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Equipment Discussions >> Equipment

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OneDaveT
sage
*****

Reged: 10/24/11

Loc: IL, USA
Re: Wood Tripods new [Re: JoeinWV]
      #6193713 - 11/13/13 11:05 PM

Here's my AstroTech voyager head on an Oberwerk tripod


http://www.cloudynights.com/ubbthreads/download.php?Number=5078547


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Wood Tripods new [Re: brianb11213]
      #6193992 - 11/14/13 05:36 AM

Quote:

Throw away the legs & substitute Berlebach Planet, far less vibration & damping time under 1/4 sec.




Put that on the Houston-Fearless and there would be no damping time, no vibration.. And the Houston-Fearless is actually lighter.

It's also worth noting that the Berlebach upgrade was more than just the tripod legs, it was also the tripod hub (wood right?) The hub itself is much larger in diameter, this provides much greater rotational stiffness. The reduced damping times might not be due so much to the legs but rather to the improved hub design.

Jon


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hottr6
Carpal Tunnel
*****

Reged: 06/28/09

Loc: 7,500', Magdalena Mtns, NM
Re: Wood Tripods new [Re: SteveG]
      #6194370 - 11/14/13 11:25 AM

Quote:

You'll notice the surveyors tripods, the Houston Fearless, and the renowned Rob Miller tripods all share something in common......



Um..... 3 legs? A triangular head? They keep things out of the dewy grass?



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Old Dinosaur
Carpal Tunnel
*****

Reged: 05/08/07

Loc: Down there on the river
Re: Wood Tripods new [Re: hottr6]
      #6194378 - 11/14/13 11:31 AM

I guess I like them all.
5 wood.
5 metal.


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roscoe
curmudgeon
*****

Reged: 02/04/09

Loc: NW Mass, inches from VT
Re: Wood Tripods new [Re: hottr6]
      #6194433 - 11/14/13 12:01 PM

Quote:

They keep things out of the dewy grass?




Yep, your knees............


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SteveG
Post Laureate
*****

Reged: 09/27/06

Loc: Seattle, WA
Re: Wood Tripods new [Re: hottr6]
      #6194477 - 11/14/13 12:22 PM

Quote:

Quote:

You'll notice the surveyors tripods, the Houston Fearless, and the renowned Rob Miller tripods all share something in common......



Um..... 3 legs? A triangular head? They keep things out of the dewy grass?






I believe Jon answered with the technical term "six element tripod design". Note the very wide stance where the legs attach to the hub.


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JonNPR
sage
*****

Reged: 03/04/13

Loc: Oregon
Re: Wood Tripods new [Re: OneDaveT]
      #6194605 - 11/14/13 01:35 PM

Dave, did you need any special adapter work in order to mount the head on the Oberwerk?

Jon


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hottr6
Carpal Tunnel
*****

Reged: 06/28/09

Loc: 7,500', Magdalena Mtns, NM
Re: Wood Tripods [Re: SteveG]
      #6194713 - 11/14/13 02:28 PM

Quote:

Quote:

Quote:

You'll notice the surveyors tripods, the Houston Fearless, and the renowned Rob Miller tripods all share something in common......



Um..... 3 legs? A triangular head? They keep things out of the dewy grass?






I believe Jon answered with the technical term "six element tripod design". Note the very wide stance where the legs attach to the hub.




Gottit, but I would argue that many tripod designs have "6 elements" (actually, it is really 9). The awful tubular legs have only 3.

Perhaps a key feature of the more expensive designs (except surveyor's tripods) is the triangular nature of each leg, like a crutch. As you noted, the components of each leg are wide apart at the hub, but the components come together at the feet.


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don clement
Vendor (Clement Focuser)


Reged: 02/02/11

Loc: Running Springs, California
Re: Wood Tripods new [Re: George9]
      #6194836 - 11/14/13 03:46 PM

Quote:

Quote:

Of course the accessory tray fails to add any bracing. Follow the lines of force in a tripod and the best way to brace is from leg to leg at the extremities. Not though a center rod either. Three element tripods also are lacking despite large diameter elements. That's where the six element tripod is way more rigid. Again follow the lines of force a look at designs such as the six element that use the least bending forces on each element and maximize elements in tension and compression. Bending moments can cause vibration and then dampening materials are needed e.g. wood. IMO the six element tripod design is the best
with cables running from the extremities of each leg to leg- not through a central rod or accessory tray.

Don




Along the same lines, I find that the best stability is gotten by sinking the tips of the legs into the grass rather than relying on a cable. My AP/Baader tripod is perfectly rigid when sunk into the ground. Then you effectively have six triangles holding it rigid. The accessory tray is irrelevant to stability. Even the aftermarket braces don't add much because their attachment point on the tripod leg is not that stable. The only thing I added was a cord between pairs of legs just so it was easier to line up the accessory tray attachments. And rubber feet for when I store it in the house (I see that's now an option).

George




I use my six element tripod on asphalt sometimes so digging into grass is not always an option. The aircraft cables that are connected leg to leg on the six element tripod I built don't just attach but there is a tensioning that preloads each leg ( made of two elements ) to a center bolt that bears on the upper ring. This preload also takes up any play in the spherical rod connections and makes for an almost solid feel with no measurable vibration issues and therefor no need for additional dampening. In fact this 10lb tripod is as stiff and rigid as any tripod of similar dimensions and in fact is more rigid than my Houston-Fearless when the legs on the Houston-Fearless are extended any amount at all. The leg extension basically defeats the six element design of the Houston-Fearless and adds three lengths of unsupported cantilever tubing. Note there is no wood used in my six element tripod because there is no need for dampening the structure being very sound from the start. IMO the addition of dampening is an afterthought or band aid fix to poor tripod design methods.

Don


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George9
sage


Reged: 12/11/04

Re: Wood Tripods new [Re: don clement]
      #6198101 - 11/16/13 12:31 PM

I get it now. The tensioning should work well. George

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Space_Girl1234
member


Reged: 03/06/11

Re: Wood Tripods new [Re: George9]
      #6201067 - 11/18/13 04:02 AM

Do you have a picture of a 9 element tripod so I can build one?

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