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Hard to say because:
1. If it's an ordinary o-ring it does look broken.
2. If it's of some other material it might be made that way.
Can you tell whether the ends "look" broken, or are made that way.
Where from? Perhaps between the two parts of the flange that the screws tighten???
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Also, your thread is the only ref to "o-ring for manfrotto..." I could see, and there are no schematics I can find.
Do you have a manual with a schematic?
CC, Image editing OK.
Most likely: If it's made of rubber(ie. flexible) then it's broken .. very easy fix.
Less likely: it's it's made of metal(possibly still flexible, but very little springiness) then it may not be broken, and could be a circlip/retaining ring of some type.
I doubt that Manfrotto have made such a hefty metallic retaining ring, so my theory is that it's a rubbery ring used to protect or soften something.
I'm looking at both my Manfrotto tripods(NOT HEADS!!!) and there are rubber rings tightly located at the top of the extension column.
What they appear to do is to cushion the top of the column from a metal to metal hard impact when you collapse the column, and hence likely to wear from a metal to metal surface conjunction.
The rubber O ring is extremely cheap to acquire.
I have a rubber O ring kit that has hundreds of different sized rings of various thickenesses and I think I paid about $5 for the kit at a junk-hardware shop.
I use them for resealing leaky taps and sometimes in automotive repairs etc.
The inner diameter of the rubber ring is 24mm and the other diameter is 30mm(hence a 6mm thickness in the rubber).
Many/any hardware store should have something similar to suit.
The rubber ring is a tight fitment, meanign that it needs to be stretched over the centre column to fit tightly .. otherwise it'll be loose and slide up and down the column(not good).
It's there to simply the metal surface of the underside of the head plate from hitting the metal surface of the top of the spider(leg holder thingy!)
Each set of legs are different, and the way you remove the column to refit this rubber ring will vary.
If you have a two part column, then as you unscrew the bottom(most) retaining screw on the column, the very top of the column will start to come loose.
Most of these two part columns have a 100mm/4" top stud.(it's more a solid stud/spike design, as opposed to a hollow tube)
That's the easier of the two design to replace. When the top stud of the column comes loose, the ring is located in that section, and you don't need to feed the entire column through the spider.
If you have the single piece column design, this one is most likely a little more easy to actually remove. At the bottom(most) end of the column is a rubbery cap. Simply pull it to remove it.
Undo the holding screw for the column and slide the column all the way up and out.
The harder part is to slide the rubber O ring back up the long tube again to fit it all together.
if you need any more help just holler.
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ps. It's not an urgent item to repair!
That is you don't need to using the or centre column just because this rubber ring is broken.
It's just that over time, if you do keep the stored all closed up the aluminium/metal surfaces will wear with movement relative to each other.
So until you fix the rubber ring, just be sure to keep a few millimeters of gap between the 's head base and the 's spider.
ALSO! if in the unlikely chance that this piece is not the rubber O ring, then I have no idea what it is on your that's broken.
(but my feeling is that this is just the standard rubber o ring as they all have)
Thanks for the quick reply. It is a rubber ring but the split could be either way; that is made that way as the split looks pretty perfect but the inside is a bit rough. Not smooth like the outside. I got the schematic of thisand no where was there mention of any "O" ring or any replacement part "O" ring. Which is strange because they could have charged me an arm and leg. I will go and check my box of rings as I'm pretty sure I will have one to fit. I had not noticed this "O" ring before so was a little confused as to it's exact location. I suppose it makes sense to cushion the blow as I drop the centre pole. My centre pole has a plastic cap with a push-in button to release the pole through the top opening. cheers Brian
UPDATE: Well would you believe that not one "O" ring of the correct size, but I found a rubber flat washer that should do the job. It does cushion the fall of the centre shaft so looks like a fix has been found. Thanks for your help and thanks too to Aust. photog. cheers Brian
Last edited by bricat; 15-10-2015 at 1:23pm. Reason: update
As long as the metal to metal surface has been eliminated, you should be ok.
If it's a loose fit, it may be a PITA if it's flapping about being only a flat washer.
If you need one(for proper fitment), I have heaps in my kit!
I have a 141RC and can't see any 'O' rings, or even any where that one would fit.
The base of the head doesn't give me the impression that there is, or was, the provision to fit an 'O' ring.
Mine just screws down on to the upright bolt on the and when tight there is no movement visible at all.
These O rings are on the (manfrotto) itself if it has a centre column.
Manfrotto use them on their tripods(eg. like an 055).
Your manufacturer may not use them.
If you look at Brian's (where you can see the centre column), the O ring sits tightly on the centre column shaft right up against the ridge of the head base plate.
From memory, I think the head base plate unscrews from the shaft via a large bolt inside the top of the base plate. So with the head unit mounted you can't see it.
To see it, you remove the head first and then in the centre of the base plate should be a large nut/bolt and that's another way to get to the O ring.