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Old May 20th, 2012, 05:42 PM   #1
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Tightening the a Fluid Head

Greetings to all! I was wondering if any of you old "Crew Dogs" had a method to ensure the 'ball' doesn't slip when performing Pans and Tilts? After I balance the Fluid Head, and cinch it down as tight as I can by hand, it always seems to 'slip'. The Vertical Drag or Counter-Balance adjustments are perfectly set, so lowering the VD or CB isn't the answer.

I considered using 'chalk' on the 'seat' and 'ball', but it seems too messy and using 'Gaffer's-Tape' doesn't appear to be an option. Any ideas?

Regards,

J.
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Old May 20th, 2012, 05:57 PM   #2
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Re: Tightening the a Fluid Head

The ball shouldn't slip under normal use. Sounds like a tolerance issue either from wear or manufacturing defect. Sometimes the tie-down knob is to blame--some heads have a washer or spacer assembly that can go missing resulting in the ineffectual lockdown. What kind of head is it?
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Old May 20th, 2012, 06:17 PM   #3
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Re: Tightening the a Fluid Head

Hi, James.................

Please tell me this is your venerable Gitzo you're talking about and not the new Vinten VB?


CS
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Old May 20th, 2012, 07:18 PM   #4
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Re: Tightening the a Fluid Head

It's gotta be the Gitzo, couldn't be the VB.

Undo and remove the clamp knob from the head and remove the head from the sticks.

Inspect the clamp knob "grip cup" carefully - that's the bit at the top of the clamp knob that's designed to grip the underside of the half bowl on the sticks and swivel when it's "bit" to allow the knob to be fully tightened.

Most modern ones are made from HD plastic, most of the older ones were metal. Check that it hasn't warped/ deformed/ broken.

If it appears to be intact, inspect the inside outer rim of the cup closely, that's the bit that actually "bites" on the underside of the half bowl. It should be slightly rough to the touch - I'm talking fine grade wet and dry abrasive paper here, not woodwork rasp.

(Check the clamp knob cup on your VB, that's what you should have).

If, with time and use, it's ended up polished smooth, a bit of attention with a piece of the aforementioned wet and dry will impart the rough surface required for it to "get a grip".

If the cup is damaged you'll need a new clamp knob, I can't see anyone selling the cup as a part, though stranger things have happened.


CS
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Old May 21st, 2012, 11:15 AM   #5
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Re: Tightening the a Fluid Head

Chris, Chas., et al...unfortunately, neither the Gitzo or V-B. It's the Sachtler FSB-8 and CF/75 sticks. I'm kind of surprised and pleased you mentioned using sand-cloth (sand paper). I'd considered it, however, I have a bad tendency to use a 'big hammer' for all problems. Heh, heh! I have some 600 grit sand-cloth and I'll give it a shot. I just think both surfaces are machined so well, they're too smooth. I need a little extra 'surface tension'.

Thanks for the suggestion!

Best regards,

J.
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Old May 21st, 2012, 10:23 PM   #6
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Re: Tightening the a Fluid Head

Th FSB heads and CF 75's are a particularly bad combination from the slipping point of view.

Despite the coating on the underside of the half bowl being slightly dimpled (for want of a better word) it is extraordinarilly slippery to the touch.

The half ball on the head and the receiver bearing ring are machined as smooth as a babies behind as well, great for getting extremely accurate leveling, just not a lot of friction there, and the clamp cup friction rim doesn't really have any, friction, that is.

If roughening the clamp cup surface doesn't do the job, I'm a bit stuck with what to suggest for the half bowl underside.


CS
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Old May 21st, 2012, 11:54 PM   #7
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Re: Tightening the a Fluid Head

Hi James,

To tighten effectively the ball should make contact with the outer rim of the tripod bowl. A simple test is to slacken off the locking knob and slip a narrow strip of paper between bowl and ball, then retighten the locking knob. It should not be possible to pull out the strip of paper without tearing it. If you cannot pull out the strip of paper loosen the clamp knob and then remove the strip. Look for signs of compression on the paper strip – if all is well they should correspond to the outer edge of the bowl.

If you could not clamp the paper strip when tightening the locking knob try Charles’s suggestion of placing an extra washer between locking knob and its cup as the problem may be that the that you have not enough thread to fully tighten ball to bowl.

At one stage I remachined a tripod bowl that had become distorted. It took a long time to set up accurately but it can done.
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Old May 22nd, 2012, 11:12 AM   #8
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Re: Tightening the a Fluid Head

Alistair, Chris, & Chas....thank you all for the thoughtful responses. I 'scuffed-up' both pieces, we'll see how that works. I'll also take a look at adding a washer to the assembly.

Best regards to all,

J.
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Old May 22nd, 2012, 04:46 PM   #9
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Re: Tightening the a Fluid Head

Ah, yes, washer.

I've been giving my FSB/ CF 75 combo a pretty serious scrute (as in scrutinise) and the only washer I can imagine that will achieve anything but a world of grief, would be a tough fabric backed rubber (think bicycle tyre sort of) one large enough to fit the entire clamp knob cup but with segments removed from the radius so that it will "cup" to match the cup/ half bowl underside.

It can be only millimetres larger than the clamp cup diameter, else it will seriously restrict your levelling angles.

If that can't "get a grip", nothing will.


CS
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Old May 22nd, 2012, 07:31 PM   #10
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Re: Tightening the a Fluid Head

Hi, Chris! I'm not awfully interested in modifying my Sachtler CF 75 or having to enlist the services of a Machine Shop. Heh, heh! However, if I could find something workable without having to permanently modify the sticks or head I'd give it a try. I can tell you, roughing-up the 'ball and cup' helped to some degree, but it still loosens-up after awhile.

I think it's one of those endearing 'little quirks' of the CF 75 Sticks and I'll learn to live with it until it annoys me to the point I choose to make a change.

Bottom line, I really 'love' the FSB-8 Fluid-Head and I 'like' the CF 75 sticks. : ) If I win the LOTTO, I would look really hard at the CF-100ENG HD 2CF.

Regards,

J.
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Old May 22nd, 2012, 07:58 PM   #11
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Re: Tightening the a Fluid Head

Quote:
CF-100ENG HD 2CF

Now THAT's a serious set of sticks, makes the 75 CF's look like a 5 stone weakling by comparison.


CS
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Old May 22nd, 2012, 11:58 PM   #12
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Re: Tightening the a Fluid Head

The ball leveling tripod top has been around for a long time and is a well-proven design. It has two basic requirements, firstly to permit adjustment of level. This works best if the mating surfaces slip readily over one another – this is facilitated by having smooth bearing surfaces. Roughened surfaces will not slide so smoothly and a rubberized washer between the surfaces would most likely make fine adjustments very difficult.

The second requirement is to be able to securely lock the selected position. This is done by drawing the ball into the cup and it grips best if the ball is supported near the rim of the bowl.

Assuming that it all worked OK when new there is not much that can go wrong. Any wear would be obvious on inspection as would any cracks. Testing point(s) of contact can be done easily with strips of paper as mentioned above. These tests would help detect any distortion.

The next point to check, and this is where the washers come in, is to make sure that the clamping mechanism has not reached the limit of its travel prematurely. This can happen if the stud protruding from the base of the ball or the locking (clamping) knob have insufficient thread. In this case turning the locking knob would stop the tightening before full pressure could be applied.

The photo shows a clamping knob from an early Miller, the knob has an internally threaded blind hole that limits how far the knob can be screwed to a stud. Also shown is partially threaded stud. Obviously there is a limit to how far this knob can travel on this stud. There is also a cup that engages with the lower surface of the tripod bowl. Between the cup and the knob is a red washer, every time the knob is tightened some wear of this washer occurs. As the wear on this washer proceeds more of the threads will be used, MAYBE to the point where the threads jam before adequate clamping pressure is applied. IF this is the case the simplest remedy is to replace or add washers.

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Old May 23rd, 2012, 12:19 AM   #13
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Re: Tightening the a Fluid Head

No washers in the Sachtler design of the FSB head/ 75 CF sticks.

Plenty of travel on the clamp bolt, far in excess of anything required to ensure it was tight.

All the mating surfaces are simply too darn smooth for anything to get a grip - I can replicate the exact same situation here with my FSB6 & 75 CF's.

The head ball, receiver bowl, bowl underside and clamp cup are machined/ manufactured to a level where you couldn't even get a fag (roll your own cigarette, for those not in the know**) paper in any of the mating surfaces, and all those surfaces are as smooth as a babies butt.

Actually, better, as most of them are mirror smooth.

Simply not enough friction, is all.


CS

Last edited by Chris Soucy; May 23rd, 2012 at 02:22 AM. Reason: ** Americans, what do they know?
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Old May 23rd, 2012, 08:29 AM   #14
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Re: Tightening the a Fluid Head

When you tighten the ball head you do not know what the effective compressive stress applied to the ball joint is. This is because the thread friction is unknown.
Variations in the thread geometries and surface finishes can cause wide variations in friction under load.
My suggestion is to apply a thread lubricant and if at all possible use TriFlo teflon lube.
This should increase the joint compressive stress considerably for a given torque.
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Old May 23rd, 2012, 09:22 AM   #15
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Re: Tightening the a Fluid Head

Frank...I hadn't considered using a PTFE based lubricant to increase the torque and compressive load. I just happen to have a jug of "BreakFree CLP", a PTFE -based lubricant, this will be my next attempt to snug things up. The idea of using a fiber-washer between the 'Cup' and the 'Clampimg Screw assembly', is also a possibility, but as Chris points out, it would have to be very thin. The design is such, by removing the 'C-Clip', I think you can disassemble the the 'Cup' and 'Clamping Screw assembly' and you might be able to insert a fiber-washer between the 'Cup' and 'Clamping Screw', however, I'm not sure how friendly it would be to re-assemble. Pretty tight tolerances.

Chris...yes, I know what "Fag" means to my 'Kiwi' and 'U.K.' cousins. Heh, heh! I've 'rolled a few' in my day. Tobacco of course. : )

Thank you gentlemen for your generous thoughts and suggestions. You've given me several good ideas.

Best regards to all,

J.
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