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mackinto2000
7-Oct-2010, 22:30
I've recently purchased a Sinar F, and I'm a bit puzzled about the monorail clamp. This is the original F style, where the rail passes through a hole in the clamp, and cannot be removed unless you slide it out. (See http://photo.net/large-format-photography-forum/00ABg8 for images of a similar clamp.)

On one side is a lever that tightens the clamp onto the monorail. On the other side is a level that, as far as I can see, does nothing. It will turn with slight resistance through a full 360 degrees without hitting any stops. It's attached to a shaft that runs though the thin bottom plate of the clamp, and I can't see that there's much room for any kind of mechanism that it could be attached to.

Does anyone know what this clamp is supposed to be for?

Thanks,

Alasdair

erie patsellis
8-Oct-2010, 04:52
So simple, you'll probably go duh, but it's to lock the clamp from rotating on the tripod.

Frank Petronio
8-Oct-2010, 07:08
I'd probably do some metal surgery so your quick release plate sets properly. One lever locks the rail rotation, the other lever provides tension against the tripod screw.

It is their lightest, smallest, and cheapest rail clamp, being plastic. But if it isn't cracked already then it is as good as any of them.

Armin Seeholzer
8-Oct-2010, 08:33
The best and stronges rail clamp is the grey one from the Norma as far as you not use lenses shorter then 90mm!

Cheers Armin

mackinto2000
10-Oct-2010, 22:09
So simple, you'll probably go duh, but it's to lock the clamp from rotating on the tripod.

Thanks for the response. That's what I originally thought it was, but either it's broken, or I'm failing to understand how it works.

This second lever rotates on a shaft that runs horizontally into the bottom plate of the clamp. It's only a couple of mm thick, and I don't see that there's any room inside the plate for a mechanism of any kind. What's it supposed to lock against? I've tried using both 3/8 and 1/4 in threads, and in neither case to I get any increase in tension when I move the lever.

THe only thing I can think of is that the plastic of the lever body is somehow supposed to press against a specially shaped tripod head. Is that's what supposed to happen?

Yours in confusion,

Alasdair

Robert Crigan
15-Oct-2010, 04:07
As otherfs have said, the second lever is meant to tighten against the tripod screw. It's fixed to a steel rod that rotates eccentricly, like a cam. Sometimes they stop working. When mine did I just stopped using it.