Focus rail too stiff on bellows. How to fix?

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sapstar
Posts: 15
Joined: Sat Feb 13, 2021 5:01 pm
Location: London

Focus rail too stiff on bellows. How to fix?

Post by sapstar »

I have the below focus rail attached to my bellows. The movement is too stiff. I put some dry lube on the tacks at the bottom, but that didn't help. How can I loosen this?
Image
Also there is this steel plate with 2 holes? Is that something to control the tension? I tried turning it with some forceps, but unable to turn it.
Image

enricosavazzi
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Re: Focus rail too stiff on bellows. How to fix?

Post by enricosavazzi »

sapstar wrote:
Tue Apr 06, 2021 4:26 am
I have the below focus rail attached to my bellows. The movement is too stiff. I put some dry lube on the tacks at the bottom, but that didn't help. How can I loosen this?
(img)
Also there is this steel plate with 2 holes? Is that something to control the tension? I tried turning it with some forceps, but unable to turn it.
(img)
The following are generic comments that apply to most or all bellows and focusing racks with nylon-against-metal bushings, like this one. I have no specific knowledge of this bellows model.

Nylon bushings are supposed to be self-lubricating. It should not be necessary to lubricate the bushings and/or metal guides. However, if there is dirt or congealed lubricants within the bushings, the latter should be cleaned out (with a cloth wetted in water, if necessary with a couple drops of dishwashing detergent added) after sliding the prismatic metal guide out at one end of the bushing. Alcohol or stronger solvents should not be used except as a last resort, and can melt the nylon. Some people report success by using WD40, but I would not use it unless all else fails, since it may melt some plastics. The axle carrying the "focus" knob may need some lubricating fat, but not the gear (which may need cleaning, but not lubricating). While you are at it, check whether the nylon bushings are cracked. If so, they may break and let your camera fall off at any time.

Sometimes a bushing has been tightened too much against the metal guide, often in a misguided attempt to prevent the bellows from sliding down slowly when mounted vertically. Your bellows have, on each side of the bushing support, four adjustment screws to adjust the friction of the bushings against the metal guide. Adjust them so that they prevent wobbling without making it too hard to operate the "focus" knobs. Too tight increases wear of the nylon material and may encourage its cracking.

Check that the locking knobs have not been inadvertently tightened. They should only be used to lock the bellows, preferably not to increase friction to prevent sliding down under gravity.

Leave alone the nut with two holes (on the side of the bushing support, usually on the opposite side from the "focus" knob). It is not for adjusting friction.

The two threaded holes at the bottom of the base are not for adjusting friction, either. They are only for attaching the bellows base to a tripod or stand.
--ES

dickb
Posts: 342
Joined: Mon Jul 05, 2010 1:54 am

Re: Focus rail too stiff on bellows. How to fix?

Post by dickb »

Just checking, are these pieces all from the same brand, so bellows rail, focus rail and tripod mounting part? I'm asking because I have quite a few similar bellows and rails (branded Contax, Minolta, Soligor and others) and there are two standard sizes, one ever so slightly smaller than the other, or with slightly different edges or bevels on the rail. So when you mix and match these types they do fit, but either a bit too loosely or, as you are describing here, too tightly. Are the cross-sections of the top and bottom rail exactly the same?

If there is indeed a mismatch then getting the matching components, so either focus rail or tripod block, would be the ideal solution. A less optimal solution would be to DIY grind the plastic insert of the tripod block to match the bevel of the focus rail.

Anyway, there may well be a different cause for the stiffness but I would check this first.

sapstar
Posts: 15
Joined: Sat Feb 13, 2021 5:01 pm
Location: London

Re: Focus rail too stiff on bellows. How to fix?

Post by sapstar »

Thanks everyone for providing your inputs. I was able to fix the issue myself before reading the comments here... The information is useful and hopefully I will keep in mind if I run into this kind of issue in the future.

Unfortunately that involves WD40... :(.
I took the rail apart applied wd40 and wiped off all the excess. Now the rails run smooth. I see a new problem though. In couple of places the rail slider seems to just skip ahead quicker. When I took it apart, I saw that the rod which has the gear attached, is very slightly bent. So the gear seems to be applying variable pressure on the rail which probably is causing it to skip... I think I will have to live with it.

sapstar
Posts: 15
Joined: Sat Feb 13, 2021 5:01 pm
Location: London

Re: Focus rail too stiff on bellows. How to fix?

Post by sapstar »

enricosavazzi wrote:
Tue Apr 06, 2021 5:33 am
The two threaded holes at the bottom of the base are not for adjusting friction, either. They are only for attaching the bellows base to a tripod or stand.
Sorry, didn't notice this yesterday. I was referring to the second photo which shows a small steel plate with 2 tiny holes diagonally. Not the tripod mount holes.

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