Gitzo Gimbal Fluid Head

I received my new GHFG1 from Adorama (that was quick!) and I spent some time going over it.
But first a little background. I started shooting with big lenses way back before gimbal heads were introduced to photography, or at least they were not common. And I used to use a large/heavy video fluid head then. Since then I've owned/used various gimbal heads (Wimberley, Benro, ProMediaGear, etc) over the years. And for the last several years I have abandoned them altogether and have been using a leveling pan/tilt head instead. I've often wanted to go back to a fluid head but there wasn't an option I could justify... video heads up to the task are big/heavy/expensive. RRS makes a fluid gimbal that I highly suspect is better, but it costs 3x as much as this head.
The reason I wanted a fluid head is because a little bit of resistance goes a long way towards eliminating wobbles and camera shake. Which ensures smoother movements/tracking and sharper images. Part of the reason I quit using gimbal heads as none of them had very good drag systems. You know how having VR turned on can make tracking easier/smoother? Fluid drag does the same thing... most of that jumping around in the viewfinder is you, not the animal/bird.

And then this thing shows up on the market and at a very reasonable price!
My main concerns were that there weren't any good reviews and everything I saw had smaller kit mounted. It's only rated to 17.64 lbs and the camera/lens combination I primarily use weighs right at 15lbs. My general rule of thumb for tripods/heads is that they should be rated for at least 2x what you're going to put on it if you want any real stability/reliability. Having taken this thing completely apart, I am quite confident the noted limit is for optimum performance and not structural.
Here's a stock image as I didn't take any "overview" pictures.
The first thing I noticed was that it's big/chunky. I don't really care because it doesn't weigh a lot, it's just under 3lbs/1.4kg, just slightly less than the Wimberley WH-200 and most other comparables. The knobs are nice and large with rubberized grips, both are big pluses in cold weather.
You may also note that the cradle/clamp isn't quite centered... that means this is definitely just a dedicated long lens head; no multi purpose applications here (i.e. stitched pano's).
When it was delivered it was quite cold, it was right about freezing out and I guess the truck wasn't heated. Right away I mounted it on my tripod and I noticed the drag levels seemed quite high, more on that later. The next thing I did was check for play/function of the various bits.
One thing I always do is check to see if the knobs are captive or if they might be prone to working loose and falling off. Especially with something like this where the knobs will generally be left loose. The knobs are captive, or rather I believe they are meant to be... the tilt knob came off. The knobs also have a lot of range that is useless, they go from completely off to "locked" in about 1/2 turn. The other knobs are of the spring indexed type where the knob can be repositioned.
In the end I put a tiny bit of lightweight loctite on the retaining screw (the blurry part with GITZO on it) and put it back together...problem solved. But when it came off I found my first discovery... this head uses proper "finned" type fluid (grease) cartridges top and bottom... at this price I wasn't sure it would. This isn't the only way to make a fluid head, but it's a common way found on many more expensive video heads.
The specs for the head states that the tilt azimuth has "fluid cartridge with fixed drag," but I wouldn't quite agree with that. The way the tilt locking knob functions is by pulling these two components together until the swing arm binds against the fiber washer. When you compress the grease into a smaller area it increases the resistance somewhat. But the range of adjustment is quite small. With the locking knob full loose these parts are the farthest apart. They're still close enough to be "sealed" I would say, but that allows a bit more room for the grease to move around in. And since it's the grease that keeps those concentric fins separated/centered, that leads to a slight amount of lateral give to the swingarm... I do *not* think it's really anything to be concerned with.
Once it was back together I mounted my camera/lens on it and centered it's CG at the pivot point. It's a D5 and 400/2.8. and the lens has a low foot with integrated arca swiss groves. I found that the safety pin in the clamp interfered with my lens foot and needed to be removed. Both the setup and pin issue are well described in the manual... and that's all that is explained. It also warns that there is no safety with the pin removed, but my lens foot has the safety stops at either end so it's a non-issue.
I then went to mount the pan bar out of curiosity. This is when I realized that the mounting knob for the pan bar has very limited travel unless the cradle is fully lowered... the indexing capability helps, but not enough IMO. With this particular camera/lens combination the bar isn't any farther out than the camera body is. It's only about 11" max (it can be set a bit shorter). With the low foot on the lens the arm barely clears the camera body, and if angled upwards it contacts the camera body. The length and angle of pan bar are personal preference, but a longer arm provides for finer/smoother control. None of this much matters to me as I bought this for photography, not video. But if I were going to use this for video with this kind of combination I would want a longer bar and  more clearance.
The specifications for the pan axis sates that it has "1 step plus variable PTFE friction". In this case it's true. The pan locking knob simply pushes a small aluminum block against the outside of the base... this is not a very smooth friction for adding dampening, and it's not intended to be. But it's also "open" to getting grit in there... IMO, that's a potential problem. You can see the block in this picture.
I also found exposed grease in areas that will only collect grit over time. I found it inside the mounting screw hole and on the sliding shafts of the clamp.
A little bit of cleanup and it should be fine.
Now to revisit the cold dampening issue... on playing with the head while it was cold I think something internal came loose as most of the panning fluid dampening disappeared and I was hearing a light grinding noise kind of like that made by worn ball bearings. So today I put the head in the freezer for an hour and checked the change in resistance (grease viscosity) on the tilt azimuth. when it was warm the resistance was barely measurable on this cheap spring scale.
But when cold it went up to more than half a pound.

And that's only at freezing (32f/0c)... the head is rated for down to 14f/-10c. I would expect an even more significant difference at the minimum temp. This may be the biggest issue for this head... there are essentially no adjustments for the viscous drag, and I've been out taking pics in temps below 14*f before. One thing to note though, the grease can be kept warm or loosened by working it (friction).
And that brings me to the panning mechanism... as I said, something must have come loose due to the cold temperature of the head. Time to explore some more.
Under the panning cap there is a screw for setting the PTFE friction noted in the specs. There is nothing in the manual about this.
Under this screw is a couple of washers and a thrust bearing.
To disassemble it farther, after removing the tensioning nut, you remove one of the black plugs in the side and insert an allen wrench or something similar into one of the holes in the upper base. You can actually use two as there are two holes in the head and upper base, I just used the one.
Next make sure the panning lock is loose and turn the head counterclockwise a couple of turns. The friction of the lower base to the tripod should hold it and the upper base and lower base should start to separate (I didn't have the correct pin-spanner wrench for the lower base). You can continue turning the head to separate them, but I re-locked the panning knob and unscrewed the assembly from the tripod, and then finished separating the base by hand.

This is the upper base assembly. The center black nut is what came loose... there was no thread locker of any sort. Those five holes are how it couples to the fluid cartridge.
At the top there is a large thrust bearing which carries the panning load, and then a bit farther down there are a pair of wave washers in between PTFE washers. What the tension adjusting screw does is pull all of those things together which flattens the wave washers between the PTFE washers. There is no adjustment for the spacing of the two halves of the fluid cartridge, so unlike the tilt axis the fluid drag really is fixed. This is the "1 step plus variable PTFE friction" I noted from the specs earlier. This friction adjustment also affects the break away force required for the "whip-pan" function. Also note that there is no environmental seal between that main thrust bearing and the outside... but you would probably have to work pretty hard to get contaminates that far inside.
These are the base parts. The black nut (lower left) is what came loose on my head. Going from the lower left to the upper right, all of those parts are assembled in order and the nut screws onto the post seen in the previous image, attaching the upper base to the head. At the upper left is the lower base with the fluid cartridge. The upper base and lower base screw together. And the tensioning screw goes into the lower base, pulling the head slightly down and compressing the wave washers.
Unlike the tilt cartridge this one is not fixed. If the resistance becomes greater than the resistance of the PTFE and wave washers are applying the assembly breaks free and the panning motion is born solely on the large thrust bearing inside without fluid dampening... so what I was hearing earlier was indeed bearings. I found that the resistance in the fluid cartridge seemed very high and no matter how I reassembled things I wasn't getting any fluid dampening, just the bearings. So I cleaned out the fluid cartridge and repacked it with silicone grease until I got a very firm resistance when reassembled. The key was getting the black nut secured correctly (I used a small amount of green loctite). If you over tighten the nut, you reduce the minimum preload setting of the wave washers.

There was a lot of stray grease inside as well... I guess the cartridges were overfilled.
When I refilled them I made sure grease came out of the weep holes evenly and cleaned up the excess before reassembly. I was not very particular in removing the original lithium grease... I just scraped the bulk of it out with a plastic toothpick thing.
The grease I used is MolyKote 33 medium (NLGI-2) which is a silicone and lithium type rated for -100f/-73c to 400f/204c. I put it back in the freezer for a few hours to ensure the grease I used would be suitable and now everything seems fine. I have very little increase in fluid drag at -4f/-20c (the temp of our chest freezer, previously I used the regular freezer). That grease is really expensive, but you don't need much at all (less than 1oz). I do think that NGLI-2 is a little lighter than the original grease, so the fluid dampening is probably a little lighter than it was originally, but not significantly so IMO.

To reassemble the base the process is reversed. But you will probably want to have the fluid cartridge separated into it's two halves with each half properly seated in the upper and lower base before screwing them back together. Otherwise it is hard to get the fluid cartridge properly seated on both sides... 
I should note that it's probably better to get a replacement if you encounter such an issue. But if cold temps can cause internals to come loose (there was no thread lock used anywhere) or the grease to gum up and become problematic, this could be an issue waiting to show up years from now. On the other hand, it's pretty easy to service once you figure out how all the parts are held together... and repacking it with a different grease would allow it to function more uniformly over a greater temperature range.
I should also note that the rated temperature range (14f/-10c to 122f/50c) already probably well exceeds that of your camera. And I've heard of this head working fine at much colder temperatures than 14f/-10, just like I've used my DSLRs at colder temperatures. So, maybe you shouldn't go fixing something that's not broken...

Initially after it malfunctioned I was going to return it... a lot of the little things were just a bit disappointing in terms of QC, I expect more from Gitzo products (even if it's Manfrotto now). But one month later on and I'm still happy with it so I think I'll be keeping it... it does what I want better than any other gimbal head I've used (and I've used most of them). Now we'll see what long term use shows up.
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