Carbon Fibre tripod

[Swagman105]

I was looking to improve the stability of my Carbon Fibre Tripod. Have seen optional weight bags which can be slung between the legs of a CF tripod into which weights can be placed to improve the inertial property of the tripod.
I felt this was a little inelegant so decided to use one of my old counterweights as shown in the attached photos.
I first needed to take the bottom knurled plastic knob from the shaft. Just a matter of a grub screw to reveal the bottom of the M12 centre shaft. Then I needed a way to connect the M8 threaded counterweight to the bottom of the shaft
The best I could come up with was an internally M12 threaded 35mm long hex collar into which a M12 to M8 thread reducer could be screwed. Then it just was a matter of some M8 hook and eye bolts to link everything together. There is still the option of doing away with the eye and hook bolts and screwing to the counterweight directly using a length of M8 threaded rodding.
I was only able to get the M8 eye bolt locally from a marine store. I had to go to aliexpress to find the M12 hex collar, M12 to M8 reducer and the M8 hook bolt.
Just posting in case others might think this worthwhile to try.
PS The bottom 10mm of the centre shaft was unthreaded so the hex collar needed to be about 35mm long to span that unthreaded section.

[leon]

Hey Geoff, yes that would certainly work and give more stability, however how would it go if there was a breeze and had some sway, it would have to hang dead still at all times if you were imaging, maybe.:shrug:

Just my two cents worth.:thumbsup:

Leon:thumbsup:

[Swagman105]

Yes good thought.
I still have the option of dispensing with the eye and hook bolts and replacing them with say a 300mm or even longer length of M8 threaded rod. That would make the weight system fully rigid.
My thinking though is that any wind is probably going to have more of an effect on the greater surface area of the rest of the rig than on a small yet very dense object like a solid iron counterweight. In that case having the counterweight swinging freely like a pendulum should tend to work or pull back against the direction of any movement of the rest of the rig.
I remember on a trip to Taiwan going to the top of the then world's second tallest building in Taipei. Because it is in an earthquake zone it has a huge pendulum built into the structure designed to dampen the amplitude of sway caused by earthquakes.
Hoping some similar effect might work with this. It's all about moderating the amplitude of any movement caused by the wind or any other factors. BTW I am not anticipating imaging during an earthquake, but we live on a busy road and can often feel the effects of heavy trucks as vibrations on our concrete driveway.
The other adverse possible outcomes could be the establishment of permanent oscillations or even high amplitude resonances.
So I guess the proof of the pudding is going to be in the eating.

[Peter Ward]

While it may sound counter intuitive, dangling a weight from the tripod is not
the best solution.

A mount system works best when it has high stiffness and low weight. These two things give the system a higher natural vibration frequency, which dampen out far more quickly than low frequency systems.

You'd do better by replacing a low stiffness component rather than adding mass to the system. (This is also why the three bolt "rat cage" you see as a levelling system to an EQ mount are really bad ideas).

Have a read of Roth's Compendium of Practical Astronomy (Vol1) if you'd like to know more about this :thumbsup:

[croweater]

Hi Peter. Would another tripod spreader lower down be a better solution?
Cheers, Richard

[Peter Ward]

Absolutely. Increases rigidity with minimal mass increase.

FYI Losmandy used to call the non-structural parts of his EQ mounts "dead metal" they only added to the system mass, but did nothing to increase its rigidity.

His later model mounts had significant internal machining that removed that
useless metal and make the mount lighter but just as rigid.