
135520135521

[erie patsellis]

The pinned gear's sole purpose is to keep the threaded bolt from rotating.

(Going from memory...) Unscrewing the locking lever fully and extract the threaded shaft, make note of washers, shims and the like, remove four tabs making sure washers, etc are noted and reassembled In the same order/location.


Lightly lubricate the rotating mechanism (I use a dry lube instead that doesn't attract dirt and gunk).

Separate the two halves, clean thoroughly and deburr as necessary. On threaded fasteners I chase threads when possible with a tap or die.

Assembly is the reverse if disassembly as the Bentley manuals were so fond of saying.

[tonyowen]

Unscrewing the locking lever fully and extract the threaded shaft. Lightly lubricate the rotating mechanism - Separate the two halves, clean thoroughly and deburr as necessary. "... as the Bentley manuals were so fond of saying".
Thanks for response - I'm slightly confused.
1] Are you saying that the frame holder unit (which holds the ground glass and the dark-slide holder) needs to be removed prior to taking out the rotating unit?
2] Also does the locking lever need to be removed prior to taking out the rotating unit?
3] You say "separate the two halves"(after lightly lubricating the rotating mechanism) - is this a mis-placed sentence of are there three parts to the rotating mechanism? I'd assumed there were two pieces the rotatable part and a fixed part that formed the rear support for the bellows.
4] Don't know much about Bentley except my wife is distantly related to the family. However, when I worked at Rolls Royce the manuals and other instructions were unambiguous, fully detailed with no grammatical quirks.
regards
Tony