What is the fluid in a fluid head?

GenJerDan said:
:) Yeah, but I'm supplying most everything else.
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Well hell...can ya get me some two-ply charmin? This one-ply-albanian-100-grit shi*paper is making me want to put rhino lining on my ass....

C'mon...you fly boys can afford it :)
 
Fly boys? Fly boys?! I signed up for Fun Travel and Adventure, then switched over to pay-me-more and don't-make-me-dress-funny side of the house.

(And now sit here and write programs so the people sending to and receiving stuff from downrange can keep track of what went where.)

So. What's your APO address? I'll MPS some to ya. The commissaries are coming up on case-lot sales. :)
 
Man, you guys are hardcore. I don't think I would try to build my own fluid head. It's just not practical to do and still save money. A true fluid head has no contact between the rotating and stationary parts other than through the ball bearings. The drag is created by shearing action of a fluid between two surfaces that are placed very close to each other and moving respective to each other. This means those two surfaces must be made very precisely and aligned very precisely. Also, there is a limit to how much drag you can create with just one surface interfacing with another. That's why the big guys like Cartoni and OConnor use multiple disc or sectors interwoven with the stationary parts to get higher drag. And this is just to create drag. To make the drag adjustable, you have to have a few more doohickeys. Then there's the issue of counterbalance, which is its own mechanism in itself!

Anyhow, I didn't mean to discourage you guys. Just trying to lay out the challenge ahead of you. Good luck with your projects!
 
So I looked into the gearhead thing. The tilt mechanism was cost-prohibitive. Next I get a chance I'll ask him about the fluid head--I couldn't describe how it was made well enough to get the idea across. Thanks to tnle2's descriptions of the challenges involved I should describe it much better next time.
 
> In the old O'Connor heads it is a thick, clear, silicone based oil. You can buy it by the quart from them. Notorious for leaking.

I just got an old O'Connor #30 head from ebay. It did move ok but not perfectly so I took it apart. "Thick" doesn't begin to describe the stuff in it, it is an opaque dark gray and very nearly solid. Roughly the consistency of silly putty. I called O'Conner and they sell a #30 fluid head fluid for $90 (but the tech says "it really never goes bad.") They will overhaul the head for $1100 (!)
 
fluid head design

fluid head design

tnle2 said:
... Also, there is a limit to how much drag you can create with just one surface interfacing with another. That's why the big guys like Cartoni and OConnor use multiple disc or sectors interwoven with the stationary parts to get higher drag. And this is just to create drag. To make the drag adjustable, you have to have a few more doohickeys.
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Looking inside my O'Connor Model 30 fluid head, it is quite simple. For the pan action anyway, there is just one shaft bearing and two thrust bearings. The fluid drag part is just a plain sleeve bearing surface against a smooth shaft, in a chamber filled with a viscous grease. The sleeve is split into two parts and they are clamped together against the shaft with the adjustment knob, to provide stronger drag. I have it apart right now, so I can provide a photo if anyone's interested.
 
Glad to help. For what it's worth, I suspect the "Model 30 fluid" that O'Connor uses for this head may be a polydimethylsiloxane (silicone oil), like Dow Corning 200 fluid. It comes in a wide range of thicknesses, I would guess this stuff has a viscocity around 100,000 centistokes (cSt.) Here is a viscocity reference from clearcoproducts.com

Viscosity cSt. ----- material
-----------------------------------------
1 to 5 cSt. -------- water
10 cSt. ------------- kerosene
350 cSt. ----------- Sae-30 motor oil
1,000 cSt ---------- light syrup
10,000 cSt. -------- honey
50,000 cSt. -------- ketchup
60,000 cSt -------- thick molasses
100,000 cSt. ------ hot tar
100,000 cSt. ------ O'Connor #30 head fluid (I'm guessing)
250,000 cSt. ------ peanut butter
1,000,000 cSt. ---- paste/caulk
 
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